Cancer chemopreventive effects of oral feeding alpha-tocopherol on ultraviolet light B induced photocarcinogenesis of hairless mouse.

Ultraviolet light is the most common cause of skin cancers in humans and several effects of ultraviolet light B (UVB: 290-320 nm) are thought to contribute to skin photocarcinogenesis. The generation of free radicals and related oxidants produced by UVB exposure, result in photocarcinogenesis by directly damaging DNA. On the other side, activating of transcription factor, activator protein 1 (AP-1) induced by UVB exposure causes tumor promotion. alpha-tocopherol has two principal physiological activities and one is an antioxidant activity through which alpha-tocopherol protects unsaturated fatty acids, protein and DNA from oxidation. The other activity is to stabilize the structure of the biomembrane. In addition to these two activities, it has been recently established that alpha-tocopherol plays important roles in cell signal transduction. In course of these studies, we examined such effects of alpha-tocopherol on UVB induced skin photocarcinogenesis in hairless mice. These results indicate that oral feeding of alpha-tocopherol including diet exhibited a marked inhibitory effects on both tumor incidence and multiplicity in UVB induced mouse skin photocarcinogenesis.