MiR-129-2 functions as a tumor suppressor in glioma cells by targeting HMGB1 and is down-regulated by DNA methylation

MicroRNA (miRNA) dysregulation is causally related to cancer development and progression, and recent reports have revealed that DNA methylation constitutes an important mechanism for miRNA deregulation in cancer. MiR-129-2 has been reported to be down-regulated and functions as a tumor suppressor in a few human cancers. However, the involvement of miR-129-2 in the pathology of glioma and the mechanism underlying miR-129-2 regulation in glioma cells remain unclear. In this study, we performed quantitative PCR to investigate the level of miR-129-2 in 21 pairs of glioma tumors and matched adjacent tissues and found that miR-129-2 is down-regulated in glioma tumors. In vitro cell growth, apoptosis, cell migration, and invasion assays revealed that miR-129-2 functions as a tumor suppressor in glioma cells. Luciferase reporter assay found that miR-129-2 could directly target high-mobility group box 1 (HMGB1) and inhibit its expression in glioma cells. Methylation-specific PCR found that DNA methylation in upstream regions of miR-129-2 occured more frequently in cancer tissues than in adjacent tissues. Demethylation of miR-129-2 by 5-aza-2′-deoxycytidine treatment and quantitative PCR analysis revealed that miR-129-2 expression is epigenetically regulated in glioma cells. Taken together, our data suggested that miR-129-2 functions as a tumor suppressor in glioma cells by directly targeting HMGB1 and is down-regulated by DNA methylation, which may provide a novel therapeutic strategy for treatment of glioma.