Genetic alterations in main candidate genes during melanoma progression

// Maria Cristina Sini 1, * , Valentina Doneddu 2, * , Panagiotis Paliogiannis 3, * , Milena Casula 1 , Maria Colombino 1 , Antonella Manca 1 , Gerardo Botti 4 , Paolo A. Ascierto 4 , Amelia Lissia 2 , Antonio Cossu 2 and Giuseppe Palmieri 1 1 Unit of Cancer Genetics, Institute of Biomolecular Chemistry, National Research Council, Sassari, Italy 2 Department of Surgical, Microsurgical and Medical Sciences, University of Sassari, Sassari, Italy 3 Department of Clinical and Experimental Medicine, University of Sassari, Sassari, Italy 4 Istituto Nazionale Tumori, Fondazione Pascale, Napoli, Italy * These authors contributed equally to this work Correspondence to: Valentina Doneddu, email: valentinadoneddu@gmail.com Keywords: malignant melanoma; fluorescence in situ hybridization (FISH) analysis; genetic heterogeneity; mutation analysis; oncogenic driver genes Received: March 02, 2017      Accepted: November 13, 2017      Published: January 03, 2018 ABSTRACT Cutaneous melanoma is a common and aggressive human skin cancers. Much is actually known about the molecular mechanisms underlying melanoma pathogenesis. The aim of the study was to evaluate any possible correlation between mutations in main growth-controlling genes ( BRAF, NRAS, CDKN2A ) and copy number variations in frequently amplified candidate genes ( MITF, EGFR, CCND1, cMET, and cKIT ) during melanoma initiation and progression. A large series of primary and secondary melanoma tissue samples ( N = 274) from 232 consecutively-collected patients of Italian origin as well as 32 tumor cell lines derived from primary and metastatic melanomas underwent mutation screening and fluorescence in situ hybridization (FISH) analysis. Overall, BRAF, NRAS, and CDKN2A were found mutated in 62.5%, 12.5% and 59% cell lines and in 47%, 16%, 12% tumor tissues, respectively. Quite identical mutation patterns between primary tumors and metastatic lesions were found for BRAF and NRAS genes; mutations of CDKN2A gene appeared to be instead selected during tumor progression. In cell lines, high rates of gene amplifications were observed (varying from 12.5% for cKIT to 50% for MITF ); vast majority of cell lines (75%) presented at least one amplified gene. Conversely, prevalence of gene amplification was significantly and progressively decreasing in melanoma metastases (12%) and primary melanomas (4%). Our findings suggest that gene amplifications may be acquired during the late phases of melanoma evolution and mostly act as “passenger” or “non-causative” alterations.