Human papillomavirus type 16 E6-enhanced susceptibility to apoptosis induced by TNF in A2780 human ovarian cancer cell line.

In our study, we show that expression of HPV-16 E6 sensitizes TNF-induced cytotoxicity of human ovarian cancer cell line A2780. This effect is not related to a different number of TNF receptors present on cell membrane. The major induction of massive apoptosis induced by TNF is not p53- and p21(waf-1)-dependent but it is principally related to NF-kappaB inhibition in A2780/E6 cells. Consistently to NF-kappaB inhibition a rapidly release of cytochrome c and severe induction of DNA fragmentation are seen in A2780/E6 cells. Also in human colon cancer cell line HCT-116/E6 the expression of HPV-16 E6 enhances TNF-cytotoxicity. This effect is not present in the HCT-116/mu-p53 clone (transfected with a dominant-negative mutated p53 transgene). Thus, taken together all these observations suggest that HPV-16 E6 sensitizes A2780 and HCT-116 cells to TNF; this effect is not p53-dependent, but it is essentially mediated through an inhibition in activating NF-kappaB activities.