Targeting the PPM1D phenotype; 2,4-bisarylthiazoles cause highly selective apoptosis in PPM1D amplified cell-lines

Article abstract of DOI:10.1016/j.bmcl.2014.05.067

The metal-dependent phosphatase PPM1D (WIP1) is an important oncogene in cancer, with over-expression of the protein being associated with significantly worse clinical outcomes. In this communication we describe the discovery and optimization of novel 2,4

Full text of DOI:10.1016/j.bmcl.2014.05.067

Accepted Manuscript
Targeting the PPM1D phenotype; 2,4-bisarylthiazoles cause highly selective
apoptosis in PPM1D amplified cell-lines
Matthew D. Cheeseman, Amir Faisal, Sydonia Rayter, Olivier R. Barbeau,
Andrew Kalusa, Maura Westlake, Rosemary Burke, Michael Swan, Rob van
Montfort, Spiros Linardopoulos, Keith Jones
PII:
S0960-894X(14)00576-9
DOI:
http://dx.doi.org/10.1016/j.bmcl.2014.05.067
BMCL 21681
Reference:
Bioorganic & Medicinal Chemistry Letters
To appear in:
Received Date:
Revised Date:
Accepted Date:
26 March 2014
16 May 2014
20 May 2014
Please cite this article as: Cheeseman, M.D., Faisal, A., Rayter, S., Barbeau, O.R., Kalusa, A., Westlake, M., Burke,
R., Swan, M., Montfort, R.v., Linardopoulos, S., Jones, K., Targeting the PPM1D phenotype; 2,4-bisarylthiazoles
cause highly selective apoptosis in PPM1D amplified cell-lines, Bioorganic & Medicinal Chemistry Letters (2014),
doi: http://dx.doi.org/10.1016/j.bmcl.2014.05.067
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers
we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and
review of the resulting proof before it is published in its final form. Please note that during the production process
errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Graphical Abstract
To create your abstract, type over the instructions in the template box below.
Fonts or abstract dimensions should not be changed or altered.
Targeting the PPM1D phenotype: 2,4-
bisarylthiazoles cause highly selective
apoptosis in PPM1D amplified cell-lines
Leave this area blank for abstract info.
Matthew D. Cheeseman, Amir Faisal, Sydonia Rayter, Olivier R. Barbeau, Andrew Kalusa, Maura
Westlake, Rosemary Burke, Michael Swan, Rob van Montfort, Spiros Linardopoulos, Keith Jones

Bioorganic & Medicinal Chemistry Letters
journal homepage: www.els evier.com
Targeting the PPM1D phenotype; 2,4-bisarylthiazoles cause highly selective
apoptosis in PPM1D amplified cell-lines
Matthew D. Cheeseman,a Amir Faisal,a Sydonia Rayter,a Olivier R. Barbeau,a Andrew Kalusa,a Maura
Westlake,a Rosemary Burke,a Michael Swan,a Rob van Montfort,a Spiros Linardopoulos,a Keith Jonesa,*
aCRUK Cancer Therapeutics Unit, The Institute of Cancer Research, London, SM2 5NG, U.K.
ARTICLE INFO
ABSTRACT
Article history:
Received
The metal-dependent phosphatase PPM1D (WIP1) is an important oncogene in cancer, with
over-expression of the protein being associated with significantly worse clinical outcomes. In
this communication we describe the discovery and optimization of novel 2,4-bisarylthiazoles
that phenocopy the knockdown of PPM1D, without inhibiting its phosphatase activity. These
compounds cause growth inhibition at nanomolar concentrations, induce apoptosis, activate p53
and display impressive cell-line selectivity. The results demonstrate the potential for targeting
phenotypes in drug discovery when tackling challenging targets or unknown mechanisms.
Revised
Accepted
Available online
Keywords:
Keyword_1 PPM1D
Keyword_2 Phenotype
Keyword_3 Apoptosis
Keyword_4 p53
2009 Elsevier Ltd. All rights reserved.
Keyword_5 2,4-Bisarylthiazole
Metal-dependent phosphatases play an important role in cell
signaling pathways and have been implicated in a number of
disease areas, including cancer. This family of proteins utilize
metal ions, typically magnesium(II), to catalyze the
dephosphorylation of serine and threonine residues on their target
proteins.1 Effectively, the role of the phosphatase is the opposite
to serine/threonine kinases, which phosphorylate their target
proteins. Metal-dependent phosphatases should represent a rich
source of targets to antagonize signaling pathways that induce
exploitable cellular phenotypes with potential for drug discovery.
Unfortunately, whilst kinases have become the second most
widely exploited target class for drug discovery, phosphatases
remain a long way behind. This lack of progress can be attributed
to the difficulties in mimicking the phosphopeptide substrates of
these proteins with drug-like small molecules.2
published inhibitor of PPM1D that can replicate the knockdown
phenotype.6
Phenotypic screens can offer a potential advantage when
dealing with challenging targets as complete understanding of the
mechanism by which a small molecule antagonizes a particular
pathway is not necessary. Even if the small molecule does not
bind to the target protein of interest, the critical signaling
pathway, of which that protein is part, can be assayed. If the
compound inhibits the pathway either upstream or downstream of
the target protein, a similar phenotype can be observed. The
small molecule can be developed without knowledge of the
actual target, circumventing the need to inhibit a potentially
undruggable protein.7
In this communication we describe the discovery and
development of a novel series of 2,4-bisarylthiazoles. These
compounds display potent in vitro cellular growth inhibition and
remarkable cell-line selectivity, which closely phenocopies
PPM1D siRNA knockdown.
Protein phosphatase Mg2+/Mn2+ dependent 1D (PPM1D), also
known as WIP1 and PP2Cδ, is a member of the PP2C family of
protein phosphatases and is located on the 17q23 chromosome.3
This metal-dependent phosphatase has been proposed to be an
important target in oncology. Over-expression of PPM1D
observed in tumor samples has been associated with aggressive
cancers and significantly diminished patient outcomes.4 Also, we
recently showed that siRNA knockdown of the PPM1D gene
selectively caused growth inhibition and apoptosis in cell-lines
that possess 17q23 chromosomal amplification, whilst non-
amplified cell-lines were unaffected.5 These results indicate the
potential role of PPM1D as an oncogene and a driver of
tumourigenesis. However, the difficulties associated with metal-
dependent phosphatases as drug targets mean there remains no
In our previous studies into the role of PPM1D as an oncogene
we were able to demonstrate that only cancer cell-lines with
PPM1D amplification, and which still possessed wild-type p53,
were susceptible to PPM1D siRNA knockdown, leading to
growth-inhibition and apoptosis.8 The tumor suppressor protein
p53 has been described as the “guardian of the genome”9 and is a
known substrate of PPM1D.10 We were able to show that
selective knockdown of PPM1D in susceptible cell-lines resulted
in increased levels of phosphoserine15-p53. Although, this did
not confirm a direct role for PPM1D-mediated dephosphorylation

of p53 as a driver of tumorigenesis in PPM1D-amplified cell-
lines, it did confirm phosphoserine15-p53 as an important
biomarker for the inhibition of the PPM1D pathway.
During a recent drug discovery program to investigate
substrate-competitive inhibitors of PPMID, we developed an
assay cascade involving initial assessment of compounds for
PPM1D inhibition using a malachite-green dephosphorylation
assay.11 Subsequent evaluation of hits from the biochemical
screen was then carried out by assaying for cell-line selectivity in
a growth inhibition assay between the PPM1D amplified cell-
line, SMOV2,12 and the non-amplified cell-line, TOV21G,13
using the SRB methodology.14 Finally, the induction of
biomarkers, phosphoserine15-p53 (P-S15-p53) and cleaved
PARP, were assayed via Western blot analysis. It was during this
process that we serendipitously discovered the 2,4-bisarylthiazole
compound 1 (Figure 1).
Scheme 1 Hantzsch thiazole synthesis
Firstly, the role of the 2-phenyl group and the importance of
the 4-fluoro substituent were investigated (Table 1). It was clear
that the 4-fluoro substituent of 1 was crucial to the activity
observed against the SMOV2 cell-line. Replacement with
hydrogen (Entry 2) resulted in a 200-fold drop in activity. Also,
the activity of the 4-fluoro group could not be replicated with
similar lipophilic substituents (Entries 3-4) or with potential
hydrogen bond acceptors (Entries 5-6). The position of the
fluorine substituent was also crucial as moving this group to the
3-postion (Entry 7) again caused a large drop in activity. No
compound displayed any measurable activity against the
TOV21G cell-line. The importance of the 4-fluoro substituent to
the activity of 1 was surprising but not without precedent. A
number of fluorophilic sites have been identified in various
proteins that are crucial for the activity of their respective
ligands.15 Owing to the importance of the 4-fluoro substituent for
activity this group was included in all subsequent compound
design.
Figure 1 2,4-Bisarylthiazole hit which phenocopies PPM1D knockdown
4-Fluorophenyl thiazole 1 displayed only weak inhibition of
PPM1D in the biochemical phosphatase assay, returning an IC50
= 23 µM. However, when this compound was analyzed in a 5-day
SRB assay against the SMOV2 cell-line, which was sensitive to
PPM1D siRNA knockdown, 1 gave a GI50 = 10 nM. In contrast,
when 1 was assayed against the TOV21G cell-line, which was
Table 1 SAR surrounding the 4-fluoro substituent of the thiazole series
insensitive to PPM1D knockdown, the compound gave a GI50
>
50 µM. Furthermore, 4-fluorophenyl thiazole 1 clearly induced
our biomarker for PPM1D inhibition, P-S15-p53, and caused cell
death through apoptosis, as indicated by cleaved PARP. Neither
biomarker was observed in the insensitive TOV21G cell-line
(Figure 2 and data not shown).
SMOV2 5db
TOV21G 5db
GI50 (µM)a
Entry
Compound
R
GI50 (µM)a
1
2
3
4
5
6
1
2
3
4
5
6
0.010
2.0
>50
>50
>50
>50
>50
>50
[1](μM)
0
1.25 2.5
5
0.63
24
Cleaved PARP
2.0
P-S15-p53
GAPDH
2.8
7
7
0.85
>50
Figure 2 Western blot analysis of 1 in SMOV2 cells
a
All results are an average of at least n=2, see supporting material for
conditions; b growth inhibition was analyzed after 5 days
It appeared unlikely that such potent growth-inhibition of the
SMOV2 cell-line could be caused by direct inhibition of PPM1D,
due to the modest activity of 1 in the biochemical phosphatase
assay. However, the remarkable selectivity of 1 for the PPM1D
amplified cell-line compared to the non-amplified cell-line led us
to hypothesize a potential role for PPM1D, or the PPM1D
pathway, in the activity of 1 against SMOV2. We therefore
decided to investigate further this novel and highly active small
molecule.
Substitution at the 2- and 3-positions of the phenyl group was
then investigated. Growth inhibition assays are known to be
dependent on the timeframe in which they are measured.16 Owing
to the low nanomolar activity of 1 in the 5-day assay we were
concerned that any improvements in activity would be difficult to
assess and SAR would be lost; therefore, we reduced the assay
window to 3 days in all subsequent experiments (Table 2).
Following the discovery of 4-fluorophenyl thiazole 1, we
decided to investigate the SAR leading to the potent growth-
inhibition observed against the SMOV2 cell-line. All compounds
in this series were generated by the Hantzsch thiazole synthesis
from the corresponding phenyl thioamides and α-
haloacetophenones (Scheme 1).

Table 2 2- and 3-position substitution of the thiazole series
Owing to the significantly increased activity of 2-methyl-4-
fluoro thiazole 12, this compound was tested in the PPM1D
malachite-green biochemical phosphatase assay but gave an IC50
> 100 µM. This result confirmed that the observed cellular
phenotype was not caused by the direct inhibition of the
phosphatase activity of PPM1D.17 The SAR surrounding the
benzoxazolidinone motif was then investigated (Table 3).
SMOV2 3db
TOV21G 3db
GI50 (µM)a
Entry
1
Compound
R
GI50 (µM)a
1
0.13
>50
Substitution of the benzoxazolidinone motif by oxindole 16
(Entry 1) and benzimidazolidinone 17 (Entry 2) were well
tolerated, returning equipotent compounds. Substitution at the 3-
position urea nitrogen, 18 (Entry 3), still gave a highly active
compound but substitution at the 4-position nitrogen 19 (Entry 4)
resulted in a dramatic loss of activity, indicating a possible role
for this group as a hydrogen bond donor.
2
3
8
9
0.29
0.25
>50
>50
4
5
6
7
8
9
10
11
12
13
14
15
>50
1.6
>50
>50
>50
>50
>50
>50
The compounds in the thiazole series generally displayed low
solubility, presumably due to their high lipophilicity (12 cLogP =
4.1) and low sp3-fraction.18 Since the SAR of this chemotype
indicated that the 2-position methylene group tolerated
substitution with little change in activity, we decided to further
explore this position in order to allow some control of the
physicochemical properties of these compounds (Table 4).
0.002
0.013
5.7
Table 4 2-Methylene solubilizing group analogues
0.023
a
All results are an average of at least n=2, see supporting material for
conditions, b growth inhibition was analyzed after 3 days
SMOV2 TOV21G
3db GI50
(µM)a
4-Fluorophenyl thiazole 1 (Entry 1) gave a GI50 = 130 nM in
the 3-day SRB assay against the SMOV2 cell-line, a 10-fold drop
in activity compared to the 5-day assay. Substitution at the 3-
position of the phenyl ring was well tolerated with the small
substituents fluoro (Entry 2) and methyl (Entry 3); however, the
incorporation of larger groups, such as trifluoromethyl (Entry 4),
and polar substituents, such as hydroxyl (Entry 5), significantly
reduced activity. These results suggest that the 4-fluoro-
substituent could be involved in a direct interaction that is
disrupted by proximal groups. Substitution at the 2-position was
more successful. Incorporation of a methyl group (Entry 6)
resulted in a ~50-fold increase in activity. This activity could be
maintained with larger substituents (Entry 7) as long as a
methylene group is directly attached to the phenyl ring, such as
benzyl alcohol 15 (Entry 9). In contrast, the reversed methyl
ether 14 (Entry 8) displayed a remarkable drop in activity. All
compounds again displayed no measurable growth inhibition
against the TOV21G cell-line.
Entry Compound
R
X
3db GI50
(µM)a
cLogPc
1
2
20
21
O
O
0.010
>50
>50
3.4
3.3
0.52
3
4
22
23
O
O
0.040
0.003
>50
>50
3.5
2.6
5
24
O
0.013
>50
4.2
6
7
25
26
O
0.002
0.013
>50
>50
3.1
3.1
NH
a
All results are an average of at least n=2, see supporting material for
c
conditions, growth inhibition was analyzed after 3 days, cLogP was
calculated using Chemdraw (12.0.2.1076)
b
Direct substitution at the 2-benzylic position was well
tolerated with small substituents, such as dimethylamine 20
(Entry 1), but a significant amount of activity was lost with larger
groups, such as morpholine 21 (Entry 2). We decided to extend
further out from the bisarylthiazole ring system to avoid what
appeared to be a clash with larger substituents. Homologating to
give dimethylamine ethylene 22 still resulted in a significant drop
in activity when compared to methyl derivative 12. Since
benzylic alcohol analogue 15 (Table 2, Entry 9) had retained
significant activity we decided to incorporate this motif into our
design. Aminoether 23 (Entry 4) displayed equipotency with
methyl analogue 12. The amine motif of 23 could be further
expanded to give tertiary amines such as 24, which displayed
good activity in the cellular assay. Finally, the benzoxazolidinone
MEM-ether 25 (Entry 6) and benzylimidazolidinone MEM-ether
26 (Entry 7) both displayed excellent activity with reduced
lipophilicity, as judged by cLogP.
Table 3 Benzoxazolidinone analogues
SMOV2 3db
TOV21G 3db
GI50 (µM)a
Entry
1
Compound
R
GI50 (µM)a
16
0.002
>50
>50
2
3
17
18
0.001
0.003
>50
>50
>50
Having optimized the 2,4-bisarylthiazole chemotype for
selective growth-inhibition of the PPM1D amplified cell-line
SMOV2 versus the non-amplified cell-line TOV21G, we decided
to assess how general this PPM1D amplification phenotype was
and whether our compounds were able to exploit this
4
19
a
All results are an average of at least n=2, see supporting material for
conditions, b growth inhibition was analyzed after 3 days

susceptibility. Benzimidazolidinone MEM-ether 26 was
examined in a 5-day SRB growth inhibition assay against various
PPM1D amplified and non-amplified cell-lines (Table 5).
Oestman, A.; Hellberg, C.; Boehmer, F. D. Nat. Rev. Cancer 2006, 6, 307;
Berndt, N. Emerging Therapeutic Targets 2000, 4, 581.
2 McCluskey, A.; Sim, A. T. R.; Sakoff, J. J. Med. Chem. 2002, 45, 1151.
3 Li, J; Yang, Y.; Peng, Y.; Austin, R. J.; van Eyndhoven, W. G.; Nguyen, K.
C.; Gabriele, T.; McCurrach, M. E.; Marks, J. R.; Hoey, T.; Lowe, S. W.;
Powers, S. Nat. Genet. 2002, 31, 133; Lambros, M. B. K.; Natrajan R.;
Geyer, F. C.; Lopez-Garcia, M. A.; Dedes, K. J.; Savage, K.; Lacroix-Triki,
M.; Jones, R. L.; Lord, C. J.; Linardopoulos, S.; Ashworth, A.; Reis-Filho, J.
S. Mod. Pathol. 2010, 23, 1334.
Table 5 Cell-line selectivity screen
4
PPM1D Non-
Amplified Cell-
lines
5-Day SRB
PPM1D
Amplified
Cell-lines
SMOV2
MCF7
5-Day SRB
assayb GI50
(µM)a
0.002
0.005
0.010
Lu, X.; Nguyen, T-A; Moon, S-H; Darlington, Y.; Sommer, M.;
Donehower, L. A.; Cancer and Metastasis Rev. 2008, 27, 123.
Tan, D. S. P.; Lambros, M. B. K.; Rayter, S.; Natrajan, R.; Vatcheva, R.;
assayb GI50
(µM)a
20
5
TOV21G
HeLa
Gao, Q.; Marchio, C.; Geyer, F. C.; Savage, K.; Parry, S.; Fenwick, K.;
Tamber, N.; MacKay, A.; Dexter, T.; Jameson, C.; McCluggage, W. G.;
Williams, A.; Graham, A.; Faratian, D.; El-Bahrawy, M.; Paige, A. J.; Gabra,
H.; Gore, M. E.; Zvelebil, M.; Lord, C. J.; Kaye, S. B.; Ashworth, A.; Reis-
Filho, J. S. Clin. Cancer Res. 2009, 15, 2269.
5.6
3.9
15
CAMA1
MDA MB 231
KPL1
a
All results are an average of at least n=2, see supporting material for
conditions, b growth inhibition was analyzed after 5 days
6
A recent publication by Kumar and coworkers describes a number of
alanine derivatives that were characterized as allosteric non-competitive
inhibitors of PPM1D phosphatase activity: Gilmartin,A. G.; Faitg, T. H.;
Richter, M.; Groy, A.; Seefeld, M. A.; Darcy, M. G.; Peng, X.; Federowicz,
K.; Yang, J.; Zhang, S-Y; Minthorn, E.; Jaworski, J-P; Schaber, M.; Martens,
S.; McNulty, D. E.; Sinnamon, R. H.; Zhang, H.; Kirkpatrick, R. B.; Nevins,
N.; Cui, G.; Pietrak, B.; Diaz, E.; Jones, A.; Brandt, M.; Schwartz, B.;
Heerding, D. A.; Kumar, R. Nat. Chem. Bio. 2014, 10, 181.
The non-amplified PPM1D cell-lines HeLa, CAMA1 and
MDA MB 231 were included with TOV21G in this small
selectivity screen.19 None of these four cell-lines was sensitive to
26, all returning GI50 > 1 µM and displaying no induction of the
biomarker P-S15-p53 when analyzed by Western blot. The two
breast cancer cell-lines MCF7 and KPL1 were included in the
cell-line selectivity screen as both are known to possess
significant PPM1D amplification, and are susceptible to PPM1D
siRNA knockdown.20 All three cell-lines displayed high
sensitivity to 26, leading to potent low nanomolar growth-
inhibition. MEM-ether 26 also displayed clear induction of P-
S15-p53, our biomarker for inhibition of the PPM1D pathway,
and cleaved PARP, indicating apoptosis, in the SMOV2 cell-line
(data not shown). The average selectivity-factor between the
PPM1D amplified and PPM1D non-amplified cell-lines in this
small panel was 1850-fold for compound 26.
7 Cai, S. X.; Drewe, J.; Kasibhatla, S. Curr. Med. Chem. 2006, 13, 2627.
8
Rayter, S.; Elliott, R.; Travers, J.; Rowlands, M. G.; Richardson, T. B.;
Boxall, K.; Jones, K.; Linardopoulos, S.; Workman, P.; Aherne, W.; Lord, C.
J.; Ashworth, A. Oncogene 2008, 27, 1036.
9 Lane, D. P. Nature 1992, 358, 15.
10
Park, H. K.; Panneerselvam, J.; Dudimah, F. D.; Dong, G.; Sebastian, S.;
Zhang, J.; Fei, P. Cell Cycle 2011, 10, 2574.
11
Conditions for this assay were adapted from: Hayashi, R.; Tanoue, K.;
Durell, S. R.; Chatterjee, D. K.; Miller Jenkins, L. M.; Appella, D. H.;
Appella, E. Biochemistry 2011, 50, 4537, using the cyclic-peptide described
within as a positive control. The protein used for this assay was a splice
variant of PPM1D comprising 420 residues of the 605 residue full-length
protein. For details see the supplementary data.
12 The SMOV2 cell-line was a donation and had previously been shown to be
both amplified and to over-express PPM1D and was sensitive to siRNA
knockdown of PPM1D, see: ref. 5 and Yonamine, K., Hayashi, K.; Iida, T.
Hum. Cell 1999, 12, 139.
In this communication we have described our discovery of a
novel series of cytotoxic 2,4-bisarylthiazoles. The chemical series
displayed excellent activity and remarkable selectivity for the
growth inhibition and apoptosis of PPM1D amplified cell-lines,
without any significant inhibition of PPM1D phosphatase
activity. The chemotype displayed clear SAR, with particular
importance for the cellular activity associated with the 4-
fluorophenyl substituent. We were also able to develop a vector
on the scaffold that could be used to change the physicochemical
properties of the compounds. Whether these compounds inhibit
the PPM1D pathway is more difficult to confirm. The cell-line
selectivity and the induction of the P-S15-p53 biomarker support
a role for PPM1D in their activity. However, the number of cell-
lines tested represents only a fraction of those available. More
work is needed to identify PPM1D-amplified cell-lines from
commercially available sources that are susceptible to PPM1D
siRNA knockdown. Also, the P-S15-p53 biomarker is not unique
for PPM1D and no unique substrates of PPM1D are currently
known. We believe this series of novel 2,4-bisarylthiazoles
demonstrate interesting biology and we are currently pursuing
their molecular target. This work shows that the PPM1D-
amplified phenotype may represent a viable oncology target.
13 The TOV21G cell-line was purchased from ATCC and had previously been
shown to be non-amplified and not to over-express PPM1D or to be sensitive
to siRNA knockdown of PPM1D, see: ref. 5.
14 Vichai, V.; Kirtikara, K. Nat. Protocols 2006, 1, 1112.
15
Hughes, D. L.; Sieker, L. C.; Bieth, J.; Dimicoli, J. L. J. Mol. Biol. 1982,
162, 645; Cox, C. D.; Breslin, M. J.; Mariano, B. J.; Coleman, P. J.; Buser, C.
A.; Walsh, E. S.; Hamilton, K.; Huber, H. E.; Kohl, N. E.; Torrent, M.; Yan,
Y.; Kuo, L. C.; Hartman, G. D. Bioorg. Med. Chem. Lett. 2005, 15, 2041.
16
Houghton, P.; Fang, R.; Techatanawat, I.; Steventon, G.; Hylands, P. J.;
Lee, C. C. Methods 2007, 42, 377.
17 No compounds of this chemotype displayed IC50<20 µM when assayed
against PPM1D.
18 Lovering, F.; Bikker, J.; Humblet, C. J. Med. Chem. 2009, 52, 6752.
19
The HeLa cell-line was purchased from ATCC and has previously been
shown to be non-amplified and not to over-express PPM1D and to be
insensitive to siRNA knockdown of PPM1D, see ref. 8. CAMA1 and MDA
MB 231 were purchased from ATCC and are known to be non-amplified and
not to over-express PPM1D and were insensitive to siRNA knockdown of
PPM1D, see: Parssinen, J.; Alarmo, E-L; Karhu, R.; Kallioniemi, A. Cancer
Genet. Cytogenet. 2008, 182, 33.
20
MCF7 was purchased from ATCC and KPL1 was purchased from the
Leibniz Institute DSMZ-German Collection of Microorganisms and Cell
Cultures. Both cell-lines have previously been shown to be amplified and to
over-express PPM1D and are sensitive to siRNA knockdown of PPM1D, see
ref. 8.
Acknowledgements
This work was supported by Cancer Research UK grant
numbers C309/A8274 and C309/A11566, and by The Institute of
Cancer Research.
References and notes
1
Lazo, J. S.; Wipf, P. Curr. Opin. Invest. Drugs 2009, 10, 1297; Hardy, S.;
Julien, S. G.; Tremblay, M. L. Anti-Cancer Agents Med. Chem. 2012, 12, 4;