PMID- 36202792 OWN - NLM STAT- PubMed-not-MEDLINE LR - 20221010 IS - 2058-7716 (Print) IS - 2058-7716 (Electronic) IS - 2058-7716 (Linking) VI - 8 IP - 1 DP - 2022 Oct 6 TI - Inhibition of mTOR signaling protects human glioma cells from hypoxia-induced cell death in an autophagy-independent manner. PG - 409 LID - 10.1038/s41420-022-01195-y [doi] LID - 409 AB - 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 in glioma cells, 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. We analyzed autophagic activity, cell growth, viability and oxygen consumption following (co-)treatment with the mTOR inhibitors torin2 or rapamycin, and autophagy inhibitors bafilomycin A1 or MRT68921. 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 cell growth and oxygen consumption. Quantitative proteomics 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. CI - (c) 2022. The Author(s). FAU - Dive, Iris AU - Dive I AUID- ORCID: 0000-0003-1096-5626 AD - Dr. Senckenberg Institute of Neurooncology, University Hospital Frankfurt, Goethe University, Frankfurt am Main, Germany. iris.dive@kgu.de. AD - University Cancer Center Frankfurt (UCT), University Hospital Frankfurt, Goethe University, Frankfurt am Main, Germany. iris.dive@kgu.de. AD - Frankfurt Cancer Institute (FCI), University Hospital Frankfurt, Goethe University, Frankfurt am Main, Germany. iris.dive@kgu.de. AD - German Cancer Consortium (DKTK), Partner Site Frankfurt/Mainz, Frankfurt am Main, Germany. iris.dive@kgu.de. AD - Institute of Biochemistry II, Goethe University, Frankfurt am Main, Germany. iris.dive@kgu.de. FAU - Klann, Kevin AU - Klann K AD - Frankfurt Cancer Institute (FCI), University Hospital Frankfurt, Goethe University, Frankfurt am Main, Germany. AD - Institute of Biochemistry II, Goethe University, Frankfurt am Main, Germany. FAU - Michaelis, Jonas B AU - Michaelis JB AD - Frankfurt Cancer Institute (FCI), University Hospital Frankfurt, Goethe University, Frankfurt am Main, Germany. AD - Institute of Biochemistry II, Goethe University, Frankfurt am Main, Germany. FAU - Heinzen, Dennis AU - Heinzen D AD - Dr. Senckenberg Institute of Neurooncology, University Hospital Frankfurt, Goethe University, Frankfurt am Main, Germany. FAU - Steinbach, Joachim P AU - Steinbach JP AD - Dr. Senckenberg Institute of Neurooncology, University Hospital Frankfurt, Goethe University, Frankfurt am Main, Germany. AD - University Cancer Center Frankfurt (UCT), University Hospital Frankfurt, Goethe University, Frankfurt am Main, Germany. AD - Frankfurt Cancer Institute (FCI), University Hospital Frankfurt, Goethe University, Frankfurt am Main, Germany. AD - German Cancer Consortium (DKTK), Partner Site Frankfurt/Mainz, Frankfurt am Main, Germany. FAU - Munch, Christian AU - Munch C AUID- ORCID: 0000-0003-3832-090X AD - Frankfurt Cancer Institute (FCI), University Hospital Frankfurt, Goethe University, Frankfurt am Main, Germany. AD - Institute of Biochemistry II, Goethe University, Frankfurt am Main, Germany. FAU - Ronellenfitsch, Michael W AU - Ronellenfitsch MW AD - Dr. Senckenberg Institute of Neurooncology, University Hospital Frankfurt, Goethe University, Frankfurt am Main, Germany. AD - University Cancer Center Frankfurt (UCT), University Hospital Frankfurt, Goethe University, Frankfurt am Main, Germany. AD - Frankfurt Cancer Institute (FCI), University Hospital Frankfurt, Goethe University, Frankfurt am Main, Germany. AD - German Cancer Consortium (DKTK), Partner Site Frankfurt/Mainz, Frankfurt am Main, Germany. LA - eng PT - Journal Article DEP - 20221006 PL - United States TA - Cell Death Discov JT - Cell death discovery JID - 101665035 PMC - PMC9537540 COIS- The authors declare no competing interests. EDAT- 2022/10/07 06:00 MHDA- 2022/10/07 06:01 PMCR- 2022/10/06 CRDT- 2022/10/06 23:14 PHST- 2022/05/06 00:00 [received] PHST- 2022/09/16 00:00 [accepted] PHST- 2022/09/15 00:00 [revised] PHST- 2022/10/06 23:14 [entrez] PHST- 2022/10/07 06:00 [pubmed] PHST- 2022/10/07 06:01 [medline] PHST- 2022/10/06 00:00 [pmc-release] AID - 10.1038/s41420-022-01195-y [pii] AID - 1195 [pii] AID - 10.1038/s41420-022-01195-y [doi] PST - epublish SO - Cell Death Discov. 2022 Oct 6;8(1):409. doi: 10.1038/s41420-022-01195-y.