An 8q24 gene desert variant associated with prostate cancer risk confers differential in vivo activity to a MYC enhancer

Abstract

Genome-wide association studies (GWAS) routinely identify risk variants in noncoding DNA, as exemplified by reports of multiple single nucleotide polymorphisms (SNPs) associated with prostate cancer in five independent regions in a gene desert on 8q24. Two of these regions also have been associated with breast and colorectal cancer. These findings implicate functional variation within long-range cis-regulatory elements in disease etiology. We used an in vivo bacterial artificial chromosome (BAC) enhancer-trapping strategy in mice to scan a half-megabase of the 8q24 gene desert encompassing the prostate cancer-associated regions for long-range cis-regulatory elements. These BAC assays identified both prostate and mammary gland enhancer activities within the region. We demonstrate that the 8q24 cancer-associated variant rs6983267 lies within an in vivo prostate enhancer whose expression mimics that of the nearby MYC proto-oncogene. Additionally, we show that the cancer risk allele increases prostate enhancer activity in vivo relative to the non-risk allele. This allele-specific enhancer activity is detectable during early prostate development and throughout prostate maturation, raising the possibility that this SNP could assert its influence on prostate cancer risk before tumorigenesis occurs. Our study represents an efficient strategy to build experimentally on GWAS findings with an in vivo method for rapidly scanning large regions of noncoding DNA for functional cis-regulatory sequences harboring variation implicated in complex diseases.