Identification of a non-phosphorylated, cell permeable, small molecule ligand for the Stat3 SH2 domain

Article abstract of DOI:10.1016/j.bmcl.2011.06.056

Signal transducer and activator of transcription 3 (Stat3) protein is a cytosolic transcription factor that is aberrantly activated in numerous human cancers. Inhibitors of activated Stat3-Stat3 protein complexes have been shown to hold therapeutic promis

Full text of DOI:10.1016/j.bmcl.2011.06.056

Bioorganic & Medicinal Chemistry Letters 21 (2011) 5605–5609
Contents lists available at ScienceDirect
Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
Identification of a non-phosphorylated, cell permeable, small molecule ligand
for the Stat3 SH2 domain
Brent D. G. Page a, Steven Fletcher a, Peibin Yue b, Zhihua Li c, Xiaolei Zhang b, Sumaiya Sharmeen d,
Alessandro Datti e, Jeffrey L. Wrana e,f, Suzanne Trudel c, Aaron D. Schimmer d, James Turkson b,
Patrick T. Gunning a,
⇑
a Department of Chemistry, University of Toronto Mississauga, 3359 Mississauga Road, Mississauga, ON, Canada L5L 1C6
b Department of Molecular Biology and Microbiology, Burnett College of Biomedical Sciences, University of Central Florida, Orlando, FL 32826, USA
c Princess Margaret Hospital, McLaughlin Centre for Molecular Medicine, 620 University Avenue, Toronto, ON, Canada M5G 2C1
d Ontario Cancer Institute/Princess Margaret Hospital, 610 University Avenue, Toronto, ON, Canada M5G 2M9
e Center for Systems Biology, Samuel Lunenfeld Research Institute, Mount Sinai Hospital, Toronto, ON, Canada M5G 1X5
f Department of Molecular Genetics, University of Toronto, ON, Canada M5S 1A8
a r t i c l e i n f o
a b s t r a c t
Article history:
Available online 30 June 2011
Signal transducer and activator of transcription 3 (Stat3) protein is a cytosolic transcription factor that is
aberrantly activated in numerous human cancers. Inhibitors of activated Stat3–Stat3 protein complexes
have been shown to hold therapeutic promise for the treatment of human cancers harboring activated
Stat3. Herein, we report the design and synthesis of a focused library of salicylic acid containing Stat3
SH2 domain binders. The most potent inhibitor, 17o, effectively disrupted Stat3–phosphopeptide com-
plexes (Ki = 13 lM), inhibited Stat3–Stat3 protein interactions (IC50 = 19 lM) and silenced intracellular
Stat3 phosphorylation and Stat3-target gene expression profiles. Inhibition of Stat3 function in both
breast and multiple myeloma (MM) tumor cells correlated with induced cell death (EC50 = 10 and
16 lM, respectively).
Keywords:
Stat3
Cancer therapeutics
Jak/Stat pathway
Protein–protein interaction
Inhibitors of apoptosis
Ó 2011 Elsevier Ltd. All rights reserved.
Introduction: As a master regulator of oncogenic cellular
processes, signal transducer and activator of transcription (Stat) 3
protein has become the focus of molecularly targeted anti-cancer
therapeutic development. Stat3 protein is a cytosolic transcription
factor that plays a key role in mediating cell division and apopto-
sis.1,2 Stat3 signaling is initiated by extracellular cytokine3 or
growth factor4 receptor stimulation and results in the expression
of anti-apoptotic proteins that control cell growth and survival.2,5
As part of the signaling cascade, Stat3 is recruited to the intracellu-
lar domain of the target receptor, where it is phosphorylated on
Tyr705.6–8 Once phosphorylated, Stat3 dissociates, binds another
activated Stat3 monomer through reciprocal Src Homology 2
(SH2) domain–phosphotyrosine interactions and translocates to
the nucleus. Once in the nucleus, dimeric Stat3 binds to DNA and
promotes the transcription of proteins that govern cell cycling
and prevent apoptosis.5–8 In healthy cells, Stat3 activity is transient
and tightly controlled by supressors of cytokine signaling, phos-
phpatases and proteosomal degradation.9 In many human cancers,
however, Stat3 activity is hyperactivated leading to overexpression
and accumulation of anti-apoptotic proteins within the cell. Ele-
vated levels of Stat3 activation confer resistance to natural apopto-
tic cues and allows for rapid proliferation and de novo
tumorogenesis. Aberrantly activated Stat3 is found in numerous
human cancers including leukemia and lymphoma, as well as can-
cers of the breast, prostate, lung, head, neck, and ovaries.2,9–11
Numerous studies have demonstrated that inhibition of Stat3
activation leads to reduced levels of Stat3-target gene expression
profiles and correlates with programmed cell death.12–14 To date,
effective disruption of Stat3 function has been achieved primarily
through inhibition of transcriptionally active Stat3–Stat3 dimers.
The Stat3–Stat3 binding complex is characterized by large, non-
contiguous intrafacial surface areas possessing few targetable
binding sites.12 As a result, the development of potent small-mol-
ecule Stat3 inhibitors remains a challenging task. The majority of
published Stat3 inhibitors bind Stat3’s phosphopeptide binding
SH2 domain (Fig. 1).11–13,15–17
We have recently identified a potent salicylic acid-based Stat3
inhibitor, 7 (SF-1-0666 (or 27 h)18) after a structure–activity rela-
tionship (SAR) study of compound 1 (S3I-201, Fig. 1). Inhibitor 7
showed promising anti-Stat3 activity both in vitro, disrupting Stat3
protein–phoshopeptide and Stat3–Stat3 protein–protein interac-
tions and elicited in vivo suppression of breast tumor xenografts.19
Moreover, fluorescence polarization binding experiments showed
that 7 is selective for Stat3’s SH2 domain cf. Stat5 and Stat1 iso-
⇑
Corresponding author.
E-mail address: patrick.gunning@utoronto.ca (P.T. Gunning).
forms (Stat3 Ki = 15 lM; Stat5, Ki >25 lM; Stat1, Ki >25 lM).
0960-894X/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2011.06.056

5606
B. D. G. Page et al. / Bioorg. Med. Chem. Lett. 21 (2011) 5605–5609
O
O
(100–0.19 lM final concentrations). The fluorescent probe was
O
O
HO
S
HN
S
added at a final concentration of 10 nM. Protein, inhibitor and
probe were combined and incubated for 15 min prior to analysis.
Polarized fluorescence was plotted against concentration and fitted
using a standard dose response curve. Ki values were calculated
using the formula below where [STAT3] = 150 nM and Kd = 150 nM.
O
O
NH
S
O
O
O
OH
O
O
HO
HO
OH
O
HO
2
3
1
STA-21
Cpd188
S3I-2001
IC50
H
N
Ki ¼
H
O
N
½STAT3ꢀ
O
N
O
1 þ
Kd
O
S
O
N
O
NO2
N
O
Whole cell cytotoxicity assays: Human cell lines, DU145, OCI-
AML2 and JJN3 were prepared in 96 well plates and treated with
varying concentration of inhibitor. After 72 h, cell growth and via-
bility was measured with the CellTiter96 aqueous non-radioactive
(MTS) assay according to the manufacturer’s instructions (Prome-
ga, Madison, WI) and as described previously.22 Relative viability
was plotted versus concentration and EC50 was determined by fit-
ting to a standard dose response curve.
O
P
HO
N
HO
O
4
5
6
STX-0119
Stattic
S3I-M2001
Figure 1. Small molecule Stat3 SH2 domain binders.
Immunoblotting: Cells were lysed in lysis buffer (50 mM Tris–
HCl, 1 mM EDTA, 1% NP-40, 150 mM NaCl) for 30 min on ice, then
freeze/thaw once at ꢁ80 °C and clarified by centrifugation at
12000g for 15 min. Proteins were separated by 6.5–15% sodium
dodecyl–polyacrylamide gel electrophoresis (SDS–PAGE) and
immunoblotted with the specified antibody. Protein bands were
visualized using secondary antibodies coupled to horseradish per-
oxidase and the Chemiluminescence Reagent Plus (from Perkin
Elmer Life Sciences) according to the manufacturer’s instructions.
Anti-cMyc was purchased from Santa Cruz, anti-survivin from
NOVUS Biologicals, Anti-Mcl-1, and anti-Bcl-xL from BD Biosci-
ences, (Mississauga, ON), anti-phospho STAT3, anti-STAT3 and
anti-PARP are from Cell Signaling Technology, (Pickering, ON).
Results and discussion: A family of 16 novel sulfonamide ana-
logs of 7 were prepared as outlined in Scheme 1. Briefly, 4-amino-
salicylic acid (8) was doubly benzylated in one pot using potassium
tert-butoxide and benzyl bromide. Next, aniline 9 was reductively
aminated with 4-cyclohexylbenzaldehyde using NaCNBH3. In par-
allel, we TFA protected the amino group of sarcosine tert-butyl es-
ter (11) to furnish 12, and then removed the tert-butyl ester under
acidic conditions (TFA/CH2Cl2) to yield the carboxylic acid, 13. Con-
densation of 13 with secondary aniline 10 furnished tertiary
amide, 14. The TFA protecting group was then removed by LiOH
mediated hydrolysis revealing secondary amine, 15. In the penulti-
mate step we coupled a diverse variety of sulfonyl chlorides to 15,
yielding compounds, 16a–o. Finally, hydrogenolysis conditions
(H2, 10% Pd/C) were employed to debenzylate the salicylic acid
moiety, exposing final compounds 17a–o. Of note, in cases where
hydrogenolysis conditions were incompatable with the sulfonyl
substituent (17f, 17j, 17k, and 17n), we employed a step-wise,
TFA mediated debenzylation of phenol, followed by LiOH hydroly-
sis of the benzyl ester (Scheme 1, steps i and j).23
Figure 2. GOLD docking studies of 7 bound to Stat3’s SH2 domain.6
Encouragingly, 7 showed negligible effects against ‘healthy’ cells
lacking activated Stat3 (NIH3T3, TE-71, and HPDEC) and selectively
killed cancer cells harboring aberrant Stat3 activity.19 GOLD20
docking studies revealed that compound 7 binds to the pTyr-bind-
ing portion of the SH2 domain, with the salicylic acid making inter-
actions with Lys591, Glu594 and Arg609.6,19 In addition, the
hydrophobic cyclohexyl-benzyl appendage forms van der Waal’s
interactions with a series of predominantly hydrophobic residues
(Fig. 2).
In this study we investigated the binding significance of the tol-
uene-sulfonamide substituent to Stat3-SH2 domain recognition.
We herein report an SAR of the sulfonamide portion of compound
7, and present novel analogs, including 17o, which exhibited im-
proved inhibition of Stat3 function both in vitro and in whole cell
tumor models of breast and multiple myeloma cancers.
Materials and methods. Electrophoretic Mobility Shift Assay:
EMSA analysis was performed as previously reported.6,19 Nuclear
extracts of NIH3T3/vSrc cells were pre-incubated with varying
concentrations of compounds for 30 min at room temperature
prior to incubation with 32P-labeled oligonucleotide probe, hSIE
(high affinity sis-inducible element from the c-fos gene, m67 vari-
ant, 50-AGCTTCATTTCCCGTAAATCCCTA) for 30 min at 30 °C before
subjecting to EMSA analysis. DNA-binding activities were mea-
sured for each band at each concentration of inhibitor and quanti-
fied using ImageQuant. Results were plotted as percent of control
from which an IC50 value could be derived.
We first assessed for inhibitor induced Stat3–Stat3 dimer dis-
ruption using a routinely used Electrophoretic Mobility Shift Assay
(EMSA), which measures dimer disruption through inhibition of
DNA binding.24 As illustrated in Table 1, varying the sulfonamide
substituent resulted in varying degrees of inhibition potency. We
incorporated a range of appendages to cater for the relatively
amphiphilic pocket composed of residues Ile634, Ser636, Glu594
and the hydrophobic chain of Lys591. In general, hydrophobic R
groups afforded the most potent inhibitors. The polar 17h, incorpo-
rating a 1-methyl-1H-imidazole group, lost all inhibitory potency
Fluorescence polarization assay: As previously reported,6,21 fluo-
rescence polarization experiments were performed on an Infinite
M1000 (Tecan, Crailsheim, Germany) using black 384-round bot-
tom well plates (Corning), and buffer containing 50 mM NaCl,
10 mM Hepes, pH 7.5, 1 mM EDTA, and 2 mM dithiothreitol and
a final concentration of 5% DMSO. Stat3 protein (150 nM) was
treated with varying concentrations of inhibitor compounds
(IC50 >300
17a significantly reduced activity, (17a (meta-) IC50 = 118.8
cf. 7 (para-) IC50 = 35 M)). The bulkier 2,4,6-tri-methylphenyl
substituted inhibitor, 17b exhibited weaker activity than the par-
ent compound 7, with an IC50 = 51.9 M. The larger biphenyl sul-
fonamide, 17c, was a modest inhibitor of Stat3 dimerization
lM). Interestingly, employing the meta-tolyl isomer
lM
l
l

B. D. G. Page et al. / Bioorg. Med. Chem. Lett. 21 (2011) 5605–5609
5607
Scheme 1. Reagents and conditions: (a) BnBr (2 equiv), KOtBu, DMF, 0 °C, 16 h, 73%; (b) 4-cyclohexylbenzaldehyde, AcOH, NaCNBH3, rt, 16 h, 79%; (c) (CF3CO)2O, DIPEA,
CH2Cl2, rt, 3 h, 96%; (d) TFA/CH2Cl2, 1:1, rt, 5 h, 100%; (e) 10, PPh3Cl2, CHCl3, 60 °C, 12 h, 97%; (f) LiOHꢂH2O, THF/H2O, 3:1, rt, 10 min, 98%; (g) RSO2Cl, DIPEA, CH2Cl2, rt, 16 h,
78–98%; (h) H2, 10% Pd/C, MeOH/THF, 1:1, rt, 1–16 h, 85–100%; or for 17f, 17j, 17k, and 17n: (i) LiOHꢂH2O, THF/H2O, 3:1, rt, 24 h, 73–89%; j) TFA / CH2Cl2, 1:2, rt, 16 h, 65–92%.
(IC50 = 65.4
(IC50 = 79.2
l
l
M), as was the 2-naphthyl derivative, 17d
M). Notably, bis-aryl sulfonyl derivatives substituted
proteins found in the nuclear extracts. Taken together, the EMSA
and FP results suggest that we are able to disrupt Stat3–phosho-
peptide and Stat3–Stat3 complexation events by effectively block-
ing the Stat3 SH2 domain.
at the 1-position, including, 17e (R = 1-naphthyl, IC50 = 28.8
17f (R = 8-quinolinyl, IC50 = 25 M) and 17g (R = dansyl,
IC50 = 29 M) proved to be active Stat3 inhibitors. Taken together,
lM),
l
l
Since blockage of Stat3 signaling in compromised cell lines
leads to induced apoptosis,25 we reasoned that our most potent
inhibitors would kill cells harboring activated Stat3. Thus, we em-
ployed an MTS assay to assess the whole cell potency of select
inhibitors including, 7, 17e, and 17o, which showed activity in both
EMSA and FP-assays.26,27 DU145 (prostate), MDA-468 (breast) and
JJN3 (multiple myeloma) cancer cells were incubated for 72 h with
varying concentrations of inhibitors and relative viability assessed
colorometrically after treatment with MTS for 3 h. Notably, com-
pound 17o displayed an approximately 2-fold increase in potency
these data suggest that substitution of the ortho- and meta-tolyl
positions of 7, with a second aryl group is better tolerated than
in the para position. In general, replacement of the methyl group
in the para-tolyl moiety of 7 with different isosteres (F, Br, Cl,
OMe, NO2) led to a reduction in Stat3 inhibitory activity. However,
17o, incorporating a pentafluorophenyl sulfonamide substituent,
proved to be the most active of the phenyl sulfonamide series. In-
deed, 17o was approximately 2-fold more potent as the parent
compound 7 (17o, IC50 = 19 lM cf. 7, IC50 = 35 lM).
Next, we investigated the binding potency of select agents
against Stat3’s SH2 domain via a routinely used fluorescence polar-
ization assay, the results of which are shown in Table 2. Encourag-
over 7, with IC50 values of 10, 23, and 17 lM in breast, prostate and
MM cells, respectively (Table 3). Compound 17e showed lower
activity in cells than both 7 and 17o, possibly a result of increased
lipophilicity and poorer water solubility (17e, log P = 5.95 vs 17o,
log P = 5.74). We noted that 17o exhibited much improved water
solubility over both 7 and 17e. While the in vitro activities of
17o and 7 are comparable, we postulated that the resultant in-
crease in cellular activity may be a result of greater cell permeabil-
ity and reduced aggregation/precipitation.
ingly, compounds 17b (Ki = 8.0
lM), 17c (Ki = 6.2
lM), 17g
(Ki = 13.3 M), 17k (Ki = 11.0 M) and 17o (Ki = 12.8 l
l
l
M) exhibited
improved activity compared to compound 7. Although similar
trends were observed in the EMSA and FP data, there are some
notable deviations between the two data sets of data. For example,
compound 17b, IC50 = 51.9
more potent in the FP assay (Ki = 8.0
l
M in the EMSA assay is significantly
l
M). As previously reported,6
Due to the promising cytotoxic activity observed in tumor cells,
17o was assayed for inhibition of Stat3 phosphorylation in both
MDA-468 and JJN3 cell lines harboring activated Stat3 (Fig. 3).28,29
this anomaly between EMSA analysis of nuclear extracts, and the
FP assay is likely due to the presence of other Stat isoforms and

5608
B. D. G. Page et al. / Bioorg. Med. Chem. Lett. 21 (2011) 5605–5609
Table 1
EMSA inhibition data for the disruption of the Stat3–Stat3–DNA complex by
Table 3
sulfonamide analogs 7 and 17a–17o
Whole cell MTS data. Cells were treated with varying concentrations of inhibitors for
72 h
O
O
R
N
S
N
O
N
O
R
N
S
HO
O
HO
O
O
OH
O
OH
Inhibitor
R
IC50
(lM)
Inhibitor
R
IC50
(lM)
Inhibitor
R
MDA-468
17.0 4.4
EC50
(
l
M) DUI 45
JJN3
7
35
9
17h
>300
7
37.2 12.4
74.5 30.2
93.3 15.8
17a
17b
118.8 1.9
51.9 2.4
65.4 7.1
17i
17j
17k
126.2 5.3
90.3 4.5
17e
17o
46.5 12.4
10.9 3.0
106. 13.7
16.7 0.7
F
F
F
F
22.7 8.5
N
F
17c
17d
67.2 2.6
>300
N
N
79.2 11.2 17l
N
NC
17e
17f
28.8
2
17m
17n
67.4 4.9
62.2 3.2
Br
Cl
24.6 3.4
28.8 1.9
F
MeO
F
F
F
F
O2N
17g
17o
19.7 5.4
F
Table 2
Fluorescence polarization assay binding data (Ki values in
l
M)
Figure 3. SDS–PAGE and Western blotting analysis of whole cell lysates prepared
from MDA-468 human breast cancer and multiple myeloma JJN3 cells, untreated
(DMSO, control) or treated with 17o (15
125 M) for 24 h and subjected to immunoblotting analysis for pY705Stat3, Stat3,
c-Myc, Bcl-xL, Mcl-1 and Survivin.
lM), 17e (125 or 150 lM), and 7 (100 or
l
O
O
R
N
S
N
HO
O
O
OH
Inhibitor
R
Ki (
l
M)
Inhibitor
R
Ki (
l
M)
period revealed that 17o effectively reduced levels of Stat3 down-
stream targets, including, cMYC, Bcl-xL and Survivin. We presume
that the resultant cytotoxicity observed after 72 h incubation is a
result of 17o/7-induced inhibition of intracellular Stat3 signaling.
The data shows that 17o is a more potent whole cell inhibitor of
Stat3 function than lead compound, 7, presumably due to improved
solubility and cell permeability. We will conduct further investiga-
tions to elucidate the biological and biochemical mechanisms of
17o’s improved anti-cancer activity which will be published
elsewhere.
Conclusion: We have presented the design and synthesis of a
novel family of Stat3 inhibitors that exhibit promising in vitro
binding potency for the Stat3 SH2 domain, as well as improved tu-
mor whole cell activity. Most notably, hit compound, 17o, showed
an approximately 2- to 4-fold increase in in vitro activity compared
to lead agent, 7, and nearly 6-fold higher potency in JJN3 MM tu-
mor cells. Future studies seek to evaluate the in vivo properties
of 17o in MM and breast tumor xenograft models. Thus, to date,
17o represents the most potent Stat3 inhibitor derived from the
salicylic acid-based class of inhibitors.
7
15.5 4.7
8.0 2.4
17g
13.3 0.6
>100
17b
17h
N
17c
17e
6.2 2.0
17i
30.6 11
11.0 0.3
N
N
26.5 0.4
17k
N
NC
F
F
F
F
Cl
17f
41.0 0.4
17o
12.8 0.3
F
As a control, Western blot analysis showed that control inhibitor, 7
effectively knocked down Stat3 phosphorylation at approximately
100
ingly, 17o inhibited Stat3 phosphorylation at significantly lower
concentrations (20 M) in intact cells after 24 h. Furthermore,
immunoblotting analysis of the same cell lines after the same time
l
M in both MDA-468 and JJN3 cancer cells. Most encourag-
Acknowledgments
l
This work was supported by NSERC (PTG), University of Toronto
(PTG), Canadian Foundation for Innovation (PTG) and by the Na-

B. D. G. Page et al. / Bioorg. Med. Chem. Lett. 21 (2011) 5605–5609
5609
14. Turkson, J.; Kim, J. S.; Zhang, S.; Yuan, J.; Huang, M.; Glenn, M.; Haura, E.; Sebti,
S.; Hamilton, A. D.; Jove, R. Mol. Cancer Ther. 2004, 3, 261.
15. Bhasin, D.; Cisek, K.; Pandharkar, T.; Regan, N.; Li, C.; Pandit, B.; Lin, J.; Li, P. K.
Bioorg. Med. Chem. Lett. 2008, 18, 391.
tional Cancer Institute Grants CA106439 (JT) and CA128865 (JT)
and an Ontario Graduate Schoralship (BDGP). Aaron Schimmer is
a Leukemia and Lymphoma Society Scholar in Clinical Research.
16. Matsuno, K.; Masuda, Y.; Uehara, Y.; Sato, H.; Muroya, A.; Takahashi, O.;
Yokotagawa, T.; Furuya, T.; Okawara, T.; Otsuka, M.; Ogo, N.; Ashizawa, T.;
Oshita, C.; Tai, S.; Ishii, H.; Akiyama, Y.; Asai, A. A. C. S. Med. Chem. Lett. 2010, 1,
371.
Supplementary data
17. Xu, X.; Kasembeli, M. M.; Jiang, X.; Tweardy, B. J.; Tweardy, D. J. PLoS ONE 2009,
4.
18. Fletcher, S.; Page, B. D. G.; Zhang, X.; Yue, P.; Li, Z. H.; Sharmeen, S.; Singh, J.;
Zhao, W.; Schimmer, A. D.; Trudel, S.; Turkson, J.; Gunning, P. T. ChemMedChem
2011, In Press, doi:10.1002/cmdc.201100194.
19. Zhang, X.; Yue, P.; Fletcher, S.; Zhao, W.; Gunning, P. T.; Turkson, J. Biochem.
Pharmacol. 2010, 79, 1398.
20. Jones, G.; Willett, P.; Glen, R. C.; Leach, A. R.; Taylor, R. J. Mol. Biol. 1997, 267,
727.
Supplementary data (characterization of all chemical com-
pounds and representative results from EMSA, FP and whole cell
cytotoxicity assays) associated with this article can be found, in
the online version, at doi:10.1016/j.bmcl.2011.06.056.
References and notes
21. Schust, J.; Berg, T. Anal. Biochem. 2004, 330, 114.
1. Page, B. D. G.; Ball, D. P.; Gunning, P. T. Exp. Opin. Ther. Pat. 2011, 21, 65.
2. Fletcher, S.; Drewry, J. A.; Shahani, V. M.; Page, B. D. G.; Gunning, P. T. Biochem.
Cell Biol. 2009, 87, 825.
3. Leonard, W. J. Nat. Med. 1996, 2, 968.
4. Herrington, J.; Carter-Su, C. Trends Endocrin. Met. 2001, 12, 252.
5. Darnell, J. E., Jr. Science 1997, 277, 1630.
6. Fletcher, S.; Singh, J.; Zhang, X.; Yue, P.; Page, B. D. G.; Sharmeen, S.; Shahani, V.
M.; Zhao, W.; Schimmer, A. D.; Turkson, J.; Gunning, P. T. ChemBioChem 2009,
10, 1959.
7. Bromberg, J.; Darnell, J. E., Jr. Oncogene 2000, 19, 2468.
8. Bowman, T.; Garcia, R.; Turkson, J.; Jove, R. Oncogene 2000, 19, 2474.
9. Lai, S. Y.; Johnson, F. M. Drug Resist. Update. 2010, 13, 67.
10. Fletcher, S.; Turkson, J.; Gunning, P. T. ChemMedChem 2008, 3, 1159.
11. Schust, J.; Sperl, B.; Hollis, A.; Mayer, T. U.; Berg, T. Chem. Biol. 2006, 13, 1235.
12. Gunning, P. T.; Glenn, M. P.; Siddiquee, K. A.; Katt, W. P.; Masson, E.; Sebti, S.
M.; Turkson, J.; Hamilton, A. D. ChemBioChem 2008, 9, 2800.
13. Siddiquee, K.; Zhang, S.; Guida, W. C.; Blaskovich, M. A.; Greedy, B.; Lawrence,
H. R.; Yip, M. L. R.; Jove, R.; McLaughlin, M. M.; Lawrence, N. J.; Sebti, S. M.;
Turkson, J. Proc. Natl. Acad. Sci. U.S.A. 2007, 104, 7391.
22. Simpson, C. D.; Mawji, I. A.; Anyiwe, K.; Williams, M. A.; Wang, X.; Venugopal,
A. L.; Gronda, M.; Hurren, R.; Cheng, S.; Serra, S.; Zavareh, R. B.; Datti, A.;
Wrana, J. L.; Ezzat, S.; Schimmer, A. D. Cancer Res. 2009, 69, 2739.
23. Fletcher, S.; Gunning, P. T. Tetrahedron Lett. 2008, 49, 4817.
24. Turkson, J.; Ryan, D.; Kim, J. S.; Zhang, Y.; Chen, Z.; Haura, E.; Laudano, A.; Sebti,
S.; Hamilton, A. D.; Jove, R. J. Biol. Chem. 2001, 276, 45443.
25. Bromberg, J. J. Clin. Invest. 2002, 109, 1139.
26. Scudiero, D. A.; Shoemaker, R. H.; Paull, K. D.; Monks, A.; Tierney, S.; Nofziger,
T. H.; Currens, M. J.; Seniff, D.; Boyd, M. R. Cancer Res. 1988, 48, 4827.
27. Alley, M. C.; Scudiero, D. A.; Monks, A.; Hursey Czerwinski, M. L. M. J.; Fine, D.
L.; Abbott, B. J.; Mayo, J. G.; Shoemaker, R. H.; Boyd, M. R. Cancer Res. 1988, 48,
589.
28. Sartor, C. I.; Dziubinski, M. L.; Yu, C. L.; Jove, R.; Ethier, S. P. Cancer Res. 1997, 57,
978.
29. Brenne, A. T.; Ro, T. B.; Waage, A.; Sundan, A.; Borset, M.; Hjorth-Hansen, H.
Blood 2002, 99, 3756.