Deletion of the MGMT gene in familial melanoma

Genetic profiling of a rare condition: co-occurrence of albinism and multiple primary melanoma in a Caucasian family

Multiple primary melanoma (MPM) is a rare condition, whose genetic basis has not yet been clarified. Only 8-12% of MPM are due to germline mutations of CDKN2A. However, other genes (POT1, BRCA1/2, MC1R, MGMT) have been demonstrated to be involved in predisposition to this pathology.

To our knowledge, this is the first family study based on two siblings with the rare coexistence of MPM and oculocutaneous albinism (OCA), an autosomal recessive disease characterized by the absence or decrease in pigmentation in the skin, hair, and eyes.

In this study, we evaluated genes involved in melanoma predisposition (CDKN2A, CDK4, MC1R, MITF, POT1, RB1, MGMT, BRCA1, BRCA2), pathogenesis (BRAF, NRAS, PIK3CA, KIT, PTEN), skin/hair pigmentation (MC1R, MITF) and in immune pathways (CTLA4) to individuate alterations able to explain the rare onset of MPM and OCA in indexes and the transmission in their pedigree.

From the analysis of the pedigree, we were able to identify a “protective” haplotype with respect to MPM, including MGMT p.I174V alteration. The second generation offspring is under strict follow up as some of them have a higher risk of developing MPM according to our model.

Genetic predisposition to melanoma

Malignant melanoma is a rare, often fatal form of skin cancer with a complex multigenic etiology. The incidence of melanoma is increasing at an alarming rate. A number of heritable factors contribute to a patient's overall melanoma risk, including response to ultraviolet light, nevus number, and pigmentation characteristics, such as eye and hair color. Approximately 5%-10% of melanoma cases are familial, yet the majority of familial cases lack identifiable germ-line mutations in known susceptibility genes. Additionally, most familial melanomas lack germ-line mutations in genes that are commonly mutated in sporadic melanoma. Candidate and systematic genome-wide association studies have led to an improved understanding of the risk factors for melanoma and the identification of susceptibility genes. In this review, we provide an overview of the major risk factors and known genes implicated in familial melanoma susceptibility.

DNA Methylation Levels of Melanoma Risk Genes Are Associated with Clinical Characteristics of Melanoma Patients

In melanoma development, oncogenic process is mediated by genetic and epigenetic mutations, and few studies have so far explored the role of DNA methylation either as predisposition factor or biomarker. We tested patient samples for germline CDKN2A methylation status and found no evidence of inactivation by promoter hypermethylation. We have also investigated the association of clinical characteristics of samples with the DNA methylation pattern of twelve genes relevant for melanomagenesis. Five genes (BAP1, MGMT, MITF, PALB2, and POT1) presented statistical association between blood DNA methylation levels and either CDKN2A-mutation status, number of lesions, or Breslow thickness. In tumors, five genes (KIT, MGMT, MITF, TERT, and TNF) exhibited methylation levels significantly different between tumor groups including acral compared to nonacral melanomas and matched primary lesions and metastases. Our data pinpoint that the methylation level of eight melanoma-associated genes could potentially represent markers for this disease both in peripheral blood and in tumor samples.