MicroRNA-32 inhibits the proliferation, migration and invasion of human colon cancer cell lines by targeting E2F transcription factor 5.

MicroRNAs to be essential therapeutic targets for the treatment of diseases such as cancer. Colon cancer is one of the prevalent cancers and causes tremendous human mortality. The treatment of colon cancer is limited by late diagnosis and lack of efficient therapeutic targets. Herein, the therapeutic potential of the miR-32 was explored in colon cancer. Expression analysis was carried out by quantitative Real-time polymerase chain reaction (qRT-PCR). Transfections were performed by Lipofectamine® 2000 reagent. The cell counting kit 8 (CCK-8) assay was used to determine cell viability. The 4', 6-diamidino-2-phenylindole (DAPI) and annexin V/Propidium Iodide (PI) assays were used for the detection of apoptosis. Transwell assays were used to determine cell migration and invasion. The expression of the proteins was estimated by Western blotting. The results showed that the expression of miR-32 was aberrantly downregulated in all colon cancer cells. Overexpression of miR-32 caused significant (p<0.01) decline in the viability in SW-948 cells via induction of apoptosis. The induction of apoptosis was also accompanied by the upregulation of Bax and downregulation of Bcl-2 expression. Overexpression of miR-32 also caused the arrest of the SW-498 cells in the G2/M phase of cell cycle and inhibited their migration and invasion. TargetScan analysis showed E2F transcription factor 5 (E2F5) to be the potential target of miR-32, which was also confirmed by dual luciferase reporter assay. The expression of E2F5 was significantly (p<0.01) upregulated in the colon cancer cells and overexpression of miR-32 caused a considerable decline in the expression of E2F5 in the SW-948 cells. E2F5 silencing also inhibited the growth of the SW-948 cells via induction of apoptosis and G2/M cell cycle arrest. MiR-32 overexpression also inhibited the migration and invasion of the SW-948 cells. However, rescue assay revealed E2F5 to be essential for the tumor suppressive effects of miR-32. The findings of the present study reveal that miR-32 acts as a tumor suppressor in colon cancer cells and may have therapeutic implications in colon cancer treatment.