Genetic variants in pigmentation genes, pigmentary phenotypes, and risk of skin cancer in Caucasians

Abstract

Human pigmentation is a polygenic quantitative trait with high heritability. Although a large number of single nucleotide polymorphisms (SNPs) have been identified in pigmentation genes, very few SNPs have been examined in relation to human pigmentary phenotypes and skin cancer risk. We evaluated the associations between 15 SNPs in 8 candidate pigmentation genes (TYR, TYRP1, OCA2, SLC24A5, SLC45A2, POMC, ASIP and ATRN) and both pigmentary phenotypes (hair color, skin color and tanning ability) and skin cancer risk in a nested case-control study of Caucasians within the Nurses' Health Study (NHS) among 218 melanoma cases, 285 squamous cell carcinoma (SCC) cases, 300 basal cell carcinoma (BCC) cases and 870 common controls. We found that the TYR Arg402Gln variant was significantly associated with skin color (p-value = 7.7 x 10(-4)) and tanning ability (p-value = 7.3 x 10(-4)); the SLC45A2 Phe374Leu variant was significantly associated with hair color (black to blonde) (p-value = 2.4 x 10(-7)), skin color (p-value = 1.1 x 10(-7)) and tanning ability (p-value = 2.5 x 10(-4)). These associations remained significant after controlling for MC1R variants. No significant associations were found between these polymorphisms and the risk of skin cancer. We observed that the TYRP1 rs1408799 and SLC45A2 1721 C>G were associated with melanoma risk (OR, 0.77; 95% CI, 0.60-0.98 and OR, 0.75; 95% CI, 0.60-0.95, respectively). The TYR Ser192Tyr was associated with SCC risk (OR, 1.23; 95% CI, 1.00-1.50). The TYR haplotype carrying only the Arg402Gln variant allele was significantly associated with SCC risk (OR, 1.35; 95% CI, 1.04-1.74). The OCA2 Arg419Gln and ASIP g.8818 A>G were associated with BCC risk (OR, 1.50; 95% CI, 1.06-2.13 and OR, 0.73; 95% CI, 0.53-1.00, respectively). The haplotype near ASIP (rs4911414[T] and rs1015362[G]) was significantly associated with fair skin color (OR, 2.28; 95% CI, 1.46-3.57) as well as the risks of melanoma (OR, 1.68; 95% CI, 1.18-2.39) and SCC (OR, 1.54; 95% CI, 1.08-2.19). These associations remained similar after adjusting for pigmentary phenotypes and MC1R variants. The statistical power of our study was modest and additional studies are warranted to confirm the associations observed in the present study. Our study provides evidence for the contribution of pigmentation genetic variants, in addition to the MC1R variants, to variation in human pigmentary phenotypes and possibly the development of skin cancer.

Figure 1. The function of select pigmentation genes in the pigmentation pathway

Induction of POMC/α-MSH activates the MC1R, inducing cAMP production in melanocyte. This elevated signaling leads to eumelanin production, resulting in the maturation of the pheomelanosome to the eumelanosome. Attractin (ATRN) is a low-affinity receptor for agouti signaling protein (ASIP), an antagonist of MC1R. Some proteins, such as TYR, TYRP1, P-protein, SLC24A5, and MATP, are involved in inducing melanization of pheomelanosome or eumelanosome, as described in the text.