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Wang Y, Vandewalle N, De Veirman K, Vanderkerken K, Menu E, De Bruyne E. Targeting mTOR signaling pathways in multiple myeloma: biology and implication for therapy. Cell Commun Signal 2024; 22:320. [PMID: 38862983 PMCID: PMC11165851 DOI: 10.1186/s12964-024-01699-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2024] [Accepted: 06/03/2024] [Indexed: 06/13/2024] Open
Abstract
Multiple Myeloma (MM), a cancer of terminally differentiated plasma cells, is the second most prevalent hematological malignancy and is incurable due to the inevitable development of drug resistance. Intense protein synthesis is a distinctive trait of MM cells, supporting the massive production of clonal immunoglobulins or free light chains. The mammalian target of rapamycin (mTOR) kinase is appreciated as a master regulator of vital cellular processes, including regulation of metabolism and protein synthesis, and can be found in two multiprotein complexes, mTORC1 and mTORC2. Dysregulation of these complexes is implicated in several types of cancer, including MM. Since mTOR has been shown to be aberrantly activated in a large portion of MM patients and to play a role in stimulating MM cell survival and resistance to several existing therapies, understanding the regulation and functions of the mTOR complexes is vital for the development of more effective therapeutic strategies. This review provides a general overview of the mTOR pathway, discussing key discoveries and recent insights related to the structure and regulation of mTOR complexes. Additionally, we highlight findings on the mechanisms by which mTOR is involved in protein synthesis and delve into mTOR-mediated processes occurring in MM. Finally, we summarize the progress and current challenges of drugs targeting mTOR complexes in MM.
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Affiliation(s)
- Yanmeng Wang
- Translational Oncology Research Center (TORC) - Team Hematology and Immunology (HEIM), Vrije Universiteit Brussel (VUB), Jette, Belgium
| | - Niels Vandewalle
- Translational Oncology Research Center (TORC) - Team Hematology and Immunology (HEIM), Vrije Universiteit Brussel (VUB), Jette, Belgium
| | - Kim De Veirman
- Translational Oncology Research Center (TORC) - Team Hematology and Immunology (HEIM), Vrije Universiteit Brussel (VUB), Jette, Belgium
- Translational Oncology Research Center (TORC) - Team Hematology and Immunology (HEIM), Universitair Ziekenhuis Brussel (UZ Brussel), Jette, Belgium
| | - Karin Vanderkerken
- Translational Oncology Research Center (TORC) - Team Hematology and Immunology (HEIM), Vrije Universiteit Brussel (VUB), Jette, Belgium
| | - Eline Menu
- Translational Oncology Research Center (TORC) - Team Hematology and Immunology (HEIM), Vrije Universiteit Brussel (VUB), Jette, Belgium.
| | - Elke De Bruyne
- Translational Oncology Research Center (TORC) - Team Hematology and Immunology (HEIM), Vrije Universiteit Brussel (VUB), Jette, Belgium.
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Ma G, Sun Y, Cai F, Zhang M, Liang H, Deng J, Zhang R, Zhang L. DEPTOR as a novel prognostic marker inhibits the proliferation via deactivating mTOR signaling pathway in gastric cancer cells. Exp Cell Res 2023; 427:113598. [PMID: 37054772 DOI: 10.1016/j.yexcr.2023.113598] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2022] [Revised: 02/15/2023] [Accepted: 04/09/2023] [Indexed: 04/15/2023]
Abstract
Aberrantly activated mTOR signaling pathway is commonly found in malignancies including gastric cancer (GC). DEPTOR, as a naturally occurred inhibitor of mTOR, functions in the pro- or anti-tumor manner depending on distinct tumor contexts. However, the roles of DEPTOR in GC remain largely unknown. In this study, DEPTOR expression was identified to be significantly decreased in GC tissues compared with matched normal gastric tissues, and reduced DEPTOR level was indicative of poor prognosis in patients. Restored DEPTOR expression inhibited the propagation in AGS and NCI-N87 cells, whose DEPTOR levels are low, via deactivating mTOR signaling pathway. Likewise, cabergoline (CAB) attenuated the proliferation in AGS and NCI-N87 cells via partially rescuing DEPTOR protein level. Targeted metabolomics analysis showed that several key metabolites, such as l-serine, significantly changed in AGS cells with DEPTOR restoration. These results revealed the anti-proliferation function of DEPTOR in GC cells, suggesting that restored DEPTOR expression using CAB may be a potential therapeutic approach for patients with GC.
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Affiliation(s)
- Gang Ma
- Department of Gastric Surgery, Tianjin Medical University Cancer Institute and Hospital, National Clinical Research Center for Cancer, China; Key Laboratory of Cancer Prevention and Therapy, Tianjin, China; Tianjin's Clinical Research Center for Cancer, Tianjin, 300060, China
| | - Yi Sun
- Department of Anatomy, Histology and Embryology, School of Basic Medical Sciences, Peking University, Beijing, 100191, China
| | - Fenglin Cai
- Department of Gastric Surgery, Tianjin Medical University Cancer Institute and Hospital, National Clinical Research Center for Cancer, China; Key Laboratory of Cancer Prevention and Therapy, Tianjin, China; Tianjin's Clinical Research Center for Cancer, Tianjin, 300060, China
| | - Mengmeng Zhang
- Department of Gastric Surgery, Tianjin Medical University Cancer Institute and Hospital, National Clinical Research Center for Cancer, China; Key Laboratory of Cancer Prevention and Therapy, Tianjin, China; Tianjin's Clinical Research Center for Cancer, Tianjin, 300060, China
| | - Han Liang
- Department of Gastric Surgery, Tianjin Medical University Cancer Institute and Hospital, National Clinical Research Center for Cancer, China; Key Laboratory of Cancer Prevention and Therapy, Tianjin, China; Tianjin's Clinical Research Center for Cancer, Tianjin, 300060, China
| | - Jingyu Deng
- Department of Gastric Surgery, Tianjin Medical University Cancer Institute and Hospital, National Clinical Research Center for Cancer, China; Key Laboratory of Cancer Prevention and Therapy, Tianjin, China; Tianjin's Clinical Research Center for Cancer, Tianjin, 300060, China
| | - Rupeng Zhang
- Department of Gastric Surgery, Tianjin Medical University Cancer Institute and Hospital, National Clinical Research Center for Cancer, China; Key Laboratory of Cancer Prevention and Therapy, Tianjin, China; Tianjin's Clinical Research Center for Cancer, Tianjin, 300060, China
| | - Li Zhang
- Department of Gastric Surgery, Tianjin Medical University Cancer Institute and Hospital, National Clinical Research Center for Cancer, China; Key Laboratory of Cancer Prevention and Therapy, Tianjin, China; Tianjin's Clinical Research Center for Cancer, Tianjin, 300060, China.
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An mTORC1 to HRI signaling axis promotes cytotoxicity of proteasome inhibitors in multiple myeloma. Cell Death Dis 2022; 13:969. [PMID: 36400754 PMCID: PMC9674573 DOI: 10.1038/s41419-022-05421-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2022] [Revised: 11/05/2022] [Accepted: 11/08/2022] [Indexed: 11/19/2022]
Abstract
Multiple myeloma (MM) causes approximately 20% of deaths from blood cancers. Notwithstanding significant therapeutic progress, such as with proteasome inhibitors (PIs), MM remains incurable due to the development of resistance. mTORC1 is a key metabolic regulator, which frequently becomes dysregulated in cancer. While mTORC1 inhibitors reduce MM viability and synergize with other therapies in vitro, clinically, mTORC1 inhibitors are not effective for MM. Here we show that the inactivation of mTORC1 is an intrinsic response of MM to PI treatment. Genetically enforced hyperactivation of mTORC1 in MM was sufficient to compromise tumorigenicity in mice. In vitro, mTORC1-hyperactivated MM cells gained sensitivity to PIs and hypoxia. This was accompanied by increased mitochondrial stress and activation of the eIF2α kinase HRI, which initiates the integrated stress response. Deletion of HRI elevated the toxicity of PIs in wt and mTORC1-activated MM. Finally, we identified the drug PMA as a robust inducer of mTORC1 activity, which synergized with PIs in inducing MM cell death. These results help explain the clinical inefficacy of mTORC1 inhibitors in MM. Our data implicate mTORC1 induction and/or HRI inhibition as pharmacological strategies to enhance MM therapy by PIs.
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Vega M, Chen Y, Shi Y, Gera J, Lichtenstein A. Turnover of the mTOR inhibitor, DEPTOR, and downstream AKT phosphorylation in multiple myeloma cells, is dependent on ERK1-mediated phosphorylation. J Biol Chem 2022; 298:101750. [PMID: 35216969 PMCID: PMC8933699 DOI: 10.1016/j.jbc.2022.101750] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2021] [Revised: 01/27/2022] [Accepted: 01/28/2022] [Indexed: 11/27/2022] Open
Abstract
DEPTOR is a 48 kDa protein upregulated in multiple myeloma (MM) cells. DEPTOR inhibits mTOR and, by repressing a negative feedback loop, promotes AKT activation. We previously identified a compound that binds to DEPTOR in MM cells and induces its proteasomal degradation. To identify the mechanism of degradation, here, we screened for drug-induced posttranslational modifications and identified reduced phosphorylation of DEPTOR on serine 235 (S235). We show that an S235 phosphomimetic DEPTOR mutant was resistant to degradation, confirming the importance of this posttranslational modification. In addition, a DEPTOR mutant with a serine-to-alanine substitution at S235 could only be expressed upon concurrent proteasome inhibition. Thus, S235 phosphorylation regulates DEPTOR stability. Screening the DEPTOR interactome identified that the association of USP-7 deubiquitinase with DEPTOR was dependent upon S235 phosphorylation. Inhibition of USP-7 activity resulted in DEPTOR polyubiquitination and degradation. A scansite search suggested that ERK1 may be responsible for S235 phosphorylation, which was confirmed through the use of inhibitors, ERK1 knockdown, and an in vitro kinase assay. Inhibition of ERK1 also downregulated AKT phosphorylation. To test if DEPTOR phosphorylation mediated this crosstalk, MM cells were transfected with WT or phosphomimetic DEPTOR and exposed to ERK inhibitors. Although WT DEPTOR had no effect on the inhibition of AKT phosphorylation, the phosphomimetic DEPTOR prevented inhibition. These results indicate that ERK1 maintains AKT activity in MM cells via phosphorylation of DEPTOR. We propose that DEPTOR-dependent crosstalk provides MM cells with a viability-promoting signal (through AKT) when proliferation is stimulated (through ERK).
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Affiliation(s)
- Mario Vega
- Hematology-Oncology, Greater Los Angeles VA-UCLA Healthcare Center, UCLA and Jonsson Comprehensive Cancer Center, UCLA, Los Angeles, California
| | - Yu Chen
- Molecular Instrumentation Center, UCLA and Jonsson Comprehensive Cancer Center, UCLA, Los Angeles, California
| | - Yijiang Shi
- Hematology-Oncology, Greater Los Angeles VA-UCLA Healthcare Center, UCLA and Jonsson Comprehensive Cancer Center, UCLA, Los Angeles, California
| | - Joseph Gera
- Hematology-Oncology, Greater Los Angeles VA-UCLA Healthcare Center, UCLA and Jonsson Comprehensive Cancer Center, UCLA, Los Angeles, California
| | - Alan Lichtenstein
- Hematology-Oncology, Greater Los Angeles VA-UCLA Healthcare Center, UCLA and Jonsson Comprehensive Cancer Center, UCLA, Los Angeles, California.
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Heimhalt M, Berndt A, Wagstaff J, Anandapadamanaban M, Perisic O, Maslen S, McLaughlin S, Yu CWH, Masson GR, Boland A, Ni X, Yamashita K, Murshudov GN, Skehel M, Freund SM, Williams RL. Bipartite binding and partial inhibition links DEPTOR and mTOR in a mutually antagonistic embrace. eLife 2021; 10:e68799. [PMID: 34519269 PMCID: PMC8439657 DOI: 10.7554/elife.68799] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2021] [Accepted: 07/31/2021] [Indexed: 12/16/2022] Open
Abstract
The mTORC1 kinase complex regulates cell growth, proliferation, and survival. Because mis-regulation of DEPTOR, an endogenous mTORC1 inhibitor, is associated with some cancers, we reconstituted mTORC1 with DEPTOR to understand its function. We find that DEPTOR is a unique partial mTORC1 inhibitor that may have evolved to preserve feedback inhibition of PI3K. Counterintuitively, mTORC1 activated by RHEB or oncogenic mutation is much more potently inhibited by DEPTOR. Although DEPTOR partially inhibits mTORC1, mTORC1 prevents this inhibition by phosphorylating DEPTOR, a mutual antagonism that requires no exogenous factors. Structural analyses of the mTORC1/DEPTOR complex showed DEPTOR's PDZ domain interacting with the mTOR FAT region, and the unstructured linker preceding the PDZ binding to the mTOR FRB domain. The linker and PDZ form the minimal inhibitory unit, but the N-terminal tandem DEP domains also significantly contribute to inhibition.
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Affiliation(s)
- Maren Heimhalt
- MRC Laboratory of Molecular BiologyCambridgeUnited Kingdom
| | - Alex Berndt
- MRC Laboratory of Molecular BiologyCambridgeUnited Kingdom
| | - Jane Wagstaff
- MRC Laboratory of Molecular BiologyCambridgeUnited Kingdom
| | | | - Olga Perisic
- MRC Laboratory of Molecular BiologyCambridgeUnited Kingdom
| | - Sarah Maslen
- MRC Laboratory of Molecular BiologyCambridgeUnited Kingdom
| | | | | | - Glenn R Masson
- MRC Laboratory of Molecular BiologyCambridgeUnited Kingdom
| | - Andreas Boland
- Department of Molecular Biology, University of GenevaGenevaSwitzerland
| | - Xiaodan Ni
- MRC Laboratory of Molecular BiologyCambridgeUnited Kingdom
| | | | | | - Mark Skehel
- MRC Laboratory of Molecular BiologyCambridgeUnited Kingdom
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Morales-Martinez M, Lichtenstein A, Vega MI. Function of Deptor and its roles in hematological malignancies. Aging (Albany NY) 2021; 13:1528-1564. [PMID: 33412518 PMCID: PMC7834987 DOI: 10.18632/aging.202462] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2020] [Accepted: 12/10/2020] [Indexed: 12/12/2022]
Abstract
Deptor is a protein that interacts with mTOR and that belongs to the mTORC1 and mTORC2 complexes. Deptor is capable of inhibiting the kinase activity of mTOR. It is well known that the mTOR pathway is involved in various signaling pathways that are involved with various biological processes such as cell growth, apoptosis, autophagy, and the ER stress response. Therefore, Deptor, being a natural inhibitor of mTOR, has become very important in its study. Because of this, it is important to research its role regarding the development and progression of human malignancies, especially in hematologic malignancies. Due to its variation in expression in cancer, it has been suggested that Deptor can act as an oncogene or tumor suppressor depending on the cellular or tissue context. This review discusses recent advances in its transcriptional and post-transcriptional regulation of Deptor. As well as the advances regarding the activities of Deptor in hematological malignancies, its possible role as a biomarker, and its possible clinical relevance in these malignancies.
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Affiliation(s)
- Mario Morales-Martinez
- Molecular Signal Pathway in Cancer Laboratory, UIMEO, Oncology Hospital, Siglo XXI National Medical Center, IMSS, México City, México
| | - Alan Lichtenstein
- Department of Medicine, Hematology-Oncology Division, Greater Los Angeles VA Healthcare Center, UCLA Medical Center, Jonsson Comprehensive Cancer Center, Los Angeles, CA 90024, USA
| | - Mario I Vega
- Molecular Signal Pathway in Cancer Laboratory, UIMEO, Oncology Hospital, Siglo XXI National Medical Center, IMSS, México City, México.,Department of Medicine, Hematology-Oncology Division, Greater Los Angeles VA Healthcare Center, UCLA Medical Center, Jonsson Comprehensive Cancer Center, Los Angeles, CA 90024, USA
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Jabłońska E, Białopiotrowicz E, Szydłowski M, Prochorec-Sobieszek M, Juszczyński P, Szumera-Ciećkiewicz A. DEPTOR is a microRNA-155 target regulating migration and cytokine production in diffuse large B-cell lymphoma cells. Exp Hematol 2020; 88:56-67.e2. [PMID: 32702393 DOI: 10.1016/j.exphem.2020.07.005] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2020] [Revised: 06/24/2020] [Accepted: 07/15/2020] [Indexed: 12/24/2022]
Abstract
MicroRNA-155 (MiR-155) is involved in normal B-cell development and lymphomagenesis, affecting cell differentiation, motility, and intracellular signaling. In this study, we searched for new targets of MiR-155 potentially involved in deregulation of the B-cell receptor pathway (BCR) in diffuse large B-cell lymphoma (DLBCL). We report that MiR-155 represses DEPTOR (an mTOR phosphatase) and c-CBL (SYK ubiquitin E3 ligase) through direct 3'-untranslated region interactions. In primary DLBCLs, MiR-155 exhibits a reciprocal expression pattern with DEPTOR and c-CBL. Inhibition of MiR-155 decreased expression of NFκB target genes and sensitized DLBCL cells to ibrutinib, confirming the role of MiR-155 in the modulation of BCR signaling. As the function of DEPTOR in DLBCLs has never been addressed, we first evaluated its expression in a series of 76 newly diagnosed DLBCL patients. DEPTOR protein expression was markedly lower in more aggressive nongerminal center-like (non-GCB) DLBCLs than in GCB tumors. In cell line models, inhibition of DEPTOR expression favored the migration of DLBCL cells toward the CXCL12 gradient. Finally, loss or gain of DEPTOR modulated the expression of specific pro-inflammatory cytokines and chemokines. We thus identified DEPTOR as a new MiR-155 target that is differentially expressed between GCB- and non-GCB-type DLBCLs and modulates cell migration and cytokine expression in DLBCL cells.
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Affiliation(s)
- Ewa Jabłońska
- Department of Experimental Hematology, Institute of Hematology and Transfusion Medicine, Warsaw, Poland
| | - Emilia Białopiotrowicz
- Department of Experimental Hematology, Institute of Hematology and Transfusion Medicine, Warsaw, Poland
| | - Maciej Szydłowski
- Department of Experimental Hematology, Institute of Hematology and Transfusion Medicine, Warsaw, Poland
| | | | - Przemysław Juszczyński
- Department of Experimental Hematology, Institute of Hematology and Transfusion Medicine, Warsaw, Poland.
| | - Anna Szumera-Ciećkiewicz
- Department of Diagnostic Hematology, Institute of Hematology and Transfusion Medicine, Warsaw, Poland.
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