MC1R CpG island regulates MC1R expression and is methylated in a subset of melanoma tumours.

Melanocortin 1 receptor (MC1R) is a G protein-coupled receptor expressed in melanocytes where it plays an important role in skin pigmentation and in the UV response, and has implications in melanoma development. Here we show that methylation of a CpG island (CGI) within the MC1R gene can control expression of MC1R in melanoma. This CGI overlaps with a potential enhancer region, and is unmethylated in normal melanocytes but highly methylated in other skin cells, suggesting a melanocyte specific function. Analysis showed that MC1R was the only gene significantly differentially expressed by methylation of this region. Within several data sets, this region is methylated in a subset of melanoma tumours (55%-74% of tumours) and results in reduced MC1R expression and significantly longer overall survival.