CDKN2A and cutaneous squamous cell carcinoma: The identification of aberrant methylation in genes such as Cip1/p21 and p16 INK4a [182], genes of the cadherin and laminin families [183], and the inactivation of the RB1/p16 and p53 pathways in cutaneous squamous cell carcinoma [184], as well as other studies, supports the notion that important epigenetic changes are mediated by chronic sun or UV radiation exposure.