Background  Both survivin and lung resistance related protein (LRP) are related to the chemoresistances in hepatocellular carcinoma (HCC). But the relationship between survivin and LRP is indefinite. The aim of this study was to investigate the effects of down-regulation of survivin on LRP expressions and the reversal of chemoresistances in HCC both in vitro and in vivo.
Methods  The expressions of survivin were detected by RT-PCR and Western blotting in HCC cell line SMMC-7721 and SMMC-7721/ADM. The sensitivities of these two cell lines to ADM were evaluated by MTT assays. SiRNA which targeted survivin was transfected into SMMC-7721/ADM cells, then the sensitivity of SMMC-7721/ADM cells to ADM and the expressions of survivin and LRP were detected respectively. SMMC-7721/ADM cells were transplanted subcutaneously into nude mice to establish xenograft tumors. Antitumor activities of RNA interference (RNAi) targeting survivin, various doses of ADM and combination therapies were observed respectively. Possible toxicities were evaluated. LRP expression changes were tested. Student′s t test was used for evaluating statistical significance.
Results  The expressions of survivin in SMMC-7721/ADM cell line showed significant elevation compared to those in SMMC-7721 cell line (P <0.05). Positive siRNA down-regulated the expressions of survivin significantly (P <0.05). SiRNA targeting survivin could sensitize SMMC-7721/ADM cells to ADM and down-regulate the expressions of LRP significantly (P <0.05). Growths of the tumors were significantly inhibited in positive siRNA group as compared with those in the control group from the 8th day (P <0.05). Combination therapies caused significant tumor inhibitions compared with tumors of nude mice in the other three groups respectively (P <0.05). No toxicities were found in nude mice treated by siRNA and combination therapies. The expressions of LRP were markedly reduced in tumors treated with siRNA targeting survivin (P <0.05).
Conclusions  Down regulation of survivin gene by RNAi can increase chemosensitivity of HCC both in vitro and in vivo. The reversal of drug resistance may be reduced through the inhibitions of LRP.