Melatonin and metformin inhibit skin carcinogenesis and lipid peroxidation induced by benz(a)pyrene in female mice.

Outbred female SHR mice (n=200) were divided at random into 4 groups, 50 per group. Benz(a)pyrene solution in acetone was applied onto a skin site on the back during 26 weeks. In parallel, the animals received melatonin, metformin, or both.