Role of key-regulator genes in melanoma susceptibility and pathogenesis among patients from South Italy

Background. Several genetic alterations have been demonstrated to contribute to the development and progression of melanoma. In this study, we further investigated the impact of key-regulator genes in susceptibility and pathogenesis of such a disease.Methods. A large series (N = 846) of sporadic and familial cases originating from South Italy was screened for germline mutations inp16CDKN2A,BRCA2, andMC1Rgenes by DHPLC analysis and automated DNA sequencing. Paired primary melanomas and lymph node metastases from same patients (N = 35) as well as melanoma cell lines (N = 18) were analyzed for somatic mutations inNRAS, BRAF,andp16CDKN2Agenes.Results. For melanoma susceptibility, investigations at germline level indicated thatp16CDKN2Awas exclusively mutated in 16/545 (2.9%) non-Sardinian patients, whereasBRCA2germline mutations were observed in 4/91 (4.4%) patients from North Sardinia only. TwoMC1Rgermline variants, Arg151Cys and Asp294His, were significantly associated with melanoma in Sardinia. Regarding genetic events involved in melanoma pathogenesis at somatic level, mutually-exclusive mutations ofNRASandBRAFgenes were observed at quite same rate (about two thirds) in cultured andin vivomelanomas (either primary or metastatic lesions). Conversely,p16CDKN2Agene alterations were observed at increased rates moving from primary to metastatic melanomas and melanoma cell lines. Activation of the ERK gene product was demonstrated to be consistently induced by a combination of molecular alterations (NRAS/BRAFmutations andp16CDKN2Asilencing).Conclusion. Our findings further clarified that: a) mutation prevalence in melanoma susceptibility genes may vary within each specific geographical area; b) multiple molecular events are accumulating during melanomagenesis.