Aberrant hypermethylation of CpG islands in tumor suppressor genes (TSGs) contributes to colorectal tumorigenesis. To identify new colorectal cancer (CRC) screening marker, we investigated DNA methylation alterations in novel TSGs. Using HumanMethylation450 BeadChip arrays, CpG regions in BEND5 were the most highly methylated among all genomic regions in 26 colorectal tumors compared to paired non-neoplastic tissues from a Taiwan cohort. Therefore, BEND5 was selected for further analysis. Quantitative methylation-specific real-time PCR revealed that 86.7% (117/135) of CRC patients exhibited hypermethylated BEND5. Real-time reverse transcription PCR identified that BEND5 mRNA expression was downregulated in 68% (32/47) of the analyzed samples. BEND5 hypermethylation was associated with poor overall survival (OS) in Taiwan patients with early-stage CRC (P = 0.037). In a CRC tissue set from South Korea, OS was higher in patients with high BEND5 protein expression than in those with low BEND5 protein expression (P = 0.037) by using immunohistochemistry assays. Consistently, BEND5 hypermethylation was associated with poor OS in patients with early-stage CRC in The Cancer Genome Atlas (TCGA) data set (P = 0.003). Multivariate Cox proportional hazards regression analysis further supported that hypermethylation of BEND5 genes was significantly associated with OS in Taiwan and TCGA CRC patients (P = 0.023 and 0.033, respectively). Finally, the cell model assay with transient transfection of BEND5 or si-BEND5 knockdown indicated that BEND5 inhibited cancer cell proliferation. In conclusion, epigenetic alteration in the candidate TSG BEND5 contributes to colorectal cancer development and is a prognostic marker of CRC.
Keywords: BEND5; DNA methylation; colorectal cancer; prognostic marker; tumor suppressor genes.