MicroRNA-645 (miR-645) has been implicated in numerous types of human cancers including colon cancer. However, the effects and mechanisms of action of miR-645 dysregulation on the growth and malignancy of colorectal cancer (CRC) remain unclear. In this study, we demonstrated that miR-645 knockdown significantly diminished CRC cell migration and invasion and repressed epithelial-mesenchymal transition (EMT). Conversely, miR-645 overexpression enhanced CRC cell migration, invasion, and EMT. In vivo assays confirmed that miR-645 knockdown substantially reduced CRC growth and metastasis. Regarding the mechanism, ephrin-A5 (EFNA5) was identified as a direct target gene of miR-645. MiR-645 specifically targeted the 3′-untranslated region of EFNA5 mRNA and hindered its expression. EFNA5 knockdown attenuated the effects of miR-645 knockdown on CRC cell migration and invasion. Additionally, we noted a statistically significant inverse correlation between EFNA5 mRNA and miR-645 levels in tumors from 28 patients with CRC. Hence, miR-645 acts as an oncogenic miRNA that may increase CRC cell migration, invasiveness, and metastasis by targeting EFNA5.
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