Cancer Prevention Program
Adenomatous polyps, also referred to as ademomas, are well-established precursor lesions to colorectal cancer (CRC). Other polyps commonly found in the colon and rectum are hyperplastic polyps (HPs). HPs have long been considered benign lesions. However, recent evidence suggests that HPs and the histogenetically-related serrated adenomas may progress to malignancy along a separate “serrated pathway”. There is compelling and consistent data that links both high and low penetrance genes to CRC, and it is likely that specific genes or genotypes may be associated with different colorectal neoplastic pathways. Recently, genomic studies of colorectal cancer have made great strides with genome-wide association studies (GWAS) identifying 10 CRC susceptibility loci at different sites in the human genome; these loci may be relevant to the genesis and progression of precursor lesions, such as certain types of colorectal polyps. In this application, we propose to determine the risk of adenomas and HPs associated with: 1) the specific polymorphisms identified through GWAS, including the following: 8q24 (rs6983267), 18q21/SMAD7 (rs4939827), 15q13/CRAC1 (rs4779584), 10p14 (rs10795668), 8q23.3/EIF3H (rs16892766), 11q23 (rs3802842), 14q22.2/BMP4 (rs4444235), 16q22.1/CDH1 (rs9929218), 19q13.1/RHPN2 (rs10411210), 20p12.3 (rs961253), and 2) the genes or regions of the genome that house these loci using a tagSNP approach. This research is ancillary to an existing study, “Colon cancer pathways: hyperplastic polyps and adenomas” (CA 097325), aimed at comparing the epidemiologic risk factors and molecular features of adenomas and HPs with the goal of learning more about the clinical importance of HPs and the serrated adenoma pathway. Our study population includes 1,765 colonoscopy-defined adenoma cases, HP cases, and controls who were members of a large integrated health plan. All participants completed standardized interviews covering demographics and colorectal-cancer risk factors. In addition, study participants provided buccal cell samples for DNA analysis, and all cases are undergoing a standardized pathology review to confirm the diagnosis and to further categorize the pathologic features of their polyps. This proposed project will increase the body of knowledge surrounding the mechanisms for early colorectal carcinogenesis and help elucidate the genes important to different colorectal cancer pathways. In addition, it may provide clues about the clinical importance of HPs and other polyps hypothesized to be on the serrated pathway, including sessile serrated polyps, by linking these lesions to known CRC susceptibility genes.
Most colorectal cancers (CRC) arise from polyps, but the genes important to colorectal polyps have not been fully characterized, and the debate about the clinical importance of some polyps, such as hyperplastic polyps (HPs) is ongoing. Recent genome wide association studies of CRC have indentified 10 loci that are associated with CRC. By examining these same loci in relation to adenomas and HPs we will learn more about genes and mechanisms involved in early carcinogenesis and further characterize the malignant potential of HPs.