Association of genetic variants in CDK6 and XRCC1 with the risk of dysplastic nevi in melanoma-prone families

Dysplastic nevi (DN) is a strong risk factor for cutaneous malignant melanoma (CMM), and it frequently occurs in melanoma-prone families. To identify genetic variants for DN, we genotyped 677 tagSNPs in 38 melanoma candidate genes that are involved in pigmentation, DNA repair, cell cycle control, and melanocyte proliferation pathways in a total of 504 individuals (310 with DN, 194 without DN) from 53 melanoma-prone families (23 CDKN2A mutation positive and 30 negative). Conditional logistic regression, conditioning on families, was used to estimate the association between DN and each SNP separately, adjusted for age, sex, CMM and CDKN2A status. P-values for SNPs in the same gene were combined to yield gene-specific p-values. Two genes, CDK6 and XRCC1, were significantly associated with DN after Bonferroni correction for multiple testing (P=0.0001 and 0.00025, respectively), whereas neither gene was significantly associated with CMM. Associations for CDK6 SNPs were stronger in CDKN2A mutation positive families (rs2079147, P(interaction)=0.0033), whereas XRCC1 SNPs had similar effects in mutation-positive and negative families. The association for one of the associated SNPs in XRCC1 (rs25487) was replicated in two independent datasets (random effect meta-analysis: P<0.0001). Our findings suggest that some genetic variants may contribute to DN risk independently of their association with CMM in melanoma-prone families.