RESUMO
<p><b>OBJECTIVE</b>To explore the influence of knock-down of miR-21 expression on the radiosensitivity of radioresistant glioma SHG-44 cells and its mechanism.</p><p><b>METHODS</b>Radioresistant cell line SHG-44(R) cells were established from radiosensitive parental SHG-44 glioma cells. Then the expression levels of miR-21 in SHG-44(R) and SHG-44 were determined by quantitative real-time PCR. The effect of miR-21 on the radiosensitivity was assessed in SHG-44(R) with miR-21 inhibitor to decrease the miR-21 expression.</p><p><b>RESULTS</b>miR-21 was up-regulated 1.49-fold in SHG-44(R) cells relative to the SHG-44 cells. But after transfection with As-miR-21, the miR-21 expression in SHG-44(R) cells was knocked down significantly. As-miR-21 combined with radiation could synergistically enhanced mitotic death and apoptosis of SHG-44(R) cells, with SER of D(0) and D(q) being equal to 1.48 and 1.54, respectively. Expression levels of caspase-3 in the radiation group, AS-miR-21 transfection group and combination group were 2.24 ± 0.14, 2.05 ± 0.19 and 5.72 ± 0.45, respectively, and its expression in the combination group was higher than that in the other two groups.</p><p><b>CONCLUSIONS</b>miR-21 may be involved in the formation of radioresistance of glioma cells and as a potential target for enhancing the response of radioresistant-glioma cells to radiotheapy.</p>