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 in p16(CDKN2A), BRCA2, and MC1R genes 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 in NRAS, BRAF, and p16(CDKN2A) genes. RESULTS: For melanoma susceptibility, investigations at germline level indicated that p16(CDKN2A) was exclusively mutated in 16/545 (2.9%) non-Sardinian patients, whereas BRCA2 germline mutations were observed in 4/91 (4.4%) patients from North Sardinia only. Two MC1R germline variants, Arg151Cys and Asp294His, were significantly associated with melanoma in Sardinia. Regarding genetic events involved in melanoma pathogenesis at somatic level, mutually-exclusive mutations of NRAS and BRAF genes were observed at quite same rate (about two thirds) in cultured and in vivo melanomas (either primary or metastatic lesions). Conversely, p16(CDKN2A) gene 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/BRAF mutations and p16(CDKN2A) silencing). 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.

Role of the EGF +61A>G polymorphism in melanoma pathogenesis: an experience on a large series of Italian cases and controls.

BACKGROUND: A single nucleotide polymorphism (61A>G) in the epidermal growth factor (EGF) gene has been implicated in both melanoma pathogenesis and increased melanoma risk. To further evaluate this association, we conducted a case-control study in a clinic-based Italian population. METHODS: Individuals with less than 10 (N = 127) or more than 100 (N = 128) benign nevi, and patients with cutaneous melanoma (N = 418) were investigated for the EGF +61A>G polymorphism, using an automated sequencing approach. RESULTS: Overall, no difference in EGF genotype frequencies was observed among subjects with different number of nevi as well as when non-melanoma healthy controls were compared with the melanoma patients. However, a heterogeneous distribution of the frequencies of the G/G genotype was detected among cases and controls originating from North Italy (21.1 and 18.3%, respectively) vs. those from South Italy (12.6 and 17.1%, respectively). CONCLUSION: Our findings further suggest that EGF +61A>G polymorphism may have a limited impact on predisposition and/or pathogenesis of melanoma and its prevalence may vary in different populations.

Factors predicting the occurrence of germline mutations in candidate genes among patients with cutaneous malignant melanoma from South Italy.

Clinical predictors for germline mutations of candidate genes in large clinic based population of patients with cutaneous malignant melanoma (CMM) are widely awaited. Using denaturing high-performance liquid chromatography (DHPLC) analysis and DNA sequencing, 557 consecutively-collected CMM patients originating from South Italy were screened for CDKN2A germline mutations; subsets of them were screened for mutations in the BRAF and BRCA2 genes. Seven CDKN2A mutations were detected in 14 (2.5%) CMM patients. Relative risk of carrying a CDKN2A mutation for CMM patients was demonstrated to significantly increase with the presence of familial recurrence of melanoma (risk ratio (RR)=6.31; p=0.0009), multiple primary melanomas (RR=3.43; p=0.0014), and early onset age (RR=4.56; p=0.0026). All CDKN2A mutations were observed in non-Sardinian patients (14/441; 3.2%), whereas BRAF and BRCA2 genes were found mutated in Sardinian patients (3/116; 2.6%). Such indicators of the presence of CDKN2A mutations will be useful in counselling patients about undergoing genetic testing. Our findings strongly suggest that mutation rates of candidate cancer genes may deeply vary among CMM patients from different geographical areas.

Serial detection of circulating tumour cells by reverse transcriptase-polymerase chain reaction assays is a marker for poor outcome in patients with malignant melanoma.

BACKGROUND: Detection of circulating malignant cells (CMCs) through a reverse transcriptase-polymerase chain reaction (RT-PCR) assay seems to be a demonstration of systemic disease. We here evaluated the prognostic role of RT-PCR assays in serially-taken peripheral blood samples from patients with malignant melanoma (MM). METHODS: One hundred forty-nine melanoma patients with disease stage ranging from I to III were consecutively collected in 1997. A multi-marker RT-PCR assay was used on peripheral blood samples obtained at time of diagnosis and every 6 months during the first two years of follow-up (total: 5 samples). Univariate and multivariate analyses were performed after 83 months of median follow-up. RESULTS: Detection of at least one circulating mRNA marker was considered a signal of the presence of CMC (referred to as PCR-positive assay). A significant correlation was found between the rate of recurrences and the increasing number of PCR-positive assays (P = 0.007). Presence of CMC in a high number (> or =2) of analysed blood samples was significantly correlated with a poor clinical outcome (disease-free survival: P = 0.019; overall survival: P = 0.034). Multivariate analysis revealed that presence of a PCR-positive status does play a role as independent prognostic factors for overall survival in melanoma patients, adding precision to the predictive power of the disease stage. CONCLUSION: Our findings indicated that serial RT-PCR assay may identify a high risk subset of melanoma patients with occult cancer cells constantly detected in blood circulation. Prolonged presence of CMCs seems to act as a surrogate marker of disease progression or a sign of more aggressive disease.