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ABSTRACT: A common strategy for preparing tryptophan-derived epidithiodioxopiperazine (ETP) natural products containing a hydroxyl substituent adjacent to a quaternary carbon stereocenter is reported. This strategy is exemplified by enantioselective total syntheses of four heptacyclic ETP natural products-gliocladine C (6), leptosin D (7), T988C (8), and bionectin A (9)-starting with the di-(tert-butoxycarbonyl) derivative 17 of the trioxopiperazine natural product gliocladin C, which is readily available by enantioselective chemical synthesis. In addition, total syntheses of the enantiomer of gliocladine C (ent-6) and gliocladin A (11), the di(methylthio) congener of bionectin A, are reported. These syntheses illustrate a synthetic strategy wherein diversity in the dioxopiperazine unit of ETP natural products is introduced at a late stage in a synthetic sequence. In vitro cytotoxicity of compounds in this series against invasive human prostrate (DU145) and melanoma (A2058) cancer cell lines is described and compared to that of chaetocin A (4).
Journal of the American Chemical Society 03/2013; · 9.91 Impact Factor
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ABSTRACT: The total syntheses of amphidinolide B(1) and the proposed structure of amphidinolide B(2) have been accomplished. Key aspects of this work include the development of a practical, non-transition-metal-mediated method for the construction of the C(13)-C(15) diene, the identification of α-chelation and dipole minimization models for diastereoselective methyl ketone aldol reactions, the discovery of a spontaneous Horner-Wadsworth-Emmons macrocyclization strategy, and the development of a novel late stage method for construction of an allylic epoxide moiety. The originally proposed structure for amphidinolide B(2) and diastereomers thereof display potent antitumor activities with IC(50) values ranging from 3.3 to 94.5 nM against human solid and blood tumor cells. Of the different stereoisomers, the proposed structure of amphidinolide B(2) is over 12-fold more potent than the C(8,9)-epimer and C(18)-epimer in human DU145 prostate cancer cells. These data suggest that the epoxide stereochemistry is a significant factor for anticancer activity.
The Journal of Organic Chemistry 02/2013; · 4.45 Impact Factor
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Sangkil Nam,
Wei Wen,
Anne Schroeder,
Andreas Herrmann,
Hua Yu,
Xinlai Cheng,
Karl-Heinz Merz,
Gerhard Eisenbrand,
Hongzhi Li,
Yate-Ching Yuan,
Richard Jove
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ABSTRACT: Constitutively-activated JAK/Stat3 or Src/Stat3 signaling plays a crucial role in tumor cell survival, proliferation, angiogenesis and immune suppression. Activated JAK/Stat3 or Src/Stat3 has been validated as a promising molecular target for cancer therapy. However, prolonged inhibition of Src family kinases (SFKs) leads to reactivation of signal transducer and activator of transcript 3 (Stat3) and tumor cell survival through altered JAK/Stat3 interaction. This compensatory feedback suggests that dual inhibition of Janus kinases (JAKs) and SFKs might be a promising strategy for targeting downstream Stat3 signaling in the clinic. In this study, we identify that the natural product derivative E738 is a novel dual inhibitor of JAKs and SFKs. The IC(50) values of E738 against recombinant JAKs and SFKs in vitro are in the ranges of 0.7-74.1 nM and 10.7-263.9 nM, respectively. We observed that phosphorylation of both Jak2 and Src was substantially inhibited in the submicromolar range by E738 in cultured human pancreatic tumor cells, followed by blockade of downstream Stat3 activation. E738 down-regulated expression of the Stat3 target proteins Mcl-1 and survivin, associated with induction of apoptosis. Computational models and molecular dynamics simulations of E738/Tyk2 or E738/Src in silico suggest that E738 inhibits both tyrosine kinase 2 (Tyk2) and Src as an ATP-competitive ligand. Moreover, the planar E738 molecule demonstrates a strong binding affinity in the compact ATP-binding site of Tyk2. In sum, E738 is the first dual inhibitor of JAKs and SFKs, followed by inhibition of Stat3 signaling. Thus, according to in vitro experiments, E738 is a promising new therapeutic agent for human pancreatic cancer treatment by blocking both oncogenic pathways simultaneously.
Molecular oncology 11/2012; · 4.10 Impact Factor
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Lucy Liu,
Marina Kritsanida,
Prokopios Magiatis,
Nicolas Gaboriaud,
Yan Wang,
Jun Wu,
Ralf Buettner,
Fan Yang, Sangkil Nam,
Leandros Skaltsounis,
Richard Jove
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ABSTRACT: STAT3 and Akt signaling have been validated as potential molecular targets for treatment of cancers including melanoma. These small molecule inhibitors of STAT3 or Akt signaling are promising for developing anti-melanoma therapeutic agents. MLS-2438, a novel 7-bromoindirubin, a derivative of the natural product indirubin, was synthesized with a bromo-group at the 7-position on one indole ring and a hydrophilic group at the 3'-position on the other indole ring. We tested the anticancer activity of MLS-2438 and investigated its mechanism of action in human melanoma cell lines. Here, we show that MLS-2438 inhibits viability and induces apoptosis of human melanoma cells associated with inhibition of STAT3 and Akt signaling. Several pro-apoptotic Bcl-2 family proteins are involved in the MLS-2438 mediated apoptosis. MLS-2438 inhibits Src kinase activity in vitro and phosphorylation of JAK2, Src, STAT3 and Akt in cultured cancer cells. In contrast to the decreased phosphorylation levels of JAK2, Src, STAT3 and Akt, phosphorylation levels of the MAPK (Erk1/2) signaling protein were not reduced in cells treated with MLS-2438. These results demonstrate that MLS-2438, a novel natural product derivative, is a Src inhibitor and potentially regulates kinase activity of JAK2 and Akt in cancer cells. Importantly, MLS-2438 suppressed tumor growth with low toxicity in a mouse xenograft model of human melanoma. Our findings support further development of MLS-2438 as a potential small-molecule therapeutic agent that targets both STAT3 and Akt signaling in human melanoma cells.
Cancer biology & therapy 11/2012; 13(13). · 2.64 Impact Factor
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Sangkil Nam,
Jun Xie,
Angela Perkins,
Yuelong Ma,
Fan Yang,
Jun Wu,
Yan Wang,
Rong-Zhen Xu,
Wendong Huang,
David A Horne,
Richard Jove
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ABSTRACT: Persistent Jak/Stat3 signal transduction plays a crucial role in tumorigenesis and immune development. Activated Jak/Stat3 signaling has been validated as a promising molecular target for cancer therapeutics discovery and development. Berbamine (BBM), a natural bis-benzylisoquinoline alkaloid, was identified from the traditional Chinese herbal medicine Berberis amurensis used for treatment of cancer patients. While BBM has been shown to have potent antitumor activities with low toxicity in various cancer types, the molecular mechanism of action of BBM remains largely unknown. Here, we determine the antitumor activities of 13 synthetic berbamine derivatives (BBMDs) against human solid tumor cells. BBMD3, which is the most potent in this series of novel BBMDs, exhibits over 6-fold increase in biological activity compared to natural BBM. Moreover, BBMD3, directly inhibits Jak2 autophosphorylation kinase activity in vitro with IC(50)0.69μM. Autophosphorylation of Jak2 kinase at Tyr1007/1008 sites also was strongly inhibited in the range of 15μM of BBMD3 in human melanoma cells at 4h after treatment. Following inhibition of autophosphorylation of Jak2, BBMD3 blocked constitutive activation of downstream Stat3 signaling in melanoma cells. BBMD3 also down-regulated expression of the Stat3 target proteins Mcl-1and Bcl-x(L), associated with induction of apoptosis. In sum, our findings demonstrate that the novel berbamine derivative BBMD3 is an inhibitor of the Jak2/Stat3 signaling pathway, providing evidence for a molecular mechanism whereby BBMD3 exerts at least in part the apoptosis of human melanoma cells. In addition, BBMD3 represents a promising lead compound for development of new therapeutics for cancer treatment.
Molecular oncology 06/2012; 6(5):484-93. · 4.10 Impact Factor
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Fan Yang,
Veronica Jove,
Ralf Buettner,
Hong Xin,
Jun Wu,
Yan Wang, Sangkil Nam,
Yibing Xu,
Tasnim Ara,
Yves A DeClerck,
Robert Seeger,
Hua Yu,
Richard Jove
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ABSTRACT: Neuroblastoma is the most common extracranial solid tumor in the pediatric population. Sorafenib (Nexavar), a multikinase inhibitor, blocks cell proliferation and induces apoptosis in certain types of cancers. Here, we tested antitumor effects of sorafenib (≤ 10 µM) on four human neuroblastoma cell lines, CHLA255, CHLA171, CHLA90 and SK-N-AS. Sorafenib inhibited cell proliferation and induced apoptosis of neuroblastoma tumor cells in a dose-dependent manner. Sorafenib inhibited phosphorylation of Signal Transducer and Activator of Transcription 3 (STAT3) proteins at Tyr705 in these cells, associated with inhibition of phosphorylated JAK2, an upstream kinase that mediates STAT3 phosphorylation. Expression of a constitutively-activated STAT3 mutant (pSTAT3-C) partially blocked the antitumor effects of sorafenib on neuroblastoma cells. Sorafenib also inhibited the phosphorylation of STAT3 induced by IL-6 and sphingosine-1-phosphate (S1P), a recently identified regulator for STAT3, in these tumor cells. Moreover, sorafenib downregulated phosphorylation of MAPK (p44/42) in neuroblastoma cells, consistent with inhibition of their upstream regulators MEK1/2. Sorafenib inhibited expression of cyclin E, cyclin D1/D2/D3, key regulators for cell cycle, and the antiapoptotic proteins Mcl-1 and survivin. Finally, sorafenib suppressed the growth of human neuroblastoma cells in a mouse xenograft model. Taken together, these findings suggest the potential use of sorafenib for the treatment of pediatric neuroblastomas.
Cancer biology & therapy 05/2012; 13(7):534-41. · 2.64 Impact Factor
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Sangkil Nam,
Anna Scuto,
Fan Yang,
Wenyong Chen,
Sungman Park,
Hwa-Seung Yoo,
Heiko Konig,
Ravi Bhatia,
Xinlai Cheng,
Karl-Heinz Merz,
Gerhard Eisenbrand,
Richard Jove
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ABSTRACT: Indirubin is the major active anti-tumor component of a traditional Chinese herbal medicine used for treatment of chronic myelogenous leukemia (CML). While previous studies indicate that indirubin is a promising therapeutic agent for CML, the molecular mechanism of action of indirubin is not fully understood. We report here that indirubin derivatives (IRDs) potently inhibit Signal Transducer and Activator of Transcription 5 (Stat5) protein in CML cells. Compound E804, which is the most potent in this series of IRDs, blocked Stat5 signaling in human K562 CML cells, imatinib-resistant human KCL-22 CML cells expressing the T315I mutant Bcr-Abl (KCL-22M), and CD34-positive primary CML cells from patients. Autophosphorylation of Src family kinases (SFKs) was strongly inhibited in K562 and KCL-22M cells at 5 μM E804, and in primary CML cells at 10 μM E804, although higher concentrations partially inhibited autophosphorylation of Bcr-Abl. Previous studies indicate that SFKs cooperate with Bcr-Abl to activate downstream Stat5 signaling. Activation of Stat5 was strongly blocked by E804 in CML cells. E804 down-regulated expression of Stat5 target proteins Bcl-x(L) and Mcl-1, associated with induction of apoptosis. In sum, our findings identify IRDs as potent inhibitors of the SFK/Stat5 signaling pathway downstream of Bcr-Abl, leading to apoptosis of K562, KCL-22M and primary CML cells. IRDs represent a promising structural class for development of new therapeutics for wild type or T315I mutant Bcr-Abl-positive CML patients.
Molecular oncology 02/2012; 6(3):276-83. · 4.10 Impact Factor
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Yan Tian, Sangkil Nam,
Lucy Liu,
Fumiko Yakushijin,
Kenichi Yakushijin,
Ralf Buettner,
Wei Liang,
Fan Yang,
Yuelong Ma,
David Horne,
Richard Jove
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ABSTRACT: Melanoma is generally refractory to current chemotherapy, thus new treatment strategies are needed. In this study, we synthesized a series of spirooxindole derivatives (SOID-1 to SOID-12) and evaluated their antitumor effects on melanoma. Among the 12 spirooxindole derivatives, SOID-8 showed the strongest antitumor activity by viability screening. SOID-8 inhibited viability of A2058, A375, SK-MEL-5 and SK-MEL-28 human melanoma cells in a dose- and time-dependent manner. SOID-8 also induced apoptosis of these tumor cells, which was confirmed by positive Annexin V staining and an increase of poly(ADP-ribose) polymerase cleavage. The antiapoptotic protein Mcl-1, a member of the Bcl-2 family, was downregulated and correlated with SOID-8 induced apoptosis. In addition, SOID-8 reduced tyrosine phosphorylation of Signal Tansducer and Activator of Transcription 3 (STAT3) in both dose- and time-dependent manners. This inhibition was associated with decreased levels of phosphorylation of Janus-activated kinase-2 (JAK2), an upstream kinase that mediates STAT3 phosphorylation at Tyr705. Accordingly, SOID-8 inhibited IL-6-induced activation of STAT3 and JAK2 in melanoma cells. Finally, SOID-8 suppressed melanoma tumor growth in a mouse xenograft model, accompanied with a decrease of phosphorylation of JAK2 and STAT3. Our results indicate that the antitumor activity of SOID-8 is at least partially due to inhibition of JAK2/STAT3 signaling in melanoma cells. These findings suggest that the spirooxindole derivative SOID-8 is a promising lead compound for further development of new preventive and therapeutic agents for melanoma.
PLoS ONE 01/2012; 7(11):e49306. · 4.09 Impact Factor
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Lucy Liu, Sangkil Nam,
Yan Tian,
Fan Yang,
Jun Wu,
Yan Wang,
Anna Scuto,
Panos Polychronopoulos,
Prokopios Magiatis,
Leandros Skaltsounis,
Richard Jove
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ABSTRACT: STAT3 is persistently activated and contributes to malignant progression in various cancers. Janus activated kinases (JAK) phosphorylate STAT3 in response to stimulation by cytokines or growth factors. The STAT3 signaling pathway has been validated as a promising target for development of anticancer therapeutics. Small-molecule inhibitors of JAK/STAT3 signaling represent potential molecular-targeted cancer therapeutic agents. In this study, we investigated the role of JAK/STAT3 signaling in 6-bromoindirubin-3'-oxime (6BIO)-mediated growth inhibition of human melanoma cells and assessed 6BIO as a potential anticancer drug candidate. We found that 6BIO is a pan-JAK inhibitor that induces apoptosis of human melanoma cells. 6BIO directly inhibited JAK-family kinase activity, both in vitro and in cancer cells. Apoptosis of human melanoma cells induced by 6BIO was associated with reduced phosphorylation of JAKs and STAT3 in both dose- and time-dependent manners. Consistent with inhibition of STAT3 signaling, expression of the antiapoptotic protein Mcl-1 was downregulated. In contrast to the decreased levels of phosphorylation of JAKs and STAT3, phosphorylation levels of the Akt and mitogen-activated protein kinase (MAPK) signaling proteins were not inhibited in cells treated with 6BIO. Importantly, 6BIO suppressed tumor growth in vivo with low toxicity in a mouse xenograft model of melanoma. Taken together, these results show that 6BIO is a novel pan-JAK inhibitor that can selectively inhibit STAT3 signaling and induces tumor cell apoptosis. Our findings support further development of 6BIO as a potential anticancer therapeutic agent that targets JAK/STAT3 signaling in tumor cells.
Cancer Research 06/2011; 71(11):3972-9. · 7.86 Impact Factor
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ABSTRACT: Two new five-membered-ring polyketide endoperoxides, epiplakinic acid F methyl ester (1) and epiplakinidioic acid (3), and a peroxide-lactone, plakortolide J (2), were isolated from the Puerto Rican sponge Plakortis halichondrioides, along with two previously reported cyclic peroxides, 4 and 5. The structures of the new metabolites were determined by spectroscopic and chemical analyses. The absolute stereostructures of 1, 2, and 5 were determined by degradation reactions followed by application of Kishi's method for the assignment of absolute configuration of alcohols. Biological screening of cycloperoxides 1-5 and semisynthetic analogues 7-12 for cytotoxic activity against various human tumor cell lines revealed that compounds 3, 4, and 11 are very active. Upon assaying for antimalarial and antitubercular activity, some of the compounds tested showed strong activity against the pathogenic microbes Plasmodium falciparum and Mycobacterium tuberculosis.
Journal of Natural Products 10/2010; · 3.13 Impact Factor
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ABSTRACT: As a critical factor in the induction of angiogenesis, vascular endothelial growth factor (VEGF) has become an attractive target for anti-angiogenesis treatment. However, the side effects associated with most anti-VEGF agents limit their chronic use. Identification of naturally occurring VEGF inhibitors derived from diet is a potential alternative approach, with the advantage of known safety. To isolate natural inhibitors of VEGF, we established an in vitro tyrosine kinase assay to screen for diet-based agents that suppress VEGFR2 kinase activity. We found that a water-based extract from cinnamon (cinnamon extract, CE), one of the oldest and most popular spices, was a potent inhibitor of VEGFR2 kinase activity, directly inhibiting kinase activity of purified VEGFR2 as well as mitogen-activated protein kinase- and Stat3-mediated signaling pathway in endothelial cells. As a result, CE inhibited VEGF-induced endothelial cell proliferation, migration and tube formation in vitro, sprout formation from aortic ring ex vivo and tumor-induced blood vessel formation in vivo. Depletion of polyphenol from CE with polyvinylpyrrolidone abolished its anti-angiogenesis activity. While cinnamaldehyde, a component responsible for CE aroma, had little effect on VEGFR2 kinase activity, high-performance liquid chromatography-purified components of CE, procyanidin type A trimer (molecular weight, 864) and a tetramer (molecular weight, 1152) were found to inhibit kinase activity of purified VEGFR2 and VEGFR2 signaling, implicating procyanidin oligomers as active components in CE that inhibit angiogenesis. Our data revealed a novel activity in cinnamon and identified a natural VEGF inhibitor that could potentially be useful in cancer prevention and/or treatment.
Carcinogenesis 12/2009; 31(3):481-8. · 5.70 Impact Factor
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ABSTRACT: A series of ageladine A analogs that include 2-aminoimidazo[4,5-c]azepines (seven-membered rings) and 2-amino-3H-imidazo[4,5-c]pyridine (six-membered rings) derivatives were synthesized and evaluated for their anticancer effects against several human cancer cell lines and MMP-2 inhibition in vitro. Only compounds possessing the aromatic azepine (seven-membered ring) core showed anticancer activity with IC(50) values in the low micromolar range.
Bioorganic & medicinal chemistry letters 11/2009; 20(1):83-6. · 2.65 Impact Factor
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Fan Yang,
Timothy E Van Meter,
Ralf Buettner,
Michael Hedvat,
Wei Liang,
Claudia M Kowolik,
Nilesh Mepani,
Janni Mirosevich, Sangkil Nam,
Mike Y Chen,
Gary Tye,
Mark Kirschbaum,
Richard Jove
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ABSTRACT: Medulloblastomas are the most frequent malignant brain tumors in children. Sorafenib (Nexavar, BAY43-9006), a multikinase inhibitor, blocks cell proliferation and induces apoptosis in a variety of tumor cells. Sorafenib inhibited proliferation and induced apoptosis in two established cell lines (Daoy and D283) and a primary culture (VC312) of human medulloblastomas. In addition, sorafenib inhibited phosphorylation of signal transducer and activator of transcription 3 (STAT3) in both cell lines and primary tumor cells. The inhibition of phosphorylated STAT3 (Tyr(705)) occurs in a dose- and time-dependent manner. In contrast, AKT (protein kinase B) was only decreased in D283 and VC312 medulloblastoma cells and mitogen-activated protein kinases (extracellular signal-regulated kinase 1/2) were not inhibited by sorafenib in these cells. Both D-type cyclins (D1, D2, and D3) and E-type cyclin were down-regulated by sorafenib. Also, expression of the antiapoptotic protein Mcl-1, a member of the Bcl-2 family, was decreased and correlated with apoptosis induced by sorafenib. Finally, sorafenib suppressed the growth of human medulloblastoma cells in a mouse xenograft model. Together, our data show that sorafenib blocks STAT3 signaling as well as expression of cell cycle and apoptosis regulatory proteins, associated with inhibition of cell proliferation and induction of apoptosis in medulloblastomas. These findings provide a rationale for treatment of pediatric medulloblastomas with sorafenib.
Molecular Cancer Therapeutics 12/2008; 7(11):3519-26. · 5.23 Impact Factor
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ABSTRACT: CD46 is one of the complement-regulatory proteins expressed on the surface of normal and tumor cells for protection against complement-dependent cytotoxicity. Cancer cells need to access the blood circulation for continued growth and metastasis, thus exposing themselves to destruction by complement system components. Previous studies have established that the signal transducers and activators of transcription 3 (STAT3) transcription factor is persistently activated in a wide variety of human cancer cells and primary tumor tissues compared with their normal counterparts. Using microarray gene expression profiling, we identified the CD46 gene as a target for activated STAT3 signaling in human breast and prostate cancer cells. The CD46 promoter contains two binding sites for activated STAT3 and mutations introduced into the major site abolished STAT3 binding. Chromatin immunoprecipitation confirms binding of STAT3 to the CD46 promoter. CD46 promoter activity is induced by activation of STAT3 and blocked by a dominant-negative form of STAT3 in luciferase reporter assays. CD46 mRNA expression is induced by interleukin-6 and by transient transfection of normal human epithelial cells with a persistently active mutant construct of STAT3, STAT3C. Furthermore, we show that inhibition of STAT3-mediated CD46 cell surface expression sensitizes DU145 prostate cancer cells to cytotoxicity in an in vitro complement lysis assay using rabbit anti-DU145 antiserum and rabbit complement. These results show that activated STAT3 signaling induces the CD46 promoter and protects human cancer cells from complement-dependent cytotoxicity, suggesting a potential mechanism whereby oncogenic signaling contributes to tumor cell evasion of antibody-mediated immunity.
Molecular Cancer Research 09/2007; 5(8):823-32. · 4.29 Impact Factor
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ABSTRACT: Dasatinib (BMS-354825) is a novel, oral, potent, multi-targeted kinase inhibitor of Bcr-Abl and Src family kinases (SFK) and is a promising cancer therapeutic agent. Preclinical data indicate that dasatinib is 325-fold more potent than imatinib against cells expressing wild-type Bcr-Abl, and that dasatinib is active against 18 of 19 Bcr-Abl mutations known to cause imatinib resistance. Phase I clinical data show that dasatinib is well tolerated and highly effective for the treatment of imatinib-resistant/imatinib-intolerant chronic myelogenous leukemia (CML) and Philadelphia chromosome-positive acute lymphoblastic leukemia. However, the molecular mechanism of action of dasatinib is not fully understood. In this study, we confirm that dasatinib inhibits tyrosine phosphorylation of SFKs, including Src, Hck, and Lyn, in K562 human CML cells. Significantly, downstream signal transducer and activator of transcription 5 (Stat5) signaling is also blocked by dasatinib as shown by decreases in levels of phosphorylated Stat5 and Stat5 DNA-binding activities. In addition, dasatinib down-regulates expression of Stat5 target genes, including Bcl-x, Mcl-1, and cyclin D1. Consistent with these results, blockade of Stat5 signaling by dasatinib is accompanied by inhibition of cell proliferation and induction of apoptosis. Surprisingly, Stat5 DNA-binding activities are enhanced with increasing cell density, which is associated with resistance to apoptosis by dasatinib. Our findings indicate that inhibition of Stat5 signaling downstream of Bcr-Abl/SFKs contributes to the action of dasatinib, and, conversely, that increasing cell density up-regulates Stat5 activation and confers resistance to dasatinib. Moreover, the level of phosphorylated Stat5 in CML cells represents a mechanistically relevant biomarker for monitoring inhibition of Bcr-Abl signaling by dasatinib in CML patients using convenient immunocytochemical assays.
Molecular Cancer Therapeutics 05/2007; 6(4):1400-5. · 5.23 Impact Factor
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Tanya Gritsko,
Ann Williams,
James Turkson,
Satoshi Kaneko,
Tammy Bowman,
Mei Huang, Sangkil Nam,
Ibrahim Eweis,
Nils Diaz,
Daniel Sullivan,
Sean Yoder,
Steve Enkemann,
Steven Eschrich,
Ji-Hyun Lee,
Craig A Beam,
Jin Cheng,
Susan Minton,
Carlos A Muro-Cacho,
Richard Jove
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ABSTRACT: Signal transducer and activator of transcription 3 (Stat3) protein is persistently activated in breast cancer and promotes tumor cell survival. To gain a better understanding of the role of constitutive Stat3 signaling in breast cancer progression, we evaluated the expression profile of potential Stat3-regulated genes that may confer resistance to apoptosis.
Stat3 signaling was blocked with antisense oligonucleotides in human MDA-MB-435s breast cancer cells and Affymetrix GeneChip microarray analysis was done. The candidate Stat3 target gene Survivin was further evaluated in molecular assays using cultured breast cancer cells and immunohistochemistry of breast tumor specimens.
Survivin, a member of the inhibitor of apoptosis protein family, was identified as a potential Stat3-regulated gene by microarray analysis. This was confirmed in Survivin gene promoter studies and chromatin immunoprecipitation assays showing that Stat3 directly binds to and regulates the Survivin promoter. Furthermore, direct inhibition of Stat3 signaling blocked the expression of Survivin protein and induced apoptosis in breast cancer cells. Direct inhibition of Survivin expression also induced apoptosis. Increased Survivin protein expression correlates significantly (P = 0.001) with elevated Stat3 activity in primary breast tumor specimens from high-risk patients who were resistant to chemotherapy treatment.
We identify Survivin as a direct downstream target gene of Stat3 in human breast cancer cells that is critical for their survival in culture. Our findings suggest that activated Stat3 signaling contributes to breast cancer progression and resistance to chemotherapy by, at least in part, inducing expression of the antiapoptotic protein, Survivin.
Clinical Cancer Research 02/2006; 12(1):11-9. · 7.74 Impact Factor
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ABSTRACT: Src family kinases (SFK) are currently being investigated as targets for treatment strategies in various cancers. The novel SFK/Abl inhibitor, dasatinib (BMS-354825), is a promising therapeutic agent with oral bioavailability. Dasatinib has been shown to inhibit growth of Bcr-Abl-dependent chronic myeloid leukemia xenografts in nude mice. Dasatinib also has been shown to have activity against cultured human prostate and breast cancer cells. However, the molecular mechanism by which dasatinib acts on epithelial tumor cells remains unknown. In this study, we show that dasatinib blocks the kinase activities of the SFKs, Lyn, and Src, in human prostate cancer cells at low nanomolar concentrations. Moreover, focal adhesion kinase and Crk-associated substrate (p130(CAS)) signaling downstream of SFKs are also inhibited at similar concentrations of dasatinib. Consistent with inhibition of these signaling pathways, dasatinib suppresses cell adhesion, migration, and invasion of prostate cancer cells at low nanomolar concentrations. Therefore, dasatinib has potential as a therapeutic agent for metastatic prostate cancers harboring activated SFK and focal adhesion kinase signaling.
Cancer Research 11/2005; 65(20):9185-9. · 7.86 Impact Factor
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Sangkil Nam,
Ralf Buettner,
James Turkson,
Donghwa Kim,
Jin Q Cheng,
Stephan Muehlbeyer,
Frankie Hippe,
Sandra Vatter,
Karl-Heinz Merz,
Gerhard Eisenbrand,
Richard Jove
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ABSTRACT: Stat3 protein has an important role in oncogenesis and is a promising anticancer target. Indirubin, the active component of a traditional Chinese herbal medicine, has been shown previously to inhibit cyclin-dependent kinases, resulting in cell cycle arrest. Here, we show that the indirubin derivatives E564, E728, and E804 potently block constitutive Stat3 signaling in human breast and prostate cancer cells. In addition, E804 directly inhibits Src kinase activity (IC(50) = 0.43 microM) in an in vitro kinase assay. Levels of tyrosyl phosphorylation of c-Src are also reduced in cultured cells 30 min after E804 treatment. Tyrosyl phosphorylation of Stat3, which is known to be phosphorylated by c-Src, was decreased, and constitutive Stat3 DNA binding-activity was suppressed in cells 30 min after E804 treatment. The antiapoptotic proteins Mcl-1 and Survivin, which are encoded in target genes of Stat3, were down-regulated by indirubin derivatives, followed by induction of apoptosis. These results demonstrate that E804 directly blocks the Src-Stat3 signaling pathway, suggesting that the antitumor activity of indirubin compounds is at least partially due to inhibition of this pathway.
Proceedings of the National Academy of Sciences 05/2005; 102(17):5998-6003. · 9.68 Impact Factor
