Living reference work entry
Skin carcinogenesis is multistep process by which a number of distinct phases occur to form malignant skin tumors. The first step in skin carcinogenesis is initiation, which is a reversible process during genetic mutations, gene activation, or inactivation occur. Examples of initiation are mutations in the v-Ha- rasoncogene or inactivation of the p53 tumor suppressor gene. The next phase of carcinogenesis is tumor promotion, characterized by a reversible phase of clonal expansion of initiated cells containing mutations/inactivated genes, with a dysregulation of apoptosis of the initiated cells, as well as by the accumulation of epigenetic changes such as DNA methylation, inflammation characterized by infiltration of activated leukocytes, and the production of growth factors, cytokines, and reactive intermediates, including oxygen free radicals and nitrogen radicals which stimulate the formation of DNA damage, with the inhibition of DNA repair enzymes. These alterations...
KeywordsClonal Expansion Actinic Keratosis Skin Tumor Epidermal Keratinocytes Skin Carcinogenesis
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