Identification of modifier genes for cutaneous malignant melanoma in melanoma-prone families with and without CDKN2A mutations.

CDKN2A is a major susceptibility gene for cutaneous malignant melanoma (CMM), but the variable penetrance and clinical manifestations among mutation carriers suggest the existence of modifier factors. The goal of this study was to identify modifier genes for CMM in CMM-prone families with or without CDKN2A mutations. We genotyped 537 individuals (107 CMM) from 28 families (19 CDKN2A+, 9 CDKN2A-) for 1,536 SNPs in 152 genes involved in DNA repair, apoptosis and immune response pathways. We used conditional logistic regression to account for family ascertainment and differences in disease prevalence among families. Pathway- and gene-based permutation analyses were used to assess the risk of CMM associated with genes in the 5 pathways (DNA repair, apoptosis, TNF/NFkappaB, TH1:TH2 and other immune regulation). Our analyses identified some candidate genes such as FAS, BCL7A, CASP14, TRAF6, WRN, IL9, IL10RB, TNFSF8, TNFRSF9 and JAK3 that were associated with CMM risk (p<0.01, gene-based test). After correction for multiple comparisons, IL9 remained significant (Bonferroni p<0.05). The effects of some genes were stronger in CDKN2A-positive families (BCL7A and IL9), while some were stronger in CDKN2A-negative families (BCL2L1). Our findings support the hypothesis that common genetic polymorphisms in DNA repair, apoptosis and immune response pathways may modify the risk of CMM in CMM-prone families with or without CDKN2A mutations.