RESUMEN
<p><b>OBJECTIVE</b>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.</p><p><b>METHODS</b>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.</p><p><b>RESULTS</b>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).</p><p><b>CONCLUSION</b>Inhibition of miR-9 expression promoted UV-induced ROS damage in nasopharyngeal carcinoma cells.</p>