Mst1 regulates glioma cell proliferation via the AKT/mTOR signaling pathway

Mammalian sterile 20-like 1 (Mst1), an upstream serine/threonine-specific protein kinase of the Hippo pathway, is reported to play important roles in tumor suppression and organ size regulation in mammals via regulating cell proliferation and survival. However, whether it is involved in the pathogenesis of malignant gliomas remains poorly understood. Therefore, in the present work, we examined the effect and mechanism of Mst1 on the proliferation and apoptosis of malignant glioma cells. The cell proliferation and growth of glioma cells were examined by EdU incorporation and CCK-8 assay. In addition, the cell apoptosis was assessed by flow cytometry. We found that down-regulation of Mst1 promoted glioma cell proliferation and growth, but inhibited the cell apoptosis. Consistent with this, over-expression of Mst1 inhibited glioma cell proliferation and growth. Interestingly, Mst1 did not affect the phosphorylation of YAP1, the key downstream molecule of Hippo pathway. However, Mst1 was found to bind to AKT in glioma cell and negatively regulated AKT and mTOR activity. Finally, the increased cell proliferation rate induced by Mst1 down-regulation was partially abolished by down-regulation of AKT1. Meanwhile, glioma cell growth inhibition induced by Mst1 over-expression was partially rescued by over-expression of AKT1. Taken together, these findings suggest that Mst1 regulates proliferation of glioma cells via AKT/mTOR signaling pathway.