DNA Methylation Markers, Genes and Breast Cancer Risk

PROJECT SUMMARY Genome-wide association studies (GWAS) have identified common variants in ~200 genetic loci associated with breast cancer risk. However, it is difficult to translate these findings to disease prevention and treatment because causal genes and underlying mechanisms in these loci are largely unknown. Increasing evidence suggests that epigenetic regulation may be on the causal pathway between genetic variants and diseases. DNA methylation, one of the most frequent and important epigenetic modifications, plays a crucial role in cancer development. However, it is almost impossible to collect pre-diagnostic breast tissues to profile the methylome from a large number of participants. Herein, we propose a novel -omics approach: a methylation- wide association study (MeWAS) using genetic instruments. In Aim 1, we will build race-specific prediction models using genome wide methylation and genetic data in fresh-frozen breast samples from 600 cancer-free women of African-, Asian- and European- ancestry (200 per race). These models will then be applied to the GWAS data from three large consortia, including ~123,000 cases and ~106,000 controls of European, ~25,000 cases and ~25,000 controls of Asian-, ~20,000 cases and ~20,000 controls of African- ancestry to impute methylation levels. The genetically predicted methylation levels will be tested in association with breast cancer overall and by estrogen receptor and HER2 status. In Aim 2, we will perform a series of integrative functional analyses to evaluate the functions of promising methylation sites and the potential target genes regulated by these methylation sites. In Aim 3, we will select the top 20 methylation sites and their target genes for in vitro functional assays to assess their influence on major cell functions related to cancer biology. Given the strong pilot data, unique resources from three large genetic consortia, and our team's extensive expertise and experience, we are uniquely positioned to conduct this project. The findings will greatly improve our understanding of the genetic and biological basis of breast cancer pathogenesis and facilitate the translation of genetic findings to prevention and treatment.