Dataset Information

Genetic profiling of mucosal melanoma

ABSTRACT: Primary mucosal melanomas (MMs) arise from melanocytes located in mucosal membranes lining the respiratory, gastrointestinal and urogenital tracts. MMs frequently present late and have a poor prognosis; the 5-year survival rate is only 14%. MM makes up only ~1.4% of all melanomas and it is this rarity that makes knowledge of the genetic changes that contribute to its pathogenesis limited to a small number of exome/genome studies and other targeted studies. Thus to investigate the somatic alterations and mutation spectra in MM genomes, we have extracted genomic DNA from formalin-fixed, paraffin-embedded (FFPE) human MMs, and subjected them to whole exome sequencing. Given the propensity of MM to metastasize, we will also be sequencing metastatic MM lesions; primary and metastatic lesions from the same individual represent an excellent opportunity to identify potential drivers of metastasis in MM. Finally we will sequence ‘normal’ DNA from the same individual, where possible, to exclude germline variations.

PROVIDER: EGAS00001001115 | EGA |

REPOSITORIES: EGA

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Project description:Cutaneous, ocular and mucosal melanomas are histologically indistinguishable tumors that are driven by different spectrum of genetic alterations. With current methods, identification of the site of origin of a melanoma metastasis is challenging, in particular when the metastasis is the first tumor manifestation. Genome wide DNA methylation profiling has shown promise for the identification of the site of tumor origin in various settings. Here we explore the DNA methylation landscape of melanomas from different sites and analyze if different melanoma origins can be distinguished by their epigenetic profile. We performed DNA methylation analysis, next generation DNA panel sequencing and copy number analysis of 82 non-cutaneous and 25 cutaneous melanoma samples. We further analyzed eight normal melanocyte cell culture preparations by DNA methylation profiling. DNA methylation analysis clearly separated uveal melanomas from melanomas of other primary sites while mucosal, conjunctival and cutaneous melanomas were epigenetically almost identical. Still, we observed DNA methylation differences in cancer-related genes, such as low frequencies of RARB and CDKN2A promoter methylation in mucosal melanomas, while conjunctival melanomas frequently harbored APC promoter methylation. Furthermore, all investigated melanomas of the paranasal sinus showed loss of PTEN expression, mainly caused by promoter methylation. This was less frequently seen in melanomas of other sites. Copy number analysis revealed recurrent amplifications in mucosal melanomas, including chromosome 4q, 5p, 11q and 12q. Most melanomas of the oral cavity showed gains of chromosome 5p with TERT amplification while 11q amplifications were enriched in melanomas of the nasal cavity. Mucosal, conjunctival and cutaneous melanomas show a surprisingly similar DNA methylation profile and identification of the site of origin by DNA methylation testing is likely not feasible. Still, our study shows that there are DNA methylation differences on the gene level in known tumor drivers, related to the anatomical primary site.

Dataset Information

Genetic profiling of mucosal melanoma

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