Enhancing Proteasome-Dependent Targeted Protein Degradation by mTOR inhibition
Ontology highlight
ABSTRACT:
ORGANISM(S): Homo Sapiens
SUBMITTER: 
Yong Cang
PROVIDER: PXD065306 | iProX | Mon Jun 23 00:00:00 BST 2025
REPOSITORIES: iProX
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Project description:mTOR is a central regulator of mammalian metabolism and physiology. Aberrant hyperactivation of this pathway promotes tumor growth and metastasis and drives tumor resistance to chemotherapy and cancer drugs, making mTOR an attractive cancer therapeutic target. mTOR inhibitors have been approved to treat cancer, however, the basis for drug sensitivity remains poorly understood. Here, whole exome sequencing of three chromophobe renal cell carcinoma (chRCC) patients with exceptional mTOR inhibitor sensitivity, uncovered USP9X deubiquitinase as the only mutated gene shared by the tumors. The clonal characteristics of the mutations, revealed by studying multiple patients’ primary and metastatic samples along the years, together with the low USP9X mutation rate in unselected chRCC series, reinforced a causal link between USP9X and mTOR inhibitor sensitivity. Rapamycin treatment of USP9X depleted HeLa and renal cancer 786-O cells and the pharmacological inhibition of USP9X, confirmed a crucial role of this protein in the patients’ sensitivity to mTOR inhibition. As no direct effect of USP9X in mTORC1 was detected, we performed ubiquitylome analyses that identified p62 as a direct USP9X target. Increased p62 ubiquitination and an augmented rapamycin effect upon bortezomib treatment, together with p62 and LC3 immunofluorescence assays, suggested that dysregulated autophagy in USP9X depleted cells can synergize with mTOR inhibitors. In summary, here we show that USP9X constitutes a potential novel marker of sensitivity to mTOR inhibitors in chRCC patients and represents a clinically exploitable strategy that could increase sensitivity to these drugs
2023-06-14 | PXD040496 | Pride
Project description:Introduction: Glioma-associated microglia/macrophages (GAM) constitute the predominant immune cell population in glioblastoma (GB). Both GB cells and GAM exhibit upregulated mTOR signaling. This study aimed to investigate the effects of pharmacological mTOR inhibition (mTORi) specifically on GAM.Materials and Methods: We conducted a comprehensive analysis of the GAM phenotype, including whole transcriptome analyses and cytokine profiling. Effects were investigated in a tumor cell/GAM co-culture model under mTORi with rapamycin or torin2 or under treatment with temozolomide, the standard chemotherapy agent for GB patients.Results: In our in vitro model, mTORi had significant effects on central biological functions of GAM, resulting in reduced proliferation and oxygen consumption. Additionally, treatment with mTORi induced a pro-inflammatory phenotype in microglial cells.Conclusions: Our findings demonstrate the profound relevance of mTOR signaling on GAM biology. Moreover, they provide rationales for therapeutic interventions targeting mTOR signaling specifically in GAM as a potential novel treatment strategy.
2025-07-28 | GSE242829 | GEO
Project description:The mechanistic target of rapamycin (mTOR) is a central regulator of cell growth and an attractive anti-cancer target that integrates diverse signals to control cell proliferation. Previous studies using mTOR inhibitors have shown that mTOR targeting suppresses gene expression and cell proliferation. To date, however, mTOR targeted therapies in cancer have seen very limited efficacy, and one key issue is related to the development of evasive resistance. In this manuscript, through the use of a gene targeting mouse model, we have found that inducible deletion of mTOR in hematopoietic stem cells (HSCs) results in a loss of quiescence and increased proliferation. Adaptive to the mTOR loss, mTOR-/- HSCs increase chromatin accessibility and activate global gene expression, contrary to the effects of short-term inhibition by mTOR inhibitors. Mechanistically, such genomic changes are due to a rewiring and adaptive activation of the ERK/MNK/eIF4E signaling pathway that enhances the protein translation of RNA polymerase II (RNAP II), which in turn leads to increased c-Myc gene expression, allowing the HSCs to thrive despite loss of a functional mTOR pathway. This adaptive mechanism can also be utilized by leukemia cells undergoing long-term mTOR inhibitor treatment to confer resistance to mTOR drug targeting. The resistance can then be counteracted by MNK, CDK9, or c-Myc inhibition. These results provide new insights into the physiological role of mTOR in mammalian stem cell regulation and implicate a novel mechanism of evasive resistance in the context of mTOR targeting.
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Project description:We have used ChIP-seq to profile binding of the estrogen receptor (ER) to chromatin in response to two mTOR inhibitors, i.e. everolimus (RAD001) and vistusertib (AZD2014). Two hours of treatment with these inhibitors significantly affected mTOR signaling, but surprisingly did not affect binding of ER to chromatin. This suggests that these mTOR inhibitors work through largely ER-independent mechanisms.
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Project description:Esophageal squamous cell carcinoma (OSCC) is a lethal digestive tract malignancy with limited effective interventions. This study aims to explore a new potential inhibitor on OSCC and investigate the underlying mechanisms. Based on a drug screen of an FDA-proven library consisting of 1404 compounds, we demonstrated that Omipalisib, a dual PI3K/mTOR inhibitor, markedly inhibited cell proliferation and colony formation in a panel of OSCC cell lines. Mechanistically, Omipalisib induced G0/G1 phase cell cycle arrest and apoptosis. Moreover, RNA-seq, KEGG and GSEA confirmed that the PI3K/mTOR signalling pathway is the primary target of Omipalisib in OSCC cells. Omipalisib treatment suppressed the PI3K/mTOR signalling pathway. Furthermore, Omipalisib exerted a significant antineoplastic effect on OSCC tumour xenografts in BALB/c nude mice without obvious side effects. The present study supports the rationale for using Omipalisib as a therapeutic approach for OSCC cases and suggests the potential clinical evaluation of this strategy.
2020-01-11 | GSE143462 | GEO
Project description:The PI3K/mammalian target of rapamycin (mTOR) pathway is dysregulated in over 50% of human GBM but remains a challenging clinical target. Inhibitors against PI3K/mTOR mediators have limited clinical efficacy as single agents. Gene expression profiling after PI3K/mTOR inhibition treatment was analyzed by Affymetrix microarrays.
2016-05-20 | GSE79316 | GEO
Project description:The mammalian target of rapamycin (mTOR) is a central regulator of cell growth and proliferation in response to growth factor and nutrient signaling. Consequently, this kinase is implicated in metabolic diseases including cancer and diabetes so there is great interest in understanding mTOR regulatory networks. mTOR exists in two functionally distinct complexes, mTORC1 and mTORC2, and whereas the natural product rapamycin only inhibits a subset of mTORC1 functions, recently developed ATP-competitive mTOR inhibitors have revealed new roles for both complexes. To examine the complete spectrum of mTOR responsive cellular processes, we compared the transcriptional profiles of mammalian cells treated with rapamycin versus the ATP-competitive inhibitor PP242. Our analysis provides a genome-wide view of the transcriptional outputs of mTOR signaling that are insensitive to rapamycin. Gene expression in mouse NIH3T3 cells was measured after 18 hour treatment with DMSO (control), 50 nM rapamycin, or 2 uM PP242. Four independent experiments were performed for each condition.
2011-03-15 | E-GEOD-27784 | biostudies-arrayexpress
Project description:We report the impact of mTOR inhibition on RNA expression in AT/RT patient derived cell lines
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Project description:Phosphatidylinositol-3-kinase (PI3K)/Akt/mammalian target of rapamycin (mTOR) pathway activation contributes to mantle cell lymphoma (MCL) pathogenesis and drug resistance. However, the use of mTOR inhibitors as single agents have shown limited clinical efficacy in relation with drug activation of feedback loops. Selective PI3K inhibition or dual PI3K/mTOR catalytic inhibition are different therapeutic approaches developed to achieve effective pathway blockage. Here, we evaluated the antitumor activity of a mTOR inhibitor, a pan-PI3K inhibitor and a dual PI3K/mTOR inhibitor in primary MCL cells. We found that dual PI3K/mTOR inhibitor modulated angiogenesis, tumor invasiveness and cytokine signaling compared to a mTOR inhibitor and a pan-PI3K inhibitor in MCL. We used microarrays to compare the effect of these three compounds in MCL and identified distinct classes of down-regulated genes modulated by each compound. Global RNA expression in primary cells from two MCL patients treated with a mTOR inhibitor, a pan-PI3K inhibitor and a dual PI3K/mTOR inhibitor for 8 hours
2013-12-14 | E-GEOD-53309 | biostudies-arrayexpress