NVP-BEZ235, a novel dual PI3K/mTOR inhibitor, enhances the radiosensitivity of human glioma stem cells in vitro

Abstract

Aim: NVP-BEZ235 is a novel dual PI3K/mTOR inhibitor and shows dramatic effects on gliomas. The aim of this study was to investigate the effects of NVP-BEZ235 on the radiosensitivity and autophagy of glioma stem cells (GSCs) in vitro. Methods: Human GSCs (SU-2) were tested. The cell viability and survival from ionizing radiation (IR) were evaluated using MTT and clonogenic survival assay, respectively. Immunofluorescence assays were used to identify the formation of autophagosomes. The apoptotic cells were quantified with annexin V-FITC/PI staining and flow cytometry, and observed using Hoechst 33258 staining and fluorescence microscope. Western blot analysis was used to analyze the expression levels of proteins. Cell cycle status was determined by measuring DNA content after staining with PI. DNA repair in the cells was assessed using a comet assay. Results: Treatment of SU-2 cells with NVP-BEZ235 (10-320 nmol/L) alone suppressed the cell growth in a concentration-dependent manner. A low concentration of NVP-BEZ235 (10 nmol/L) significantly increased the radiation sensitivity of SU-2 cells, which could be blocked by co-treatment with 3-MA (50 µmol/L). In NVP-BEZ235-treated SU-2 cells, more punctate patterns of microtubule-associated protein LC3 immunoreactivity was observed, and the level of membrane-bound LC3-II was significantly increased. A combination of IR with NVP-BEZ235 significantly increased the apoptosis of SU-2 cells, as shown in the increased levels of BID, Bax, and active caspase-3, and decreased level of Bcl-2. Furthermore, the combination of IR with NVP-BEZ235 led to G 1 cell cycle arrest. Moreover, NVP-BEZ235 significantly attenuated the repair of IR-induced DNA damage as reflected by the tail length of the comet. Conclusion: NVP-BEZ235 increases the radiosensitivity of GSCs in vitro by activating autophagy that is associated with synergistic increase of apoptosis and cell-cycle arrest and decrease of DNA repair capacity.

MiR-99a Enhances the Radiation Sensitivity of Non-Small Cell Lung Cancer by Targeting mTOR

“…AZD2014 is an inhibitor of mTOR and has been shown to enhance radiation sensitivity, apoptosis, and DNA damage, and to suppress proliferation and clonogenicity [30, 31]. For example, this inhibitor of the mTOR pathway enhanced the radiosensitivity of prostate cancer and glioma stem cells [32, 33]. Consistent with the role of mTOR observed in previous studies, we found that AZD2014 enhanced cellular sensitivity to radiation; by contrast, upregulating mTOR expression decreased radiation sensitivity.…”

P7170: A Novel Molecule with Unique Profile of mTORC1/C2 and Activin Receptor-like Kinase 1 Inhibition Leading to Antitumor and Antiangiogenic Activity

“…3A). P7170 treatment induced G 1 -S cell-cycle arrest with an increase in G 1 population from 52.3% (DMSO controls) to 65.9% (30 nmol/L P7170-treated cells) and sub-G 1 population increased from 1.1% to 63.3% (1,000 nmol/L P7170-treated cells), an observation consistent with the growth arrest and cell death expected with PI3K/AKT/ mTOR signal inhibition (27). This considerable increase in the sub-G 1 population observed following P7170 treatment was dose-and time dependent (Fig.…”

Essential role of autophagy in fucoxanthin-induced cytotoxicity to human epithelial cervical cancer HeLa cells

“…The autophagic process during G 1 arrest can repair cell damage to avoid cell death [28] . Some inhibitors of the AKT signaling pathway, such as NVP-BEZ235, induce tumor cell autophagy and cell cycle arrest [29] . Our results demonstrated that fucoxanthin induced cell cycle arrest at the G 0 /G 1 phase via inhibiting the AKT signaling pathway and that fucoxanthin also regulated the expression of cell cycle-related proteins by upregulating p21 expression and downregulating CDK2 and cyclin D1 expression.…”