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Glioma initiating/stem cells, differentiation, iTRAQ analysis by QSTAR Elite

ABSTRACT: Glioma initiating/stem cells (GIC/GSC) are considered responsible for the therapeutic resistance and recurrence of malignant glioma. To clarify the molecular mechanism of GIC/GSC maintenance/differentiation, we established GIC/GSC clones, having the potential to differentiate into malignant gliomas, from glioblastoma patient’s tissues, and subjected to DNA microarray/iTRAQ based integrated proteomics. 21,857 mRNAs and 8,471 proteins were identified and integrated into a gene/protein expression analysis chart (iPEACH). The data integration and extraction of global proteins and mRNAs revealed that, during the GIC/GSC differentiation, cell adhesion molecules including integrin aV/ECMs and RAS-MAPK/PI3K signalings were significantly up-regulated, meanwhile, SOX2, CD133, and specific proteoglycans/synthetic-enzymes/metabolic pathways were obviously down-regulated. Among them, we focused proteoglycans and their synthetic-enzymes. GIC/GSC differentiation was significantly associated with the decrease of CSPG (CS-modified form) and dramatically induced by the CS-degradation enzyme which also induces the up-regulation of ERK-AKT signaling and GFAP without any other agents. Importantly, these differentiation processes were also associated with the interaction of CSPG (CS-unmodified form) and integrin-aV, and suppressed by integrin-inhibitors/CS administrations significantly. Combination treatments of a cancer-drug Temozolomide and these GIC/GSC-differentiation inhibitors suppressed glioma progression, increased the chemosensitivities, and led the longer survival of mouse xenograft-models. Functional integrated proteomics for the first time demonstrates that the GIC/GSC induces the specific proteoglycans to regulate GIC/GSC stemness/differentiation via the integlin signalings which may be a clinical target against malignant gliomas.

ORGANISM(S): Homo Sapiens (human)

SUBMITTER: Norie Araki

PROVIDER: PXD008332 | JPOST Repository | Fri Nov 30 00:00:00 GMT 2018

REPOSITORIES: jPOST

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Project description:Although malignant gliomas frequently show aberrant activation of the mammalian target of rapamycin (mTOR), mTOR inhibitors have performed poorly in clinical trials. Besides regulating cell growth and translation, mTOR controls the initiation of autophagy. By recycling cellular components, autophagy can mobilize energy resources, and has thus been attributed cancer-promoting effects. Here, we asked whether the activation of autophagy represents an escape mechanism to pharmacological mTOR inhibition, and explored co-treatment with mTOR and autophagy inhibitors as a therapeutic strategy. Mimicking conditions of the glioma microenvironment, glioma cells were exposed to nutrient starvation and hypoxia. Following treatment with mTOR inhibitor torin2 or rapamycin, and autophagy inhibitors bafilomycin A1 or MRT68921, we analyzed autophagic activity, cell growth, viability and oxygen consumption. Changes in global proteome were quantified by mass spectrometry. In the context of hypoxia and starvation, autophagy was strongly induced in glioma cells, and further increased by mTOR inhibition. While torin2 enhanced glioma cell survival, co-treatment with torin2 and bafilomycin A1 failed to promote cell death. Importantly, treatment with bafilomycin A1 alone also protected glioma cells from cell death. Mechanistically, both compounds significantly reduced glioma growth and oxygen consumption. Mass spectrometry analysis showed that bafilomycin A1 induced broad changes in the cellular proteome. More specifically, proteins downregulated by bafilomycin A1 were associated with the mitochondrial respiratory chain and ATP synthesis. Taken together, our results show that activation of autophagy does not account for the cytoprotective effects of mTOR inhibition in our in vitro model of the glioma microenvironment. Our proteomic findings suggest that the pharmacological inhibition of autophagy induces extensive changes in the cellular proteome that can support glioma cell survival under nutrient-deplete and hypoxic conditions. These findings provide a novel perspective on the complex role of autophagy in gliomas and may have implications for the design of future trials.

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Glioma initiating/stem cells, differentiation, iTRAQ analysis by QSTAR Elite

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