Effects Of RNAi Targeted To STAT3 And CPP In Inducing Apoptosis And On STAT3 Signaling In Human Hepatocellular Carcinoma

Objective: To investigate the effects of RNAi targeted to STAT3 and CPP in inducing apoptosis and on STAT3 signaling in human hepatocellular carcinoma cell line SMMC7721. The research will provide theoretical and experimental basis for further development and clinical application of CPP, and for targeting STAT3 signaling pathway therapy for cancer.Methods: 1 Applying RNAi technique to specifically silence STAT3 gene in SMMC7721 cells, the protein expressions of STAT3 in cells were determined by Western blot.2 Effect of RNAi on SMMC7721 cell apoptosis was determined by flow cytometry. Expression of apoptosis- associated genes survivin and bcl-2 was determined by semi-quantitative RT-PCR.3 Inhibitory effects of CPP in different concentrations and different time on SMMC7721 proliferation were detected by MTT.4 The expressions of STAT3 mRNA in SMMC7721 cells treated with CPP were determined by semi-quantitative RT-PCR. 5 Effects of CPP on cell apoptosis of SMMC7721 cells under various times were detected using flow cytometry. Effects of CPP on apoptosis associated genes survivin and bcl-2 mRNA expression were detected by semi-quantitative RT-PCR.Results: 1 RNAi technology can effectively and specifically silence the expression of STAT3.2 Compared to the control group, the apoptosis rate was significantly increased after RNAi silencing STAT3 (P<0.01). Expression of survivin and bcl-2 mRNA was significantly inhibited (P<0.01).3 A concentration-dependent and time-dependent proliferation inhibition of CPP was demonstrated in SMMC7721. The inhibitory rate was(48.31±2.10)% at 2.5μg/ml concentration for 24 h.4 The results of semi-quantitative RT-PCR showed that STAT3 mRNA expression in cells treated with CPP were significantly decreased compared to the control group (P<0.01).5 CPP can significantly increase the apoptosis rate of SMMC7721. The apoptosis rate of SMMC7721 cells treated with 2.5μg/ml CPP for 12, 24, 48h increased significantly compared to the control group (P<0.01). Expression of apoptosis associated genes survivin and bcl-2 mRNA was significantly decreased compared to the control group (P<0.01). Conclusion: 1 The RNAi technology targeted to STAT3 can effectively silence STAT3 expression in SMMC7721.2 RNAi targeted to STAT3 can induce apoptosis and down-regulate expression of bcl-2 and survivin mRNA.3 CPP has significant inhibitory effect on the human hepatocellular carcinoma cell line SMMC7721 proliferation.4 CPP can inhibit the expression of STAT3 in SMMC7721.5 CPP can induce apoptosis in human hepatocellular carcinoma cell line SMMC7721, and down-regulate bcl-2 and survivin mRNA, suggesting that the probable apoptosis-inducing mechanism of CPP is related to the down-regulation of bcl-2 and survivin mRNA expression and inhibition of STAT3 signaling.