cK5-rtTA mice and cK5-rtTA/Tet-E2/E4/E5 mice were treated with both 7,12-dimethylbenz(a)anthracene (DMBA), a skin carcinogen which causes multiple mutations and initiates tumorigenesis in the skin, and 12-O-tetradecanoylphorbol-13-acetate (TPA), a tumor promoter [23] (Fig. 4a). Here, KRT5 is linked to neoplasm.