[Inhibition of micro RNA-9 expression promotes UV-induced ROS damage in nasopharyngeal carcinoma cells].

Objective To investigate the effects of down-regulated miR-9 expression on ultraviolet rays （UV）-induced reactive oxygen species （ROS） damage in nasopharyngeal carcinoma （NPC） cells. Methods The NPC cells were transfected with inhibitors of miR-9 by lipofectamine to decrease the expression of miR-9, and the cells transfected with inhibitor control as the control. ROS levels following UV exposure were examined with DCF-DA method and the concentration of glutathione was analyzed via the benzoic acid method; DNA damage and apoptosis also were evaluated. Results There was significant difference in ROS levels between miR-9 expression-inhibited cells and control cells （26 895 ± 218 vs 15 765± 927, t = 39.754, P < 0.001） , and also there were significant differences in DNA damage rates （28.0% ± 10.0% vs 23.6% ±9.2% ） and in apoptosis rates （8.0% ±0.9% vs 4.5% ±0.8%） following UV exposure between two groups of cells. The miR-9 expression-inhibited cells showed lower level （1.87 ± 0.15） μmol/L of glutathione compared with the control cells （9.85 ± 0.15）μmol/L （t = -48.832, P<0.001）. Conclusion Inhibition of miR-9 expression promoted UV-induced ROS damage in nasopharyngeal carcinoma cells. Key words: Nasopharyngeal neoplasms; MicroRNAs; Reactive oxygen species; Ultraviolet rays