The dependence of radio-sensitization efficiency on mitochondrial targeting with NaGdF4:Yb,Er nanoparticles.

Radio-sensitization is highly desired to reduce side-effect of the harsh dose of radiation therapy (RT), for which nanoparticles with high atomic number elements provide a promising tool. However, insufficient knowledge on utilizing the interaction between nanoparticles and cancerous cells hampers the improvement of therapeutic outcome. We herein employed NaGdF4:Yb,Er nano-crystals as the sensitizer, and modified them with a tumor targeting agent and a mitochondria targeting moiety, separately and jointly, to achieve varied extent of mitochondrial accumulation. We observed that NaGdF4:Yb,Er nano-crystal, even unmodified with targeting ligands, is effective for radio-sensitization. Furthermore, the extent of mitochondrial targeting was responsible for sensitization efficiency both in vitro and in vitro. By RNA sequencing technique, the result was ascribed to the reactive oxygen species (ROS) mediated TNF-JNK pathway and cell cycle arrest besides breaking DNA, in contrast to only DNA damage only with those untargeted nanoparticles. Our work indicated that ROS generated by the irradiation can be utilized by activating an alternative apoptotic pathway with mitochondrial targeting nanoparticles, and therefore may suggest an approach for the enhancement of radio-sensitization. STATEMENT OF SIGNIFICANCE: Radiosensitization by nanoparticles could reduce the burden of cancer due to lowering the dose of radiation therapy and reducing side-effect. How to fully utilize the interactions of irradiation-nanoparticles-biotissues remains a challenge for improving the outcome of radiosensitization. In this manuscript, by modifying tumor-targeting and mitochondria-targeting ligands on nanoparticles, separately and jointly, we demonstrated that the radiosensitization efficiency of NaGdF4:Yb,Er nanoparticle depends on the extent of accumulation near mitochondria. By RNA-seq technique, the RT sensitization with mitochondrial targeting was ascribed to ROS-mediated TNF-JNK pathway and cell cycle arrest, in contrast to only DNA breaks with untargeted nanoparticles. The results suggested a strategy for better utilization of the energy of therapeutic irradiation and demonstrate that subcellular targeting is a potent factor for designing nanoparticulate radiosensitizers.

The therapeutic value of XL388 in human glioma cells.

XL388 is a highly efficient and orally-available ATP-competitive PI3K-mTOR dual inhibitor. Its activity against glioma cells was studied here. In established and primary human glioma cells, XL388 potently inhibited cell survival and proliferation as well as cell migration, invasion and cell cycle progression. The dual inhibitor induced significant apoptosis activation in glioma cells. In A172 cells and primary human glioma cells, XL388 inhibited Akt-mTORC1/2 activation by blocking phosphorylation of Akt and S6K1. XL388-induced glioma cell death was only partially attenuated by a constitutively-active mutant Akt1. Furthermore, it was cytotoxic against Akt1-knockout A172 glioma cells. XL388 downregulated MAF bZIP transcription factor G (MAFG) and inhibited Nrf2 signaling, causing oxidative injury in glioma cells. Conversely, antioxidants, n-acetylcysteine, pyrrolidine dithiocarbamate and AGI-106, alleviated XL388-induced cytotoxicity and apoptosis in glioma cells. Oral administration of XL388 inhibited subcutaneous A172 xenograft growth in severe combined immunodeficient mice. Akt-S6K1 inhibition and MAFG downregulation were detected in XL388-treated A172 xenograft tissues. Collectively, XL388 efficiently inhibits human glioma cell growth, through Akt-mTOR-dependent and -independent mechanisms.

Lnc-THOR silencing inhibits human glioma cell survival by activating MAGEA6-AMPK signaling.

Long non-coding RNA THOR (Lnc-THOR) binds to IGF2BP1, essential for its function. We here show that Lnc-THOR is expressed in human glioma tissues and cells. Its expression is extremely low or even undetected in normal brain tissues, as well as in human neuronal cells and astrocytes. We show that Lnc-THOR directly binds to IGF2BP1 in established and primary human glioma cells. shRNA-mediated Lnc-THOR knockdown or CRISPR/Cas9-induced Lnc-THOR knockout potently inhibited cell survival and proliferation, while provoking glioma cell apoptosis. Contrarily, forced overexpression of Lnc-THOR promoted glioma cell growth and migration. Importantly, Lnc-THOR shRNA or knockout activated MAGEA6-AMPK signaling in glioma cells. AMPK inactivation, by AMPKα1 shRNA, knockout, or dominant-negative mutation (T172A), attenuated Lnc-THOR shRNA-induced A172 glioma cell apoptosis. Moreover, CRISPR/Cas9-induced IGF2BP1 knockout activated MAGEA6-AMPK signaling as well, causing A172 glioma cell apoptosis. Significantly, Lnc-THOR shRNA was ineffective in IGF2BP1 KO A172 cells. In vivo, Lnc-THOR silencing or knockout potently inhibited subcutaneous A172 xenograft tumor growth in mice. MAGEA6 downregulation and AMPK activation were detected in Lnc-THOR-silenced/-KO A172 tumor tissues. Taken together, Lnc-THOR depletion inhibits human glioma cell survival possibly by activating MAGEA6-AMPK signaling.

MAGEA6 promotes human glioma cell survival via targeting AMPKα1.

Melanoma antigen A6 (MAGEA6)/TRIM28 complex is a cancer-specific ubiquitin ligase, which degradates tumor suppressor protein AMP-activated protein kinase (AMPK). We show that MAGEA6 is uniquely expressed in human glioma tissues and cells, which is correlated with AMPKα1 downregulation. It is yet absent in normal brain tissues and human astrocytes/neuronal cells. MAGEA6 knockdown by targeted-shRNA in glioma cells restored AMPKα1 expression, causing mTORC1 in-activation and cell death/apoptosis. Reversely, AMPKα1 knockdown or mutation ameliorated glioma cell death by MAGEA6 shRNA. In vivo, Glioma xenograft tumor growth in mice was largely inhibited following expressing MAGEA6 shRNA. AMPKα1 upregulation and mTORC1 inhibition were observed in MAGEA6 shRNA-bearing xenograft tissues. Collectively, MAGEA6 promotes glioma cell survival possibly via targeting AMPKα1.