Genetic Instability & Risk for Esophageal Carcinoma

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DESCRIPTION (provided by applicant): This application builds on the esophageal cancer (EC) infrastructure that we have created with institutional funds to explore the role of genetic instability using a panel of markers including telomere dysfunction and DNA damage/or repair as predictors of esophageal adenocarcinoma (EAC) risk. In addition, we will perform genotypic/phenotypic correlations and correlate surrogate markers (peripheral blood lymphocytes (PBLs)) with genetic alterations in target tissue (tumor) to further expand our understanding of EAC tumorigenesis. We will accrue 600 patients with EAC from M.D. Anderson Cancer Center who have not received chemotherapy or radiotherapy and are residents of Texas. We will also recruit 600 controls identified from population-based random digit dialing in the Texas area. The controls will be matched to the patients by sex, age (} 5 years), ethnicity, and residency. Comprehensive epidemiologic profiles will be obtained by personal interview on smoking history, alcohol consumption, dietary intake, body mass index (BMI), physical activity, cancer family history, occupational exposures, previous medical history, and prescription drug use, etc. There are three Aims: 1) Assess markers of genetic instability in surrogate tissue (PBLs). 1.1. Determine overall telomere length in PBLs in all cases and controls using a high-throughput quantitative real-time method. Our hypothesis is that individuals with shortened telomeres are at greater risk for EAC than those with long telomeres. In addition, we will determine chromosome specific telomere length (17p, 2p, and XpYp) in PBLs in all cases and controls using a modified real-time PCR based single telomere length analysis (STELA) method. Our hypothesis is that chromosome 17p telomere shortening is specifically associated with increased risk for EAC. 1.2. Estimate the frequencies of single-nucleotide polymorphisms (SNPs) in genes in telomere length maintenance pathway. Our hypothesis is that adverse genotypes of the telomere length maintenance pathway are associated with an increased risk for EAC. 1.3. Quantify benzo[a]pyrene diol-epoxide (BPDE)}induced (reflecting net results of initial DNA damage and nucleotide excision repair [NER] capacity) and ?-radiation- induced genetic damage (reflecting net results of initial DNA damage and base excision repair [BER] as well as double-stranded-break repair [DSB] capacities) in PBLs, as measured by the Komet 4.0 image system. Our hypothesis is that cases exhibit higher levels of induced genetic damage compared with controls. 1.4. Estimate the frequencies of SNPs in DNA repair genes implicated in the NER, BER, and the DSB pathways. Our hypothesis is that adverse genotypes of the NER, BER, and DBS pathways are associated with an increased risk for EAC. 2) Assess genotype-phenotype associations for markers of susceptibility. 2.1 Compare telomere length in PBLs with the frequencies of SNPs in genes in telomere length maintenance pathway. Our hypothesis is that the adverse genotypes of telomere length maintenance pathway will predict telomere dysfunction. 2.2. Compare mutagen-induced DNA damage as measured by the comet assay, with the frequencies of SNPs in DNA repair genes. Our hypothesis is that the adverse genotypes of the NER pathway will predict higher levels of BDPE-induced DNA damage and that the adverse genotypes of the BER and DSB pathways will predict higher levels of ?-radiation}induced DNA damage. 3) Correlate markers in surrogate (PBLs) and target tissue. We will determine chromosomal aberrations, which constitute an index of genetic instability, in adjacent normal tissue and tumor tissue of 200 EAC using Illumina's Human CNV370 SNP array. Our hypothesis is that individuals with short telomeres, adverse genotypes, and/or high levels of mutagen- induced DNA damage are at a higher risk for chromosomal aberrations in the target tissue. We will integrate comprehensive epidemiologic data with the genetic data from the studies described above to assess EAC risk. The ability to rapidly screen individuals for risk, using minimally invasive procedures (blood samples), has immense clinical implication, such as intensive screening and chemopreventive interventions. PUBLIC HEALTH RELEVANCE: Esophageal cancer (EC) is the seventh leading cause of death from cancer among American men, and more than 90% of patients diagnosed with esophageal cancer will ultimately die of their disease. The vast majority of ECs are either esophageal squamous-cell carcinomas (ESCC) or esophageal adenocarcinoma (EAC). Once a rare tumor representing <10% of ECs in U.S., EAC is currently the cancer with the fastest increasing incidence in this country. In the past few decades, the incidence of EAC has increased by approximately 6-fold and replaced ESCC as the most common histological type in this country since the mid 1990s, whereas ESCC still predominates in eastern countries. The reason for this dramatic increase of EAC in western countries is unknown. In this application, we will recruit 600 EAC patients and 600 controls. We will collect comprehensive epidemiologic profiles and perform a series of genetic and biochemical assays. We will assess the associations between a variety of epidemiologic factors, such smoking history, alcohol consumption, dietary intake, obesity, physical activity, cancer family history, occupational exposures, previous medical history, etc., with the risk of EAC. We will also assess biomarkers that may predict the development of EAC. The long-term goal of this project is to build up a comprehensive risk assessment model for EAC and shed light on the dramatic increase of EAC incidence. The ability to identify high-risk subgroups of individuals for EAC will provide immense public health benefit for those high-risk people who may be subjected to close surveillance and chemoprevention.