Methylation of DIRAS1 promotes colorectal cancer progression and may serve as a marker for poor prognosis

Abstract Background DIRAS1 is a new member of the Ras gene family. It was described as a potential tumor suppressor in human glioblastomas and esophageal cancer. The role of DIRAS1 in colorectal cancer remains unclear. Methods To explore the epigenetic changes and function of DIRAS1 in human colorectal cancer, we studied ten colorectal cancer cell lines and 146 primary colorectal cancer samples and 50 matched adjacent samples using semi-quantitative reverse transcription PCR, immunohistochemistry, methylation-specific PCR and bisulfite sequencing, western blot, flow cytometry, and transwell assays. Results DIRAS1 expression was found in DKO and HCT116 cells, while reduced expression was detected in LoVo, SW48, LS180, and SW620 cells, and there was no expression detected in DLD1, HT29, RKO, and SW480 cells. Complete methylation was found in the promoter region of DLD1, HT29, RKO, and SW480 cells. Partial methylation was detected in LoVo, LS180, SW48, and SW620 cells, and unmethylation was found in DKO and HCT116 cells. These results indicate that promoter region methylation correlated with loss of/reduced expression of DIRAS1. Re-expression of DIRAS1 was induced by 5-aza-2′-deoxycytidine, suggesting that the expression of DIRAS1 is regulated by promoter region methylation. DIRAS1 was methylated in 47.3% (69/146) of primary colorectal cancer samples, no methylation was found in non-cancerous colonic tissue samples. Methylation of DIRAS1 was significantly associated with TNM stage (P