TP53 and cutaneous squamous cell carcinoma: To shed further light in skin photocarcinogenesis, we used the types of skin cells that differ in their p53 status: NHEK(p53wt), HaCaT(p53mut), and SCL-1 (no p53 protein expressed) cells as an in vitro model for normal skin, actinic keratoses, and cutaneous squamous cell carcinomas respectively.