Tumor suppressive microRNAs (miRNAs) are increasingly implicated in the development of anti-tumor therapy by reprogramming gene network that are aberrantly regulated in cancer cells. This study aimed to determine the therapeutic potential of putative tumor suppressive miRNA, miR-138, against glioblastoma (GBM). Whole transcriptome and miRNA expression profiling analyses on human GBM patient tissues identified miR-138 as one of the significantly downregulated miRNAs with an inverse correlation with CD44 expression. Transient overexpression of miR-138 in GBM cells inhibited cell proliferation, cell cycle, migration, and wound healing capability. We unveiled that miR-138 negatively regulates the expression of CD44 by directly binding to the 3′ UTR of CD44. CD44 inhibition by miR-138 resulted in an inhibition of glioblastoma cell proliferation in vitro through cell cycle arrest as evidenced by a significant induction of p27 and its translocation into nucleus. Ectopic expression of miR-138 also increased survival rates in mice that had an intracranial xenograft tumor derived from human patient-derived primary GBM cells. In conclusion, we demonstrated a therapeutic potential of tumor suppressive miR-138 through direct downregulation of CD44 for the treatment of primary GBM.

Glioblastoma (GBM) is one of the most deadly cancers and poorly responses to chemotherapies, such as temozolomide (TMZ). Dysregulation of intrinsic signaling pathways in cancer cells are often resulted by dysregulated tumor suppressive microRNAs (miRNAs). Previously, we found miR-138 as one of tumor suppressive miRNAs that were significantly down-regulated in GBM. In this study, we demonstrated that ectopic over-expression of miR-138 sensitizes GBM cells to the treatment of TMZ and increased apoptotic cell death. Mechanistically, miR-138 directly repressed the expression of Survivin, an anti-apoptotic protein, to enhance caspase-induced apoptosis upon TMZ treatment. Using an intracranial GBM xenograft mice model, we also showed that combination of miR-138 with TMZ increases survival rates of the mice compared to the control mice treated with TMZ alone. This study provides strong preclinical evidence of the therapeutic benefit from restoration of miR-138 to sensitize the GBM tumor to conventional chemotherapy.