Substantial evidence has shown that numerous microRNAs (miRNAs) are deregulated in colorectal cancer (CRC) and that their dysregulation is involved in CRC formation and progression. miRNA-based targeted therapy that inhibits or restores expression may be a promising therapeutic approach for anti-cancer therapy. Therefore, a comprehensive investigation of the mechanisms underlying CRC occurrence and development may help identify effective therapeutic targets for the therapy of CRC, thus improving the prognosis of patients with this disease. This study showed that miRNA-532 (miR-532) was significantly down-regulated in CRC tissues and cell lines. Low miR-532 expression strongly correlated with aggressive clinicopathological characteristics, including tumor size, lymphatic metastasis and TNM stage. Exogenous expression of miR-532 restricted cell proliferation, colony formation, migration and invasion; promoted cell apoptosis in vitro; and reduced tumor growth in vivo. Mechanistically, insulin-like growth factor 1 receptor (IGF-1R) was determined to be a novel direct target gene of miR-532 in CRC. In clinical CRC tissues, the expression of miR-532 was inversely correlated with that of IGF-1R, which was clearly overexpressed in CRC tissues. Furthermore, IGF-1R silencing simulated the tumor-suppressing roles of miR-532 in CRC. Moreover, recovered IGF-1R expression antagonized the inhibitory effects of miR-532 overexpression on CRC cells. Notably, miR-532 overexpression inhibited activation of the PI3K/Akt signaling pathway in CRC, both in vitro and in vivo. These results indicate that miR-532 plays an important role in CRC development, partly by directly targeting IGF-1R and regulating the PI3K/Akt signaling pathway. Thus, the miR-532/IGF-1R axis has clinical significance in the therapy of patients with CRC.
Keywords: Colorectal cancer; PI3K/Akt pathway; insulin-like growth factor 1 receptor; microRNA-532.