Effects Of STAT3Gene Silencing On Proliferation And Apoptosis Of Stomach Cancer Cells

ObjectiveStomach cancer is one of the most frequent malignant tumors in China,its happening is a complex process with multi-genes, multi-steps and multi-stages.STAT3,as an important member of signal transducers and activators of transcription family, is a bifunctional protein coupling the tyrosine phosphorylation signaling pathways present in the cytoplasm. It is critical to cell proliferation, apoptosis, invasion, metastasis, angiogenesis and immune evasion. Thus, STAT3is a potential target for tumor therapy.To construct siRNA expression vectors targeting STAT3gene and to examine the inhibitory effect of the siRNAs on the expression of STAT3and its effect on proliferation and apoptosis of stomach cancer cell lines MGC-803(wide-type p53) and HGC-27(mutated p53).Methods1. Two STAT3-siRNA fragments were synthesized, and then transfected into MGC-803and HGC-27cells.2. STAT3mRNA and protein were examined by RT-PCR and Western blot respectively after transfection..3. Inhibition on proliferation was determined by the MTT assay.4. The influence on apoptosis was detected by Western blot.Results1. The two STAT3-siRNA expression vectors were found to contain the correct siRNA sequences, as confirmed by sequencing, ultraviolet spectrophotometer analysis, and enzymatic digestion.2. Results of RT-PCR and Western blot showed that the abundances of STAT3mRNA and protein were significantly decreased relative to both the control and si-NC groups (P<0.05), results with STAT3-siRNA1being more pronounced than with STAT3-siRNA2.3. MTT assay showed that, after transfection, cell proliferation in the siRNA group was reduced significantly compared with the si-NC group.4. Western blot showed that in MGC-803cell line, compared with both the control and si-NC groups,silence of STAT3can upregulated ace-p53, caspase3expression(P<0.05)and downregulated p-STAT3,bcl-2,survivin expression (P<0.05),but the level of bax had no change after silencing STAT3by RNAi (P>0.05);While in HGC-27cell line, compared with both the control and si-NC groups,silence of STAT3can upregulated ace-p53expression(P<0.05)and downregulated p-STAT3, bcl-2, survivin expression(P<0.05),but the level of caspase3and bax had no change after silencing STAT3by RNAi (P>0.05)Conclusion1. Expression of STAT3-siRNA in stomach cell lines MGC-803and HGC-27can effectively inhibit STAT3expression.2. Down-regulation of STAT3of stomach cell lines MGC-803and HGC-27can suppress cell proliferation and promote cell apoptosis which suggests that STAT3may serve as a potential target for gene therapy of stomach cancer.3. In HGC-27cell line,silence of STAT3can upregulated ace-p53, caspase3expression and downregulated p-STAT3,bcl-2,survivin expression,but the level of bax had no change after silencing STAT3by RNAi;While in HGC-27cell line, silence of STAT3can upregulated ace-p53expression and downregulated p-STAT3, bcl-2, survivin expression,but the level of caspase3and bax had no change after silencing STAT3by RNAi. STAT3can regulate the influence of wide-type p53on apoptosis.