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. Melatonin, metformin, and their combination promoted significant reduction of the number and size of skin tumors. In mice receiving no therapy, benz(a)pyrene applications increased the concentrations of malonic dialdehyde in the serum and skin tumor tissue in comparison with the concentrations in the sera and skin of intact mice. Melatonin, metformin, and their combination normalized LPO level.