Because keratinocytes have a finite lifespan in culture, we therefore generated H-Ras-dependent malignant keratinocytes (squamous cell carcinoma [SCC] cells) after two-stage chemical carcinogenesis using DMBA/TPA (McLean et al., 2001, Quintanilla et al., 1986). The gene discussed is HRAS; the disease is squamous cell carcinoma.