Stat3-siRNA induces Fas-mediated apoptosis in vitro and in vivo in breast cancer.
Stat3, a member of the signal transducer and activator of transcription family, has the potential to mediate cell survival, growth and differentiation. Stat3 is constitutively activated in numerous cancers, including >50% of breast cancers. Previous studies demonstrated that constitutively activated Stat3 plays an important role in breast cancer development and progression by promoting cell proliferation and inhibiting apoptosis. The present study was designed to investigate the potential use of RNA interference (RNAi) to block Stat3 expression and activation, as well as the subsequent effect on human breast cancer cell growth. Our studies show that knockdown of STAT3 expression by siRNA reduced expression of Bcl-xL and survivin in MDA-MB-231 cells, and also led to Fas mediated intrinsic apoptotic pathway by activating caspases -8, -9, -3 and PARP1 cleavage. In nude mice, pRNAi-Stat3 significantly suppressed tumor growth compared with controls. It also suppressed Stat3 expression, and downregulated BcL-xL and upregulated Fas, Fas-L and cleaved caspase-3 expression within the tumor, which significantly induced apoptosis and led to tumor suppression. Thus, targeting Stat3 signaling using siRNA may serve as a novel therapeutic strategy for the treatment of breast cancers expressing constitutively activated Stat3.
Department of Cancer Biology and Pharmacology, University of Illinois College of Medicine at Peoria, Peoria, IL 61605, USA.
Sateesh
S
Kunigal
Sajani S
SS
Lakka
Prasanna Kumar
PK
Sodadasu
Norman
N
Estes
Jasti S
JS
Rao
D000818:Animals; D017209:Apoptosis / Q000187:drug effects* / Q000235:genetics; D001943:Breast Neoplasms / Q000235:genetics / Q000473:pathology*; D002470:Cell Survival / Q000187:drug effects / Q000235:genetics; D053222:Fas Ligand Protein / Q000378:metabolism / Q000502:physiology; D053200:Fas-Associated Death Domain Protein / Q000378:metabolism; D005260:Female; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D051379:Mice; D008819:Mice, Nude; D008954:Models, Biological; D011485:Protein Binding / Q000187:drug effects; D034741:RNA, Small Interfering / Q000494:pharmacology*; D050796:STAT3 Transcription Factor / Q000037:antagonists & inhibitors* / Q000235:genetics; D014407:Tumor Cells, Cultured; D023041:Xenograft Model Antitumor Assays; D019014:fas Receptor / Q000502:physiology*
D053222:Fas Ligand Protein; D053200:Fas-Associated Death Domain Protein; D034741:RNA, Small Interfering; D050796:STAT3 Transcription Factor; C494086:STAT3 protein, human; D019014:fas Receptor