Downregulation of microRNA-21 enhances radiosensitivity in nasopharyngeal carcinoma

Radioresistance severely restricts the clinical treatment of nasopharyngeal carcinoma (NPC). microRNAs (miRs) have been demonstrated to affect cancer progression and radiosensitivity. Thus, the aim of the present study was to identify miRs associated with radioresistance in NPC. A radioresistant NPC cell line (CNE-2-1) was established by continuously exposing CNE-2 cells to radiation. Subsequently, high-throughput sequencing technology was used to detect the regulation of miRs in radioresistant CNE-2-1 cells, and it was observed that miR-21 was among the three most upregulated miRs in CNE-2-1 cells. Therefore, the expression levels of miR-21 were quantified using reverse transcription-quantitative polymerase chain reaction. Finally, the function of miR-21 was investigated by downregulating the expression in the CNE-2-1 cells. The results indicated that the expression of miR-21 was significantly increased in the CNE-2-1 cells, as compared with the CNE-2 cells. In addition, downregulation of miR-21 resulted in enhanced radiosensitivity in the CNE-2-1 cells, as demonstrated by the inhibition in cell viability of these radioresistant cells. Further analysis indicated that miR-21 was able to inhibit the proliferation of CNE-2-1 cells at the G1 phase of the cell cycle. Therefore, these results indicated that miR-21 was able to regulate radioresistance in NPC cells; however, further studies are required to confirm this hypothesis.