Effect of simultaneous silencing of HPV-18 E6 and E7 on inducing apoptosis in HeLa cells.

The objective of this investigation was to determine if simultaneous silencing of the human papillomavirus type 18 (HPV-18) E6 and E7 oncogenes using RNA interference (RNAi) would be a potential therapeutic approach against the carcinogenic activity of this virus. Two synthetic double-stranded oligonucleotides, encoding short hairpin transcripts corresponding to HPV-18 E6 and E7 genes, were cloned into pGenesilence (pGS) 1.0 vectors to produce pGS-E6, pGS-E7, and pGS-(E6+E7), respectively. Our results showed that the expression of HPV-18 E6 class 1 and HPV-18 E7 in HeLa cells was markedly decreased after being transfected with pGS-E6, pGS-E7, and pGS-(E6+E7) vectors. Of the three vectors, pGS-(E6+E7) had a greater ability to decrease the growth rate of HeLa cells, inhibit colony formation in soft agar, and significantly reduce tumor growth in nude mice. We also found that depletion of HPV-18 E6 and E7 in this manner promoted apoptosis of HeLa cells. Our data showed that simultaneously decreasing HPV-18 E6 and E7 gene expression in HeLa cells by RNAi could significantly inhibit tumor growth under in vitro conditions and in nude mice. These data suggest that gene therapy may be a possible therapeutic approach for HPV-positive cervical cancers.