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Genetic alterations in main candidate genes during melanoma progression.

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.

SUBMITTER: Sini MC

PROVIDER: S-EPMC5823576 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Although melanoma is the least frequent type of skin cancer, it accounts for the majority of skin cancer-related deaths. Large-scale sequencing efforts have led to the classification of melanoma into four major subtypes (i.e., BRAF-mutant, NRAS-mutant, NF1-deficient, and triple wild-type). These sequencing studies have also revealed that melanoma genomes are some of the most mutated genomes of all cancers and therefore have a high neoantigen load. These findings have resulted in the development and clinical use of targeted therapies against the oncogenic BRAF→MEK→ERK pathway and immune checkpoint inhibitors for the treatment of metastatic melanoma. Although some patients with metastatic melanoma benefit immensely from these transformative therapies, others either become resistant or do not respond at all. These clinical challenges have intensified the search for new drug targets and drugs that can benefit patients who are either intrinsically resistant or have acquired resistance to targeted therapies and immunotherapies. Numerous signaling pathways and oncogenic drivers can cause changes in mRNA transcription that in turn drive melanoma initiation and progression. Transcriptional regulation of mRNA expression is necessary to maintain cell identity and cellular plasticity via the regulation of transcription factor expression and function, promoter/enhancer activities, chromatin regulators, and three-dimensional genome organization. Transcriptional deregulation can arise due to genetic and/or non-genetic alterations in the genome. Specifically, these deregulated transcriptional programs can become liabilities for melanoma cells due to their acquired dependencies on these programs for survival, which can be harnessed to develop new therapies for melanoma. In this article, we present an overview of the mechanisms that result in the transcriptional deregulation of mRNA expression in melanoma cells and assess how these changes facilitate melanoma initiation and progression. We also describe how these deregulated transcriptional pathways represent new opportunities for the development of unconventional and potentially impactful treatments for metastatic melanoma.

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Genetic alterations in main candidate genes during melanoma progression.

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