U.S. patent application number 12/993079 was filed with the patent office on 2011-05-19 for dual labeling methods for measuring cellular proliferation.
This patent application is currently assigned to LIFE TECHNOLOGIES CORPORATION. Invention is credited to Jolene Bradford, Scott Clarke.
Application Number | 20110118142 12/993079 |
Document ID | / |
Family ID | 41100505 |
Filed Date | 2011-05-19 |
United States Patent
Application |
20110118142 |
Kind Code |
A1 |
Clarke; Scott ; et
al. |
May 19, 2011 |
DUAL LABELING METHODS FOR MEASURING CELLULAR PROLIFERATION
Abstract
The present invention provides a method for measuring cellular
nascent nucleic acid synthesis by dual pulse labeling of nucleic
acid. The first pulse labeling of nucleic acid with a nucleoside
analog allows establishment of a baseline nucleic acid synthesis
rate. Pulse labeling of the nucleic acid with a second nucleoside
analog then allows measurement of any changes to nucleic acid
synthesis. The nucleic acid synthesis can be measured as cell
proliferation, DNA, or gene expression, RNA. This method does not
require a potentially artifact-inducing intermediary wash step
between pulse labels. Additionally, this method may be used to
screen compounds for their affect on cellular proliferation by
treating cells or an organism with the test compound simultaneous
to or before treatment with a competitive nucleoside analog.
Inventors: |
Clarke; Scott; (Eugene,
OR) ; Bradford; Jolene; (Eugene, OR) |
Assignee: |
LIFE TECHNOLOGIES
CORPORATION
Carlsbad
CA
|
Family ID: |
41100505 |
Appl. No.: |
12/993079 |
Filed: |
May 14, 2009 |
PCT Filed: |
May 14, 2009 |
PCT NO: |
PCT/US09/44024 |
371 Date: |
February 1, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61054102 |
May 16, 2008 |
|
|
|
Current U.S.
Class: |
506/10 |
Current CPC
Class: |
C12Q 2525/101 20130101;
C12Q 1/6809 20130101; C12Q 1/6809 20130101; C12Q 1/6804 20130101;
C12Q 2565/1025 20130101; C12Q 1/6846 20130101; C12Q 1/6846
20130101; C12Q 2565/1025 20130101; C12Q 2525/101 20130101 |
Class at
Publication: |
506/10 ;
435/6 |
International
Class: |
C40B 30/06 20060101
C40B030/06; C12Q 1/68 20060101 C12Q001/68 |
Claims
1. A method for measuring a change in cellular nucleic acid
synthesis: a) incubating a sample with an effective amount of a
first nucleoside or nucleotide analog to form a primary incubated
sample; b) incubating the primary incubated sample with at least
one second nucleoside or nucleotide analog to form a secondary
incubated sample; c) incubating the secondary incubated sample with
a first labeling reagent and at least one second labeling reagent
to form a labeled sample; d) detecting the labeled sample wherein a
level of incorporation of the first and at least one second
nucleoside or nucleotide analog is measured, wherein a difference
in a level of incorporation of the at least one second nucleoside
or nucleotide analog relative to the level of incorporation of the
first nucleoside or nucleotide analog is measured as a change in
cellular nucleic acid synthesis, with the proviso that either the
first nucleoside or nucleotide or the at least one second
nucleoside or nucleotide contains a bioorthogonal functional
moiety.
2. A method for measuring a change in cellular DNA synthesis: a)
incubating a sample with an effective amount of a first nucleoside
or nucleotide analog to form a primary incubated sample; b)
incubating the primary incubated sample with at least one second
nucleoside or nucleotide analog to form a secondary incubated
sample; c) incubating the secondary incubated sample with a first
labeling reagent and at least one second labeling reagent to form a
labeled sample; d) detecting the labeled sample wherein a level of
incorporation of the first and at least one second nucleoside or
nucleotide analog is measured, wherein a difference in a level of
incorporation of the at least one second nucleoside or nucleotide
analog relative to the level of incorporation of the first
nucleoside or nucleotide analog is measured as a change in cellular
DNA synthesis, with the proviso that either the first nucleoside or
nucleotide or the at least one second nucleoside or nucleotide
contains a bioorthogonal functional moiety.
3. A method for measuring a change in cellular RNA synthesis: a)
incubating a sample with an effective amount of a first nucleoside
or nucleotide analog to form a primary incubated sample; b)
incubating the primary incubated sample with at least one second
nucleoside or nucleotide analog to form a secondary incubated
sample; c) incubating the secondary incubated sample with a first
labeling reagent and at least one second labeling reagent to form a
labeled sample; d) detecting the labeled sample wherein a level of
incorporation of the first and at least one second nucleoside or
nucleotide analog is measured, wherein a difference in a level of
incorporation of the at least one second nucleoside or nucleotide
analog relative to the level of incorporation of the first
nucleoside or nucleotide analog is measured as a change in cellular
RNA synthesis, with the proviso that either the first nucleoside or
nucleotide or the at least one second nucleoside or nucleotide
contains a bioorthogonal functional moiety.
4. The method according to claim 1 wherein the sample is treated
with a test compound simultaneous to or before treatment with the
at least one second nucleoside or nucleotide analog.
5. The method according to claim 1, wherein the first analog
contains a bioorthogonal functional moiety.
6. The method according to claim 1, wherein the at least one second
analog contains a bioorthogonal functional moiety.
7. The method according to claim 1, wherein the first analog or the
at least one second analog contains a halogen moiety.
8. The method according to claim 1, wherein the bioorthogonal
functional moiety can undergo a [3+2] cycloaddition reaction.
9. The method according to claim 1, wherein the bioorthogonal
functional moiety can undergo a Staudinger ligation reaction.
10. The method according to claim 1, wherein the bioorthogonal
functional moiety contains an azido, alkyne or phosphine
moiety.
11. The method according to claim 1, wherein at least one, but not
all, of the first and second analogs are ethynyl-deoxyuracil
(EdU).
12. The method according to claim 1, wherein least one, but not
all, of the first and second analogs are 5-azido-2'-deoxyuracil
(AzdU).
13. The method according to claim 7, wherein the halogen moiety is
bromo, chloro or iodo.
14. The method according to claim 1, wherein at least one, but not
all, of the first and second analogs are BrdU.
15. The method according to claim 1, wherein the first labeling
reagent and second labeling reagent is an antibody or a label that
contains a bioorthogonal functional moiety.
16. The method according to claim 15, wherein the bioorthogonal
functional moiety can undergo a [3+2] cycloaddition reaction.
17. The method according to claim 15, wherein the bioorthogonal
functional moiety can undergo a Staudinger ligation reaction.
18. The method according to claim 15, wherein the bioorthogonal
functional moiety is an azido, alkyne or phosphine moiety.
19. The method according to claim 15, wherein the label is a
fluorescent dye.
20. The method according to claim 15, wherein the antibody is an
anti-BrdU antibody.
21. The method according to claim 15, wherein the first labeling
reagent or second labeling reagent is a dye-labeled azide.
22. The method according to claim 21, wherein the dye-labeled azide
is selected from the group consisting of: rhodamine-azide, Alexa
Fluor.RTM. 350-azide, Alexa Fluor.RTM. 488-azide, Alexa Fluor.RTM.
555-azide, Alexa Fluor.RTM. 568-azide, Alexa Fluor.RTM. 568-azide,
Alexa Fluor.RTM. 594-azide, Alexa Fluor.RTM. 633-azide, Alexa
Fluor.RTM. 647-azide, Alexa Fluor.RTM. 680-azide, Pacific Blue.TM.
azide, Cascade Blue.RTM. azide, fluorescein-azide, cyanine-azide,
dapoxyl-azide and tetramethylrhodamine (TMR)-azide.
23. The method according to claim 1, wherein incubating the first
labeling reagent with the secondary incubated sample in a manner
such that a covalent bond is formed between the first nucleoside
analog and the labeling reagent.
24. The method according to claim 1, wherein incubating the second
labeling reagent with the secondary incubated sample in a manner
such that a covalent bond is formed between the second nucleoside
analog and the labeling reagent.
25. The method according to claim 1, wherein incorporation of said
first nucleoside analog and said at least one second nucleoside
analog is detected by flow cytometry.
26. The method according to claim 1, wherein incorporation of said
first nucleoside analog and said at least one second nucleoside
analog is detected by fluorescence microscopy.
27. The method according to claim 1, wherein incorporation of said
first nucleoside analog and said at least one second nucleoside
analog is detected by multi-well plate assay.
28. The method according to claim 1, wherein incorporation of said
first nucleoside analog and said at least one second nucleoside
analog is detected by imaging.
29. The method according to claim 1, wherein incorporation of said
first nucleoside analog and said at least one second nucleoside
analog is detected by high content screening.
30. The method according to claim 1, wherein the sample is an
organism or cells in cell culture.
31. A method for screening compounds for effects on cellular
proliferation or gene expression comprising: a) incubating a sample
with an effective amount of a first nucleoside or nucleotide analog
to form a primary incubated sample; b) treating the primary
incubated sample with a test compound to form a treated sample; c)
incubating the treated sample with at least one second nucleoside
or nucleotide analog simultaneous to or after treating the primary
incubated sample with the test compound to form a secondary
incubated sample; d) incubating the secondary incubated sample with
a first labeling reagent and at least one second labeling reagent
to form a labeled sample; e) detecting the labeled sample wherein a
level of incorporation of the first and at least one second
nucleoside or nucleotide analog is measured, wherein a difference
in a level of incorporation of the at least one second nucleoside
or nucleotide analog relative to the level of incorporation of the
first nucleoside or nucleotide analog is measured as an effect of
the screening compounds on cellular proliferation or gene
expression, with the proviso that either the first nucleoside or
nucleotide or the at least one second nucleoside or nucleotide
contains a bioorthogonal functional moiety.
32. The method according to claim 30, wherein the sample is an
organism or cells in cell culture.
33. A kit for measuring a change in cellular nucleic acid
synthesis, wherein the kit comprises: a) a first nucleoside or
nucleotide analog; b) at least one second nucleoside or nucleotide
analog, wherein in at least the first analog or the at least one
second nucleoside or nucleotide analog contains a bioorthogonal
functional moiety; c) a first labeling reagent; and d) a second
labeling reagent.
Description
FIELD OF THE INVENTION
[0001] The present disclosure relates to methods for the dual pulse
labeling of nucleic acid.
DESCRIPTION OF RELATED ART
[0002] Pulse labeling cellular DNA for the purpose of determining
the rate of growth is typically performed by the addition of a
nucleic acid sugar analog (nucleoside) to the medium that a cell is
grown in, or in the drinking water of the animal it is being fed
to, or by injection in the animal which is being labeled. A timed
exposure to a DNA analog with the potential of incorporation of
that analog into the actively synthesized DNA is defined as a
pulse. Standard methods for pulse labeling DNA include use of
5-bromo 2'-deoxyuridine (BrdU) or radioactively-labeled nucleoside
analogs.
[0003] Methods for detecting BrdU-labeled DNA or
radioactively-labeled DNA are well known in the art. For example,
cells containing BrdU-labeled DNA may be treated with an anti-BrdU
monoclonal antibody followed by a fluorescently-labeled secondary
antibody. The fluorescent label may then be visualized and
quantified by standard techniques, including plate assays,
fluorescence microscopy, imaging, high content screening, or flow
cytometry.
[0004] Dissecting complex cellular processes, including cell
proliferation, requires the ability to track biomolecules as they
function within their native habitat. In recent years, an
alternative tool for tagging biomolecules has emerged from the
chemical biology community--the bioorthogonal chemical reporter.
The use of bioorthogonal reactive moieties has been described for
the detection of metabolites and post-translational modifications
using the azide moiety as a bioorthogonal chemical reporter. Once
introduced into target biomolecules, either metabolically or
through chemical modification, the azide can be tagged with probes
using one of three highly selective reactions: the Staudinger
ligation, the Cu(I)-catalyzed azide-alkyne cycloaddition, or the
strain-promoted [3+2] cycloaddition. Agard et al. J Am Chem. Soc.
2004 Nov. 24; 126(46):15046-7
[0005] The use of bioorthogonal chemical reporter molecules has
previously been used in labeling of nucleic acid through the
incorporation of nucleoside analogs. Thus, one can pulse label DNA
using bioorthogonal labeling such as the Staudinger ligation,
Cu(I)-catalyzed [3+2] cycloaddition of azides and alkynes ("click
chemistry") or "copper-less" click chemistry independently
described by Barry Sharpless and Carolyn Bertozzi. Sharpless et al.
Angew Chem Int Ed Engl. 2002 Mar. 15; 41(6):1053-7 (herein
incorporated fully by reference); Meldal et al. J. Org. Chem. 2002,
67, 3057 (herein incorporated fully by reference); Agard et al. J
Am Chem. Soc. 2004 Nov. 24; 126(46):15046-7 (herein incorporated
fully by reference); U.S. Pat. No. 7,122,703; US Publication No.
2003000516671. Click chemistry and the Staudinger ligation have
been adapted to measure cellular proliferation through the direct
detection of nucleotide incorporation. See Salic, et al., Methods
and Compositions for Labeling Nucleic Acids, U.S. Publication No.
20070207476 and 20070099222 (filed Oct. 27, 2006) (herein
incorporated fully by reference).
[0006] The term "click chemistry" refers to a [3+2] cycloaddition
reaction when performed in the presence of a copper (I) catalyst.
The copper (I) catalyst may consist of copper(I) ions or a
copper(I) chelating moiety. The copper(I) chelating moiety may be
"any entity characterized by the presence of two or more polar
groups that can participate in the formation of a complex
(containing more than one coordinate bond) with copper(I) ions."
Salic et al., U.S. Pat. App. No. 20070207476 (supra). Copper(I)
chelating agents are well known in the art and include, but are not
limited to, neocuproine and bathocuproine disulphonate. Salic et
al., U.S. Pat. App. No. 20070207476 and Sharpless et al., US
Publication No. 2003000516671.
[0007] [3+2] cycloaddition reactions are also known as 1,3 dipolar
cycloadditions, and may occur between 1,3-dipoles and
dipolarophiles. Examples of 1,3-dipoles and dipolarphiles are well
known in the art. As one example, the 1,3-dipole may be an azide,
and the dipolarphile may be an alkyne.
[0008] Click chemistry techniques to pulse label DNA involve
treating a cell with a first nucleoside analog containing a
reactive unsaturated group such that the first nucleoside analog is
incorporated into newly synthesized DNA. Then, the cell is
contacted with a reagent comprising a second reactive unsaturated
group attached to a label, such that a [3+2] cycloaddition occurs
between the first and second reactive unsaturated groups.
[0009] The following descriptions of [3+2] cycloaddition reactions
to pulse label DNA are provided as examples only and are not
intended to limit the scope of the present invention.
[0010] As one example of pulse labeling DNA using click chemistry,
cells are treated with an effective amount of an alkyne-modified
nucleoside analog, for example, ethynyl-deoxyuracil (EdU), for a
defined period of time such that the EdU is incorporated into newly
synthesized DNA. After being pulse labeled with EdU, the cells are
fixed, permeabilized, and reacted, in the presence of a copper(I)
catalyst, with a dye-labeled azide. A covalent bond is formed
between the dye and the incorporated nucleoside analog, via a [3+2]
cycloaddition reaction, and the dye label may then be measured
using standard methods, including, but not limited to, flow
cytometry, fluorescence microscopy, imaging, multi-well plate
assays, or high content screening.
[0011] In a second example of pulse labeling DNA using click
chemistry, cells are treated with an effective amount of an
azide-modified nucleoside analog, for example,
5-azido-2'-deoxyuracil (AzdU), for a defined period of time such
that AzdU is incorporated into the newly synthesized DNA. After
this pulse labeling with AzdU, the cells are fixed, permeabilized
and reacted, in the presence of a copper(I) catalyst, with a
dye-labeled alkyne. As a result of a [3+2] cycloaddition reaction
between the azide and alkyne moieties, a covalent bond is formed.
The dye label may then be measured using standard methods,
including, but not limited to, flow cytometry, fluorescence
microscopy, imaging, multi-well plate assays, or high content
screening.
[0012] One alternative to click chemistry, which takes advantage of
strained [3+2] cycloaddition reactions without using a copper(I)
catalyst, has been described by Bertozzi et al. is the
"copper-less" click chemistry reaction. Bertozzi et al.,
Compositions and methods for modification of biomolecules, U.S.
Patent App. No. 20060110782 (filed Oct. 31, 2005)(herein
incorporated fully by reference).
[0013] For example, cells may be first treated with an effective
amount of an azide-modified nucleoside analog, for example, AzdU,
for a defined period of time such that the azide-modified
nucleoside analog is incorporated into newly synthesized DNA. After
this pulse of AzdU, cells are treated with an effective amount of a
compound or molecule with a reactive cycloalkyne moiety such that a
strained [3+2] cycloaddition reaction occurs between the azide and
cycloalkyne moieties. The cycloalkyne may be modified to further
comprise a dye label, which may then be measured using standard
methods, including but not limited to, flow cytometry, fluorescence
microscopy, imaging, multi-well plate assays, or high content
screening. Cycloalkynes that may be used in strained [3+2]
cycloaddition reactions in order to pulse label DNA include, but
are not limited to: cyclooctynes, difluorocyclooctynes,
heterocycloalkynes, dichlorocyclooctynes, dibromocyclooctynes, or
diiodocyclooctynes.
[0014] Other chemistries known in the art may be applied to the
pulse labeling of DNA. For example, azide-phosphine chemistry
described by Bertozzi et al., also know as the Staudinger ligation,
may be used to detect incorporation of an azide-modified nucleoside
analog, e.g. AzdU, into newly synthesized DNA. See Bertozzi et al.,
Chemoselective ligation, U.S. Patent App. No. 20070037964 (filed
Sep. 19, 2006) (herein incorporated fully by reference). Cells are
first contacted with an effective amount of an azide-modified
nucleoside analog, e.g. AzdU, for a defined period of time. Then,
cells are reacted with an engineered phosphine moiety. One example
of an engineered phosphine moiety is 2-diphenylphosphanyl-benzoic
acid methyl ester. When azide-phosphine chemistry is used to pulse
label DNA, the engineered phosphine moiety further comprises a dye
label. Once the reaction between the azide and phosphine moieties
has taken place, the dye label may then be measured using standard
methods, including, but not limited to, flow cytometry,
fluorescence microscopy, imaging, multi-well plate assays, or high
content screening.
[0015] In some experiments, it is desirable to pulse label DNA with
two different nucleoside analogs such that a baseline proliferation
rate may be established. Current methods known in the art,
including those described above, require removal of the first pulse
label of nucleoside analog from the culture medium or organism
before addition of the second pulse label. This wash requirement
introduces artifacts that affect quantification of DNA synthesis.
Therefore, there is a need in the art for a method for the dual
pulse labeling of DNA without an intermediary wash step.
SUMMARY OF INVENTION
[0016] This invention provides methods of using two or more
nucleoside analogs to pulse label nucleic acid to measure baseline
and a change in cellular nucleic acid synthesis.
[0017] In one embodiment is provided a method for measuring a
change in cellular nucleic acid synthesis, wherein the method
comprises: [0018] a) incubating a sample with an effective amount
of a first nucleoside or nucleotide analog to form a primary
incubated sample; [0019] b) incubating the primary incubated sample
with at least one second nucleoside or nucleotide analog to form a
secondary incubated sample; [0020] c) incubating the secondary
incubated sample with a first labeling reagent and at least one
second labeling reagent to form a labeled sample; [0021] d)
detecting the labeled sample wherein a level of incorporation of
the first and at least one second nucleoside or nucleotide analog
is measured, [0022] wherein a difference in a level of
incorporation of the at least one second nucleoside or nucleotide
analog relative to the level of incorporation of the first
nucleoside or nucleotide analog is measured as a change in cellular
nucleic acid synthesis, [0023] with the proviso that either the
first nucleoside or nucleotide or the at least one second
nucleoside or nucleotide contains a bioorthogonal functional
moiety.
[0024] In other embodiments are provided methods for measuring a
change in cellular RNA synthesis, methods for measuring a change in
cellular DNA synthesis, and methods for screening compounds for
effects on cellular proliferation or gene expression.
[0025] In certain aspects the first and/or second nucleoside analog
contains a bioorthogonal functional moiety, wherein the functional
moiety can undergo a [3+2] cycloaddition reaction or a Staudinger
ligation. In one instance the bioorthogonal functional moiety
contains an azido, alkyne or phosphine moiety. In a particular
aspect the nucleoside analog is ethynyl-deoxyuracil (EdU) or
5-azido-2'-deoxyuracil (AzdU). At least the first or the second
nucleoside analog contains a bioorthogonal functional moiety.
[0026] In another embodiment the first or second nucleoside analog
contains a halogen moiety, which may be bromo, chloro or iodo. In
one aspect the nucleoside analog is BrdU.
[0027] Also provided are a first and at least one second labeling
reagent, wherein the labeling reagent covalently or non-covalently
bond to the incorporated nucleoside analog. In one embodiment, the
first labeling reagent and second labeling reagent is an antibody
or a label that contains a bioorthogonal functional moiety. In one
aspect the label is a fluorescent dye. In another aspect the
antibody is an anti-BrdU antibody.
[0028] In certain aspects the bioorthogonal function moiety is an
azide, wherein the labeling reagent is rhodamine-azide, Alexa
Fluor.RTM. 350-azide, Alexa Fluor.RTM. 488-azide, Alexa Fluor.RTM.
555-azide, Alexa Fluor.RTM. 568-azide, Alexa Fluor.RTM. 568-azide,
Alexa Fluor.RTM. 594-azide, Alexa Fluor.RTM. 633-azide, Alexa
Fluor.RTM. 647-azide, Pacific Blue.TM. azide, Cascade Blue.RTM.
azide, fluorescein-azide, cyanine-azide, or tetramethylrhodamine
(TMR)-azide.
[0029] In certain embodiments of the present invention, detecting
incorporation of the first nucleoside analog and the at least one
competitive nucleoside analog may further comprise using flow
cytometry, fluorescence microscopy, imaging, high content
screening, or multi-well plate assays.
[0030] In one embodiment of the present invention, cellular
proliferation is measured by: treating a cell with an effective
amount of a first nucleoside analog; treating the cell with an
effective amount of at least one second nucleoside analog;
detecting incorporation of the first nucleoside analog; and
detecting incorporation of the at least one competitive nucleoside
analog.
[0031] In certain embodiments of the present invention, treatment
of cells with the first pulse label of a nucleoside analog is
followed by the administration of a specific course of treatment or
testing. These test treatments or test compounds may cause an
intended alteration of cellular proliferation, as in the case of
screening for cancer therapeutic drugs by the addition of the drug
to the culture medium system or to the animal being tested. This
treatment would be simultaneous to or followed by a pulse from the
second nucleoside analog (e.g. the addition of BrdU), without an
interruption in the course of treatment for the removal of the
first nucleoside analog or clearance in the case of an animal.
[0032] In certain embodiments of the present invention, the method
of measuring cellular proliferation is performed on a cell selected
from, but not limited to, the group consisting of: a Jurkat cell, a
MOLT4 cell, a HeLa cell, a COS7 cell, a CHOK1 cell, an A549 cell, a
3T3 cell, phorbitol-stimulated peripheral blood lymphocytes, U266,
H929, L1210, K562, EL4, SK-BR3, HL60, MCF7, A431, and BT-474.
[0033] In another embodiment is provided a kit for measuring a
change in cellular nucleic acid synthesis, wherein the kit
comprises: a first nucleoside or nucleotide analog; at least one
second nucleoside or nucleotide analog, wherein in at least the
first analog or the at least one second nucleoside or nucleotide
analog contains a bioorthogonal functional moiety; a first labeling
reagent; and a second labeling reagent. Additional kit components
include buffers, detection reagents and instructions for using the
kit components to measure a change in cellular nucleic acid
synthesis.
BRIEF DESCRIPTION OF THE FIGURES
[0034] FIG. 1 presents a graph showing populations of cells treated
with a first pulse label of EdU (10 .mu.M) and a second pulse label
of BrdU (10 .mu.M), as detected by flow cytometry. The graph is
divided into four quadrants with the first quadrant (Q1) located in
the upper left hand corner, the second quadrant (Q2) located in the
upper right hand corner, the third quadrant (Q3) located in the
lower left hand corner, and the fourth quadrant (Q4) located in the
lower right hand corner. Populations of cells in quadrant Q3 (lower
left) are negative for both EdU (first pulse) and BrdU (second
pulse). Populations of cells in quadrant Q2 (upper right) are
positive for both EdU (first pulse) and BrdU (second pulse).
[0035] FIG. 2 presents a series of graphs showing populations of
cells treated with a first pulse label of EdU (10 .mu.M) and a
second pulse label of BrdU (10 .mu.M) as detected by flow
cytometry. The first graph (left) is divided into four quadrants
with the first quadrant (Q1) located in the upper left hand corner,
the second quadrant (Q2) located in the upper right hand corner,
the third quadrant (Q3) located in the lower left hand corner, and
the fourth quadrant (Q4) located in the lower right hand corner.
Populations of cells in quadrant Q3 (lower left) are negative for
both EdU (first pulse) and BrdU (second pulse). Populations of
cells in quadrant Q2 (upper right) are positive for both EdU (first
pulse) and BrdU (second pulse). The middle plot is a graph of EdU
vs. DNA cell cycle. Gating applied with P4>P1 demonstrates that
some of the EdU-positive cells are BrdU-negative. These are the
cells which have passed out of the synthesis phase of the cell
cycle during the initial thirty minute pulse of EdU only
incorporation (first pulse) before the BrdU-incorporation (second
pulse).
[0036] FIG. 3A presents a series of graphs showing populations of
cells treated with a first pulse label of EdU (10 .mu.M) and a
second pulse label of BrdU (10 .mu.M) as detected by flow
cytometry. The first graph (left) is divided into four quadrants
with the first quadrant (Q1) located in the upper left hand corner,
the second quadrant (Q2) located in the upper right hand corner,
the third quadrant (Q3) located in the lower left hand corner, and
the fourth quadrant (Q4) located in the lower right hand corner.
Populations of cells in quadrant Q3 (lower left) are negative for
both EdU (first pulse) and BrdU (second pulse). Populations of
cells in quadrant Q2 (upper right) are positive for both EdU (first
pulse) and BrdU (second pulse). The middle plot is a graph of EdU
vs. DNA cell cycle with gating P5>P1. The middle plot shows a
subpopulation of BrdU-positive cells which are EdU-negative, this
subpopulation being the population of cells entering the DNA
synthesis phase of the cell cycle after the first pulse of thirty
minutes of EdU-only incorporation. FIG. 3B presents a graph showing
populations of cells treated with simultaneous pulse of EdU at a
concentration of 20 .mu.M and BrdU at a concentration of 10 .mu.M
as detected by flow cytometry. The graph is divided into four
quadrants with the first quadrant (Q1) located in the upper left
hand corner, the second quadrant (Q2) located in the upper right
hand corner, the third quadrant (Q3) located in the lower left hand
corner, and the fourth quadrant (Q4) located in the lower right
hand corner. Populations of cells in quadrant Q3 (lower left) are
negative for both EdU and BrdU. Populations of cells in quadrant Q2
(upper right) are positive for both EdU and BrdU. This plot shows
there is only positive signal detected from the BrdU, and no signal
detected from the EdU, demonstrating the BrdU is preferentially
incorporated over EdU.
[0037] FIG. 4 presents a series of graphs showing populations of
cells treated with a first pulse label of EdU (10 .mu.M) and a
second pulse label of BrdU (10 .mu.M) as detected by flow
cytometry. The first graph (left) is divided into four quadrants
with the first quadrant (Q1) located in the upper left hand corner,
the second quadrant (Q2) located in the upper right hand corner,
the third quadrant (Q3) located in the lower left hand corner, and
the fourth quadrant (Q4) located in the lower right hand corner.
Populations of cells in quadrant Q3 (lower left) are negative for
both EdU (first pulse) and BrdU (second pulse). Populations of
cells in quadrant Q2 (upper right) are positive for both EdU (first
pulse) and BrdU (second pulse). The Q4 quadrant are cells labeled
in the first pulse with EdU but not labeled in the second pulse
with BrdU because they have moved into G2/M and are no longer
synthesizing DNA. The Q1 quadrant subpopulation are cells not
labeled in the first pulse with EdU but have just entered into the
DNA synthesis phase during the second pulse and are labeled with
BrdU. The middle plot is a graph of EdU vs. cycle. In the middle
and left graphs, subpopulations moving into or out of the DNA
synthesis phase of the cell cycle show only a single label.
[0038] FIG. 5 presents a series of graphs showing that when cells
are treated with EdU and BrdU simultaneously, only a population of
DNA labeled with BrdU is detected by flow cytometry. The first
graph on the left shows a plot of EdU vs. DNA cell cycle only
treated with a single pulse label of EdU. The second graph shows a
plot of BrdU vs. DNA cell cycle only treated with a single pulse
label of BrdU. The third and fourth graphs show the dual parameter
plot of fluorescent nucleotide label vs. DNA cell cycle treated
with EdU and BrdU simultaneously. Only BrdU was incorporated into
cells treated simultaneously with EdU and BrdU, as shown in the
third and fourth graphs.
[0039] FIG. 6 presents a depiction of incorporation of nucleoside
analogs into DNA. On the left side of the depiction, EdU is
incorporated into the DNA double helix. When EdU is incorporated
into the DNA, the analog is easily accessible for labeling with the
Alexa Fluor.RTM. azide without requiring a denaturation step. The
right side of the depiction shows that denaturation is required for
standard antibody-based labeling of incorporated BrdU.
[0040] FIG. 7 present a series of result graphs, labeled A through
C, showing populations of cells (Ramos B-lymphocytes) treated with
a first pulse label of EdU (20 .mu.M) and a second pulse label of
BrdU (10 .mu.M) as detected by flow cytometry.
[0041] FIG. 8 present a series of result graphs, labeled A through
C, showing populations of cells (K562 human lymphoblast from
chronic myelogenous leukemia cells) treated with a first pulse
label of EdU (20 .mu.M) and a second pulse label of BrdU (10 .mu.M)
as detected by flow cytometry.
[0042] FIGS. 9-1 through 9-3 present a series of result graphs,
labeled A through I, showing populations of cells (TF-1a human
erythroblast cells). The graphs A through G show the population of
the cells treated with a first pulse label of EdU (20 .mu.M) and a
second pulse label of BrdU (10 .mu.M) with the time of the pulses
varied, as detected by flow cytometry. The graphs H and I show the
population of the cells treated with one pulse only, with graph H
showing the result of a pulse label of EdU (20 .mu.M) only and
graph I showing result of a pulse label of BrdU (10 .mu.M) only, as
detected by flow cytometry.
[0043] FIG. 10 present a series of result graphs, labeled A through
F, showing populations of cells (THP-1 monocyte cells) treated with
a first pulse label of EdU (20 .mu.M) and a second pulse label of
BrdU (10 .mu.M) as detected by flow cytometry.
[0044] FIG. 11 shows the percentage of cells (Jurkat T-cell
lymphocyte cells) which are EdU and BrdU co-positive (Q2), EdU and
BrdU co-negative (Q3), BrdU positive and EdU negative (Q1), and
BrdU negative and EdU positive (Q4) of the seven different
treatment conditions.
[0045] FIGS. 12-1 and 12-2 present a series of result graphs,
labeled A through J, showing populations of cells (Jurkat T-cell
lymphocyte cells) treated with a first pulse label of EdU (20
.mu.M) and a second pulse label of BrdU (10 .mu.M) as detected by
flow cytometry.
DETAILED DESCRIPTION OF THE INVENTION
Introduction
[0046] Herein we describe methods for measuring cellular nucleic
acid synthesis with the incorporation of bio-orthoganal nucleoside
or nucleotide analogs such that the newly synthesized cellular
nucleic acid can be dual labeled without the need for a disruptive
wash step. These analogs include, but are not limited to,
halogenated (such as BrdU), an azido modified analog, an alkyne
modified analog or a phosphine modified analog. The incorporation
of these analogs is then detected by measurement of a fluorescent
signal wherein the label is selectively attached to the nucleic
acid analog due to the functional groups of the analog and label or
through an antibody. A timed exposure to a nucleoside (or
nucleotide) analog with the potential of incorporation of that
analog into the actively synthesized cellular nucleic acid is
defined as a pulse. The pulse may be measuring baseline
proliferation, baseline gene expression, or a response to a
specific treatment.
[0047] We have found that the addition of an additional pulse with
a different nucleoside analog, which is selectively labeled,
provides a mechanism to measure both baseline proliferation and a
subsequent change in proliferation without the introduction of an
artifact of washing or clearing the analog out of the cells or
system being measured. It is also envisioned that a third pulse
could be performed, for example, but not limited to, the ability to
measure drug interaction on cell proliferation or gene expression.
A baseline synthesis rate can be recorded by the first pulse
labeling of the nucleic acid. Without interruption to remove the
first pulse, the second pulse can be started. Normally,
interruption to the cells by removing the first pulse label alters
the rate of cell proliferation and makes assessment of changes in
cell proliferations difficult. In addition the no wash step makes
the process compatible with high throughput screening (HTS). Having
two compatible methods for pulse labeling nucleic acid without the
use of radioactive nucleosides creates a very powerful tool which
in one instance can be applied to the assessment of cancer therapy
ex vivo or in vivo.
[0048] This novel dual labeling method is predicated, in part, on
the concept that either the analogs from the first pulse are all
incorporated before the addition of the second analog or that the
second analog is a competitor for the first, such that the second
analog is selectively incorporated into the nascent nucleic acid
polymer. Without wishing to be bound to a theory, it appears that
in the instance of the analogs, EdU and BrdU, that BrdU is
selectively incorporated in the presence of EdU. See, Example
3.
Definitions
[0049] Before describing the present invention in detail, it is to
be understood that this invention is not limited to specific
compositions or process steps, as such may vary. It should be noted
that, as used in this specification and the appended claims, the
singular form "a", "an" and "the" include plural references unless
the context clearly dictates otherwise. Thus, for example,
reference to "a fluorescent pH sensitive dye" includes a plurality
of dyes and reference to "a cell" includes a plurality of cells and
the like.
[0050] Unless defined otherwise, all technical and scientific terms
used herein have the same meaning as commonly understood by one of
ordinary skill in the art to which this invention is related. It is
also understood that when describing chemical moieties or molecules
that are attached to another compound that these moieties exist in
a radical form for the purposes of conjugation. The following terms
are defined for purposes of the invention as described herein.
[0051] As used herein, the term "alkyne reactive" refers to a
chemical moiety that selectively reacts with an alkyne modified
group on the nucleoside analog to form a covalent chemical bond
between the alkyne modified group and the alkyne reactive group.
Examples of alkyne-reactive groups include azides.
"Alkyne-reactive" can also refer to a molecule that contains a
chemical moiety that selectively reacts with an alkyne group.
[0052] As used herein, the term "azide reactive" refers to a
chemical moiety that selectively reacts with an azido modified
group on another molecule to form a covalent chemical bond between
the azido modified group and the azide reactive group. Examples of
azide-reactive groups include alkynes and phosphines (e.g. triaryl
phosphine). "Azide-reactive" can also refer to a molecule that
contains a chemical moiety that selectively reacts with an azido
group.
[0053] As used herein, the term "azide-selective phosphine dye"
refers to a compound, molecule or reagent that comprises an
engineered phosphine moiety with a dye label such that when reacted
with an azide, provides for production of a covalent bond between
the engineered phosphine moiety and the azide. The term "engineered
phosphine moiety" refers to a moiety comprising a phosphine and an
electrophilic moiety. One example of an engineered phosphine moiety
is 2-diphenylphosphanyl-benzoic acid methyl ester. Other engineered
phosphine moieties are known in the art. See, e.g., Bertozzi et
al., U.S. Pat. App. No. 20070037964.
[0054] As used herein the term "bioorthogonal chemical reporter" or
"bioorthogonal labeling reagent" means a detectable label that
comprises a chemical handle that will react selectively with the
present nucleoside analog once incorporated into nucleic acid to
form a covalent bond.
[0055] As used herein, the term "cell" in the context of the in
vivo applications of the invention is meant to encompass eukaryotic
and prokaryotic cells of any genus or species, with mammalian cells
being of particular interest. "Cell" is also meant to encompass
both normal cells and diseased cells, e.g., cancerous cells.
[0056] The terms "cell proliferation" and "cellular proliferation"
are used herein interchangeably and refer to an expansion of a
population of cells by the division of single cells into daughter
cells, or to the division of a single cell to daughter cells.
[0057] The term, "chemical handle" or "bioorthogonal moiety" as
used herein refers to a specific functional group, such as an
azide, alkyne, activated alkyne, phosphite, phosphine, and the
like. The chemical handle is distinct from biological reactive
groups, defined below, in that the chemical handle are moieties
that are rarely found in naturally-occurring biomolecules and are
chemically inert towards biomolecules (e.g, native cellular
components), but when reacted with an azide- or alkyne-reactive
group the reaction can take place efficiently under biologically
relevant conditions (e.g., cell culture conditions, such as in the
absence of excess heat or harsh reactants).
[0058] As used herein, the term "click chemistry" refers to the
copper-catalyzed version of a [3+2] cycloaddition reaction between
a first reactive unsaturated group on the incorporated nucleoside
analog (nucleotide analog) or labeling reagent and a second
reactive unsaturated group present on the labeling regent or
nucleoside analog (nucleotide analog). This click chemistry
reaction is described by Sharpless et al. (Sharpless et al., Angew
Chem., Int. Ed. Engl., 2002, 41:1596-1599).
[0059] As used herein, the term "competitive nucleoside analog"
refers to a nucleoside analog, which when added simultaneously to
the first nucleoside analog in a cell or an organism, results in a
population of cells that are preferentially labeled with the
competitive nucleoside analog and not the first nucleoside analog.
For example, when BrdU (competitive nucleoside analog) and EdU
(first nucleoside analog) are simultaneously added to cells in a
dual pulse experiment, only BrdU, the competitive nucleoside analog
in this pair of nucleoside analogs, is incorporated into the DNA
(see, e.g., FIG. 5 and Example 3).
[0060] As used herein, the term "copper (I) catalyst" refers to a
compound, molecule or reagent that catalyzes the [3+2]
cycloaddition reaction between a first reactive unsaturated group
on the incorporated nucleoside analog (nucleotide analog) or
labeling reagent and a second reactive unsaturated group present on
the labeling reagent or nucleoside analog (nucleotide analog). The
term "copper (I) catalyst" includes exogenous copper (I) as well as
copper chelating moieties. The term "copper chelating moieties"
refers to any compound, molecule or reagent characterized by the
presence of two or more polar groups that can participate in the
formation of a complex with copper (I) ions.
[0061] As used here, the term "copperless click chemistry" refers
to a strain-promoted [3+2] cycloaddition reaction that can be
carried out under physiological conditions, as described by
Bertozzi et al. US Publication No. 20060110782; Baskin et al. PNAS
2007 Oct. 23; 104(43):16793-7; Agard et al. J Am Chem. Soc. 2004
Nov. 24; 126(46):15046-7. The reaction is accomplished through use
of a first molecule comprising a strained cycloalkyne moiety
(typically the label), and second molecule comprising an azide
moiety (typically the nucleoside analog). The azide moiety on the
second molecule reacts, in the absence of a catalyst, with the
strained cycloalkyne moiety on the first molecule, forming a final
conjugate product comprising fused azide/cycloalkyne ring.
[0062] As used here, the term "detectable response" refers to an
occurrence of or a change in, a signal that is directly or
indirectly detectable either by observation or by instrumentation.
Typically, the detectable response is an optical response resulting
in a change in the wavelength distribution patterns or intensity of
absorbance or fluorescence or a change in light scatter,
fluorescence lifetime, fluorescence polarization, or a combination
of the above parameters.
[0063] As used here, the term "dye" refers to a compound that emits
light to produce an observable detectable signal.
[0064] As used herein, the terms "dye-labeled azide" and "azide-dye
molecule" refer to a compound or molecule with a reactive azide
group that is also labeled with a dye. Examples include, but are
not limited to: rhodamine-azide, Alexa Fluor.RTM. 350-azide
(Molecular Probes.TM./Invitrogen.TM., Carlsbad, Calif.), Alexa
Fluor.RTM. 488-azide (Molecular Probes.TM./Invitrogen.TM.,
Carlsbad, Calif.), Alexa Fluor.RTM. 555-azide (Molecular
Probes.TM./Invitrogen.TM., Carlsbad, Calif.), Alexa Fluor.RTM.
568-azide (Molecular Probes.TM./Invitrogen.TM., Carlsbad, Calif.),
Alexa Fluor.RTM. 568-azide (Molecular Probes.TM./Invitrogen.TM.,
Carlsbad, Calif.), Alexa Fluor.RTM. 594-azide, Alexa Fluor.RTM.
633-azide (Molecular Probes.TM./Invitrogen.TM., Carlsbad, Calif.),
Alexa Fluor.RTM. 647-azide (Molecular Probes.TM./Invitrogen.TM.,
Carlsbad, Calif.), Cascade Blue.RTM. azide (Molecular
Probes.TM./Invitrogen.TM., Carlsbad, Calif.), fluorescein-azide,
coumarin-azide, BODIPY-azide, cyanine-azide, or
tetramethylrhodamine (TMR)-azide.
[0065] As used herein, the term "dye-labeled cycloalkyne" refers to
a cycloalkyne that has been further modified to include a dye
label. The term "cycloalkyne" refers to compounds or molecules
which may be used in strained [3+2] cycloaddition reactions in
order to pulse label DNA. In this context, examples of cycloalkynes
include, but are not limited to: cyclooctynes,
difluorocyclooctynes, heterocycloalkynes, dichlorocyclooctynes,
dibromocyclooctynes, or diiodocyclooctynes.
[0066] As used herein, the term "dye-labeled alkyne" refers to an
alkyne that has been further modified to include a dye label.
[0067] As used herein, the term "dual labeling" refers to a
labeling process in which a nucleic acid polymer is labeled with
two detectable agents that produce distinguishable signals. The
nucleic acid polymer resulting from such a labeling process is said
to be dually labeled.
[0068] As used herein, the term "effective amount" refers to the
amount of a substance, compound, molecule, agent or composition
that elicits the relevant response in a cell, a tissue, or an
organism. For example, in the case of cells contacted with a
nucleoside analog, an effective amount is an amount of nucleoside
that is incorporated into the DNA of the cells.
[0069] As used here, the term "fluorophore" or "fluorogenic" refers
to a composition that demonstrates a change in fluorescence upon
binding to a biological compound or analyte interest. Preferred
fluorophores of the present invention include fluorescent dyes
having a high quantum yield in aqueous media. Exemplary
fluorophores include xanthene, indole, borapolyazaindacene, furan,
and benzofuran, cyanine among others. The fluorophores of the
present invention may be substituted to alter the solubility,
spectral properties or physical properties of the fluorophore.
[0070] As used here, the term "label" refers to a chemical moiety
or protein that retains it's native properties (e.g. spectral
properties, conformation and activity) when part of a labeling
reagent of the present invention and used in the present methods.
Illustrative reporter molecules can be directly detectable
(fluorophore) or indirectly detectable (hapten or enzyme). Such
reporter molecules include, but are not limited to, radio reporter
molecules that can be measured with radiation-counting devices;
pigments, dyes or other chromogens that can be visually observed or
measured with a spectrophotometer; spin labels that can be measured
with a spin label analyzer; and fluorescent moieties, where the
output signal is generated by the excitation of a suitable
molecular adduct and that can be visualized by excitation with
light that is absorbed by the dye or can be measured with standard
fluorometers or imaging systems, for example. The reporter molecule
can be a luminescent substance such as a phosphor or fluorogen; a
bioluminescent substance; a chemiluminescent substance, where the
output signal is generated by chemical modification of the signal
compound; a metal-containing substance; or an enzyme, where there
occurs an enzyme-dependent secondary generation of signal, such as
the formation of a colored product from a colorless substrate. The
reporter molecule may also take the form of a chemical or
biochemical, or an inert particle, including but not limited to
colloidal gold, microspheres, quantum dots, or inorganic crystals
such as nanocrystals or phosphors (see, e.g., Beverloo, et al.,
Anal. Biochem. 203, 326-34 (1992)). The term reporter molecule can
also refer to a "tag" or hapten that can bind selectively to a
labeled molecule such that the labeled molecule, when added
subsequently, is used to generate a detectable signal. For
instance, one can use biotin, iminobiotin or desthiobiotin as a tag
and then use an avidin or streptavidin conjugate of horseradish
peroxidase (HRP) to bind to the tag, and then use a chromogenic
substrate (e.g., tetramethylbenzidine) or a fluorogenic substrate
such as Amplex Red or Amplex Gold (Molecular Probes, Inc.) to
detect the presence of HRP. In a similar fashion, the tag can be a
hapten or antigen (e.g., digoxigenin), and an enzymatically,
fluorescently, or radioactively labeled antibody can be used to
bind to the tag. Numerous reporter molecules are known by those of
skill in the art and include, but are not limited to, particles,
fluorescent dyes, haptens, enzymes and their chromogenic,
fluorogenic, and chemiluminescent substrates, and other reporter
molecules that are described in the MOLECULAR PROBES HANDBOOK OF
FLUORESCENT PROBES AND RESEARCH CHEMICALS by Richard P. Haugland,
10.sup.th Ed., (2005), the contents of which are incorporated by
reference, and in other published sources. As used herein a
reporter molecule is not an amino acid.
[0071] As used here, the term "Labeling Reagent" refers to a
reagent used to label and detect the incorporated nucleotide
analog. In one instance, the labeling reagent comprises a label and
a chemical handle. In another instance, the labeling reagent
comprises an antibody and a label, wherein the antibody binds the
nucleoside analog.
[0072] As used herein, the term "nucleoside analog" and "nucleotide
analog" are used interchangeably and refers to a molecule or
compound that is structurally similar to a natural nucleoside or
nucleotide that is incorporated into newly synthesized nucleic
acid. In the case of nucleosides, once inside the cells, they are
phosphorylated into nucleotides and then incorporated into nascent
nucleic acid polymers. Nucleotides are difficult to get across the
cell membrane due to their charges and are more labile than
nucleosides, thus their use typically requires and additional step
and reagents for transfection to transport the nucleotides across
the lipid bilayer. The present nucleoside analogs are incorporated
into nucleic acid (DNA or RNA) in a similar manner as a natural
nucleotide wherein the correct polymerase enzyme recognizes the
analogs as natural nucleotides and there is no disruption in
synthesis. These analogs comprise a number of different moieties
which are ultimately used for detection, such as halogenated
analogs (bromo, chloro, iodo, etc.) and those that comprise a
bioorthogonal moiety such as azido, alkyne or phosphine.
[0073] As used here, the term "reactive group" refers to a group
that is capable of reacting with another chemical group to form a
covalent bond, i.e. is covalently reactive under suitable reaction
conditions, and generally represents a point of attachment for
another substance. As used herein, reactive groups refer to
chemical moieties generally found in biological systems and that
react under normal biological conditions, these are herein
distinguished from the chemical handle or bioorthogonal functional
moiety, defined above, such as the azido and activated alkyne
moieties of the present invention. As referred to herein the
reactive group is a moiety, such as carboxylic acid or succinimidyl
ester, that is capable of chemically reacting with a functional
group on a different compound to form a covalent linkage. Reactive
groups generally include nucleophiles, electrophiles and
photoactivatable groups.
[0074] As used here, the term "Staudinger ligation" refers to a
chemical reaction developed by Saxon and Bertozzi (E. Saxon and C.
Bertozzi, Science, 2000, 287: 2007-2010) that is a modification of
the classical Staudinger reaction. The classical Staudinger
reaction is a chemical reaction in which the combination of an
azide with a phosphine or phosphite produces an aza-ylide
intermediate, which upon hydrolysis yields a phosphine oxide and an
amine. A Staudinger reaction is a mild method of reducing an azide
to an amine; and triphenylphosphine is commonly used as the
reducing agent. In a Staudinger ligation, an electrophilic trap
(usually a methyl ester) is appropriately placed on a
triarylphosphine aryl group (usually ortho to the phosphorus atom)
and reacted with the azide, to yield an aza-ylide intermediate,
which rearranges in aqueous media to produce a compound with amide
group and a phosphine oxide function. The Staudinger ligation is so
named because it ligates (attaches/covalently links) the two
starting molecules together, whereas in the classical Staudinger
reaction, the two products are not covalently linked after
hydrolysis.
[0075] As used herein, the terms "test compound" and "test
treatment" refer to any substance, compound, molecule, agent,
composition, or treatment, which is tested during the claimed
methods for its affect on cellular proliferation or the cell cycle.
The affect on cellular proliferation of these "test compounds" and
"test treatments" is not limited by outcome, that is, they may
increase, decrease or not affect cellular proliferation or the cell
cycle.
[0076] As used herein, the term "reactive partner" refers to a
molecule or molecular moiety that specifically reacts with another
reactive partner, such as the present nucleoside analog and the
reporter molecule.
Dual Labeling Reagents:
[0077] In general, for ease of understanding the present invention,
the components for dual labeling of nucleic acid through the
incorporation of nucleoside or nucleotide analogs will first be
described in detail, followed by a description of the dual labeling
methods. This will be followed by some embodiments in which such
dual labeled nucleic acid is used to measure cell proliferation.
Exemplified methods are then disclosed.
[0078] Before the present invention is further described, it is to
be understood that this invention is not limited to particular
embodiments described, as such may, of course, vary. It is also to
be understood that the terminology used herein is for the purpose
of describing particular embodiments only, and is not intended to
be limiting, since the scope of the present invention will be
limited only by the appended claims.
[0079] Herein we describe a method for screening test compounds for
their effect on nascent cellular nucleic acid synthesis, wherein
two color labeling is used to measure baseline nucleic acid
synthesis compared to post-treatment synthesis. This method uses
nucleoside analogs that are "fed" to cells and incorporated into a
growing nucleic acid polymer, wherein at least one of the
nucleoside analogs comprises a bioorthogonal functional moiety.
[0080] In a particular embodiment a method for screening test
compounds for their effect on cellular proliferation is provided.
Herein we describe a method for dual labeling wherein the baseline
proliferation is measured against a change in proliferation from a
treatment of the cells, either in vivo or ex vivo. This is
accomplished by using a combination of a halogenated analogs (such
as BrdU) or nucleoside analogs comprising a chemical handle in
combination with nucleoside analogs comprising a chemical handle,
which can be selectively labeled using a labeling reagent of the
present invention. The present invention uses at least one
nucleoside (or nucleotide) analog that comprises a chemical handle,
herein also referred to as a bioorthogonal functional moiety.
[0081] Similarly, this dual labeling method can also be used to
measure cellular gene expression (RNA synthesis) in response to an
administered treatment. In this instance, the nucleic acid analogs
comprise a ribose sugar and are RNA nucleoside or nucleotide
analogs.
[0082] The advantage of this dual labeling method is that it does
not require the removal of the first pulse of nucleoside analog
from the culture medium, or animal prior to the administering of
the second pulse of nucleoside analog. The distinct advantage of
this `no wash` treatment for the additional pulse of the second
label is that baseline cell proliferation, or gene expression,
measurements can be made using the first pulsed nucleoside analog,
followed by the administration of a specific course of treatment or
testing which may cause an intended alteration of cell
proliferation, or gene expression. For example, as in the case of
screening cancer therapeutic drugs by the addition of the drug to
the culture medium system, or to the animal being tested. This
treatment would be simultaneous to or followed by a pulse from the
second nucleoside analog, without an interruption in the course of
the treatment for the removal of the first analog. At the end of
the test, the cells are prepared for detection of the two pulses of
labeling of the nucleic acid.
[0083] In one particular aspect, a nucleoside analog comprising a
bioorthogonal functional moiety is used in the first pulse followed
by a second pulse with a halogenated nucleoside analog. In another
aspect a nucleoside analog comprising a first bioorthogonal
functional moiety is used in the first pulse followed by a second
pulse with a nucleoside analog comprising a second bioorthogonal
functional moiety. These incorporated analogs are detected using
methods known in the art. For the halogenated nucleoside analogs,
antibodies that selectively recognize the particular halogen moiety
are used, which either comprise a label or are detected by a second
antibody that comprises a label. The nucleoside analogs that
comprise a bioorthogonal functional moiety are detected using
reagents comprising a complimentary bioorthogonal functional moiety
and a label, resulting in covalent attachment of the labeling
reagent to the nucleoside analog.
[0084] This dual labeling method for measuring cell proliferation
is distinguished from known methods because 1) no wash treatment is
required between the two pulses and 2) the compatibility of the two
pulse labeling conditions for detection by two color, a first and
second label, fluorescence measurement, wherein one of the
nucleoside analogs comprises a bioorthogonal functional moiety. The
first and second labels are preferably selected such that they
produce distinguishable detectable signals, in other words the
labels can be excited at the same or at different wavelengths, but
the emission is at different wavelengths.
[0085] In one particular aspect when using two thymidine analogs,
the first pulsed nucleoside, 5-ethynyl 2'-deoxyuridine (also termed
herein ethynyluracil or EdU) does not need to be removed from the
test system (cell culture or animal) when BrdU is added because EdU
does not appear to incorporate into nucleic acid when in the
presence of BrdU. This important feature, and previously
undisclosed feature of the nucleoside analogs, allows for
uninterrupted observation of baseline cell proliferation
measurements followed by the altered state of cell proliferation
incurred by the administration of a specific treatment.
Nucleoside and Nucleotide Analogs:
[0086] Both nucleoside and nucleotide analogs can be used in the
present methods for measuring nascent nucleic acid synthesis.
Nucleosides are typically used in experiments wherein the analogs
are added to cell culture or administered to animals because the
nucleoside analogs are easily taken up by live cells, wherein they
are phosphorylated into a nucleotide and then incorporated into a
growing nucleic acid polymer. In contrast nucleotides are labile
and prone to enzyme cleave, either before or after incorporation
into cells, and are generally less stable than nucleosides. In
addition, due to the additional charges from the phosphate groups,
nucleotides are not easily transported into live cells and
generally require a transfection step to get a sufficient
concentration of nucleotides across the cellular membrane. This is
not ideal for either in vivo or ex vivo/in vivo experiments where
cell perturbation should be kept to a minimum to accurately
interpret results. For these reasons, the following disclosure
generally refers to nucleosides as the analog that is added to
cells or animals, however this in no way is intended to be
limiting, wherein nucleotides are equally as important.
[0087] The nucleoside analogs can be an analog for any of the four
DNA bases (adenine (A), cytosine (C), guanine (G) or thymine (T))
or any of the four RNA bases (adenine (A), cytosine (C), guanine
(G) or uracil (U)) and include their triphosphate and
phosphoramidite forms, wherein these analogs are incorporated into
newly synthesized nucleic acid by polymerase present in the cells.
The nucleosides are modified into analogs wherein they comprise a
moiety that is ultimately used for detection of that nucleoside and
the resulting nascent nucleic acid polymer synthesized in the
presence of the nucleoside analogs.
[0088] In one embodiment the nucleoside analog is a halogenated
analog, including but not limited to a bromo, chloro, and iodo
moiety. In another embodiment the nucleoside analog comprises a
chemical handle or bioorthogonal functional moiety, including but
not limited to an azido, alkyne and phosphine moiety. Halogenated
analogs are well known in the art, e.g. BrdU, IdU, CIdU and BrUTP,
and can be purchased from a number of vendors (Sigma, Saint Louis,
Mo.; Millipore, Billerica, Mass.; Anaspec, San Jose, Calif.;
Invitrogen, Carlsbad, Calif.) Similarly the antibodies used to
detect these analogs are also commercially available (Dako,
Carpinteria, Calif.; BD Bioscience, San Diego, Calif.; EMD
Biosciences, Madison, Wis.).
[0089] The nucleoside analogs that comprise a bioorthogonal
functional moiety which are suitable for use in the methods
described herein include any nucleoside analogue, as defined
herein, that contains a reactive bioorthogonal moiety, or chemical
handle, that can undergo a [3+2] cycloaddition or Staudinger
ligation. In some embodiments, the reactive bioorthogonal moiety is
carried by the base of the nucleoside. The base carrying the
reactive bioorthogonal moiety can be a purine (e.g., adenine or
guanine) or a pyrimidine (e.g., cytosine, uracil or thymine). In
certain embodiments, the base is uracil; in some such embodiments,
uracil carries the reactive bioorthogonal moiety on the 5-position.
In certain embodiments, the base is adenine; in some such
embodiments, adenine carries the reactive bioorthogonal moiety. In
certain embodiments, the bioorthogonal moiety is indirectly
attached to the base, while in other embodiments the bioorthogonal
moiety is directly covalently attached to the base. Non-limiting
examples of the nucleoside analogues that may be used in the
methods described herein include ethynyluracil or EdU and
5-azido-2'-deoxyuracil (also termed herein azidouracil or AzdU) as
well as their triphosphate and phosphoramidite forms. EdU can be
synthesized essentially as described by C.-S. Yu and F. Oberdorfer,
Synlett, 2000, 1: 86-88; and AzdU can be synthesized using a method
similar to that described in P. Sunthankar et al., Anal. Biochem.,
1998, 258: 195-201 to synthesize azido-dUMP. EdU is also
commercially available from Berry and Associates, Inc. (Dexter,
Mich.).
[0090] In certain embodiments, the reactive bioorthogonal moiety is
carried by the sugar (ribose and deoxyribose) of the nucleoside. In
certain embodiments, the bioorthogonal moiety is indirectly
attached to the sugar, while in other embodiments the bioorthogonal
moiety is directly and covalently attached to the sugar. In certain
embodiments, the reactive bioorthogonal moiety attached to the
phosphate moiety of the nucleoside. The sugar carrying the reactive
bioorthogonal moiety can be covalently attached to a purine (e.g.,
adenine or guanine) or a pyrimidine (e.g., cytosine, uracil or
thymine). In certain embodiments, the base is uracil, while in
other embodiments the base is adenine. Non-limiting examples of the
nucleoside analogues that may be used in the methods described
herein include EdU, AzdU, or chain terminating dideoxy compounds
such as AZT; 3'-Azido-2',3'-dideoxyadenosine,
3'-Azido-3'-deoxythymidine (AZT), 5'-Azido-5'-deoxythymidine,
5-(1-ethynyl)-2'-O-methyluridine, 5-(1-propynyl)-2'-deoxyuridine,
5-(propargyloxy)-2'-deoxyuridine, 8-Azido-2'-deoxyadenosine,
3'-Azido-2',3'-dideoxyadenosine.
[0091] The reactive bioorthogonal moiety or chemical handle can be
a 1,3-dipole such as a nitrile oxide, an azide, a diazomethane, a
nitrone or a nitrile imine. In certain embodiments, the 1,3-dipole
is an azide. Alternatively, the reactive bioorthogonal functional
moiety can be a dipolarophile such as an alkene (e.g., vinyl,
propylenyl, and the like) or an alkyne (e.g., ethynyl, propynyl,
and the like). In certain embodiments, the dipolarophile is an
alkyne, such as, for example, an ethynyl group.
[0092] These bioorthogonal functional moieties described above are
non-native, non-perturbing bioorthogonal chemical moieties that
possess unique chemical functionality that can be modified through
highly selective reactions. In particular these incorporated
nucleosides are labeled using labeling reagents which comprise a
chemical handle that will selectively form a covalent bond with the
nucleoside in the presence of the cellular milieu.
Labeling Reagents:
Reagent A
[0093] In a particular embodiment, the labeling reagent is a first
antibody, which may be conjugated to a label or bound by a second
antibody that is covalently attached to a label, wherein the first
antibody binds to the incorporated nucleoside. In one aspect this
is an anti-BrdU antibody. In anther aspect the antibody is an
anti-IdU or anti-CIdU antibody. However, other antibodies which
could selectively bind to incorporated nucleoside analogs are also
envisioned.
Reagent B
[0094] In another embodiment, the labeling reagent comprises a
label and a chemical handle. A chemical handle, as defined above,
is a bioorthogonal functional moiety that selectively reacts with a
functional moiety to form a covalent bond.
Labels
[0095] As already mentioned above, the role of a label is to allow
visualization or detection of a nucleic acid polymer, e.g., DNA in
a cell, following labeling. Preferably, a label (or detectable
agent or moiety) is selected such that it generates a signal which
can be measured and whose intensity is related (e.g., proportional)
to the amount of labeled nucleic acid polymer, e.g., in a sample
being analyzed.
[0096] A label used in a labeling reagent in the methods and
compositions described herein, is any chemical moiety, organic or
inorganic, that exhibits an absorption maximum at wavelengths
greater than 280 nm, and retains its spectral properties when
covalently attached to a modified nucleoside such as, by way of
example only, an azide, and alkyne or a phosphine. Fluorophores
used in the labeling reagent in the methods and compositions
described herein include, without limitation; a pyrene (including
any of the corresponding derivative compounds disclosed in U.S.
Pat. No. 5,132,432), an anthracene, a naphthalene, an acridine, a
stilbene, an indole or benzindole, an oxazole or benzoxazole, a
thiazole or benzothiazole, a 4-amino-7-nitrobenz-2-oxa-1,3-diazole
(NBD), a cyanine (including any corresponding compounds in U.S.
Ser. Nos. 09/968,401 and 09/969,853), a carbocyanine (including any
corresponding compounds in U.S. Ser. Nos. 09/557,275; 09/969,853
and 09/968,401; U.S. Pat. Nos. 4,981,977; 5,268,486; 5,569,587;
5,569,766; 5,486,616; 5,627,027; 5,808,044; 5,877,310; 6,002,003;
6,004,536; 6,008,373; 6,043,025; 6,127,134; 6,130,094; 6,133,445;
and publications WO 02/26891, WO 97/40104, WO 99/51702, WO
01/21624; EP 1 065 250 A1), a carbostyryl, a porphyrin, a
salicylate, an anthranilate, an azulene, a perylene, a pyridine, a
quinoline, a borapolyazaindacene (including any corresponding
compounds disclosed in U.S. Pat. Nos. 4,774,339; 5,187,288;
5,248,782; 5,274,113; and 5,433,896), a xanthene (including any
corresponding compounds disclosed in U.S. Pat. Nos. 6,162,931;
6,130,101; 6,229,055; 6,339,392; 5,451,343 and U.S. Ser. No.
09/922,333), an oxazine (including any corresponding compounds
disclosed in U.S. Pat. No. 4,714,763) or a benzoxazine, a carbazine
(including any corresponding compounds disclosed in U.S. Pat. No.
4,810,636), a phenalenone, a coumarin (including an corresponding
compounds disclosed in U.S. Pat. Nos. 5,696,157; 5,459,276;
5,501,980 and 5,830,912), a benzofuran (including an corresponding
compounds disclosed in U.S. Pat. Nos. 4,603,209 and 4,849,362) and
benzphenalenone (including any corresponding compounds disclosed in
U.S. Pat. No. 4,812,409) and derivatives thereof. As used herein,
oxazines include resoruf ins (including any corresponding compounds
disclosed in U.S. Pat. No. 5,242,805), aminooxazinones,
diaminooxazines, and their benzo-substituted analogs.
[0097] Xanthene type fluorophores used in labeling reagents in the
methods and compositions described herein include, but are not
limited to, a fluorescein, a rhodol (including any corresponding
compounds disclosed in U.S. Pat. Nos. 5,227,487 and 5,442,045), or
a rhodamine (including any corresponding compounds in U.S. Pat.
Nos. 5,798,276; 5,846,737; U.S. Ser. No. 09/129,015). As used
herein, fluorescein includes benzo- or dibenzofluoresceins,
seminaphthofluoresceins, or naphthofluoresceins. Similarly, as used
herein rhodol includes seminaphthorhodafluors (including any
corresponding compounds disclosed in U.S. Pat. No. 4,945,171). In
certain embodiments, the fluorophore is a xanthene that is bound
via a linkage that is a single covalent bond at the 9-position of
the xanthene. In other embodiments, the xanthenes include
derivatives of 3H-xanthen-6-ol-3-one attached at the 9-position,
derivatives of 6-amino-3H-xanthen-3-one attached at the 9-position,
or derivatives of 6-amino-3H-xanthen-3-imine attached at the
9-position.
[0098] In certain embodiments, the fluorophores used in the
labeling reagent in the methods and compositions described herein
include xanthene (rhodol, rhodamine, fluorescein and derivatives
thereof) coumarin, cyanine, pyrene, oxazine and
borapolyazaindacene. In other embodiments, such fluorophores are
sulfonated xanthenes, fluorinated xanthenes, sulfonated coumarins,
fluorinated coumarins and sulfonated cyanines. Also included are
dyes sold under the tradenames, and generally known as Alexa Fluor,
DyLight, Cy Dyes, BODIPY, Oregon Green, Pacific Blue, IRDyes, FAM,
FITC, and ROX.
[0099] The choice of the fluorophore attached for the labeling
reagent will determine the absorption and fluorescence emission
properties of the modified nucleic acid. Physical properties of a
fluorophore label that can be used for detection of modified
nucleic acids include, but are not limited to, spectral
characteristics (absorption, emission and stokes shift),
fluorescence intensity, lifetime, polarization and photo-bleaching
rate, or combination thereof. All of these physical properties can
be used to distinguish one fluorophore from another, and thereby
allow for multiplexed analysis. In certain embodiments, the
fluorophore has an absorption maximum at wavelengths greater than
480 nm. In other embodiments, the fluorophore absorbs at or near
488 nm to 514 nm (particularly suitable for excitation by the
output of the argon-ion laser excitation source) or near 546 nm
(particularly suitable for excitation by a mercury arc lamp). In
other embodiment a fluorophore can emit in the NIR (near infra red
region) for tissue or whole organism applications. Other desirable
properties of the fluorescent labeling reagent may include cell
permeability and low toxicity, for example if labeling of the
nucleic acid polymer is to be performed in a cell or an organism
(e.g., a living animal).
[0100] In certain embodiments the labeling reagent comprises a
tandem dye or FRET dye pair. This is particularly useful to obtain
a set of labeling reagents that are excited at the same wavelength
but which have distinct emission spectra. Two dyes function as a
FRET pair when they are within close proximity, usually covalently
attached, so that the energy from the excited first dye (the donor)
is transferred the second dye (the acceptor) where the energy is
then emitted at a longer wavelength than would have been possible
by excitation only of the first dye. A particularly useful
combination is the FRET dye pairs disclosed in U.S. Pat. Nos.
7,169,939; 6,849,745; 5,945,526; 5,863,727; 5,800,996; and
6967250.
[0101] In another embodiment the labeling reagent comprises a
fluorescent nanocrystal.
[0102] For each dual labeling experiment a matched set of labeling
reagents must be selected based on the instrument being used and so
that the dyes can be appropriately excited and measured at the
correct wavelengths to distinguish between the baseline nucleic
acid synthesis and the subsequent change in nucleic acid synthesis
due to treatment. Matched pairs of fluorescent labeling dyes
typically produce signals that are spectrally distinguishable. For
example, in some embodiments, the fluorescent dyes in a matched
pair do not significantly absorb light in the same spectral range
(i.e., they exhibit different absorption maxima wavelengths) and
can be excited (for example, sequentially) using two different
wavelengths. Alternatively, the fluorescent dyes in a matched pair
may emit light in different spectral ranges (i.e., they produce a
dual-color fluorescence upon excitation). Pairs of fluorescent
labels are known in the art (see, for example, R. P. Haugland,
"Molecular Probes: Handbook of Fluorescent Probes and Research
Chemicals, supra).
[0103] The selection of a particular set of labels will depend on
the purpose of the labeling to be performed and will be governed by
several factors, such as the ease and cost of the labeling method,
the quality of sample labeling desired, the effects of the
detectable moiety on the cell or organism, the nature of the
detection system, the nature and intensity of the signal generated
by the detectable moiety, and the like. In this particular
instance, one label is selected for Reagent A and the second label
is selected for Reagent B.
Methods:
[0104] The above dual labeling components are used in the present
methods to measure cellular nascent nucleic acid synthesis by dual
pulse labeling of the cellular nucleic acid. The first pulse
labeling of nucleic acid with a nucleoside analog allows
establishment of a baseline rate of nucleic acid synthesis. Pulse
labeling of nucleic acid with an additional second nucleoside
analog then allows measurement of any changes to the nucleic acid
synthesis. This method does not require a potentially
artifact-inducing intermediary wash step between pulse labels. The
nucleic acid synthesis can be measured as cell proliferation, in
the case of DNA, or in gene expression, in the case of RNA.
Additionally, this method may be used to screen compounds for their
effect on cellular proliferation or gene expression by treating
cells or an organism with the test compound simultaneous to or
before treatment with a second nucleoside analog.
[0105] Thus, in one embodiment is provided a method for measuring a
change in cellular nucleic acid synthesis, wherein the method
comprises: [0106] a) incubating a sample with an effective amount
of a first nucleoside or nucleotide analog to form a primary
incubated sample; [0107] b) incubating the primary incubated sample
with at least one second nucleoside or nucleotide analog to form a
secondary incubated sample; [0108] c) incubating the secondary
incubated sample with a first labeling reagent and at least one
second labeling reagent to form a labeled sample; [0109] d)
detecting the labeled sample wherein a level of incorporation of
the first and at least one second nucleoside or nucleotide analog
is measured, [0110] wherein a difference in a level of
incorporation of the at least one second nucleoside or nucleotide
analog relative to the level of incorporation of the first
nucleoside or nucleotide analog is measured as a change in cellular
nucleic acid synthesis, [0111] with the proviso that either the
first nucleoside or nucleotide or the at least one second
nucleoside or nucleotide contains a bioorthogonal functional
moiety.
[0112] Thus, in one aspect is provided a method for measuring a
change in cellular DNA synthesis, which can be measured as cell
proliferation. In another aspect is provided a method for measuring
a change in cellular RNA synthesis, which can be measure as gene
expression.
[0113] In certain preferred embodiments of the present invention, a
method for screening test compounds for their effect on cellular
proliferation is provided. This method may include measuring
cellular proliferation changes in a patient during the course of
treatment for a disease with a specific compound.
[0114] Cancer cells could be removed from a patient and grown in
culture. A baseline DNA synthesis rate can be determined with the
first pulse, then a drug is added along with the second nucleoside
analog and the change of DNA synthesis rate determined, which in
the case of drug resistance/sensitivity in cancer cells would
easily be determined. Screens for compounds which either stimulate
or block DNA synthesis at various places in the cell cycle could be
greatly improved by the addition having an accurate baseline
synthesis measurement which does not alter the state of the cell
proliferation.
[0115] For example, breast cancer cells may be removed from a
patient and grown in culture. The baseline cellular proliferation
rate may be established by adding a first pulse of EdU. Then, the
cells may be treated with a chemotherapy drug, for example
tamoxifen, and treated with a second pulse label of BrdU. The
cellular proliferation rate in response to tamoxifen is then
measured by comparing incorporation of EdU to BrdU. This process
may be repeated over the course of the breast cancer patient's
treatment to ensure that the patient's cancer cells remain
responsive to the chosen chemotherapeutic agent, in this case,
tamoxifen. In this present example, the clinician would be looking
for a decrease in cellular proliferation upon treatment with the
chemotherapy drug. Once the dual pulse labeling of DNA in the
breast cancer patient's cells demonstrated no change in cellular
proliferation upon treatment with a particular drug, the clinician
could reevaluate whether the patient would benefit from continued
treatment with that drug or should be switched to a different
chemotherapeutic agent.
[0116] One of skill in the art will recognize that this method can
be adapted to screen compounds for their effect on cellular
proliferation in a number of diseases. As examples, and not
intended to limit the scope of the present invention, the following
are diseases whose progression is affected by alterations to the
normal level of cellular proliferation: breast cancer, leukemia,
colon cancer, prostate cancer, and the like (see, e.g., U.S. Pat.
No. 6,646,008 (filed Feb. 22, 2000)); neural diseases, including
neurodegenerative diseases, for example, Huntington's disease
(Curtis et al., Increased Cell Proliferation and Neurogenesis in
the Adult Human Huntington's disease brain, 100 (15) PNAS 9023-9027
(Jul. 22, 2003)), or HIV-associated dementia (Okamoto et al.,
HIV/gp120 Decreases Adult Neural Progenitor Cell Proliferation via
Checkpoint Kinase-Mediated Cell-Cycle Withdrawal and G1 Arrest, 1
Cell Stem Cell 230-236 (Aug. 16, 2007)); and other hyperplasia
diseases including, psoriasis, seborrehea, eczema, benign prostate
hyperplasia, congenital adrenal hyperplasia, endometrial
hyperplasia, squamous cell hyperplasia, sebaceous hyperplasia,
Crohn's disease, carcinoma, sarcoma, glioma and lymphoma (see U.S.
Pat. No. 7,256,034 (filed Jan. 5, 2004)).
[0117] In still further embodiments, the present invention concerns
a method for identifying new compounds, which may be termed as
"test compounds", which have a desired effect on cellular
proliferation. Depending on the application, this desired effect
may be to stimulate, to inhibit, or to not affect cellular
proliferation.
[0118] In screening methods to identify whether test compounds have
an effect on cellular proliferation, it is proposed that compounds
isolated from natural sources such as plants, animals or even
sources such as marine, forest or soil samples, may be assayed for
the presence of potentially useful pharmaceutical agents. It will
be understood that the test compounds to be screened could also be
derived from chemical compositions or man-made compounds. The test
compounds may also include proteins and peptides, such as those
derived from recombinant DNA technology or by other means,
including peptide synthesis. The test compounds may also be
antibodies, including polyclonal and monoclonal antibodies. The
test compounds may also include fragments or parts of
naturally-occurring compounds or may be only found as active
combinations of known compounds which are otherwise inactive. The
test compounds may also include nucleic acids, including, but not
limited to: DNA; ribonucleic acid (RNA); small interfering RNAs
(siRNA); and single-stranded nucleic acids, more particularly,
those designed to form in vivo triplexes.
[0119] In certain embodiments, the present invention may be used to
measure cellular proliferation following treatment with compounds
known to affect cellular proliferation. See, e.g., Nicholas R.
Cozzarelli, The Mechanism of Action of Inhibitors of DNA Synthesis,
46 ANN. REV. BIOCHEM. 641-648 (1977).
[0120] In certain embodiments of the present invention, the test
compound is administered to an organism. Organisms to which the
claimed methods may be applied include, but are not limited to:
humans, mice, rats, horses, cows, sheep, rabbits, dogs, or
cats.
[0121] Test compounds and nucleoside analogs may be administered to
organisms by a variety of methods known to persons of skill in the
art. These include oral administration (e.g. ingestion of a pill,
food or liquid containing the test compound and/or nucleoside
analogs), or by subcutaneous, intravenous or intraperitoneal
administration (e.g. by injection or topical application). The test
compound may also be administered parenterally, intraspinally, or
intracerebrally.
[0122] In certain embodiments, the present invention provides for
measuring cellular proliferation in cells, rather than an organism.
The nucleoside analogs may be added to the medium in which the
cells are grown. Similarly, if the method includes screening test
compounds for their effect on cellular proliferation, the test
compound may be added to the medium in which the cells are
grown.
[0123] The preceding discussion of test compounds effect on cell
proliferation is also intended to relate to their effect on gene
expression wherein the change in RNA synthesis is measure.
[0124] In a specific embodiment of the present invention, cellular
proliferation is measured in a cell by treating the cell with an
effective amount of EdU, followed by treatment with an effective
amount of BrdU. The EdU pulse label is detected using click
chemistry reagents, including copper sulfate (CuSO.sub.4) and a
dye-labeled azide (e.g. Alexa Fluor.RTM. 488-azide (Molecular
Probes.TM./Invitrogen.TM., Carlsbad, Calif.)). The BrdU pulse label
is detected using standard antibody-based methods. See, e.g.,
Jonathon Pines et al., Assays for CDK Activity and DNA Replication
in the Cell Cycle, CURRENT PROTOCOLS IN CELL BIOLOGY (Juan S.
Bonifacino et al. eds., John Wiley & Sons, Inc. 2003) (1998).
Both labels are then measured using flow cytometry.
[0125] In certain embodiments of the present invention, this dual
pulse labeling method may be applied to the assessment of cancer
therapy ex vivo or in vivo. Cancer cells may be removed from a
patient and grown in culture. A baseline DNA synthesis rate may be
determined with the first pulse, then a drug is added along with
the second nucleoside analog and the change of DNA synthesis rate
determined. Having an accurate baseline synthesis measurement which
does not alter the state of the cellular proliferation will greatly
improve screening methods for compounds that either stimulate or
block DNA synthesis.
[0126] In certain embodiments of the present invention, the method
for measuring cellular proliferation is performed on a neural cell.
This dual pulse labeling method may be applied to the assessment of
treatment for nervous system diseases. For instance, changes to
cellular proliferation rates of neural cells upon treatment with a
test compound may be measured by contacting neural cells with a
first pulse of a nucleoside analog; treating with a test compound;
contacting the neural cells with a competitive nucleoside analog
simultaneous to or after treatment with the test compound;
detecting incorporation of the first nucleoside analog and
detecting incorporation of the competitive nucleoside analog. Thus,
this dual pulse labeling method may be used to identify compounds
that either stimulate or inhibit neural cell proliferation.
[0127] In one embodiment of the present invention, compounds are
screened for their effects on cellular proliferation using a method
comprising the steps of: treating a cell with a first nucleoside
analog; treating the cell with a test compound; treating the cell
with at least one competitive nucleoside analog simultaneous to or
after treating the cell with the test compound; detecting
incorporation of the first nucleoside analog; and detecting
incorporation of the second nucleoside analog.
[0128] In another embodiment of the present invention, cellular
proliferation in an organism is measured by: treating an organism
with a first nucleoside analog; treating the organism with at least
one second nucleoside analog; detecting incorporation of the first
nucleoside analog; and detecting incorporation of the second
nucleoside analog.
[0129] In another embodiment of the present invention, cellular
proliferation in an organism is measured by: treating an organism
with a first nucleoside analog; treating the organism with a test
compound; treating the organism with at least one competitive
nucleoside analog simultaneous to or after treating the cells with
the test compound; detecting incorporation of the first nucleoside
analog; and detecting incorporation of the second nucleoside
analog.
Illumination
[0130] The compounds of the invention may, at any time after or
during an assay, be illuminated with a wavelength of light that
results in a detectable optical response, and observed with a means
for detecting the optical response. Upon illumination, such as by
an violet or visible wavelength emission lamp, an arc lamp, a
laser, or even sunlight or ordinary room light, the fluorescent
compounds display intense visible absorption as well as
fluorescence emission. Selected equipment that is useful for
illuminating the fluorescent compounds of the invention includes,
but is not limited to, hand-held ultraviolet lamps, mercury arc
lamps, xenon lamps, argon lasers, laser diodes, and YAG lasers.
These illumination sources are optionally integrated into laser
scanners, flow cytometer, fluorescence microplate readers, standard
or mini fluorometers, or chromatographic detectors. This
fluorescence emission is optionally detected by visual inspection,
or by use of any of the following devices: CCD cameras, video
cameras, photographic film, laser scanning devices, fluorometers,
photodiodes, quantum counters, epifluorescence microscopes,
scanning microscopes, flow cytometers, fluorescence microplate
readers, or by means for amplifying the signal such as
photomultiplier tubes. Where the sample is examined using a flow
cytometer, a fluorescence microscope or a fluorometer, the
instrument is optionally used to distinguish and discriminate
between the first pulse labeling reagent of the invention and a
second labeling reagent detectably different optical properties,
typically by distinguishing the fluorescence response of the first
fluorescent compounds of the invention from that of the second
fluorophore. Where a sample is examined using a flow cytometer,
examination of the sample optionally includes isolation of
particles within the sample based on the fluorescence response by
using a sorting device.
Kits of the Invention
[0131] In another aspect, the present invention provides kits that
includes at least one nucleoside analog and labeling reagent of the
invention. The kit will generally also include instructions for
using the nucleoside analog and labeling reagent in one or more
methods, typically for measuring a change in cellular nucleic acid
synthesis.
[0132] In an exemplary embodiment, the kit includes a first
nucleoside or nucleotide analog, at least one second nucleoside or
nucleotide analog, wherein in at least the first analog or the at
least one second nucleoside or nucleotide analog contains a
bioorthogonal functional moiety, a first labeling reagent and a
second labeling reagent. Additional kit components include buffers,
other detection reagents and standards.
[0133] A detailed description of the invention having been provided
above, the following examples are given for the purpose of
illustrating the invention and shall not be construed as being a
limitation on the scope of the invention or claims.
EXAMPLES
[0134] The following examples describe some of the preferred
embodiments of the present invention. However, it should be
understood that these examples are for illustrative purposes only
and are not meant to limit the scope of the invention.
Example 1
[0135] A standard method of preparing cultured cells for the
measurement of newly synthesized DNA (cellular proliferation) is
set up according to known conditions for cells to be actively
growing by providing the proper media and nutrient requirements. In
the present example, Jurkat cell cultures were diluted one to four
to a density of 2.times.10.sup.5 cells/ml. After these cells had
been growing for two or three days, the first nucleoside analog,
EdU, was added at 20 .mu.M, a concentration appropriate for
incorporation in the DNA of cells undergoing DNA synthesis. The
cells were grown in the presence of EdU for thirty minutes. After
thirty minutes of growth and without the removal of EdU through the
washing of the cells in fresh media, an appropriate amount of the
competitive nucleoside analog, BrdU, was added at a 10 .mu.M
concentration, and the cells were grown for thirty minutes. The
cells were then harvested, washed, fixed with 70% ice-cold ETOH and
stored at 4.degree. C. for 96 hours. The cells were then washed and
resuspended in 4M HCL for 20 minutes at room temperature. A
phosphate/citric acid buffer was added, and the cells were washed
twice and resuspended in 0.1% Triton.RTM. X-100/1% BSA/PBS at
1.times.10.sup.7/ml. Then, labeling of the EdU was performed by
adding click chemistry based reagents, including a solution
comprised of CuSO.sub.4 in Tris-buffered saline and Alexa
Fluor.RTM. 488-azide (495 nm excitation maxima/519 nm emission
maxima) (Molecular Probes.RTM./Invitrogen.TM., Carlsbad, Calif.).
The cells were then washed with 0.1% Triton.RTM. X-100/1% BSA/PBS.
After this, labeling of the BrdU was performed using the anti-BrdU
antibody Alexa Fluor.RTM. 647 conjugate (650 nm excitation
maxima/670 nm emission maxima) (Molecular
Probes.RTM./Invitrogen.TM., Carlsbad, Calif.). To detect DNA
content, a nucleic acid dye, SYTOX.RTM. Blue stain (444 nm
excitation maxima/480 nm emission maxima) (Molecular
Probes.RTM./Invitrogen.TM., Carlsbad, Calif.) was added with RNase
(Invitrogen.TM., Carlsbad, Calif.). Detection of the three labels
was performed by flow cytometry. To detect the EdU label, 488 nm
excitation was used, with a 530/30 nm bandpass. To detect the BrdU
label, 633 nm excitation was used, with a 660/20 nm bandpass. To
detect DNA content, 405 nm excitation was used, with a 450/50 nm
bandpass.
Example 2
[0136] A standard method of preparing cultured cells for the
measurement of newly synthesized DNA (cellular proliferation) is
set up according to known conditions for cells to be actively
growing by providing the proper media and nutrient requirements. In
the present example, Jurkat cell cultures were diluted one to four
to a density of 2.times.10.sup.5 cells/ml. After these cells have
been growing for two or three days the first nucleoside analog,
EdU, was added at 20 .mu.M, a concentration appropriate for
incorporation in the DNA of cells undergoing DNA synthesis. The
cells were grown in the presence of EdU for one hour. After one
hour of growth and without the removal of EdU through the washing
of the cells in fresh media, an appropriate amount of the
competitive nucleoside analog, BrdU, was added at a 10 .mu.M
concentration, and the cells were grown for thirty minutes. The
cells were then harvested, washed, fixed with 70% ice-cold ETOH and
stored at 4.degree. C. for 96 hours. The cells were then washed and
resuspended in 4M HCL for 20 minutes at room temperature. A
phosphate/citric acid buffer was added, and the cells were washed
twice and resuspended in 0.1% Triton.RTM. X-100/1% BSA/PBS at
1.times.10.sup.7/ml. Then, labeling of the EdU was performed by
adding click chemistry based reagents, including a solution
comprised of CuSO.sub.4 in Tris-buffered saline and Alexa
Fluor.RTM. 488-azide (495 nm excitation maxima/519 nm emission
maxima) (Molecular Probes.RTM./Invitrogen.TM., Carlsbad, Calif.).
The cells were then washed with 0.1% Triton.RTM. X-100/1% BSA/PBS.
After this, labeling of the BrdU was performed using the anti-BrdU
antibody Alexa Fluor.RTM. 647 conjugate (650 nm excitation
maxima/670 nm emission maxima) (Molecular
Probes.TM./Invitrogen.TM., Carlsbad, Calif.) To detect DNA content,
a nucleic acid dye, SYTOX.RTM. Blue stain (444 nm excitation
maxima/480 nm emission maxima) (Molecular
Probes.RTM./Invitrogen.TM., Carlsbad, Calif.) was added with RNase
(Invitrogen.TM., Carlsbad, Calif.). Detection of the three labels
was performed by flow cytometry. To detect the EdU label, 488 nm
excitation was used, with a 530/30 nm bandpass. To detect the BrdU
label, 633 nm excitation was used, with a 660/20 nm bandpass. To
detect DNA content, 405 nm excitation was used, with a 450/50 nm
bandpass.
Results from Examples 1-2
[0137] Since there was no treatment between the additions of the
two pulses of nucleoside analog which might result in a change in
the rate of newly synthesized DNA, the incorporation of the two
analogs should be equivalent. In the graphs several cell
subpopulations can be seen. There were cells which did not contain
either label (FIG. 1 Q3 quadrant). These cells were not actively
replicating their DNA during the testing period.
[0138] There were also cells which have both the EdU and the BrdU
label incorporated into the DNA (FIG. 1 Q2 quadrant). These cells
had continued DNA synthesis during the entire course of the test
period of both pulses and the treatment.
[0139] There was also a population of cells which only had a label
from the first pulse (EdU) (FIGS. 2 & 4). These cells were in
late synthesis phase during the labeling by EdU. This can be seen
in the mapping on the graph of total DNA vs. EdU label. By the time
the pulse of BrdU was added, these cells had quit replicating their
DNA.
[0140] There was also a population of cells which only had the
label from the second pulse (FIGS. 3 & 4). These cells were not
actively replicating their DNA during the time of the first pulse
but entered into the DNA synthesis phase during the time of the
second pulse. Treatments that cause increases or decreases in the
rate of synthesis can easily be seen and quantitated from the
patterns of the graphs of the cell populations collected by flow
cytometry.
Example 3
[0141] In a third experiment the addition of both EdU and BrdU
nucleoside analogs simultaneously results in only a population of
cells whose DNA was labeled with BrdU (FIG. 5). This third
experiment is a demonstration of the no wash requirement of the
first label, prior to the addition of the second label. The cells
were then harvested, washed, fixed with 70% ice-cold ETOH and
stored at 4.degree. C. for 96 hours. The cells were then washed and
resuspended in 4M HCL for 20 minutes at room temperature. A
phosphate/citric acid buffer was added, and the cells washed twice
and resuspended in 0.1% Triton.RTM.X-100/1% BSA/PBS at
1.times.10.sup.7/ml. Then, labeling of the EdU was performed by
adding click chemistry based reagents, including a solution
comprised of CuSO.sub.4 in Tris-buffered saline and Alexa
Fluor.RTM. 488 conjugate (495 nm excitation maxima/519 nm emission
maxima) (Molecular Probes.RTM./Invitrogen.TM., Carlsbad, Calif.).
The cells were then washed with 0.1% Triton.RTM.X-100/1% BSA/PBS.
After this, labeling of the BrdU was performed using the anti-BrdU
antibody Alexa Fluor.RTM. 647 conjugate (650 nm excitation
maxima/670 nm emission maxima) (Molecular
Probes.TM./Invitrogen.TM., Carlsbad, Calif.) To detect DNA content,
a nucleic acid dye, SYTOX.RTM. Blue stain (444 nm excitation
maxima/480 nm emission maxima) (Molecular
Probes.RTM./Invitrogen.TM., Carlsbad, Calif.) was added with RNase
(Invitrogen.TM., Carlsbad, Calif.). Detection of the three labels
was performed by flow cytometry. To detect the EdU label, 488 nm
excitation was used, with a 530/30 nm bandpass. To detect the BrdU
label, 633 nm excitation was used, with a 660/20 nm bandpass. To
detect DNA content, 405 nm excitation was used, with a 450/50 nm
bandpass. This result demonstrates that in the presence of both
nucleoside analogs, only the BrdU analog is incorporated into the
DNA, thus confirming the efficacy of the methods that do not
require a wash step prior to adding the competitive nucleoside
analog. The BrdU analog appears to be competitive with EdU when
both are present during nucleic acid synthesis.
Example 4
[0142] A standard method of preparing cultured cells for the
measurement of newly synthesized DNA (cellular proliferation) is
set up according to known conditions for cells to be actively
growing by providing the proper media and nutrient requirements. In
the present example, Jurkat cell cultures were diluted one to four
to a density of 2.times.10.sup.5 cells/ml. After these cells have
been growing for two or three days the first nucleoside analog,
EdU, was added at 20 .mu.M, a concentration appropriate for
incorporation in the DNA of cells undergoing DNA synthesis. The
cells were grown in the presence of EdU for one hour. After one
hour of growth and without the removal of EdU through the washing
of the cells in fresh media, an appropriate amount of the
competitive nucleoside analog, BrdU, was added at a 10 .mu.M
concentration, and the cells were grown for one hour. The cells
were then harvested, washed, fixed with 70% ice-cold ETOH and
stored at 4.degree. C. for 96 hours. The cells were then washed and
resuspended in 4M HCL for 20 minutes at room temperature. A
phosphate/critric acid buffer was added, and the cells washed twice
and resuspended in 0.1% TritonX/1% BSA/PBS at 1.times.10.sup.7/ml.
Labeling of the BrdU was performed using the anti-BrdU antibody
Alexa Fluor.RTM. 647 conjugate (650 nm excitation maxima/670 nm
emission maxima) (Molecular Probes.TM./Invitrogen.TM., Carlsbad,
Calif.). The cells were then washed with 0.1% TritonX/1% BSA/PBS.
After this labeling of the EdU was performed by adding click
chemistry based reagents, including a solution comprised of
CuSO.sub.4 in Tris-buffered saline and Alexa Fluor.RTM. 488-azide
(495 nm excitation maxima/519 nm emission maxima) (Molecular
Probes.TM./Invitrogen.TM., Carlsbad, Calif.). To detect DNA
content, a nucleic acid dye, SYTOX.RTM. Blue stain (444 nm
excitation maxima/480 nm emission maxima) (Molecular
Probes.TM./Invitrogen.TM., Carlsbad, Calif.) was added with RNase
(Invitrogen.TM., Carlsbad, Calif.). Detection of the three labels
was performed by flow cytometry. To detect the EdU label, 488 nm
excitation was used, with a 530/30 nm bandpass. To detect the BrdU
label, 633 nm excitation was used, with a 660/20 nm bandpass. To
detect DNA content, 405 nm excitation was used, with a 450/50 nm
bandpass.
Example 5
[0143] A standard method of preparing cultured cells for the
measurement of newly synthesized RNA (gene expression) is set up
according to known conditions for cells to be actively growing by
providing the proper media and nutrient requirements. In the
present example, HeLa cell cultures are diluted one to four to a
density of 2.times.10.sup.5 cells onto coverslips within a 6 well
plate. After these cells have been growing for two days the first
nucleoside analog, EU, is added at a concentration appropriate for
incorporation in the RNA of cells actively transcribing message.
The cells are grown in the presence of EU for one hour. After one
hour of growth and without the removal of EU through the washing of
the cells in fresh media, an appropriate amount of the competitive
nucleoside analog, BrU, is added at a 10 .mu.M concentration, and
the cells are grown for thirty minutes. The cells are then
harvested, washed, fixed with 3.7% formaldehyde/PBS for 30 minutes
at 4.degree. C. The cells are then washed in 3% BSA/PBS,
permeabilized in 1.0% Triton.RTM.X-100/PBS and denatured first with
1 M HCl at 4.degree. C. for 10 minutes followed by-2 M HCl for 30
minutes room temperature. A borate buffer is then used to
neutralize the cells. Labeling of the EU is performed by adding
click chemistry based reagents, including a solution comprised of
CuSO.sub.4 in Tris-buffered saline and Alexa Fluor.RTM. 488
conjugate (495 nm excitation maxima/519 nm emission maxima)
(Molecular Probes.RTM./Invitrogen.TM., Carlsbad, Calif.). The cells
are then washed and blocked with 1.0% Triton.RTM.X-100/3% BSA/PBS.
After this, labeling of the BrU is performed using the anti-BrdU
antibody and a secondary detection antibody Alexa Fluor.RTM. 647
conjugate (650 nm excitation maxima/670 nm emission maxima)
(Molecular Probes.RTM./Invitrogen.TM., Carlsbad, Calif. To detect
the EdU label, 470/50 nm excitation is used, with a 545/75 nm
bandpass. To detect the BrdU label, 630/50 nm excitation is used,
with a 695/55 nm bandpass. Detection of the two labels is performed
by fluorescence microscopy using standard techniques and
appropriate filters.
Example 6
[0144] A standard method of preparing cultured cells for the
measurement of newly synthesized RNA (gene expression) is set up
according to known conditions for cells to be actively growing by
providing the proper media and nutrient requirements. In the
present example, HeLa cell cultures are diluted one to four to a
density of 2.times.10.sup.5 cells onto coverslips within a 6 well
plate. After these cells have been growing for two days the first
nucleoside analog, EU, is added at a concentration appropriate for
incorporation in the RNA of cells actively transcribing message.
The cells are grown in the presence of EU for one hour. After one
hour of growth and without the removal of EU through the washing of
the cells in fresh media, an appropriate amount of .alpha.-amanitin
(100 .mu.g/mL) along with the appropriate amount of the competitive
nucleoside analog, BrU, is added at a 10 .mu.M concentration, and
the cells are grown for fifteen minutes. The cells are allowed to
grow an additional time from 5 to 30 minutes. The cells are then
harvested, washed, fixed with 3.7% formaldehyde/PBS for 30 minutes
at 4.degree. C. The cells are then washed in 3% BSA/PBS,
permeabilized in 1.0% Triton.RTM.X-100/PBS and denatured first with
1 M HCl at 4.degree. C. for 10 minutes followed by-2 M HCl for 30
minutes room temperature. A borate buffer is then used to
neutralize the cells. Labeling of the EU is performed by adding
click chemistry based reagents, including a solution comprised of
CuSO.sub.4 in Tris-buffered saline and Alexa Fluor.RTM. 488
conjugate (495 nm excitation maxima/519 nm emission maxima)
(Molecular Probes.RTM./Invitrogen.TM., Carlsbad, Calif.). The cells
are then washed and blocked with 1.0% Triton.RTM. X-100/3% BSA/PBS.
After this, labeling of the BrU is performed using the anti-BrdU
antibody and a secondary detection antibody Alexa Fluor.RTM. 647
conjugate (650 nm excitation maxima/670 nm emission maxima)
(Molecular Probes.RTM./Invitrogen.TM., Carlsbad, Calif.). Detection
of the two labels is performed by fluorescence microscopy using
standard techniques and appropriate filters. To detect the EdU
label, 470/50 nm excitation is used, with a 545/75 nm bandpass. To
detect the BrdU label, 630/50 nm excitation is used, with a 695/55
nm bandpass.
Example 7
[0145] A standard method of preparing cultured cells for the
measurement of newly synthesized RNA (gene expression) is set up
according to known conditions for cells to be actively growing by
providing the proper media and nutrient requirements. In the
present example, HeLa cell cultures are diluted one to four to a
density of 2.times.10.sup.5 cells/ml. After these cells have been
growing for two or three days to achieve 70% confluency they are
lipofected with the first nucleoside analog, EUTP to deliver the
compound to the nucleus at a concentration appropriate for
incorporation in the RNA of cells actively transcribing message.
The cells were grown in the presence of EUTP for 15 minutes. After
15 minutes of growth and without the removal of EUTP, the cells are
lipofected with the competitive nucleoside analog, BrUTP, added at
appropriate concentration and the cells are grown an additional
fifteen minutes. The cells are then allowed to grow for various
times before harvesting. The cells are then harvested, washed,
fixed with 3.7% formaldehyde/PBS for 30 minutes at 4.degree. C. The
cells are then washed in 3% BSA/PBS, permeabilized in 1.0%
Triton.RTM.X-100/PBS and denatured first with 1 M HCl at 4.degree.
C. for 10 minutes followed by-2 M HCl for 30 minutes room
temperature. A borate buffer is then used to neutralize the cells.
Labeling of the EU is performed by adding click chemistry based
reagents, including a solution comprised of CuSO.sub.4 in
Tris-buffered saline and Alexa Fluor.RTM. 488 conjugate (495 nm
excitation maxima/519 nm emission maxima) (Molecular
Probes.RTM./Invitrogen.TM., Carlsbad, Calif.). The cells are then
washed and blocked with 1.0% Triton.RTM.X-100/3% BSA/PBS. After
this, labeling of the BrU is performed using the anti-BrdU antibody
and a secondary detection antibody Alexa Fluor.RTM. 647 conjugate
(650 nm excitation maxima/670 nm emission maxima) (Molecular
Probes.RTM./Invitrogen.TM., Carlsbad, Calif.) Detection of the two
labels is performed by fluorescence microscopy using standard
techniques and appropriate filters. To detect the EdU label, 470/50
nm excitation is used, with a 545/75 nm bandpass. To detect the
BrdU label, 630/50 nm excitation is used, with a 695/55 nm
bandpass.
Example 8
[0146] A standard method of preparing cultured cells for the
measurement of newly synthesized DNA is set up according to known
conditions for cells to be actively growing by providing the proper
media and nutrient requirements. In the present example, HeLa cell
cultures are diluted one to four to a density of 2.times.10.sup.5
cells onto coverslips within a 6 well plate. After these cells have
been growing for two days the first nucleoside analog, EdU, is
added at 10 .mu.M, a concentration appropriate for incorporation in
the DNA of cells undergoing DNA synthesis. The cells are grown in
the presence of EdU for one hour. After one hour of growth and
without the removal of EdU through the washing of the cells in
fresh media, an appropriate amount of a second nucleoside analog
for the labeling of newly synthesized DNA, AzdU is added at 10 mM
along with a drug which alters cell proliferation rate and are
grown for an additional 30 minutes. After the second incubation, a
third competitive analog, BrdU, is added at a 10 .mu.M
concentration along with a second treatment which alters cell
proliferation rate, and the cells are grown for an additional
thirty minutes. The cells are then harvested, washed, fixed with
3.7% formaldehyde/PBS for 30 minutes at 4.degree. C. The cells are
then washed in 3% BSA/PBS, permeabilized in 1.0%
Triton.RTM.X-100/PBS and denatured first with 1 M HCl at 4.degree.
C. for 10 minutes followed by-2 M HCl for 20 minutes room
temperature. A borate buffer is then used to neutralize the cells.
Then, labeling of the AzU is performed by washing the cells two
times with 3% BSA in PBS, and adding the copper-less click
chemistry based reagents, including a solution comprised of Alexa
Fluor.RTM. 488-constrained cycloalkyne (495 nm excitation
maxima/519 nm emission maxima) (Molecular
Probes.TM./Invitrogen.TM., Carlsbad, Calif.) in Tris-buffered
saline. After this reaction, labeling of the EdU is performed by
adding click chemistry based reagents, including a solution
comprised of CuSO.sub.4 in Tris-buffered saline and Alexa
Fluor.RTM. 594 conjugate (590 nm excitation maxima/615 nm emission
maxima) (Molecular Probes.RTM./Invitrogen.TM., Carlsbad, Calif.).
The cells are then washed and blocked with 1.0% Triton.RTM.X-100/3%
BSA/PBS. After this, labeling of the BrdU is performed using the
anti-BrdU antibody and a secondary detection antibody Alexa
Fluor.RTM. 647 conjugate (650 nm excitation maxima/670 nm emission
maxima) (Molecular Probes.RTM./Invitrogen.TM., Carlsbad, Calif.)
Detection of the three labels is performed by fluorescence
microscopy using standard techniques. To detect the AzdU label,
470/50 nm excitation is used, with a 545/75 nm bandpass. To detect
the EdU label, 560/55 nm excitation is used, with a 645/75 nm
bandpass. To detect the BrdU label, 630/50 nm excitation is used,
with a 695/55 nm bandpass.
Example 9
[0147] A standard method of preparing cultured cells for the
measurement of newly synthesized DNA (cellular proliferation) is
set up according to known conditions for cells to be actively
growing by providing the proper media and nutrient requirements. In
the present example, Ramos human B-lymphocyte cell cultures were
diluted one to four to a density of 2.times.10.sup.5 cells/ml.
After these cells had been growing for one or two days, the first
nucleoside analog, EdU, was added at 20 .mu.M, a concentration
appropriate for incorporation in the DNA of cells undergoing DNA
synthesis. The cells were grown in the presence of EdU for two
hours. After 2 hours of growth and without the removal of EdU
through the washing of the cells in fresh media, an appropriate
amount of the competitive nucleoside analog, BrdU, was added at a
10 .mu.M concentration, and the cells were grown for 2.5 hours. The
cells were then harvested, washed, fixed with 70% ice-cold ETOH and
stored at 4.degree. C. for 96 hours. The cells were then washed and
resuspended in 4M HCL for 20 minutes at room temperature. A
phosphate/critric acid buffer was added, and the cells washed twice
and resuspended in 0.1% TritonX/1% BSA/PBS at 1.times.10.sup.7/ml.
Then, labeling of the EdU was performed by adding click chemistry
based reagents, including a solution comprised of CuSO.sub.4 in
Tris-buffered saline and Alexa Fluor.RTM. 647-azide (650 nm
excitation maxima/670 nm emission maxima) (Molecular
Probes.TM./Invitrogen.TM., Carlsbad, Calif.). The cells were then
washed with 0.1% TritonX/1% BSA/PBS. After this, labeling of the
BrdU was performed using the anti-BrdU antibody FITC conjugate (494
nm excitation maxima/518 nm emission maxima) (Exalpha Biologicals,
Inc., Maynard Calif.) To detect DNA content, a nucleic acid dye,
DAPI (358 nm excitation maxima/461 nm emission maxima) (Molecular
Probes.TM./Invitrogen.TM., Carlsbad, Calif.) was added. Detection
of the three labels was performed by flow cytometry. To detect the
BrdU label, 488 nm excitation was used, with a 530/30 nm bandpass.
To detect the EdU label, 633 nm excitation was used, with a 660/20
nm bandpass. To detect DNA content, 355 nm excitation was used,
with a 450/50 nm bandpass.
[0148] FIG. 7 presents a series of result graphs, labeled A through
C, showing populations of the cells treated with a first pulse
label of EdU (20 .mu.M) and a second pulse label of BrdU (10 .mu.M)
as detected by flow cytometry. Graph A is divided into four
quadrants with the first quadrant (Q1) located in the upper left
hand corner, the second quadrant (Q2) located in the upper right
hand corner, the third quadrant (Q3) located in the lower left hand
corner, and the fourth quadrant (Q4) located in the lower right
hand corner. Populations of cells in quadrant Q3 (lower left,
colored light blue) are negative for both EdU (first pulse) and
BrdU (second pulse). Populations of cells in quadrant Q2 (upper
right, colored dark blue) are positive for both EdU (first pulse)
and BrdU (second pulse). Populations of cells in quadrant Q1 (upper
left, colored light green) are positive for BrdU and negative for
EdU, a sub-population of BrdU-positive cells which are
EdU-negative, this sub-population being the population of cells
entering S-phase after the Edu only incorporation. Populations of
cells in Q4 (lower right, colored red) are positive for EdU and
negative for BrdU, a sub-population of EdU-positive cells
(late-stage S) which are BrdU-negative, this sub-population being
the population of cells leaving S-phase before the BrdU-incorp.
Graph B is a graph of BrdU vs. DNA content showing these same
colored populations form graph A. Graph C is a graph of EdU vs DNA
content showing these same colored populations form graph A.
Example 10
[0149] A standard method of preparing cultured cells for the
measurement of newly synthesized DNA (cellular proliferation) is
set up according to known conditions for cells to be actively
growing by providing the proper media and nutrient requirements. In
the present example, K562 human lymphoblast from chronic
myelogenous leukemia cell cultures were diluted one to four to a
density of 2.times.10.sup.5 cells/ml. After these cells had been
growing for one or two days, the first nucleoside analog, EdU, was
added at 20 .mu.M, a concentration appropriate for incorporation in
the DNA of cells undergoing DNA synthesis. The cells were grown in
the presence of EdU for two hours. After 2 hours of growth and
without the removal of EdU through the washing of the cells in
fresh media, an appropriate amount of the competitive nucleoside
analog, BrdU, was added at a 10 .mu.M concentration, and the cells
were grown for 2.5 hours. The cells were then harvested, washed,
fixed with 70% ice-cold ETOH and stored at 4.degree. C. for 96
hours. The cells were then washed and resuspended in 4M HCL for 20
minutes at room temperature. A phosphate/critric acid buffer was
added, and the cells washed twice and resuspended in 0.1%
TritonX/1% BSA/PBS at 1.times.10.sup.7/ml. Then, labeling of the
EdU was performed by adding click chemistry based reagents,
including a solution comprised of CuSO.sub.4 in Tris-buffered
saline and Alexa Fluor.RTM. 647-azide (650 nm excitation maxima/670
nm emission maxima) (Molecular Probes.TM./Invitrogen.TM., Carlsbad,
Calif.). The cells were then washed with 0.1% TritonX/1% BSA/PBS.
After this, labeling of the BrdU was performed using the anti-BrdU
antibody FITC conjugate (494 nm excitation maxima/518 nm emission
maxima) (Exalpha Biologicals, Inc., Maynard Calif.) To detect DNA
content, a nucleic acid dye, DAPI (358 nm excitation maxima/461 nm
emission maxima) (Molecular Probes.TM./Invitrogen.TM., Carlsbad,
Calif.) was added. Detection of the three labels was performed by
flow cytometry. To detect the BrdU label, 488 nm excitation was
used, with a 530/30 nm bandpass. To detect the EdU label, 633 nm
excitation was used, with a 660/20 nm bandpass. To detect DNA
content, 355 nm excitation was used, with a 450/50 nm bandpass.
[0150] FIG. 8 presents a series of result graphs, labeled A through
C, showing populations of the cells treated with a first pulse
label of EdU (20 .mu.M) and a second pulse label of BrdU (10 .mu.M)
as detected by flow cytometry. Graph A is divided into four
quadrants with the first quadrant (Q1) located in the upper left
hand corner, the second quadrant (Q2) located in the upper right
hand corner, the third quadrant (Q3) located in the lower left hand
corner, and the fourth quadrant (Q4) located in the lower right
hand corner. Populations of cells in quadrant Q3 (lower left,
colored light blue) are negative for both EdU (first pulse) and
BrdU (second pulse). Populations of cells in quadrant Q2 (upper
right, colored dark blue) are positive for both EdU (first pulse)
and BrdU (second pulse). Populations of cells in quadrant Q1 (upper
left, colored light green) are positive for BrdU and negative for
EdU, a sub-population of BrdU-positive cells which are
EdU-negative, this sub-population being the population of cells
entering S-phase after the Edu only incorporation. Populations of
cells in Q4 (lower right, colored red) are positive for EdU and
negative for BrdU, a sub-population of EdU-positive cells
(late-stage S) which are BrdU-negative, this sub-population being
the population of cells leaving S-phase before the BrdU-incorp.
Graph B is a graph of BrdU vs. DNA content showing these same
colored populations form graph A. Graph C is a graph of EdU vs DNA
content showing these same colored populations form graph A.
Example 11
[0151] A standard method of preparing cultured cells for the
measurement of newly synthesized DNA (cellular proliferation) is
set up according to known conditions for cells to be actively
growing by providing the proper media and nutrient requirements. In
the present example, TF-1a human erythroblast cell cultures were
diluted one to four to a density of 2.times.10.sup.5 cells/ml.
Culture media contains GM-CSF, or granulocyte-macrophage
colony-stimulating factor, for growth. After these cells had been
growing for one or two days, the first nucleoside analog, EdU, was
added at 20 M, a concentration appropriate for incorporation in the
DNA of cells undergoing DNA synthesis. The cells were grown in the
presence of EdU for time listed in chart 1. After initial period of
growth and without the removal of EdU through the washing of the
cells in fresh media, an appropriate amount of the competitive
nucleoside analog, BrdU, was added at a 10 M concentration, and the
cells were grown for time listed in chart 1. The cells were then
harvested, washed, fixed with 70% ice-cold ETOH and stored at
4.degree. C. until use. The cells were then washed and resuspended
in 4M HCL for 20 minutes at room temperature. A phosphate/critric
acid buffer was added, and the cells washed twice and resuspended
in 0.1% TritonX/1% BSA/PBS at 1.times.10.sup.7/ml. Then, labeling
of the EdU was performed by adding click chemistry based reagents,
including a solution comprised of CuSO.sub.4 in Tris-buffered
saline and Alexa Fluor.RTM. 647-azide (650 nm excitation maxima/670
nm emission maxima) (Molecular Probes.TM./Invitrogen.TM., Carlsbad,
Calif.). The cells were then washed with 0.1% TritonX/1% BSA/PBS.
After this, labeling of the BrdU was performed using the anti-BrdU
antibody FITC conjugate (494 nm excitation maxima/518 nm emission
maxima) (Exalpha Biologicals, Inc., Maynard Calif.) To detect DNA
content, a nucleic acid dye, DAPI (358 nm excitation maxima/461 nm
emission maxima) (Molecular Probes.TM./Invitrogen.TM., Carlsbad,
Calif.) was added. Detection of the three labels was performed by
flow cytometry. To detect the BrdU label, 488 nm excitation was
used, with a 530/30 nm bandpass. To detect the EdU label, 633 nm
excitation was used, with a 660/20 nm bandpass. To detect DNA
content, 355 nm excitation was used, with a 450/50 nm bandpass.
TABLE-US-00001 CHART 1 first pulse-20uM second pulse-10uM EdU BrdU
A 2 hours 2 hours B 2 hours 4 hours C 2 hours 8 hours D 2 hours 16
hours E 4 hours 2 hours F 8 hours 2 hours G 16 hours 2 hours H 2
hours none I none 2 hours
[0152] FIGS. 9-1 through 9-3 present a series of result graphs,
labeled as A through I, showing populations of cells (TF-1a human
erythroblast cells). The graphs A through G show the population of
the cells treated with a first pulse label of EdU (20 .mu.M) and a
second pulse label of BrdU (10 .mu.M) with the time of the pulses
varied, as detected by flow cytometry. The graphs H and I show the
population of the cells treated with one pulse only, with graph H
showing the result of a pulse label of EdU (20 .mu.M) only and
graph I showing result of a pulse label of BrdU (10 .mu.M) only, as
detected by flow cytometry.
[0153] The dual parameter graph is divided into four quadrants with
the first quadrant (Q1) located in the upper left hand corner, the
second quadrant (Q2) located in the upper right hand corner, the
third quadrant (Q3) located in the lower left hand corner, and the
fourth quadrant (Q4) located in the lower right hand corner.
Populations of cells in quadrant Q3 are negative for both EdU
(first pulse) and BrdU (second pulse). Populations of cells in
quadrant Q2 are positive for both EdU (first pulse) and BrdU
(second pulse). Populations of cells in quadrant Q1 are positive
for BrdU and negative for EdU, a sub-population of BrdU-positive
cells which are EdU-negative, this sub-population being the
population of cells entering S-phase after the Edu only
incorporation. Populations of cells in Q4 are positive for EdU and
negative for BrdU, a sub-population of EdU-positive cells
(late-stage S) which are BrdU-negative, this sub-population being
the population of cells leaving S-phase before the
BrdU-incorporation.
Example 12
[0154] A standard method of preparing cultured cells for the
measurement of newly synthesized DNA (cellular proliferation) is
set up according to known conditions for cells to be actively
growing by providing the proper media and nutrient requirements. In
the present example, TF-1a human erythroblast cell cultures were
diluted one to four to a density of 2.times.10.sup.5 cells/ml.
Culture media contains varying amounts of GM-CSF, or
granulocyte-macrophage colony-stimulating factor, at amounts equal
to full (2 ng/ml) or 1/4 (0.5 ng/ml) recommended concentration of
GM-CSF, and no GM-CSF. After these cells had been growing 18 hours,
the first nucleoside analog, EdU, was added at 20 .mu.M, a
concentration appropriate for incorporation in the DNA of cells
undergoing DNA synthesis. The cells were grown in the presence of
EdU for three hours. After initial period of growth and without the
removal of EdU through the washing of the cells in fresh media, an
appropriate amount of the competitive nucleoside analog, BrdU, was
added at a 10 .mu.M concentration, and GM-CSF was added at the same
time as the BrdU in amounts to equal the full amount recommended
for GM-CSF concentration of 2 ng/ml or kept at the same initial
concentration of GM-CSF. The cells were grown for six hours. The
cells were then harvested, washed, fixed with 70% ice-cold ETOH and
stored at 4.degree. C. until use. The cells were then washed and
resuspended in 4M HCL for 20 minutes at room temperature. A
phosphate/critric acid buffer was added, and the cells washed twice
and resuspended in 0.1% TritonX/1% BSA/PBS at 1.times.10.sup.7/ml.
Then, labeling of the EdU was performed by adding click chemistry
based reagents, including a solution comprised of CuSO.sub.4 in
Tris-buffered saline and Alexa Fluor.RTM. 647-azide (650 nm
excitation maxima/670 nm emission maxima) (Molecular
Probes.TM./Invitrogen.TM., Carlsbad, Calif.). The cells were then
washed with 0.1% TritonX/1% BSA/PBS. After this, labeling of the
BrdU was performed using the anti-BrdU antibody FITC conjugate (494
nm excitation maxima/518 nm emission maxima) (Exalpha Biologicals,
Inc., Maynard Calif.). To detect DNA content, a nucleic acid dye,
DAPI (358 nm excitation maxima/461 nm emission maxima) (Molecular
Probes.TM./Invitrogen.TM., Carlsbad, Calif.) was added. Detection
of the three labels was performed by flow cytometry. To detect the
BrdU label, 488 nm excitation was used, with a 530/30 nm bandpass.
To detect the EdU label, 633 nm excitation was used, with a 660/20
nm bandpass. To detect DNA content, 355 nm excitation was used,
with a 450/50 nm bandpass.
[0155] Chart 2 shows the percentage of cells that are EdU positive
and BrdU positive during the various CM-CSF treatments. The dual
pulse with the full amount of 2 ng/ml GM-CSF is the control and
shows the percentage of EdU and BrdU positive cell that are
expected. The dual pulse with no GM-CSF shows decreased
proliferation with both analogs, and addition of GM-CSF with just
the BrdU pulse shows some proliferative recovery of cells with an
increase of BrdU positivity. The dual pulse with 0.5 ng/ml GM-CSF
shows only a slight decrease of proliferation over control, and
does not show any proliferative recovery with addition of GM-CSF to
2 ng/ml with the BrdU pulse. This demonstrates the usefulness of
using a dual pulse system to look at changes of proliferation, with
addition of a growth factor in-between the pulses.
TABLE-US-00002 CHART 2 GM- GM- CSFconcentration CSFconcentration %
EdU % BrdU with EdU pulse with BrdU pulse Pos Pos 2 ng/ml 2 ng/ml
53.9 72.2 (control) (control) none none 38.1 44.5 none 2 ng/ml 42.3
53 0.5 ng/ml 0.5 ng/ml 57 66.3 0.5 ng/ml 2 ng/ml 57.5 65.1
Example 13
[0156] A standard method of preparing cultured cells for the
measurement of newly synthesized DNA (cellular proliferation) is
set up according to known conditions for cells to be actively
growing by providing the proper media and nutrient requirements. In
the present example, THP-1 monocyte cell cultures were diluted one
to four to a density of 2.times.10.sup.5 cells/ml. After these
cells had been growing for 1-2 days, the first nucleoside analog,
EdU, was added at 20 .mu.M, a concentration appropriate for
incorporation in the DNA of cells undergoing DNA synthesis. The
cells were grown in the presence of EdU for one hour. After initial
period of growth and without the removal of EdU through the washing
of the cells in fresh media, an appropriate amount of the
competitive nucleoside analog, BrdU, was added at a 10 .mu.M
concentration, and the cells were grown for one hour. The cells
were then harvested, washed, fixed with 70% ice-cold ETOH and
stored at 4.degree. C. until use. The cells were then washed and
resuspended in 4M HCL for 20 minutes at room temperature. A
phosphate/critric acid buffer was added, and the cells washed twice
and resuspended in 0.1% TritonX/1% BSA/PBS at 1.times.10.sup.7/ml.
Then, labeling of the EdU was performed by adding click chemistry
based reagents, including a solution comprised of CuSO.sub.4 in
Tris-buffered saline and Alexa Fluor.RTM. 647-azide (650 nm
excitation maxima/670 nm emission maxima) (Molecular
Probes.RTM./Invitrogen.TM., Carlsbad, Calif.). The cells were then
washed with 0.1% TritonX/1% BSA/PBS. After this, labeling of the
BrdU was performed using the anti-BrdU antibody FITC conjugate (494
nm excitation maxima/518 nm emission maxima) (Exalpha Biologicals,
Inc., Maynard Calif.) To detect DNA content, a nucleic acid dye,
DAPI (358 nm excitation maxima/461 nm emission maxima) (Molecular
Probes.TM./Invitrogen.TM., Carlsbad, Calif.) was added. Detection
of the three labels was performed by flow cytometry. To detect the
BrdU label, 488 nm excitation was used, with a 530/30 nm bandpass.
To detect the EdU label, 633 nm excitation was used, with a 660/20
nm bandpass. To detect DNA content, 355 nm excitation was used,
with a 450/50 nm bandpass.
[0157] FIG. 10 presents a series of result graphs, labeled A
through F, showing populations of cells (THP-1 monocyte cells)
treated with a first pulse label of EdU (20 .mu.M) and a second
pulse label of BrdU (10 .mu.M) as detected by flow cytometry. Graph
A is divided into four quadrants with the first quadrant (Q1)
located in the upper left hand corner, the second quadrant (Q2)
located in the upper right hand corner, the third quadrant (Q3)
located in the lower left hand corner, and the fourth quadrant (Q4)
located in the lower right hand corner. Populations of cells in
quadrant Q3 (lower left, colored dark green) are negative for both
EdU (first pulse) and BrdU (second pulse). Populations of cells in
quadrant Q2 (upper right, colored dark blue) are positive for both
EdU (first pulse) and BrdU (second pulse). Populations of cells in
quadrant Q1 (upper left, colored light green) are positive for BrdU
and negative for EdU, a sub-population of BrdU-positive cells which
are EdU-negative, this sub-population being the population of cells
entering S-phase after the Edu only incorporation. Populations of
cells in Q4 (lower right, colored red) are positive for EdU and
negative for BrdU, a sub-population of EdU-positive cells
(late-stage S) which are BrdU-negative, this sub-population being
the population of cells leaving S-phase before the BrdU-incorp.
Graph B is a graph of BrdU vs. DNA content showing these same
colored populations form graph A. Graph C is a graph of EdU vs DNA
content showing these same colored populations form graph A. Graphs
D and E show single parameter histograms for each EdU (graph D)
with the P3 marker showing the positive events for EdU; and BrdU
(graph E) with the P2 marker showing the positive events for
BrdU.
Example 14
[0158] A standard method of preparing cultured cells for the
measurement of newly synthesized DNA (cellular proliferation) is
set up according to known conditions for cells to be actively
growing by providing the proper media and nutrient requirements. In
the present example, Jurkat T-cell lymphocyte cell cultures were
diluted one to four to a density of 2.times.10.sup.5 cells/ml. The
cultures were treated with a cell cycle blocking agent, colchicine,
which stops proliferation at the G2M stage of the cell cycle, at
concentrations of 0, 32 nM, 75 nM, 125 nM, 250 nM, 500 nM and 1
.mu.M for 18 hours. To each condition, the first nucleoside analog,
EdU, was then added at 10 .mu.M, a concentration appropriate for
incorporation in the DNA of cells undergoing DNA synthesis. The
cells were grown in the presence of EdU for one hour. The cells
were then centrifuged to pellet the cells and remove the media with
blocking agent, and cells had replacement of fresh media. The cell
cultures were allowed to recover for two hours before an
appropriate amount of the second nucleoside analog, BrdU, was added
at a 10 .mu.M concentration, and the cells were grown for one hour.
The cells were then harvested, washed, fixed with 70% ice-cold ETOH
and stored at 4.degree. C. until use. The cells were then washed
and resuspended in 4M HCL for 20 minutes at room temperature. A
phosphate/critric acid buffer was added, and the cells washed twice
and resuspended in 0.1% TritonX/1% BSA/PBS at 1.times.10.sup.7/ml.
Then, labeling of the EdU was performed by adding click chemistry
based reagents, including a solution comprised of CuSO.sub.4 in
Tris-buffered saline and Alexa Fluor.RTM. 647-azide (650 nm
excitation maxima/670 nm emission maxima) (Molecular
Probes.TM./Invitrogen.TM., Carlsbad, Calif.). The cells were then
washed with 0.1% TritonX/1% BSA/PBS. After this, labeling of the
BrdU was performed using the anti-BrdU antibody FITC conjugate (494
nm excitation maxima/518 nm emission maxima) (Exalpha Biologicals,
Inc., Maynard Calif.). To detect DNA content, a nucleic acid dye,
DAPI (358 nm excitation maxima/461 nm emission maxima) (Molecular
Probes.TM./Invitrogen.TM., Carlsbad, Calif.) was added. Detection
of the three labels was performed by flow cytometry. To detect the
BrdU label, 488 nm excitation was used, with a 530/30 nm bandpass.
To detect the EdU label, 633 nm excitation was used, with a 660/20
nm bandpass. To detect DNA content, 355 nm excitation was used,
with a 450/50 nm bandpass.
[0159] FIG. 11 shows the percentage of cells which are EdU and BrdU
co-positive (Q2), EdU and BrdU co-negative (Q3), BrdU positive and
EdU negative (Q1), and BrdU negative and EdU positive (Q4) of the
seven different treatment conditions. The control, which has no
colchicine blocker added shows proliferation as detected by both
EdU and BrdU pulses. All of the concentrations of colchicine
treated cells shows decreased proliferation with both pulses of EdU
and BrdU, as expected. If there were some cell recovery during the
two hours after the removal of the colchicine, the BrdU percentage
is expected to increase. However, there is no recovery seen at any
colchicine concentration after the first EdU pulse from the removal
of the colchicine treatment, as seen by the second pulse of
BrdU.
[0160] FIGS. 12-1 and 12-2 present a series of result graphs,
labeled A through J, showing populations of cells treated with a
first pulse label of EdU (20 .mu.M) and a second pulse label of
BrdU (10 .mu.M) as detected by flow cytometry. Graphs A through E
represent the control cells untreated with colchicine, and Plots F
through J represent cells treated with 32 nM colchicine for 18
hours before the first pulse. Dual parameter graphs A and F are
divided into four quadrants with the first quadrant (Q1) located in
the upper left hand corner, the second quadrant (Q2) located in the
upper right hand corner, the third quadrant (Q3) located in the
lower left hand corner, and the fourth quadrant (Q4) located in the
lower right hand corner. Populations of cells in quadrant Q3 (lower
left, colored light blue) are negative for both EdU (first pulse)
and BrdU (second pulse). Populations of cells in quadrant Q2 (upper
right, colored dark blue) are positive for both EdU (first pulse)
and BrdU (second pulse). Populations of cells in quadrant Q1 (upper
left, colored light green) are positive for BrdU and negative for
EdU, a sub-population of BrdU-positive cells which are
EdU-negative, this sub-population being the population of cells
entering S-phase after the Edu only incorporation. Populations of
cells in Q4 (lower right, colored red) are positive for EdU and
negative for BrdU, a sub-population of EdU-positive cells
(late-stage S) which are BrdU-negative, this sub-population being
the population of cells leaving S-phase before the BrdU-incorp.
Graphs B and G are graphs of BrdU vs. DNA, C and H are graphs of
EdU vs DNA content showing these same colored populations form the
first plots A and F. Graphs D and I show single parameter
histograms for BrdU with two populations of cells distinguishable,
those cells which are positive for BrdU and those cells which are
negative for BrdU. Graphs E and J show single parameter histograms
for EdU with two populations of cells distinguishable, those cells
which are positive for EdU and those cells which are negative for
EdU. The control graphs (A through E) show higher EdU and BrdU
positive events, the expected proliferation for the cells, than the
graphs from the cells treated with 32 nM colchicine (F through J),
which show decreased proliferation as expected with the blocker
treatment.
* * * * *