Search

Glioblastoma multiforme (GBM) is one of the most common primary malignant adult brain tumors. It is characterized by aggressive progression and poor prognosis. There is significant need to understand the mechanism of GBM malignancy and develop improved therapeutic options for GBM patients. We systematically studied the function of PTP4A3 in the malignancy of GBM. We found that PTP4A3 was upregulated in GBM tissues and cells. Knockdown of PTP4A3 expression in GBM cells inhibited cell proliferation, migration, and invasion. PTP4A3 knockdown modulated the activity of the Akt/mTOR signaling pathway by inducing de-phosphorylation of Akt and mTOR. We identified PTP4A3 as a direct target of miR-137. MiR-137 has been reported as a tumor suppressor in GBM development. In this study, overexpression of miR-137 in GBM cells also inhibited cell proliferation, migration, and invasion. Finally, restoration of PTP4A3 expression in miR-137 overexpressing cells partially reversed the inhibition of GBM cell malignancy, and the de-phosphorylation of Akt and mTOR. We identified that PTP4A3 regulated GBM via miR-137-mediated Akt/mTOR signaling pathway.

Glioblastoma development is often associated with alteration in the activity and expression of cell cycle regulators, such as cyclin-dependent kinases (CKDs) and cyclins, resulting in aberrant cell proliferation. Recent studies have highlighted the pivotal roles of miRNAs in controlling the development and growth of glioblastoma. Here, we provide evidence for a function of miR-340 in the inhibition of glioblastoma cell proliferation. We found that miR-340 is downregulated in human glioblastoma tissue samples and several established glioblastoma cell lines. Proliferation and neurosphere formation assays revealed that miR-340 plays an oncosuppressive role in glioblastoma, and that its ectopic expression causes significant defect in glioblastoma cell growth. Further, using bioinformatics, luciferase assay and western blot, we found that miR-340 specifically targets the 3'UTRs of CDK6, cyclin-D1 and cyclin-D2, leading to the arrest of glioblastoma cells in the G0/G1 cell cycle phase. Confirming these results, we found that re-introducing CDK6, cyclin-D1 or cyclin-D2 expression partially, but significantly, rescues cells from the suppression of cell proliferation and cell cycle arrest mediated by miR-340. Collectively, our results demonstrate that miR-340 plays a tumor-suppressive role in glioblastoma and may be useful as a diagnostic biomarker and/or a therapeutic avenue for glioblastoma.

MicroRNAs (miRNA) have oncogenic or tumor-suppressive roles in the development and growth of human glioma. Glioma development is also associated with alteration in the activities and expression of cell cycle regulators, and miRNAs are emerging as important regulators of cell cycle progression. Here, we show that miR-25 is overexpressed in 91% of examined human glioma tissues and 4 out of 6 human glioma cell lines. MiR-25 increases cell proliferation in two independent glioma cell lines. Ectopic expression of miR-25 was found to reduce CDKN1C protein levels by directly targeting its 3'-untranslated region (UTR). Notably, ablation of endogenous miR-25 rescued CDKN1C expression and significantly decreased glioma cell proliferation by facilitating normal cell cycle progression. Our clinical investigation found CDKN1C and miR-25 levels were inversely correlated. Lastly, downregulation of CDKN1 by siRNA blocked the activity of miR-25 on promoting glioma cell proliferation. Overall, our results for the first time show an oncogenic role of miR-25 in human glioma by targeting CDKN1C and that miR-25 could potentially be a therapeutic target for glioma intervention.