Gene therapy of human cancer is likely to bemost effective when it is directed at targets that areexpressed in cancer cells but are lacking from othercells. Human papillomaviruses (HPV) can providesuch target, since these viruses are present in manycervical and oral cancers, and likely to be etiologicagents of the tumor. The oncogenic ability of HPVhas been assigned primarily to its two early genes, E6and E7. Continued expression of these two genes is Gene therapy of human cancer is likely to be most effective when it is directed at targets that areexpressed in cancer cells but are lacking from othercells. Human papillomaviruses (HPV) can providesuch target, since these viruses are present in manycervical and oral cancers, and likely to Be etiologicagents of the tumor. The oncogenic ability of HPVhas been assigned primarily to its two early genes, E6and E7. Continued expression of these two genes is