Abstract 5616: Assessment of differential DNA methylation by genotype in ovarian cancer cases and controls

Ovarian carcinoma is a significant cause of cancer mortality in women in the United States. Increasing evidence has demonstrated that differential methylation status in lymphocyte DNA may be linked to risk of carcinogenesis. We are investigating the differential DNA methylation in germline DNA obtained from pre-treatment ovarian cancer cases (n=256) and individually-age matched controls (n=274) using the Illumina Infinium Human Methylation 27K BeadChip. We are first studying methylation and the common moderate-risk alleles for ovarian cancer on chromosomes 2q31, 3q25, 8q24, 9p22, 17q21, and 19p13. Within each locus, we correlated single nucleotide polymorphism (SNP) genotypes with methylation values at relevant nearby CpG sites. Preliminary results are available on the first set of 84 cases and 90 controls. At 2q31, cases with TG or TT genotype at rs2072590 were hypomethylated at HOXD1 (a homeobox transcription factor) compared to cases with GG genotype (mean beta TG/TT=0.08, GG=0.09, p=0.034); and at 17q21, cases with AG or GG genotype at rs9303542 were hypomethylated at SKAP1 (a T-cell adaptor protein) compared to cases with AA genotype (mean beta AG/GG=0.14, AA=0.16, p=0.045). At these two loci, similar trends were seen among controls. Logistic regression adjusted for age and methylation chip was then used to assess the association between SNP genotype and ovarian cancer risk, with and without inclusion of the relevant methylation value. At HOXD1 rs2072590, the per-allele ovarian cancer risk of 1.34 attenuated to 1.25 with inclusion of the HOXD1 methylation value as a covariate, suggesting that the disease association may be mediated in part through methylation. Though based on preliminary data, results are consistent with a role for inherited variation on germline methylation at HOXD1 and SKAP1. Analysis of methylation on additional genotyped cases and controls is underway. Finally, because, trans effects may also exist, we are assessing relationships between genotype and methylation at other loci throughout the genome. Such correlative molecular studies have the potential to help elucidate mechanisms underlying associations from genome-wide association studies. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 5616. doi:10.1158/1538-7445.AM2011-5616