Dominant role of HPV16 E7 in anal carcinogenesis.

Ninety percent of anal cancer is associated with human papilloma viruses (HPVs). Using our previously established HPV transgenic mouse model for anal cancer, we tested the role of the individual oncogenes E6 and E7. K14E6 and K14E7 transgenic mice were treated with dimethylbenz[a]anthracene (DMBA) to the anal canal and compared to matched nontransgenic and doubly transgenic K14E6/E7 mice. K14E7 and K14E6/E7 transgenic mice developed anal tumors (papillomas, atypias and carcinomas combined) at significantly higher rates (88% and 100%, respectively) than either K14E6 or NTG mice (18% and 19%, respectively). Likewise, K14E7 and K14E6/E7 transgenic mice developed frank cancer (carcinomas) at significantly higher rates (85% and 85%, respectively) than either K14E6 or NTG mice (18% and 10%, respectively). These findings indicate that E7 is the more potent oncogene in anal cancer caused by HPVs.