CSIG-18. NERVE/GLIAL ANTIGEN (NG)2 EXPRESSION IN GLIOBLASTOMA IS REGULATED BY miR-29b-3p

Overexpression of NG2 in human glioblastoma cells is associated with an elevated drug resistance and thereby worsens clinical outcome. However, the regulatory mechanisms of NG2 expression are largely unknown. In this study, we identified miR-29b-3p as a posttranscriptional factor of NG2 expression. The basal mRNA levels of miR-29b-3p and NG2 were detected in the NG2-positive glioblastoma cell lines A1207 and U87 by qRT-PCR. The cells were transfected with miR-29b-3p-mimic or scrambled-miR (control) and the expression of NG2 was analyzed by qRT-PCR, flow cytometry and Western blot. Reporter gene analyses of the NG2 promotor region and 3’UTR were performed to study the effect of miR-29b-3p on NG2 expression. Finally, we analyzed the mRNA levels of NG2 and miR-29b-3p in samples from glioblastoma patients. We found that the two NG2-positive glioblastoma cell lines A1207 and U87 are positive for miR-29b-3p. Transfection with miR-29b-3p-mimic reduced NG2 mRNA levels in A1207 (29%±9.9; Mean±SD) and U87 (6%±2.8), resulting in a significantly decreased NG2 protein expression in A1207 (67%±6.4) and U87 (75%±4) when compared to controls. The analysis of the 3’UTR revealed that miR-29b-3p is a posttranscriptional regulator of NG2 expression. Moreover, miR-29b-3p affects the pretranscriptional NG2 expression by diminishing SP-1-dependent NG2 promotor activity. These results were confirmed by the analysis of glioblastoma patient-derived samples, demonstrating that a high NG2 expression is associated with low levels of miR-29b-3p. In conclusion, we identified miR-29b-3p as a crucial regulator of NG2 expression in glioblastoma. Hence, targeting NG2 expression by miR-29b-3p may provide a novel therapeutic strategy to overcome drug resistance in NG2-positive glioblastoma cells.