In the classic DMBA (7,12-dimethylbenz [a]anthracene) plus TPA (12-O-tetradecanoylphorbol-13-acetate) mouse model of cSCC, the mutagen DMBA promotes H-Ras mutation in 95% of tumors while repeated application TPA drives proliferation, leading to hyperplasia. The gene discussed is HRAS; the disease is skin squamous cell carcinoma.