Silencing of signal transducer and activator of transcription 3 expression by RNA interference suppresses growth of human hepatocellular carcinoma in tumor-bearing nude mice

AIM:To explore the effect of silencing of signal transducer and activator of transcription 3(STAT3) expression by RNA interference(RNAi) on growth of human hepatocellular carcinoma(HCC) in tumor-bearing nude mice in vivo.METHODS:To construct the recombinant plasmid of pSilencer 3.0-H1-STAT3-siRNA-GFP(pSH1-siRNA-STAT3) and establish the tumor-bearing nude mouse model of the HCC cell line SMMC7721,we used intratumoral injection together with electroblotting to transfect the recombinant plasmid pSH1-siRNA-STAT3 into the transplanted tumor.The weight of the nude mice and tumor volumes were recorded.STAT3 gene transcription was detected by semi-quantitative reverse transcription polymerase chain reaction(RTPCR).Level of protein expression and location of STAT3 were determined by Western blotting and immunohistochemical staining.STAT3-related genes such as survivin,c-myc,VEGF,p53 and caspase3 mRNA and protein expression were detected in tumor tissues at the same time.The terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling(TUNEL) assay was used to detect apoptosis of tumor cells.RESULTS:The weight of the treated nude mice increased,and the tumor volume decreased markedly compared with those of the mock-treated and negative control groups(P < 0.01).The results of RT-PCR and Western blotting showed that mRNA and protein levels of STAT3 declined markedly in the treated group.The change in STAT3-related gene expression in tumor tissues at the mRNA and protein level also varied,the expression of survivin,VEGF and c-myc were obviously reduced,and expression of p53 and caspase3 increased(P < 0.01).Most of the tumor tissue cells in the treated group developed apoptosis that was detected by TUNEL assay.CONCLUSION:Silencing of STAT3 expression by RNAi significantly inhibits expression of STAT3 mRNA and protein,and suppresses growth of human HCC in tumor-bearing nude mice.The mechanism may be related to down-regulation of survivin,VEGF and c-myc and up-regulation of p53 and caspase3 expression.Accordingly,the STAT3 gene may act as an important and effective target in gene therapy of HCC.