Effect of vitamins A, C and E on normal and HPV-immortalized human oral epithelial cells in culture

There is experimental and epidemiological evidence that antioxidant vitamin s can inhibit carcinogenesis. Since immortalization by Human Papilloma Viru s (HPV) is one possible early step towards carcinogenesis in oral epithelia , we studied the differential effect of vitamins A, C and E on HPV-immortal ized oral epithelial cells (IHGK) as compared to the normal counterpart. Th e dose response was determined by morphology, cell cycle by flow cytometry, and growth curve by cell number: The optimum dose in terms of inhibitory e ffect vs. toxicity was determined for each vitamin by morphology Optimum do ses were: vitamin A - 1.4x10(-5) M, vitamin C - 10(-3) M, and vitamin E - 1 0(-6) M for both HPV-immortalized and normal cells. Growth curve showed red uction of proliferation by all three vitamins, with vitamins A and E more e ffective than C for both cell types. Flow cytometry showed that vitamins A and E reduced the percentage of cells at G2 phase of cell cycle and indicat ed nn est in the S phase. This effect was greatest in the immortalized cell s with a 50% and 35% decrease of G2 for vitamins A and E respectively where as the normal counterpart showed a 48% decrease for A and a 12% increase fo r E. By organotypic culture, the morphology was not markedly different betw een the I vitamin-treated and the control cells, except for a slight increa se in the keratinization of normal cells with vitamin A. Also noted was a r eduction in number of cell layers from five layers or more for controls to only one or two for vitamin E. In conclusion, we have demonstrated that the antioxidant vitamins inhibit proliferation, and show a preferential effect on IHGK cells.