[The INK4a-ARF locus: role in the genetic predisposition to familial melanoma and in skin carcinogenesis].
The INK4a-ARF locus, localized on 9p21, encodes two tumor suppressor proteins, p16INK4a and p14ARF, acting respectively through the CDK4-pRb and the p53 pathways. Familial melanoma (comprising between 8 and 12% of all melanoma cases) is a genodermatosis transmitted as an autosomal dominant trait, often associated with clinically atypical moles (AN). Germline mutations of p16INK4a are found in up to 20-30% of melanoma prone families. Mutated families often contain more than three family members affected and/or comprise at least one relative with multiple melanomas. Most of these mutations have been shown to affect p16INK4a protein function (i.e. CDK4 binding or pRB phosphorylation). Germline mutations of p16INK4a are also found in a lesser extend in sporadic multiple melanoma and in familial pancreatic cancer. The INK4a-ARF locus plays also an important role in skin carcinogenesis. P16INK4a UV induced mutations (CC:GG > TT:AA tandem transition or C:G > T:A transition at dipyrimidic site) are found in 12% of sporadic skin carcinomas, mainly in epidermoid tumors, and seem to occur independently of p53 mutations. Xeroderma pigmentosum (XP) is characterized by an inheritable DNA repair defect (involving the nucleotid excision repair (NER) system) predisposing to skin carcinomas. In skin tumors from (XP) patients, p16INK4a UV induced mutations occur more frequently, are often multiple, and significantly associated with the presence of p53 mutations. Such data, which could be related to the XP genetic instability and indicates a possible cooperative effect of inactivation of these pathways in the tumoral process of XP skin tumors.
Soufir
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Laboratoire de biochimie B, hormonologie et génétique, Hôpital Bichat-Claude-Bernard, 46, rue Henri-Huchard, 75877 Paris Cedex 18. nadem.soufir@bch.ap-hop-paris.fr
Basset-Seguin
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D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000235:genetics* / Q000502:physiology; D019942:Genes, p16 / Q000502:physiology*; D020022:Genetic Predisposition to Disease / Q000235:genetics*; D018095:Germ-Line Mutation / Q000235:genetics; D006801:Humans; D008545:Melanoma / Q000235:genetics*; D012878:Skin Neoplasms / Q000235:genetics*; D014158:Transcription, Genetic; D025803:Tumor Suppressor Protein p14ARF / Q000235:genetics* / Q000502:physiology; D014983:Xeroderma Pigmentosum / Q000235:genetics*
D019941:Cyclin-Dependent Kinase Inhibitor p16; D025803:Tumor Suppressor Protein p14ARF