miR-21 inhibitor suppresses proliferation and migration of nasopharyngeal carcinoma cells through down-regulation of BCL2 expression

This study is to investigate the expression of miR-21 in nasopharyngeal carcinoma (NPC) cells, and the effect of miR-21 in the biological behavior and expression of B-cell lymphoma 2 (BCL2) in NPC cells. Paired NPC and adjacent non-tumor tissues were obtained from 53 patients who underwent primary surgical resection of NPC tissues. Luciferase reporter assay was performed to test whether BCL2 is a direct target of miR-21. Methylthiazolyl blue tetrazolium assay and colony assay were used to evaluate the effect of miR-21 on NPC cell proliferation. Transwell and wound-healing assays were carried out to test the effect of low expression of miR-21 on cancer cell migration and invasion. QRT-PCR and Western blotting were used to measure the levels of mRNA and protein expression, respectively. Tumor tissues showed a positive correlation between the levels of miR-21 and BCL2 protein expression. Cells transfected with miR-21 inhibitor healed slower compared the control (P < 0.05). In addition, cell migration was notably inhibited by the down-regulation of miR-21 in vitro (P < 0.05). The reduction in miR-21 expression showed a remarkable effect on the biological behavior of NPC cell clone formation (P < 0.05). Low expression of miR-21 by transfection with miRNA expression plasmid led to a decrease in BCL2 expression, which was accompanied by reduced migration and proliferation of the cancer cells. Our results demonstrated that miR-21 inhibitor down-regulated BCL2 expression level, suggesting that BCL2 might be a target gene for the initiation and development of NPC cells.