Abstract: Objective To verify whether PRMT1 inhibits apoptosis of nasopharyngeal carcinoma (NPC) cells by promoting RRM2 expression. Methods Immunohistochemistry and Western blotting were performed to detect the relative expression of PRMT1 and RRM2 in NPC and adjacent tissues and in different NPC cell lines and a normal nasal mucosal epithelial cell line (HNEpC). Experiments of PRMT1 or RRM2 overexpression or siRNA-mediated PRMT1 or RRM2 knockdown were carried out in CNE-2 cells to investigate the relationship between PRMT1 and RRM2 expressions using Western blotting. Apoptosis of the transfected cells was detected using Annexin V-FITC/PI apoptosis detection kit, and the production of intracellular reactive oxygen species (ROS) was determined using a ROS detection kit. Results Compared with adjacent tissues and HNEpC cells, NPC tissues and cell lines expressed significantly higher levels of PRMT1 and RRM2 (P<0.05). In CNE-2 cells with PRMT1 or RRM2 overexpression or knockdown, Western blotting demonstrated that PRMT1 could positively regulate the expression of RRM2 (P<0.05). Overexpression of PRMT1 or RRM2 significantly reduced intracellular ROS production and apoptosis rate of CNE-2 cells (P<0.05), and PRMT1 or RRM2 knockdown strongly increased ROS production and cell apoptosis (P<0.05). Overexpression of either PRMT1 or RRM2 significantly decreased the expressions of cleaved caspase-3 and cleaved caspase-8 proteins (P<0.05), and PRMT1 or RRM2 knockdown obviously promoted their expressions (P<0.05). PRMT1 knockdown combined with RRM2 overexpression, as compared with PRMT1 knockdown only, significantly decreased ROS production and cell apoptosis (P<0.05) as well as the protein expressions of cleaved caspase-3 and cleaved caspase-8 in CNE-2 cells (P<0.05). Conclusion The high expression of PRMT1 in NPC inhibits apoptosis of NPC cells by promoting the expression of RRM2.

Key words: nasopharyngeal carcinoma; PRMT1; RRM2; apoptosis