CDKN2A and CDK4 mutation analysis in Italian melanoma-prone families: functional characterization of a novel CDKN2A germ line mutation

Abstract

Summary Physical interaction between CDKN2A/p16 and CDK4 proteins regulates the cell cycle progression through the G1 phase and dysfunction of these proteins by gene mutation is implicated in genetic predisposition to melanoma. We analysed 15 Italian melanoma families for germ line mutations in the coding region of the CDKN2A gene and exon 2 of the CDK4 gene. One novel disease-associated mutation (P48T), 3 known pathological mutations (R24P, G101W and N71S) and 2 common polymorphisms (A148T and Nt500 G>C) were identified in the CDKN2A gene. In a family harbouring the R24P mutation, an intronic variant (IVS1, +37 G>C) of uncertain significance was detected in a noncarrier melanoma case. The overall incidence of CDKN2A mutations was 33.3%, but this percentage was higher in families with 3 or more melanoma cases (50%) than in those with only 2 affected relatives (25%). Noteworthy, functional analysis established that the novel mutated protein, while being impaired in cell growth and inhibition assays, retains some in vitro binding to CDK4/6. No variant in the p16-binding region of CDK4 was identified in our families. Our results, obtained in a heterogeneous group of families, support the view that inactivating mutations of CDKN2A contribute to melanoma susceptibility more than activating mutations of CDK4 and that other genetic factors must be responsible for melanoma clustering in a high proportion of families. In addition, they indicate the need for a combination of functional assays to determine the pathogenetic nature of new CDKN2A mutations.

Characterization of individuals at high risk of developing melanoma in Latin America: bases for genetic counseling in melanoma

“… 29 Mutation p.G101W is also frequent in Latin America, as in Mediterranean countries (Italy, France, and Spain) 7 where haplotype analysis showed a founder effect. 30 We identified four other mutations in Brazil: p.P48T (c.142C>A), previously reported in an Italian population with FM, 31 was found in four families, one of them of Italian ancestry, suggesting a possible founder effect 32 ; IVS2-105A>G and p.M53I (c.159G>C), previously reported in melanoma-prone families from the United Kingdom, Australia, and the United States 7 ; and mutation p.V43L (c.127G>C), affecting p14ARF, which has not previously been reported. In Uruguay we detected p.E88X (c.262G>T) in two families, which also was detected in two Spanish pedigrees.…”

Absence of germlineCDKN2Amutation in Sicilian patients with familial malignant melanoma: Could it be a population-specific genetic signature?

“…52,53 Germline mutations in genes encoding for CDK4 and CDKN2A, involved in regulation of the cell cycle, have been shown to confer a high risk of malignant melanoma. 54 In addition, frequent germline allelic variants in the Casp8, MTAP, MATP, MC1R, MITF and ASIP genes have been identified as low-risk susceptibility genes or as modifiers of high-risk susceptibility genes. 55 Germline CDKN2A mutations have been described in 25-40% of melanoma-prone families from several countries, and most of them are missense mutations mainly affecting p16INK4a.…”

DNA sequence and analysis of human chromosome 9

“…Chromosome 9p21 harbours the tumour suppressor gene CDKN2A and is often involved in translocations or deletions in tumour cell lines. Mutation or loss of CDKN2A is linked to familial melanoma and other tumours40. Reciprocal translocation between chromosomes 9 and 22 leads to generation of a derivative chromosome, the Philadelphia chromosome, in >90% of chronic myelogenous leukaemia and 5–15% of acute B cell lymphoblastic leukaemias41.…”