The malignant glioma remains one of the most aggressive human malignancies with extremely poor prognosis. Glioma cell invasion and migration are the main causes of death. In the current study, we studied the expression and the potential functions of tetraspanin 8 (Tspan8) in malignant gliomas. We found that Tspan8 expression level is high in both malignant glioma tissues and in several human glioma cell lines, where it formed a complex integrin α3 and rictor, the latter is a key component of mammalian target of rapamycin (mTOR) complex 2 (mTORC2). Disruption of this complex, through siRNA-mediated knockdown of anyone of these three proteins, inhibited U251MG glioma cell migration in vitro. We further showed that Tspan8-rictor association appeared required for mTORC2 activation. Knockdown of Tspan8 by the targeted siRNAs prevented mTOR-rictor (mTORC2) assembly as well as phosphorylation of AKT (Ser-473) and protein kinase C α (PKCα) in U251MG cells. Together, these results demonstrate that over-expressed Tspan8 in malignant glioma forms a complex with rictor and integrin α3 to mediate mTORC2 activation and glioma cell migration. Therefore, targeting Tspan8-rictor-integrin α3 complex may provide a potential therapeutic intervention for malignant glioma.

Here, we studied the anti-glioma cell activity by a novel AMP-activated protein kinase (AMPK) activator GSK621. We showed that GSK621 was cytotoxic to human glioma cells (U87MG and U251MG lines), possibly via provoking caspase-dependent apoptotic cell death. Its cytotoxicity was alleviated by caspase inhibitors. GSK621 activated AMPK to inhibit mammalian target of rapamycin (mTOR) and downregulate Tetraspanin 8 (Tspan8) in glioma cells. AMPK inhibition, through shRNA knockdown of AMPKα or introduction of a dominant negative (T172A) AMPKα, almost reversed GSK621-induced AMPK activation, mTOR inhibition and Tspan8 degradation. Consequently, GSK621’s cytotoxicity in glioma cells was also significantly attenuated by AMPKα knockdown or mutation. Further studies showed that GSK621, at a relatively low concentration, significantly potentiated temozolomide (TMZ)’s sensitivity and lethality against glioma cells. We summarized that GSK621 inhibits human glioma cells possibly via activating AMPK signaling. This novel AMPK activator could be a novel and promising anti-glioma cell agent.

Neuroglioma is the most common form of human primary malignant brain tumor, more and more studies recently showed only a small subpopulation of glioma cells which called glioma stem cells have true tumorigenic potential. Meanwhile, it was reported the overexpression of JMJD6 protein is closely involvement with the occurrence and development of multiple tumors, and JMJD6 is required for the differentiation of multiple organ, tissues and cells during embryogenesis. However, the influence of JMJD6 overexpression on neuroglioma development is unclear now. Hence, to explore the effects of JMJD6 expression on neuroglioma, we firstly isolated glioma stem cells by using CD133 MicroBead Kit, and identified via neurosphere-forming assay and Immunofluorescence staining. At the same time, we investigated the effects and mechanism of JMJD6 on the proliferation, migration and invasion of glioma stem cells through MTT, transwell assays and the Cignal finder cancer 10-pathway reporter array. The results demonstrated that the glioma neurosphere cells positively expressed stem cell marker SOX2, neuroectodermal stem cell marker Nestin, and also expressed astrocytes marker GFAP and neurons marker β-tubulin III fter FBS-induced differentiation for a week, which proved the glioma neurosphere cells have the self-renewal and multipotential differentiation capacity. Moreover, shRNA lentiviral vector mediated knockdown of JMJD6 in glioma stem cells led to decreased proliferation, migration and invasion, the underlying molecular mechanism is related to the weaken of Wnt signaling pathway and strengthen of p53 signaling pathway.