MC1R variants associated susceptibility to basal cell carcinoma of skin: Interaction with host factors and XRCC3 polymorphism

Abstract

The variants within the human melanocortin 1 receptor (MC1R) gene are associated with an increased risk of different skin cancers. In this study, we genotyped by direct sequencing, 529 cases of basal cell carcinoma of the skin (BCC) and 533 healthy controls for polymorphisms in the entire MC1R gene. In addition to 10 common polymorphisms, we detected 23 rare variants in the gene. The presence of any nonsynonymous MC1R variant was associated with an increased risk in the carriers (odds ratio OR 1.66, 95% confidence interval CI 1.28-2.14) corresponding to a population attributable fraction of about 27%. The odds ratio for the risk in the carriers of 2 MC1R variants was 2.69 (95% CI 1.77-4.08). The risk of BCC in the carriers of MC1R variants with fair complexion was almost twice as much as in the corresponding noncarriers. The carriers of the R163Q variant with a medium skin complexion were at a 3-fold higher risk than the noncarrier counterparts. The interaction, of effect on the BCC risk, between the MC1R variants and types of skin response to sun exposure was greater than multiplicative. We also observed a multiplicative interaction of risk due to the MC1R variants and the common allele (high risk) of the T241M polymorphism in the XRCC3 gene. Our data confirmed the status of the nonsynonymous MC1R variants as independent genetic risk factors for BCC. However, the mechanism through which the variants influence the risk likely involves complex interactions with other genetic and host risk factors. ' 2007 Wiley-Liss, Inc.Key words: MC1R; polymorphisms; basal cell carcinoma; complexion; interactions Skin pigmentation and DNA repair constitute intrinsic mechanisms evolved to prevent skin carcinogenesis. 1,2 Skin pigmentation, which inhibits DNA damage, manifests a preventive and DNA repair a corrective mechanism. A number of genes involved both in DNA repair and pigmentation, contingent to environmental and other historical selection constraints, are highly polymorphic. [3][4][5] Many of the polymorphisms in the genes involved in these processes, as a corollary, modulate the risk and contribute to the inter-individual differences in susceptibility to the skin cancers including basal cell carcinoma of skin (BCC). [6][7][8][9] The G-protein coupled Melanocortin receptor 1 (MC1R) is a pivotal component in the pathway involved in the production of melanin in melanocytes. 10 Activation of MC1R by a-MSH (a-melanocyte-stimulating hormone) leads to increased cellular cAMP. The levels of cAMP, through tyrosinase, control the switch over of synthesis from pheomelanin to photo protective eumelanin. 11 The gene encoding MC1R is highly polymorphic and many variants are associated with an increased risk of skin cancers. 12,13 More than 60 nonconservative variants of the receptor are known and at least 3 frequent variants are strongly associated with high risk phenotypes of red hair and fair skin (RHC alleles; R151C, R160W and D294H) in Caucasians. [14][15][16] Several studies have reported association between variants in the MC1R...

Phosphodiesterase 11A (PDE11A) and Genetic Predisposition to Adrenocortical Tumors

“…Interestingly, many examples of genetic susceptibility are reported also in different types of human cancers: a genetic variant of a gene encoding a member of the Ras superfamily, ARLTS1, was found predisposing patients to familial cancer (26). Recently, rare missense variants within the human melanocortin 1 receptor (MC1R), another important actor in the cAMP pathway, have been associated with a susceptibility to basal cell carcinoma of the skin (27).…”

Oral mucosal melanoma

“…1,16 Polymorphism of pigmentory genes encoding some of the above-mentioned proteins has been implicated in the pathogenesis of cutaneous melanoma, 17 and it is possible that these gene variants also play a role in the development of OMM, but further research is needed to explore this possibility.…”

“…12,13,19,20,22 Thus, some MC1R variants also play a direct role in the pathogenesis of cutaneous melanoma apart from their role in determining the cancer-prone pigmentory phenotype of red hair, blue eyes and fair skin; and it appears that the risk for melanoma is polygenic comprising interactions between MC1R variants, other pigmentory gene variants and nonmelanogenic genes including DNA repair genes, oncogenes and immuno-inflammatory genes. 17,22,23 Not only do the intermediate metabolites of melanogenesis play a role in melanomagenesis, but equally significantly they have immunosuppressive properties. If released into the microenvironment, they may contribute to evasion of immune responses by the melanoma cells, 2 thus rendering ineffective T cell-mediated immune responses against tumour-specific antigens that may directly cause lysis of tumour cells, and therefore limit tumour growth.…”

Common variants modify the age of onset for basal cell carcinomas in Gorlin syndrome

“…Variants in melanocortin 1 receptor (MC1R) gene, a major contributor to skin pigmentation, have been associated with risk of BCCs. 12 A genome-wide association study (GWAS) of over 2000 BCC cases of European ancestry in the United States replicated the strong association with the MC1R p.(Arg151Cys) missense variant (rs1805007). 13 A noncoding variant at the chromosome 6p25 locus near EXOC (rs12210050) and a variant at the 13q32 locus near UBAC2, which encodes ubiquitin-associated domain containing protein 2 (rs7335046), also reached genome-wide significance.…”