Abstract:

Objective To explore the expression of miR-125 in nasopharyngeal carcinoma tissues and the possible regulatory mechanism of biological characteristics of tumor cells. Methods Thirty cases of carcinoma and paracancerous tissues from patients with nasopharyngeal carcinoma admitted to Southern Hospital of Sixth People's Hospital Affiliated to Shanghai Jiaotong University from June 2018 to June 2019 were collected. The expressions of miR-125 and fibroblast growth factor 2 (FGF-2) mRNA were detected by fluorescent quantitative PCR. Nasopharyngeal carcinoma CNE-2 cells were transfected by miR-125 mimic (miR-125 mimic group), and negative control group was set (NC group). Transwell chamber assay was used to determine cell invasion ability, scratch healing assay was used to determine cell migration ability, WST-1 assay was used to assess cell viability, flow cytometry and electron microscopy were used respectively to detect apoptosis and autophagy, dual luciferase reporter assay was used to analyze the target of miR-125, and Western blotting was used to detect the expressions of related proteins. Results The relative expression of miR-125 mRNA in nasopharyngeal carcinoma tissues was 0.692±0.316, which was significantly lower than 1.501±0.748 in the adjacent tissues (t=5.242, P<0.001). The relative expression of FGF-2 mRNA in nasopharyngeal carcinoma tissues was 1.317±0.552, which was significantly higher than 0.783±0.241 in the adjacent tissues (t=7.360, P<0.001). The miR-125 mRNA expression of CNE-2 cells in the miR-125 mimic group was 4.091±0.145, which was significantly higher than 0.993±0.137 in the NC group (t=85.062, P<0.001). The proliferative activities of CNE-2 cells in the miR-125 mimic group at 48 and 96 h after transfection were significantly lower than those in the NC group (0.891±0.214 vs. 1.295±0.245, t=6.802, P<0.001; 0.934±0.208 vs. 1.488±0.269, t=8.924, P<0.001). The number of transmembrane cells and cell migration rate of the miR-125 mimic group were 36 000±3 820 and (39.4±6.5)%, which were significantly lower than 74 000±7 500 and (102.7±10.6)% of the NC group (t=24.728, P<0.001; t=27.883, P<0.001). The apoptosis rate of CNE-2 cells in the miR-125 mimic group was (22.5±1.4)%, which was significantly higher than that in the NC group (1.4±0.5)% (t=77.740, P<0.001). The relative expression of the apoptotic protein Bax in the miR-125 mimic group was 0.983±0.158, which was significantly higher than that in the NC group (0.418±0.122; t=15.503, P<0.001), and the relative expression of Bcl-2 was 0.688±0.174, which was significantly lower than that of the NC group (1.013±0.109; t=8.670, P<0.001). Autophagy was observed in miR-125 overexpressing CNE-2 cells by electron microscopy, and the relative expression ratio of autophagy protein LC3Ⅱ/LC3Ⅰ in the miR-125 mimic group was 2.517±0.209, which was significantly higher than 1.238±0.135 in the NC group (t=28.156, P<0.001). The expression of FGF-2 protein in the miR-125 mimic group was 0.504±0.118, which was significantly lower than 1.228±0.134 in the NC group (t=22.210, P<0.001). The double luciferase report confirmed FGF-2 as the target gene of miR-125. At 12, 24, 48 and 96 h after the transfection, the cell proliferative activities of CNE-2 cells co-transfected by FGF-2 gene plasmid and miR-125 mimic were significantly higher than those of CNE-2 cells transfected by miR-125 mimic (all P<0.05), and the apoptosis rate was significantly lower than that of CNE-2 cells transfected by miR-125 mimic [(6.2±1.5)% vs. (17.6±2.4)%, t=22.062, P<0.001]. Conclusion The expression of miR-125 is down-regulated in nasopharyngeal carcinoma tissues. Overexpression of miR-125 may inhibit the proliferation, migration and invasion of nasopharyngeal carcinoma CNE-2 cells and promote the apoptosis and autophagy of CNE-2 cells by down-regulating FGF-2 expression.

Key words: Nasopharyngeal neoplasms, miR-125, Fibroblast growth factor 2, Neoplasm metastasis