Use of adenovirus-delivered siRNA to target oncoprotein p28GANK in hepatocellular carcinoma

Background & Aims: RNA interference (RNAi) is a powerful tool to silence gene expression. The adenoviral vector expressing small interfering RNA (siRNA) is highly effective in mammalian cells. However, its potential use as a therapeutic tool to target an oncogene specifically remains to be seen. We applied the adenovirus-delivered siRNA (AdSiRNA) to inhibit a hepatocellular carcinoma (HCC) oncogene, p28(GANK), in HCC cell lines and investigated its antitumor effects. Methods: The T7-RNA polymerase system was used to screen the specific target site. Double-strand oligonucleotide for transcription of short hairpin RNA was constructed into the adenoviral vector. Four HCC cell lines were infected with the RNAi-containing adenovirus. The RNAi effects on HCC were studied in cultured cells as well as in animal models. Results: p28(GANK) expression was suppressed by up to 80% in HCC cells. Depletion of p28(GANK) inhibited HCC cell growth and tumorigenesis, enhanced dephosphorylation of RB1, and decreased transcription activity of E2F-1 in HuH-7 cells. Furthermore, depletion of p28(GANK) induced caspase-8- and caspase-9-mediated apoptosis of HCC cells. Finally, targeting p28(GANK) by adenovirus injection inhibited the growth of established tumors in nude mice. Conclusions: This study shows that the T7-system screening-based AdSiRNA can be used successfully to silence an oncogene. We proved the therapeutic potential of AdSiRNA on the treatment of HCC by targeting p28(GANK). Our results indicate that p28(GANK) may serve as a novel therapeutic target for treating HCC.