In our present study, long-term exposure of HaCaT cells to low-dose arsenite caused a reduction in the levels of keratins 5, 6, 7, 8, 10, and 17, and the cell lines derived from tumors induced by injection with arsenite-treated cells had a similar pattern of expression of keratins, except that the levels of keratins 7 and 17 were unchanged and keratin 6 levels were significantly increased in the tumor cell lines. This evidence concerns the gene KRT5 and neoplasm.