【Abstract】 Objective To investigate the effects and mechanism of microRNA-485-5p (miR-485-5p) on proliferation and apoptosis of nasopharyngeal carcinoma cells. Methods Realtime quantitative PCR (qRT-PCR) was used to detect levels of miR4855p and FOSlike antigen 2 (FOSL2) mRNA in nasopharyngeal carcinoma tissues and cell lines 6-10B and 5-8F, Western Blot was used to detect levels of FOSL2 protein in cells, and Pearson correlation was used to analyze the correlation between miR4855p and FOSL2 mRNA expression in nasopharyngeal carcinoma tissues. To construct 5-8F cells overexpressing miR-485-5p or low expressing FOSL2, miR-485-5p mimic or FOSL2 small interfering RNA was transfected into 58F cells. MTT, flow cytometry, and Western Blot were used to detect the effects of overexpression of miR-485-5p or low expression of FOSL2 on 5-8F cell proliferation, apoptosis and expression of Cyclin D1, p21, Bcl2 and Bax protein, respectively. The dual luciferase reporter gene assay verified the relationship between miR-485-5p and FOSL2. Results Compared with adjacent cancer tissues, the expression level of miR4855p reduced in nasopharyngeal carcinoma tissues (P＜0.05), while the expression level of FOSL2 mRNA increased (P＜0.05). There was a negative correlation between miR4855p and FOSL2 mRNA expression in nasopharyngeal carcinoma tissues (P＜0.05). Compared with NP69 cells, the expression levels of miR4855p in nasopharyngeal carcinoma cell lines 6-10B and 5-8F decreased (P＜0.05), while the expression levels of FOSL2 mRNA and protein increased (P＜0.05). Compared with the miR-NC group, the survival rate of 5-8F cells and the protein levels of CyclinD1 and Bcl-2 in the miR-485-5p group decreased (P＜0.05), while the apoptosis rate and the protein levels of p21 and Bax increased (P＜0.05). Compared with the siNC group, the survival rate of 5-8F cells and the protein levels of CyclinD1 and Bcl-2 in the siFOSL2 group decreased (P＜0.05), while the apoptosis rate and the protein levels of p21 and Bax increased (P＜0.05). miR-485-5p negatively regulated FOSL2 expression in 5-8F cells. Compared with the miR-485-5p+pcDNA3.0 group, the survival rate of 58F cells and the protein levels of CyclinD1 and Bcl-2 in the miR-485-5p+pcDNA3.0FOSL2 group increased (P＜0.05), while the apoptosis rate and the protein levels of p21 and Bax decreased (P＜0.05). ConclusionThe expression of miR-485-5p decreased in nasopharyngeal carcinoma tissues and cells, while the expression of FOSL2 increased; overexpression of miR-485-5p inhibits the proliferation of nasopharyngeal carcinoma cells and promotes their apoptosis through targeted negative regulation of FOSL2.Overexpressing miR-485-5p may inhibit proliferation and promotes apoptosis of nasopharyngeal carcinoma cells by targeting negatively regulated FOSL2.