MicroRNA-15 regulates the proliferation, migration and invasion of thyroid cancer cells by targeting Bcl-2.

Purpose: Thyroid cancer causes significant mortality and 1-1.5% of all the new diagnosed cancers are thyroid cancers. The incidence of thyroid cancer is increasing at an alarming rate and therapeutic targets are lacking. This study was undertaken to investigate the role and therapeutic implications of microRNA (miR)-15 in thyroid cancer. Methods: Expression analysis was performed by qRT-PCR. Transfections were performed by Lipofectamine 2000 reagent. The cell viability was determined by MTT assay. Apoptosis was detected by acridine orange (AO)/ethidium bromide (EB). The percentage of apoptotic cells was estimated by annexin V/ propidium iodide (PI) staining. Wound healing and transwell assays were used to monitor the cell migration and invasion. Protein expression was determined by western blotting. Results: The expression of miR-15 was found significantly decreased in thyroid cancer cells. Ectopic expression of miR-15 promoted the apoptosis of MDA-T35 thyroid cancer cells. The percentage of apoptotic MDA-T35 cells was 1.9% in thyroid cancer and 40.1% in miR-15 mimics transfected cells. The apoptosis promoted by miR-15 overexpression was also associated with enhancement of Bax and depletion of Bcl-2 in MDA-T35 cells. The TargetScan analysis showed Bcl-2 to be the target of miR-15. Additionally, the expression of Bcl-2 was also enhanced in all the thyroid cancer cells and miR-15 ectopic expression could cause suppression of the Bcl-2 expression in MDA-T35 cells. The wound healing assay showed that miR-5 overexpression caused decrease in the migration of MDA-T35 cells while the transwell assays showed decline in the invasion of miR-15 mimics transfected MDA-T35 cells. Conclusion: To sum up, miR-15 may exhibit therapeutic implications in thyroid cancer and may prove useful in thyroid cancer treatment.