S1935 Cathepsin B Expression and Survival After Diagnosis of Colorectal Cancer

Abstract

INTRODUCTION: Individuals with Barrett's esophagus (BE), a premalignant condition related to long-term gastroesophageal reflux, are at increased risk for esophageal adenocarcinoma (EAC). To prevent EAC, individuals with BE undergo frequent endoscopic surveillance with biopsies in order to detect esophageal dysplasia, yet this method is suboptimal due to its high cost, invasive nature, and limited accuracy. Thus, better surveillance markers for predicting the risk of dysplasia and EAC in BE patients are needed. Aberrant DNAmethylation of tumor suppressor genes has been previously shown to occur commonly in Barrett's esophagus (BE) and esophageal adenocarcinoma (EAC); some of these methylated genes may be effective markers for predicting the risk of BE progressing to EAC. HYPOTHESIS: Specific aberrantly methylated genes can be detected in individuals with BE, BE with highgrade dysplasia (HGD), and EAC, and some of these molecular alterations can be used as biomarkers that precisely distinguish BE, HGD, and EAC, suggesting they may be able to predict the progression of BE to HGD/EAC. METHODS: DNA isolated from squamous (SQ) esophageal biopsies from six individuals and HGD/EAC esophageal biopsies from nine individuals was bisulfite treated and analyzed using the Illumina GoldenGate Cancer Panel I microarray. The array results were validated by bisulfite sequencing DNA isolated from one SQ and one HGD/EAC patient. RESULTS: After filtering the array data, we identified 42 genes for further analysis, including: cell proliferation regulators (15), growth factors (8), extracellular matrix genes (5), transcription factors (5), a MAP kinase pathway member (1), a TGF β pathway member (1), and an IGF pathway gene (1). We validated five genes (ERBB4, TFPI2, NTRK3, TWIST1, and WT1) by bisulfite sequencing, confirming relatively low methylation in DNA from a SQ patient and high methylation in DNA from a HGD/ EAC patient. DISCUSSION: We identified novel hypermethylated genes using methylation microarrays in DNA samples obtained from individuals with HGD/EAC. Bisulfite sequencing of the original DNA confirmed the methylation differences between normal squamous esophagus and HGD/EAC in 5/5 genes tested. Thus, these genes might play a role in the development or progression of Barrett's esophagus, and function as part of a panel of risk stratification biomarkers for BE.