Analysis of promoter hypermethylation of death-associated protein kinase and p16 tumor suppressor genes in actinic keratoses and squamous cell carcinomas of the skin

Death-associated protein kinase is a serine/threonine protein kinase implicated in promoting apoptosis and tumor suppression, whereas p16 is a tumor suppressor gene that inhibits cyclin-dependent kinase 4 and 6 activity and arrests the cell cycle in the G1 phase. Hypermethylation of death-associated protein kinase or p16 gene with resultant gene inactivation has been described in a wide variety of human cancers. Promoter methylation of the death-associated protein kinase and p16 gene has been found in about 55% and 30% cases of head and neck squamous cell carcinoma respectively but has not yet been analyzed in cutaneous premalignant and malignant lesions. A total of 33 cases were examined for evidence of death-associated protein kinase and p16 hypermethylation. and these consist of 9 cases of spongiotic dermatitis as normeoplastic skin control, 9 cases of actinic keratosis, 8 cases of squamous cell carcinoma in situ and 7 cases of invasive squamous cell carcinoma. Death-associated protein kinase promoter methylation was detected in 1 case of squamous cell carcinoma in situ and 1 case of normeoplastic skin control but none of the cases of invasive squamous, cell carcinoma or actinic keratosis. P16 promoter methylation was detected in 1 case of invasive squamous cell carcinoma and 1 case of nonneoplastic skin control but none of the cases of squamous cell carcinoma in situ or actinic keratosis. Promoter hypermethylation of the death-associated protein kinase and p16 genes does not appear to play an important role in the development of cutaneous squamous, cell carcinoma. The data thus suggest that the mechanisms of ultraviolet-induced cutaneous carcinomas differ from those involved in the development of head and neck squamous cell carcinoma, a malignant disease induced by tobacco and alcohol exposure.