CDKN2A encodes two proteins, p16INK4a and p14ARF, both inhibitors of cellular senescence. The protein produced when the alternate reading frame (ARF) for exon 1 is transcribed instead of the standard reading frame exerts its biological effects through the p53 pathway. It mediates cell cycle arrest at the G1 and G2/M checkpoints, complementing p16’s block of G1/S progression—thereby facilitating cellular repair of DNA damage.
Mutations in CDKN2A account for 35% to 40% of familial melanomas.[62] A large case series from Britain found that CDKN2A mutations were present in 100% of families with seven to ten individuals affected with melanoma, 60% to 71% of families with four to six cases, and 14% of families with two cases.[63] A similar study of Greek individuals with melanoma found CDKN2A mutations in 3.3% of single melanoma cases, 22% of familial melanoma cases, and 57% of individuals with multiple primary melanomas.[73] Many mutations reported among families consist of founder mutations, which are unique to specific populations and the geographic areas from which they originate.[74-80]
Depending on the study design and target population, melanoma penetrance related to deleterious CDKN2A mutations differs widely. One study of 80 multiple-case families demonstrated that the penetrance varied by country, an observation that was attributed to major differences in sun exposure.[81] For example, in Australia, the penetrance was 30% by age 50 years and 91% by age 80 years; in the United States, the penetrance was 50% by age 50 years and 76% by age 80 years; in Europe, the penetrance was 13% by age 50 years and 58% by age 80 years. In contrast, a comparison of families with the CDKN2A mutation in the United Kingdom and Australia demonstrated the same cumulative risk of melanoma; for CDKN2A carriers, the risk of developing melanoma seemed independent of ambient UV radiation.[82] Another study of individuals with melanoma identified in eight population-based cancer registries and one hospital-based sample obtained a self-reported family history and sequenced