title: Sorafenib inhibits STAT3 activation to enhance TRAIL-mediated apoptosis in human pancreatic cancer cells.
abstract: Signal transducers and activators of transcription 3 (STAT3) is constitutively active in human pancreatic cancer cells and can promote cell growth and apoptosis resistance that contribute to tumorigenesis. We determined if sorafenib, a multikinase inhibitor, can induce apoptosis by targeting STAT3 signaling to enhance apoptosis induction by tumor necrosis factor-related apoptosis-inducing ligand (TRAIL). Human pancreatic cancer cell lines (PANC-1 and BxPC-3) were preincubated with sorafenib (Nexavar) alone or followed by TRAIL. Apoptosis was determined by Annexin V labeling, caspase cleavage, and Bax/Bak activation. Protein expression was analyzed by immunoblotting. Knockdown of STAT3, Mcl-1, and Bim were achieved by lentiviral small hairpin RNA. Adenoviral dominant-negative or retroviral constitutively active (CA) STAT3 were also used. Sorafenib inhibited constitutive STAT3 phosphorylation (Tyr(705)) and suppressed Mcl-1 and Bcl-x(L) proteins in a dose- and time-dependent manner. CA-STAT3 overexpression was shown to attenuate caspase-3 cleavage and suppression of Mcl-1 by sorafenib. STAT3 knockdown or a DN STAT3 was shown to downregulate Mcl-1 and Bcl-x(L) and to sensitize cells to TRAIL-mediated apoptosis. Treatment with sorafenib enhanced TRAIL-induced Annexin V staining and release of mitochondrial cytochrome c and AIF. Because the BH3-only Bim protein is a potent inducer of mitochondrial apoptosis, Bim knockdown was shown to attenuate caspase-3, caspase-9 cleavage, and Bax/Bak activation by sorafenib plus TRAIL. The suppression of STAT3 by genetic means or using sorafenib was shown to downregulate Mcl-1 and Bcl-x(L) and to sensitize cells to TRAIL-mediated apoptosis. These data indicate that targeting STAT3 may enhance treatment efficacy against pancreatic cancer.
authors.affiliation: Divisions of Oncology and Gastroenterology/Hepatology, Mayo Cancer Center, Mayo Clinic, Rochester, Minnesota 55905, USA.
authors.forename: Shengbing
authors.initials: S
authors.lastname: Huang
authors.forename: Frank A
authors.initials: FA
authors.lastname: Sinicrope
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects*; D001557:Benzenesulfonates / Q000494:pharmacology*; D002277:Carcinoma / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D004353:Drug Evaluation, Preclinical; D004357:Drug Synergism; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D009536:Niacinamide / Q000031:analogs & derivatives; D010190:Pancreatic Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D010671:Phenylurea Compounds; D010766:Phosphorylation / Q000187:drug effects; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D011725:Pyridines / Q000494:pharmacology*; D034741:RNA, Small Interfering / Q000494:pharmacology; D050796:STAT3 Transcription Factor / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D000077157:Sorafenib; D053221:TNF-Related Apoptosis-Inducing Ligand / Q000494:pharmacology*; D014407:Tumor Cells, Cultured; D051020:bcl-X Protein / Q000378:metabolism
chemical_list: D000970:Antineoplastic Agents; C494811:BCL2L1 protein, human; D001557:Benzenesulfonates; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D010671:Phenylurea Compounds; D019253:Proto-Oncogene Proteins c-bcl-2; D011725:Pyridines; D034741:RNA, Small Interfering; D050796:STAT3 Transcription Factor; C494086:STAT3 protein, human; D053221:TNF-Related Apoptosis-Inducing Ligand; D051020:bcl-X Protein; D009536:Niacinamide; D000077157:Sorafenib