MicroRNA-199a-5p suppresses the cell growth of colorectal cancer by targeting oncogene Caprin1.

MicroRNAs-199a-5p (miR-199a-5p) plays critical regulatory roles in various types of human cancers. However, the biological function and regulatory mechanisms of miR-199a-5p in colorectal cancer (CRC) remain unclear. The aim of this study was to investigate the role of miR-199a-5p in CRC and possible mechanisms of its action. The expression of miR-199a-5p in CRC tumor tissues was validated using quantitative real-time PCR (qRT-PCR). The effects of miR-199a-5p on cell proliferation and apoptosis were evaluated in vitro. Then, the association of miR-199a-5p and its downstream target was investigated in both cell line and clinical specimens. Furthermore, gain- and loss-of-function studies of cytoplasmic activation/proliferation-associated protein-1 (Caprin1) were performed to assess whether the suppressive effect of on CRC cells were via targeting Caprin1. Using a microarray platform, we focused on miR-199a-5p for further research, which was one of the most markedly downregulated miRNAs in CRC tumor tissues. Functionally, the overexpression of miR-199a-5p inhibited proliferation and induced apoptosis in both HTC116 and SW480 cells. Furthermore, cytoplasmic activation/proliferation-associated protein-1 (Caprin1), a well-known oncogene, was directly targeted by miR-199a-5p. It was also observed that Caprin1 was upregulated, and inversely correlated with miR-199a-5p levels in CRC tissues. Further investigations revealed that knockdown of Caprin1 by siRNA has similar role with miR-199a-5p overexpression in CRC cells, suggesting the oncogenic role of Caprin1 in CRC. In the contrast, we found that overexpression of Caprin1 reversed the suppressive effects of miR-199a-5p on CRC cells. Collectively, our study suggests that miR-199a-5p/Caprin1 axis may serve as potential therapeutic targets for the treatment of CRC.