Progression of actinic keratosis to squamous cell carcinoma of the skin correlates with deletion of the 9p21 region encoding the p16INK4a tumor suppressor

Actinic keratoses (AKs) are pre-neoplastic lesions that can develop into squamous cell carcinomas (SCCs) of the skin. Often AK and SCC have commonly altered p53. A status of another tumor suppressor, the p16INK4a, was reported for SCC but not for AK. A comparative study of SCC and AK human samples by loss of heterozygosity (LOH) analysis determined that the p16INK4a/ARF locus is less frequently altered in AKs than in SCCs. These LOH data highly correlated with immunohistochemical findings demonstrating the presence of p16INK4a in the AK skin samples but its absence in SCC lesions. Our results imply that progression of AK into SCC may involve inactivation of p16INK4a.