Abstract: Objective To investigate the effect of changes in DTX2 expression level on migration and invasion of colorectal cancer (CRC) cells and explore the mechanism. Methods Two CRC cell lines SW620 and LoVo were transfected with a specific shRNA targeting DTX2 (DTX2-shRNA) or a DTX2-overexpressing plasmid (pcDNA-DTX2), and the transfection efficiency was evaluated with RT-qPCR and Western blotting. Scratch and Transwell assays were used to assess the changes in migration and invasion ability of the transfected cells, and the cellular expression levels of Notch2, NICD, AKT, p-Akt and MMP-2/9 proteins were detected with Western blotting. The CRC cells were co- transfected with pcDNA-DTX2 and Notch2 siRNA to assess the effect of Notch2 knockdown on DTX2 overexpression-induced enhancement of cell migration and invasion. Results The expression levels of DTX2 at both the mRNA and protein levels were significantly decreased in CRC cells transfected with DTX2- shRNA (P<0.01) and increased in cells transfected with pcDNA-DTX2 (P<0.01). Scratch and Transwell assays showed that the migration and invasion abilities of CRC cells were significantly lowered following DTX2 knockdown (P<0.01) and were enhanced in cells with DTX2 overexpression (P<0.01). The expression levels of Notch2, NICD, p-Akt and MMP-2 proteins decreased significantly in CRC cells with DTX2 knockdown (P<0.05) and increased obviously in DTX2-overexpressing cells (P<0.05). In both of the two CRC cell lines, transfection with Notch2 siRNA obviously reversed the effect of DTX2 overexpression in promoting cell migration and invasion (P<0.01) and expressions of the related proteins. Conclusion DTX2 overexpression promotes migration and invasion of CRC cells through the Notch2/Akt axis, suggesting the potential of DTX2 as a new biological indicator of CRC.

Key words: DTX2; colorectal cancer; cell migration; cell invasion; Notch2/Akt axis