RAD18 promotes colorectal cancer metastasis by activating the epithelialmesenchymal transition pathway.

RAD18 is an E3 ubiquitinprotein ligase that has a role in carcinogenesis and tumor progression owing to its involvement in errorprone replication. Despite its significance, the function of RAD18 has not been fully examined in colorectal cancer (CRC). In the present research, by collecting clinical samples and conducting immunohistochemical staining, we found that RAD18 expression was significantly increased in the CRC tissue compared with that noted in the adjacent noncancerous normal tissues and that high expression of RAD18 was associated with lymph node metastasis and poor prognosis in CRC patients. In vitro, as determined by cell transfection, scratch, and Transwell experiments, it was also demonstrated that RAD18 increased the invasiveness and migration capacity of CRC cells (HCT116, DLD1, SW480). The signaling pathway was analyzed by western blotting and the clinical data were analyzed by immunohistochemical staining and RTPCR, indicating that the process of epithelialmesenchymal transition (EMT) may be involved in RAD18mediated migration and invasion of CRC cells. All of the above data indicate that RAD18 is a novel prognostic biomarker that may become a potential therapeutic target for CRC in the future.