Genetic susceptibility and driver genes in cutaneous melanoma

Melanoma represents approximately 2% of all cutaneous malignant neoplasias causing1% of cancer-related deaths.The mitogen-activated protein kinase (MAPK) cascade is the most relevant molecular pathway implicated in melanoma pathogenesis.This study aimed to evaluate the intra-patient molecular heterogeneity between primary melanoma and related metastases and to compare the consistency of mutational findings obtained by molecular and immunohistochemical (IHC) analyses.Overall, 69 formalin-fixed paraffin-embedded (FFPE) tissues (30 primary melanomas and 39 related metastatic lesions) belonging to 30 melanoma patients were retrieved at the Dermatology Unit, University of L’Aquila, Italy.We investigated codon 600 in exon 15 of BRAF by competitive allele-specific TaqMan PCR, exon 2 of NRAS, and exons 11, 13 and 17 of c-KIT by Sanger sequencing.c-KIT copy number was assessed by quantitative real-time PCR.The presence of BRAFV600E and NRASQ61R mutants and c-KIT expression were evaluated by IHC using the specific antibodies.BRAFV600 mutations were observed in 47.8% of samples, whereas NRASQ61 mutations were detected in 23.2%.c-KIT gene amplification was found in 4.3% of cases.Intra-patient heterogeneity between primary melanoma and related metastases was observed for BRAF and NRAS genes in 13.3% of patients each.Considering the global mutational profile of BRAF/NRAS/c-KIT genes, intra-patient heterogeneity was detected in 7 of 30 patients (23.3%).Following IHC analysis, 37.7% of samples were positive for anti-BRAFV600E VE1 immunostaining, while 14.5% of specimens were positive for anti-NRASQ61R SP174 staining.Comparison between results achieved from molecular methods and IHC showed a discrepancy of 5.1% for BRAFV600E mutation and 1.6% of NRASQ61R.Our findings confirm that intra-patient heterogeneity between primary melanoma and related metastases is relevant and independent from the methodological approach.In addition, molecular methods and IHC provided highly consistent results in the detection of BRAFV600E and NRASQ61R mutations supporting IHC as a rapid and cost-effective screening method in melanoma.Approximately 5–12% of melanoma cases occur in a familial setting.CDKN2A and CDK4 are well-known high-risk melanoma susceptibility genes.The introduction of NGS methodologies led to the identification of new melanoma susceptibility genes implicated in melanoma development including BAP1, POT1, ACD, TERF2IP and the promoter region of TERT.In addition to high-risk genes, intermediate-penetrance genes, such as MC1R and MITF, have been demonstrated to be candidate genes associated to melanoma predisposition.The project aimed to evaluate melanoma genetic predisposition in Mediterranean populations.Melanoma families were recruited from Melanostrum consortium centers in Spain (Barcelona and Valencia), Italy (L’Aquila, Rome, Cesena, Genoa and Padua) and Greece (Athens).Inclusion criteria were as follows: presence of 1st or 2nd degree relatives suffering from melanoma.Overall, 852 families with a total of 1365 affected patients and 2123 unaffected members, enrolled at MelaNostrum centers were included in the study: 520 were from Spain (61.0%), 318 were from Italy (37.3%) and 14 from Greece (1.6%).The most frequent variant was G101W detected in 27.4% of families, followed by R24P found in 7.2% of families.The presence of CDKN2A variants was significantly associated with the number of affected members in the family (p<0.0001), the presence of multiple primary melanomas in affected members (p<0.0001) and familial history of pancreatic cancer (p<0.0001).Our findings confirm the key role of CDKN2A variants and the rarity of other high-risk genes mutations in melanoma predisposition of Mediterranean populations.Moreover, our results support the importance of the genetic screening of susceptibility genes in familial melanoma patients.