Abstract
DNA hypermethylation is a common epigenetic abnormality in colorectal cancers (CRCs) and a promising class of CRC screening biomarkers. We conducted a genome-wide search for novel neoplasia-specific hypermethylation events in the colon. We applied methylation microarray analysis to identify loci hypermethylated in 17 primary CRCs relative to eight non-neoplastic colonic mucosae (NCs) from neoplasia-free subjects. These CRC-associated hypermethylation events were then individually evaluated for their ability to discriminate neoplastic from non-neoplastic cases, based on real-time quantitative methylation-specific PCR (qMSP) assays in 113 colonic tissues: 51 CRCs, nine adenomas, 19 NCs from CRC patients (CRC-NCs), and 34 NCs from neoplasia-free subjects (control NCs). A strict microarray data filtering identified 169 candidate CRC-associated hypermethylation events. Fourteen of these 169 loci were evaluated using qMSP assays. Ten of these 14 methylation events significantly distinguished CRCs from age-matched control NCs (P<0.05 by receiver operator characteristic curve analysis); methylation of visual system homeobox 2 (VSX2) achieved the highest discriminative accuracy (83.3% sensitivity and 92.3% specificity, P<1×10(-6)), followed by BEN domain containing 4 (BEND4), neuronal pentraxin I (NPTX1), ALX homeobox 3 (ALX3), miR-34b, glucagon-like peptide 1 receptor (GLP1R), BTG4, homer homolog 2 (HOMER2), zinc finger protein 583 (ZNF583), and gap junction protein, gamma 1 (GJC1). Adenomas were significantly discriminated from control NCs by hypermethylation of VSX2, BEND4, NPTX1, miR-34b, GLP1R, and HOMER2 (P<0.05). CRC-NCs were significantly distinguished from control NCs by methylation of ALX3 (P<1×10(-4)). In conclusion, systematic methylome-wide analysis has identified ten novel methylation events in neoplastic and non-neoplastic colonic mucosae from CRC patients. These potential biomarkers significantly discriminate CRC patients from controls. Thus, they merit further evaluation in stool- and circulating DNA-based CRC detection studies.