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Kiweler N, Schwarz H, Nguyen A, Matschos S, Mullins C, Piée-Staffa A, Brachetti C, Roos WP, Schneider G, Linnebacher M, Brenner W, Krämer OH. The epigenetic modifier HDAC2 and the checkpoint kinase ATM determine the responses of microsatellite instable colorectal cancer cells to 5-fluorouracil. Cell Biol Toxicol 2023; 39:2401-2419. [PMID: 35608750 PMCID: PMC10547618 DOI: 10.1007/s10565-022-09731-3] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2021] [Accepted: 05/10/2022] [Indexed: 11/02/2022]
Abstract
The epigenetic modifier histone deacetylase-2 (HDAC2) is frequently dysregulated in colon cancer cells. Microsatellite instability (MSI), an unfaithful replication of DNA at nucleotide repeats, occurs in about 15% of human colon tumors. MSI promotes a genetic frameshift and consequently a loss of HDAC2 in up to 43% of these tumors. We show that long-term and short-term cultures of colorectal cancers with MSI contain subpopulations of cells lacking HDAC2. These can be isolated as single cell-derived, proliferating populations. Xenografted patient-derived colon cancer tissues with MSI also show variable patterns of HDAC2 expression in mice. HDAC2-positive and HDAC2-negative RKO cells respond similarly to pharmacological inhibitors of the class I HDACs HDAC1/HDAC2/HDAC3. In contrast to this similarity, HDAC2-negative and HDAC2-positive RKO cells undergo differential cell cycle arrest and apoptosis induction in response to the frequently used chemotherapeutic 5-fluorouracil, which becomes incorporated into and damages RNA and DNA. 5-fluorouracil causes an enrichment of HDAC2-negative RKO cells in vitro and in a subset of primary colorectal tumors in mice. 5-fluorouracil induces the phosphorylation of KAP1, a target of the checkpoint kinase ataxia-telangiectasia mutated (ATM), stronger in HDAC2-negative cells than in their HDAC2-positive counterparts. Pharmacological inhibition of ATM sensitizes RKO cells to cytotoxic effects of 5-fluorouracil. These findings demonstrate that HDAC2 and ATM modulate the responses of colorectal cancer cells towards 5-FU.
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Affiliation(s)
- Nicole Kiweler
- Department of Toxicology, University Medical Center Mainz, 55131 Mainz, Germany
- Present Address: Department of Cancer Research, Luxembourg Institute of Health, L-1526 Luxembourg, Luxembourg
| | - Helena Schwarz
- Department of Toxicology, University Medical Center Mainz, 55131 Mainz, Germany
| | - Alexandra Nguyen
- Department of Toxicology, University Medical Center Mainz, 55131 Mainz, Germany
| | - Stephanie Matschos
- Department of General Surgery, Molecular Oncology and Immunotherapy, Schillingallee 35, 18057 Rostock, Germany
| | - Christina Mullins
- Department of General Surgery, Molecular Oncology and Immunotherapy, Schillingallee 35, 18057 Rostock, Germany
| | - Andrea Piée-Staffa
- Department of Toxicology, University Medical Center Mainz, 55131 Mainz, Germany
| | - Christina Brachetti
- Department of Toxicology, University Medical Center Mainz, 55131 Mainz, Germany
| | - Wynand P. Roos
- Department of Toxicology, University Medical Center Mainz, 55131 Mainz, Germany
| | - Günter Schneider
- Klinikum Rechts Der Isar, Medical Clinic and Polyclinic II, Technical University Munich, 81675 Munich, Germany
- Department of General, Visceral and Pediatric Surgery, University Medical Center Göttingen, 37075 Göttingen, Germany
| | - Michael Linnebacher
- Department of General Surgery, Molecular Oncology and Immunotherapy, Schillingallee 35, 18057 Rostock, Germany
| | - Walburgis Brenner
- Clinic for Obstetrics and Women’s Health, Johannes Gutenberg University Mainz, Mainz, Germany
| | - Oliver H. Krämer
- Department of Toxicology, University Medical Center Mainz, 55131 Mainz, Germany
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Mustafa AHM, Ashry R, Krämer OH. Monitoring Changes in Intracellular Reactive Oxygen Species Levels in Response to Histone Deacetylase Inhibitors. Methods Mol Biol 2023; 2589:337-344. [PMID: 36255635 DOI: 10.1007/978-1-0716-2788-4_22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
Reactive oxygen species (ROS) are induced by several chemotherapeutics. In this protocol, we describe a flow cytometry-based method for the analysis of the intracellular levels of ROS in vital leukemic cells in response to the histone deacetylase inhibitor vorinostat. This measurement of ROS using the cell-permeable dye CM-H2DCFDA indicates intracellular oxidative stress.
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Affiliation(s)
- Al-Hassan M Mustafa
- Institute of Toxicology, University Medical Center Mainz, Mainz, Germany.
- Department of Zoology, Faculty of Science, Aswan University, Aswan, Egypt.
| | - Ramy Ashry
- Institute of Toxicology, University Medical Center Mainz, Mainz, Germany
- Department of Oral Pathology, Faculty of Dentistry, Mansoura University, Mansoura, Egypt
| | - Oliver H Krämer
- Institute of Toxicology, University Medical Center Mainz, Mainz, Germany
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3
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Marx C, Marx-Blümel L, Sonnemann J, Wang ZQ. Assessment of Mitochondrial Dysfunctions After Sirtuin Inhibition. Methods Mol Biol 2023; 2589:269-291. [PMID: 36255631 DOI: 10.1007/978-1-0716-2788-4_18] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
Posttranslational modifications are important for protein functions and cellular signaling pathways. The acetylation of lysine residues is catalyzed by histone acetyltransferases (HATs) and removed by histone deacetylases (HDACs), with the latter being grouped into four phylogenetic classes. The class III of the HDAC family, the sirtuins (SIRTs), contributes to gene expression, genomic stability, cell metabolism, and tumorigenesis. Thus, several specific SIRT inhibitors (SIRTi) have been developed to target cancer cell proliferation. Here we provide an overview of methods to study SIRT-dependent cell metabolism and mitochondrial functionality. The chapter describes metabolic flux analysis using Seahorse analyzers, methods for normalization of Seahorse data, flow cytometry and fluorescence microscopy to determine the mitochondrial membrane potential, mitochondrial content per cell and mitochondrial network structures, and Western blot analysis to measure mitochondrial proteins.
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Affiliation(s)
- Christian Marx
- Leibniz Institute on Aging - Fritz Lipmann Institute (FLI), Jena, Germany.
| | - Lisa Marx-Blümel
- Department of Pediatric Hematology and Oncology, Children's Clinic, Jena University Hospital, Jena, Germany
- Research Center Lobeda, Jena University Hospital, Jena, Germany
| | - Jürgen Sonnemann
- Department of Pediatric Hematology and Oncology, Children's Clinic, Jena University Hospital, Jena, Germany
- Research Center Lobeda, Jena University Hospital, Jena, Germany
| | - Zhao-Qi Wang
- Leibniz Institute on Aging - Fritz Lipmann Institute (FLI), Jena, Germany
- Faculty of Biological Sciences, Friedrich-Schiller-University of Jena, Jena, Germany
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Halilovic M, Marx-Blümel L, Marx C, Buder K, Beck JF, Sonnemann J. Assessment of HDAC Inhibitor-Induced Endoplasmic Reticulum (ER) Stress. Methods Mol Biol 2023; 2589:253-268. [PMID: 36255630 DOI: 10.1007/978-1-0716-2788-4_17] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
The endoplasmic reticulum (ER) is a multifunctional cell organelle which is important for the folding and processing of proteins. Different endogenous and exogenous factors can disturb the ER homeostasis, causing ER stress and activating the unfolded protein response (UPR) to remove misfolded proteins and aggregates. ER stress and the UPR are associated with several human diseases, such as diabetes, Alzheimer's or Parkinson's disease, and cancer. Histone deacetylase inhibitors (HDACi) are used to treat cancer and were shown to induce ER stress/to modulate the UPR, although the exact mechanism is not fully understood and needs further research. Several approaches to monitoring ER stress exist. Here we describe methods including qPCR, Western blot, transmission electron microscopy, and fluorescence microscopy to analyze changes in mRNA and protein expression levels as well as defects in ER structures after HDAC inhibitor-induced ER stress.
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Affiliation(s)
- Melisa Halilovic
- Leibniz Institute on Aging - Fritz Lipmann Institute (FLI), Jena, Germany
| | - Lisa Marx-Blümel
- Department of Pediatric Hematology and Oncology, Children's Clinic, Jena University Hospital, Jena, Germany
- Research Center Lobeda, Jena University Hospital, Jena, Germany
| | - Christian Marx
- Center for Pandemic Vaccines and Therapeutics (ZEPAI), Paul Ehrlich Institute (PEI), Langen, Germany
| | - Katrin Buder
- Leibniz Institute on Aging - Fritz Lipmann Institute (FLI), Jena, Germany
| | - James F Beck
- Department of Pediatric Hematology and Oncology, Children's Clinic, Jena University Hospital, Jena, Germany
| | - Jürgen Sonnemann
- Department of Pediatric Hematology and Oncology, Children's Clinic, Jena University Hospital, Jena, Germany.
- Research Center Lobeda, Jena University Hospital, Jena, Germany.
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5
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Marx C, Sonnemann J, Maddocks ODK, Marx-Blümel L, Beyer M, Hoelzer D, Thierbach R, Maletzki C, Linnebacher M, Heinzel T, Krämer OH. Global metabolic alterations in colorectal cancer cells during irinotecan-induced DNA replication stress. Cancer Metab 2022; 10:10. [PMID: 35787728 PMCID: PMC9251592 DOI: 10.1186/s40170-022-00286-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2022] [Accepted: 06/09/2022] [Indexed: 01/05/2023] Open
Abstract
BACKGROUND Metabolic adaptations can allow cancer cells to survive DNA-damaging chemotherapy. This unmet clinical challenge is a potential vulnerability of cancer. Accordingly, there is an intense search for mechanisms that modulate cell metabolism during anti-tumor therapy. We set out to define how colorectal cancer CRC cells alter their metabolism upon DNA replication stress and whether this provides opportunities to eliminate such cells more efficiently. METHODS We incubated p53-positive and p53-negative permanent CRC cells and short-term cultured primary CRC cells with the topoisomerase-1 inhibitor irinotecan and other drugs that cause DNA replication stress and consequently DNA damage. We analyzed pro-apoptotic mitochondrial membrane depolarization and cell death with flow cytometry. We evaluated cellular metabolism with immunoblotting of electron transport chain (ETC) complex subunits, analysis of mitochondrial mRNA expression by qPCR, MTT assay, measurements of oxygen consumption and reactive oxygen species (ROS), and metabolic flux analysis with the Seahorse platform. Global metabolic alterations were assessed using targeted mass spectrometric analysis of extra- and intracellular metabolites. RESULTS Chemotherapeutics that cause DNA replication stress induce metabolic changes in p53-positive and p53-negative CRC cells. Irinotecan enhances glycolysis, oxygen consumption, mitochondrial ETC activation, and ROS production in CRC cells. This is connected to increased levels of electron transport chain complexes involving mitochondrial translation. Mass spectrometric analysis reveals global metabolic adaptations of CRC cells to irinotecan, including the glycolysis, tricarboxylic acid cycle, and pentose phosphate pathways. P53-proficient CRC cells, however, have a more active metabolism upon DNA replication stress than their p53-deficient counterparts. This metabolic switch is a vulnerability of p53-positive cells to irinotecan-induced apoptosis under glucose-restricted conditions. CONCLUSION Drugs that cause DNA replication stress increase the metabolism of CRC cells. Glucose restriction might improve the effectiveness of classical chemotherapy against p53-positive CRC cells. The topoisomerase-1 inhibitor irinotecan and other chemotherapeutics that cause DNA damage induce metabolic adaptations in colorectal cancer (CRC) cells irrespective of their p53 status. Irinotecan enhances the glycolysis and oxygen consumption in CRC cells to deliver energy and biomolecules necessary for DNA repair and their survival. Compared to p53-deficient cells, p53-proficient CRC cells have a more active metabolism and use their intracellular metabolites more extensively. This metabolic switch creates a vulnerability to chemotherapy under glucose-restricted conditions for p53-positive cells.
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Affiliation(s)
- Christian Marx
- Department of Toxicology, University Medical Center, Johannes Gutenberg University Mainz, Building 905, Mainz, Germany.
- Department of Biochemistry, Center for Molecular Biomedicine (CMB), Institute for Biochemistry and Biophysics, Friedrich Schiller University of Jena, Jena, Germany.
- Leibniz Institute on Aging - Fritz Lipmann Institute (FLI), Jena, Germany.
- Current Address: Center for Pandemic Vaccines and Therapeutics (ZEPAI), Paul Ehrlich Institute, Langen, Germany.
| | - Jürgen Sonnemann
- Department of Paediatric Haematology and Oncology, Jena University Hospital, Children's Clinic, Jena, Germany
- Research Center Lobeda, Jena University Hospital, Jena, Germany
| | - Oliver D K Maddocks
- Wolfson Wohl Cancer Research Centre, Institute of Cancer Sciences, University of Glasgow, Glasgow, UK
| | - Lisa Marx-Blümel
- Department of Paediatric Haematology and Oncology, Jena University Hospital, Children's Clinic, Jena, Germany
- Research Center Lobeda, Jena University Hospital, Jena, Germany
| | - Mandy Beyer
- Department of Toxicology, University Medical Center, Johannes Gutenberg University Mainz, Building 905, Mainz, Germany
| | - Doerte Hoelzer
- Department of Human Nutrition, Institute of Nutrition, Friedrich Schiller University of Jena, Jena, Germany
- Current address: Biopharmaceutical New Technologies (BioNTech) Corporation, Mainz, Germany
| | - René Thierbach
- Department of Human Nutrition, Institute of Nutrition, Friedrich Schiller University of Jena, Jena, Germany
| | - Claudia Maletzki
- Molecular Oncology and Immunotherapy, Thoracic, Vascular and Transplantation Surgery, Clinic of General, University of Rostock, VisceralRostock, Germany
- Current address: Department of Medicine, Clinic III - Hematology, Oncology, Palliative Medicine, Rostock University Medical Center, Rostock, Germany
| | - Michael Linnebacher
- Molecular Oncology and Immunotherapy, Thoracic, Vascular and Transplantation Surgery, Clinic of General, University of Rostock, VisceralRostock, Germany
| | - Thorsten Heinzel
- Department of Biochemistry, Center for Molecular Biomedicine (CMB), Institute for Biochemistry and Biophysics, Friedrich Schiller University of Jena, Jena, Germany
| | - Oliver H Krämer
- Department of Toxicology, University Medical Center, Johannes Gutenberg University Mainz, Building 905, Mainz, Germany.
- Department of Biochemistry, Center for Molecular Biomedicine (CMB), Institute for Biochemistry and Biophysics, Friedrich Schiller University of Jena, Jena, Germany.
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Alqosaibi AI, Abdel-Ghany S, Al-Mulhim F, Sabit H. Vorinostat enhances the therapeutic potential of Erlotinib via MAPK in lung cancer cells. Cancer Treat Res Commun 2022; 30:100509. [PMID: 35026535 DOI: 10.1016/j.ctarc.2022.100509] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2021] [Revised: 12/31/2021] [Accepted: 12/31/2021] [Indexed: 12/14/2022]
Abstract
BACKGROUND Lung cancer is the second most common cancer in both men and women, with an estimated 235,760 new cases and 131,880 deaths in 2021 in the US. Despite the modern therapies being available such as radiotherapy and chemotherapy, death rates are still increasing. Erlotinib (ERL) is one of the treatment options for lung cancer, although the probability for the patients to develop resistance to ERL constrains its reliability. The aim of the present study is to assess the synergetic effect of combining ERL with vorinostat (SAHA) on the progression of lung cancer cells. RESULTS Adenocarcinoma alveolar basal epithelial cells (A549) were treated with either ERL, SAHA as mono drugs or with the combination of them for 24 h. Cytotoxicity assay and cell cycle analysis along with apoptosis detection were investigated. The expression profile of CDH1, TGF1, and MAPK was also assessed. Results showed an elevation in the apoptosis level in all treatments compared to WISH; the normal human amnion-derived cells. Furthermore, the treatments caused the cell cycle to arrest at G2/M, indicating its cytotoxic activity. CONCLUSION The combination of SAHA and ERL significantly increased the level of apoptosis in lung cancer cells. Meanwhile, this combination treatment downregulated MAPK compared to the mono drugs and the control cells, suggesting the potential role of MAPK in regulating apoptosis and cell cycle machinery in lung cancer.
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Affiliation(s)
- Amany I Alqosaibi
- Department of Biology, College of Science, Imam Abdulrahman Bin Faisal University, Dammam, P. O. 4 Box 1982, Saudi Arabia
| | - Shaimaa Abdel-Ghany
- Department of Environmental Biotechnology, College of Biotechnology, Misr University for Science and Technology, Giza, Egypt
| | - Fatma Al-Mulhim
- Breast Imaging Division, KFHU, Imam Abdulrahman Bin Faisal University, Saudi Arabia
| | - Hussein Sabit
- Department of Environmental Biotechnology, College of Biotechnology, Misr University for Science and Technology, Giza, Egypt.
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7
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Marx C, Sonnemann J, Beyer M, Maddocks ODK, Lilla S, Hauzenberger I, Piée‐Staffa A, Siniuk K, Nunna S, Marx‐Blümel L, Westermann M, Wagner T, Meyer FB, Thierbach R, Mullins CS, Kdimati S, Linnebacher M, Neri F, Heinzel T, Wang Z, Krämer OH. Mechanistic insights into p53-regulated cytotoxicity of combined entinostat and irinotecan against colorectal cancer cells. Mol Oncol 2021; 15:3404-3429. [PMID: 34258881 PMCID: PMC8637561 DOI: 10.1002/1878-0261.13060] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2021] [Revised: 06/23/2021] [Accepted: 07/12/2021] [Indexed: 12/21/2022] Open
Abstract
Late-stage colorectal cancer (CRC) is still a clinically challenging problem. The activity of the tumor suppressor p53 is regulated via post-translational modifications (PTMs). While the relevance of p53 C-terminal acetylation for transcriptional regulation is well defined, it is unknown whether this PTM controls mitochondrially mediated apoptosis directly. We used wild-type p53 or p53-negative human CRC cells, cells with acetylation-defective p53, transformation assays, CRC organoids, and xenograft mouse models to assess how p53 acetylation determines cellular stress responses. The topoisomerase-1 inhibitor irinotecan induces acetylation of several lysine residues within p53. Inhibition of histone deacetylases (HDACs) with the class I HDAC inhibitor entinostat synergistically triggers mitochondrial damage and apoptosis in irinotecan-treated p53-positive CRC cells. This specifically relies on the C-terminal acetylation of p53 by CREB-binding protein/p300 and the presence of C-terminally acetylated p53 in complex with the proapoptotic BCL2 antagonist/killer protein. This control of C-terminal acetylation by HDACs can mechanistically explain why combinations of irinotecan and entinostat represent clinically tractable agents for the therapy of p53-proficient CRC.
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Affiliation(s)
- Christian Marx
- Leibniz Institute on Aging – Fritz Lipmann Institute (FLI)JenaGermany
- Department of ToxicologyUniversity Medical CenterJohannes Gutenberg University MainzGermany
- Cancer Research UK Beatson InstituteGlasgowUK
- Department of BiochemistryCenter for Molecular BiomedicineInstitute for Biochemistry and BiophysicsFriedrich Schiller University of JenaGermany
| | - Jürgen Sonnemann
- Department of Paediatric Haematology and OncologyChildren's ClinicJena University HospitalGermany
- Research Center LobedaJena University HospitalGermany
| | - Mandy Beyer
- Department of ToxicologyUniversity Medical CenterJohannes Gutenberg University MainzGermany
| | - Oliver D. K. Maddocks
- Cancer Research UK Beatson InstituteGlasgowUK
- Wolfson Wohl Cancer Research CentreInstitute of Cancer SciencesUniversity of GlasgowUK
| | | | - Irene Hauzenberger
- Department of ToxicologyUniversity Medical CenterJohannes Gutenberg University MainzGermany
| | - Andrea Piée‐Staffa
- Department of ToxicologyUniversity Medical CenterJohannes Gutenberg University MainzGermany
| | | | - Suneetha Nunna
- Leibniz Institute on Aging – Fritz Lipmann Institute (FLI)JenaGermany
| | - Lisa Marx‐Blümel
- Department of Paediatric Haematology and OncologyChildren's ClinicJena University HospitalGermany
- Research Center LobedaJena University HospitalGermany
| | | | - Tobias Wagner
- Department of BiochemistryCenter for Molecular BiomedicineInstitute for Biochemistry and BiophysicsFriedrich Schiller University of JenaGermany
- Cellular and Molecular MedicineHoward Hughes Medical InstituteUniversity of California, San DiegoLa JollaCAUSA
| | - Felix B. Meyer
- Department of Human NutritionInstitute of NutritionFriedrich Schiller University of JenaGermany
| | - René Thierbach
- Department of Human NutritionInstitute of NutritionFriedrich Schiller University of JenaGermany
| | - Christina S. Mullins
- Molecular Oncology and ImmunotherapyDepartment of Thoracic SurgeryUniversity of RostockGermany
| | - Said Kdimati
- Molecular Oncology and ImmunotherapyDepartment of General, Visceral, Vascular and Transplantation SurgeryUniversity of RostockGermany
| | - Michael Linnebacher
- Molecular Oncology and ImmunotherapyDepartment of General, Visceral, Vascular and Transplantation SurgeryUniversity of RostockGermany
| | - Francesco Neri
- Leibniz Institute on Aging – Fritz Lipmann Institute (FLI)JenaGermany
| | - Thorsten Heinzel
- Department of BiochemistryCenter for Molecular BiomedicineInstitute for Biochemistry and BiophysicsFriedrich Schiller University of JenaGermany
| | - Zhao‐Qi Wang
- Leibniz Institute on Aging – Fritz Lipmann Institute (FLI)JenaGermany
- Faculty of Biological SciencesFriedrich‐Schiller‐University of JenaGermany
| | - Oliver H. Krämer
- Department of ToxicologyUniversity Medical CenterJohannes Gutenberg University MainzGermany
- Department of BiochemistryCenter for Molecular BiomedicineInstitute for Biochemistry and BiophysicsFriedrich Schiller University of JenaGermany
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8
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Wachholz V, Mustafa AHM, Zeyn Y, Henninger SJ, Beyer M, Dzulko M, Piée-Staffa A, Brachetti C, Haehnel PS, Sellmer A, Mahboobi S, Kindler T, Brenner W, Nikolova T, Krämer OH. Inhibitors of class I HDACs and of FLT3 combine synergistically against leukemia cells with mutant FLT3. Arch Toxicol 2021; 96:177-193. [PMID: 34665271 PMCID: PMC8748367 DOI: 10.1007/s00204-021-03174-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2021] [Accepted: 09/29/2021] [Indexed: 12/12/2022]
Abstract
Acute myeloid leukemia (AML) with mutations in the FMS-like tyrosine kinase (FLT3) is a clinically unresolved problem. AML cells frequently have a dysregulated expression and activity of epigenetic modulators of the histone deacetylase (HDAC) family. Therefore, we tested whether a combined inhibition of mutant FLT3 and class I HDACs is effective against AML cells. Low nanomolar doses of the FLT3 inhibitor (FLT3i) AC220 and an inhibition of class I HDACs with nanomolar concentrations of FK228 or micromolar doses of the HDAC3 specific agent RGFP966 synergistically induce apoptosis of AML cells that carry hyperactive FLT3 with an internal tandem duplication (FLT3-ITD). This does not occur in leukemic cells with wild-type FLT3 and without FLT3, suggesting a preferential toxicity of this combination against cells with mutant FLT3. Moreover, nanomolar doses of the new FLT3i marbotinib combine favorably with FK228 against leukemic cells with FLT3-ITD. The combinatorial treatments potentiated their suppressive effects on the tyrosine phosphorylation and stability of FLT3-ITD and its downstream signaling to the kinases ERK1/ERK2 and the inducible transcription factor STAT5. The beneficial pro-apoptotic effects of FLT3i and HDACi against leukemic cells with mutant FLT3 are associated with dose- and drug-dependent alterations of cell cycle distribution and DNA damage. This is linked to a modulation of the tumor-suppressive transcription factor p53 and its target cyclin-dependent kinase inhibitor p21. While HDACi induce p21, AC220 suppresses the expression of p53 and p21. Furthermore, we show that both FLT3-ITD and class I HDAC activity promote the expression of the checkpoint kinases CHK1 and WEE1, thymidylate synthase, and the DNA repair protein RAD51 in leukemic cells. A genetic depletion of HDAC3 attenuates the expression of such proteins. Thus, class I HDACs and hyperactive FLT3 appear to be valid targets in AML cells with mutant FLT3.
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Affiliation(s)
- Vanessa Wachholz
- Department of Toxicology, University Medical Center, Johannes Gutenberg University Mainz, Mainz, Germany
| | - Al-Hassan M Mustafa
- Department of Toxicology, University Medical Center, Johannes Gutenberg University Mainz, Mainz, Germany.,Department of Zoology, Faculty of Science, Aswan University, Aswan, Egypt
| | - Yanira Zeyn
- Department of Toxicology, University Medical Center, Johannes Gutenberg University Mainz, Mainz, Germany
| | - Sven J Henninger
- Department of Toxicology, University Medical Center, Johannes Gutenberg University Mainz, Mainz, Germany
| | - Mandy Beyer
- Department of Toxicology, University Medical Center, Johannes Gutenberg University Mainz, Mainz, Germany
| | - Melanie Dzulko
- Department of Toxicology, University Medical Center, Johannes Gutenberg University Mainz, Mainz, Germany
| | - Andrea Piée-Staffa
- Department of Toxicology, University Medical Center, Johannes Gutenberg University Mainz, Mainz, Germany
| | - Christina Brachetti
- Department of Toxicology, University Medical Center, Johannes Gutenberg University Mainz, Mainz, Germany
| | - Patricia S Haehnel
- Department of Hematology, Medical Oncology and Pneumology, University Medical Center of the Johannes Gutenberg-University, Mainz, Germany.,German Consortia for Translational Cancer Research, Mainz, Germany
| | - Andreas Sellmer
- Faculty of Chemistry and Pharmacy, Institute of Pharmacy, University of Regensburg, 93040, Regensburg, Germany
| | - Siavosh Mahboobi
- Faculty of Chemistry and Pharmacy, Institute of Pharmacy, University of Regensburg, 93040, Regensburg, Germany
| | - Thomas Kindler
- Department of Hematology, Medical Oncology and Pneumology, University Medical Center of the Johannes Gutenberg-University, Mainz, Germany.,German Consortia for Translational Cancer Research, Mainz, Germany
| | - Walburgis Brenner
- Clinic for Obstetrics and Women's Health, Johannes Gutenberg University Mainz, Mainz, Germany
| | - Teodora Nikolova
- Department of Toxicology, University Medical Center, Johannes Gutenberg University Mainz, Mainz, Germany
| | - Oliver H Krämer
- Department of Toxicology, University Medical Center, Johannes Gutenberg University Mainz, Mainz, Germany.
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9
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Nguyen A, Dzulko M, Murr J, Yen Y, Schneider G, Krämer OH. Class 1 Histone Deacetylases and Ataxia-Telangiectasia Mutated Kinase Control the Survival of Murine Pancreatic Cancer Cells upon dNTP Depletion. Cells 2021; 10:2520. [PMID: 34685500 PMCID: PMC8534202 DOI: 10.3390/cells10102520] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2021] [Revised: 09/13/2021] [Accepted: 09/18/2021] [Indexed: 12/20/2022] Open
Abstract
Pancreatic ductal adenocarcinoma (PDAC) is a highly aggressive disease with a dismal prognosis. Here, we show how an inhibition of de novo dNTP synthesis by the ribonucleotide reductase (RNR) inhibitor hydroxyurea and an inhibition of epigenetic modifiers of the histone deacetylase (HDAC) family affect short-term cultured primary murine PDAC cells. We used clinically relevant doses of hydroxyurea and the class 1 HDAC inhibitor entinostat. We analyzed the cells by flow cytometry and immunoblot. Regarding the induction of apoptosis and DNA replication stress, hydroxyurea and the novel RNR inhibitor COH29 are superior to the topoisomerase-1 inhibitor irinotecan which is used to treat PDAC. Entinostat promotes the induction of DNA replication stress by hydroxyurea. This is associated with an increase in the PP2A subunit PR130/PPP2R3A and a reduction of the ribonucleotide reductase subunit RRM2 and the DNA repair protein RAD51. We further show that class 1 HDAC activity promotes the hydroxyurea-induced activation of the checkpoint kinase ataxia-telangiectasia mutated (ATM). Unlike in other cell systems, ATM is pro-apoptotic in hydroxyurea-treated murine PDAC cells. These data reveal novel insights into a cytotoxic, ATM-regulated, and HDAC-dependent replication stress program in PDAC cells.
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Affiliation(s)
- Alexandra Nguyen
- Department of Toxicology, University Medical Center, Obere Zahlbacher Str. 67, 55131 Mainz, Germany; (A.N.); (M.D.)
| | - Melanie Dzulko
- Department of Toxicology, University Medical Center, Obere Zahlbacher Str. 67, 55131 Mainz, Germany; (A.N.); (M.D.)
| | - Janine Murr
- Medical Clinic and Polyclinic II, Klinikum rechts der Isar, Technical University Munich, 81675 München, Germany; (J.M.); (G.S.)
| | - Yun Yen
- Ph.D. Program for Cancer Biology and Drug Discovery, Taipei Medical University, 250 Wu Hsing Street, Taipei 110, Taiwan;
| | - Günter Schneider
- Medical Clinic and Polyclinic II, Klinikum rechts der Isar, Technical University Munich, 81675 München, Germany; (J.M.); (G.S.)
- Department of General, Visceral and Pediatric Surgery, University Medical Center Göttingen, 37075 Göttingen, Germany
| | - Oliver H. Krämer
- Department of Toxicology, University Medical Center, Obere Zahlbacher Str. 67, 55131 Mainz, Germany; (A.N.); (M.D.)
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10
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Pons M, Zeyn Y, Zahn S, Mahendrarajah N, Page BDG, Gunning PT, Moriggl R, Brenner W, Butter F, Krämer OH. Oncogenic Kinase Cascades Induce Molecular Mechanisms That Protect Leukemic Cell Models from Lethal Effects of De Novo dNTP Synthesis Inhibition. Cancers (Basel) 2021; 13:3464. [PMID: 34298678 PMCID: PMC8304262 DOI: 10.3390/cancers13143464] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2021] [Revised: 07/07/2021] [Accepted: 07/08/2021] [Indexed: 01/15/2023] Open
Abstract
The ribonucleotide reductase inhibitor hydroxyurea suppresses de novo dNTP synthesis and attenuates the hyperproliferation of leukemic blasts. Mechanisms that determine whether cells undergo apoptosis in response to hydroxyurea are ill-defined. We used unbiased proteomics to uncover which pathways control the transition of the hydroxyurea-induced replication stress into an apoptotic program in chronic and acute myeloid leukemia cells. We noted a decrease in the serine/threonine kinase RAF1/c-RAF in cells that undergo apoptosis in response to clinically relevant doses of hydroxyurea. Using the RAF inhibitor LY3009120, we show that RAF activity determines the sensitivity of leukemic cells toward hydroxyurea. We further disclose that pharmacological inhibition of the RAF downstream target BCL-XL with the drug navitoclax and RNAi combine favorably with hydroxyurea against leukemic cells. BCR-ABL1 and hyperactive FLT3 are tyrosine kinases that causally contribute to the development of leukemia and induce RAF1 and BCL-XL. Accordingly, the ABL inhibitor imatinib and the FLT3 inhibitor quizartinib sensitize leukemic cells to pro-apoptotic effects of hydroxyurea. Moreover, hydroxyurea and navitoclax kill leukemic cells with mutant FLT3 that are resistant to quizartinib. These data reveal cellular susceptibility factors toward hydroxyurea and how they can be exploited to eliminate difficult-to-treat leukemic cells with clinically relevant drug combinations.
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Affiliation(s)
- Miriam Pons
- Department of Toxicology, University Medical Center, 55131 Mainz, Germany; (Y.Z.); (S.Z.); (N.M.)
| | - Yanira Zeyn
- Department of Toxicology, University Medical Center, 55131 Mainz, Germany; (Y.Z.); (S.Z.); (N.M.)
| | - Stella Zahn
- Department of Toxicology, University Medical Center, 55131 Mainz, Germany; (Y.Z.); (S.Z.); (N.M.)
| | - Nisintha Mahendrarajah
- Department of Toxicology, University Medical Center, 55131 Mainz, Germany; (Y.Z.); (S.Z.); (N.M.)
| | - Brent D. G. Page
- Faculty of Pharmaceutical Science, University of British Columbia, Vancouver, BC V6T 1Z4, Canada;
| | - Patrick T. Gunning
- Department of Chemical & Physical Sciences, University of Toronto, Mississauga, ON L5L 1C6, Canada;
- Department of Chemistry, University of Toronto, Toronto, ON M5S 3H6, Canada
| | - Richard Moriggl
- Institute of Animal Breeding and Genetics, University of Veterinary Medicine, 1210 Vienna, Austria;
| | - Walburgis Brenner
- Clinic for Obstetrics and Women’s Health, University Medical Center, 55131 Mainz, Germany;
| | - Falk Butter
- Institute of Molecular Biology (IMB), 55128 Mainz, Germany;
| | - Oliver H. Krämer
- Department of Toxicology, University Medical Center, 55131 Mainz, Germany; (Y.Z.); (S.Z.); (N.M.)
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11
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Yu W, Fells J, Clausen D, Liu J, Klein DJ, Christine Chung C, Myers RW, Wu J, Wu G, Howell BJ, Barnard RJO, Kozlowski J. Discovery of macrocyclic HDACs 1, 2, and 3 selective inhibitors for HIV latency reactivation. Bioorg Med Chem Lett 2021; 47:128168. [PMID: 34091041 DOI: 10.1016/j.bmcl.2021.128168] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2021] [Accepted: 05/28/2021] [Indexed: 12/13/2022]
Abstract
A series of unique macrocyclic HDACs 1, 2, and 3 selective inhibitors were identified with good enzymatic activity and high selectivity over HDACs 6 and 8. These macrocyclic HDAC inhibitors used an ethyl ketone as the zinc-binding group. Compounds 25 and 26 stood out as leads due to their low double-digit nM EC50s in the 2C4 cell-based HIV latency reactivation assay. The PK profiles of these macrocyclic HDAC inhibitors still needed improvement.
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Affiliation(s)
- Wensheng Yu
- Merck & Co., Inc., 2000 Galloping Hill Road, Kenilworth, NJ 07033, USA.
| | - James Fells
- Merck & Co., Inc., 770 Sumneytown Pike, West Point, PA 19486, USA
| | - Dane Clausen
- Merck & Co., Inc., 2000 Galloping Hill Road, Kenilworth, NJ 07033, USA
| | - Jian Liu
- Merck & Co., Inc., 2000 Galloping Hill Road, Kenilworth, NJ 07033, USA
| | - Daniel J Klein
- Merck & Co., Inc., 770 Sumneytown Pike, West Point, PA 19486, USA
| | - C Christine Chung
- Merck & Co., Inc., 2000 Galloping Hill Road, Kenilworth, NJ 07033, USA
| | - Robert W Myers
- Merck & Co., Inc., 2000 Galloping Hill Road, Kenilworth, NJ 07033, USA
| | - Jin Wu
- Merck & Co., Inc., 2000 Galloping Hill Road, Kenilworth, NJ 07033, USA
| | - Guoxin Wu
- Merck & Co., Inc., 770 Sumneytown Pike, West Point, PA 19486, USA
| | - Bonnie J Howell
- Merck & Co., Inc., 770 Sumneytown Pike, West Point, PA 19486, USA
| | | | - Joseph Kozlowski
- Merck & Co., Inc., 2000 Galloping Hill Road, Kenilworth, NJ 07033, USA
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12
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Marx C, Schaarschmidt MU, Kirkpatrick J, Marx-Blümel L, Halilovic M, Westermann M, Hoelzer D, Meyer FB, Geng Y, Buder K, Schadwinkel HM, Siniuk K, Becker S, Thierbach R, Beck JF, Sonnemann J, Wang ZQ. Cooperative treatment effectiveness of ATR and HSP90 inhibition in Ewing's sarcoma cells. Cell Biosci 2021; 11:57. [PMID: 33743824 PMCID: PMC7981928 DOI: 10.1186/s13578-021-00571-y] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2020] [Accepted: 03/12/2021] [Indexed: 11/10/2022] Open
Abstract
INTRODUCTION Ewing's sarcoma is an aggressive childhood malignancy whose outcome has not substantially improved over the last two decades. In this study, combination treatments of the HSP90 inhibitor AUY922 with either the ATR inhibitor VE821 or the ATM inhibitor KU55933 were investigated for their effectiveness in Ewing's sarcoma cells. METHODS Effects were determined in p53 wild-type and p53 null Ewing's sarcoma cell lines by flow cytometric analyses of cell death, mitochondrial depolarization and cell-cycle distribution as well as fluorescence and transmission electron microscopy. They were molecularly characterized by gene and protein expression profiling, and by quantitative whole proteome analysis. RESULTS AUY922 alone induced DNA damage, apoptosis and ER stress, while reducing the abundance of DNA repair proteins. The combination of AUY922 with VE821 led to strong apoptosis induction independent of the cellular p53 status, yet based on different molecular mechanisms. p53 wild-type cells activated pro-apoptotic gene transcription and underwent mitochondria-mediated apoptosis, while p53 null cells accumulated higher levels of DNA damage, ER stress and autophagy, eventually leading to apoptosis. Impaired PI3K/AKT/mTOR signaling further contributed to the antineoplastic combination effects of AUY922 and VE821. In contrast, the combination of AUY922 with KU55933 did not produce a cooperative effect. CONCLUSION Our study reveals that HSP90 and ATR inhibitor combination treatment may be an effective therapeutic approach for Ewing's sarcoma irrespective of the p53 status.
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Affiliation(s)
- Christian Marx
- Leibniz Institute On Aging - Fritz Lipmann Institute (FLI), Jena, Germany
| | - Marc U Schaarschmidt
- Department of Pediatric Hematology and Oncology, Children's Clinic, Jena University Hospital, Jena, Germany.,Research Center Lobeda, Jena University Hospital, Jena, Germany
| | - Joanna Kirkpatrick
- Leibniz Institute On Aging - Fritz Lipmann Institute (FLI), Jena, Germany.,Francis Crick Institute, London, UK
| | - Lisa Marx-Blümel
- Department of Pediatric Hematology and Oncology, Children's Clinic, Jena University Hospital, Jena, Germany.,Research Center Lobeda, Jena University Hospital, Jena, Germany
| | - Melisa Halilovic
- Leibniz Institute On Aging - Fritz Lipmann Institute (FLI), Jena, Germany
| | | | - Doerte Hoelzer
- Department of Human Nutrition, Institute of Nutrition, Friedrich Schiller University Jena, Jena, Germany.,Biopharmaceutical New Technologies (BioNTech) Corporation, Mainz, Germany
| | - Felix B Meyer
- Department of Human Nutrition, Institute of Nutrition, Friedrich Schiller University Jena, Jena, Germany
| | - Yibo Geng
- Leibniz Institute On Aging - Fritz Lipmann Institute (FLI), Jena, Germany.,Department of Neurosurgery, Beijing Tiantan Hospital, Capital Medical University, Beijing, China
| | - Katrin Buder
- Leibniz Institute On Aging - Fritz Lipmann Institute (FLI), Jena, Germany
| | - Hauke M Schadwinkel
- Department of Pediatric Hematology and Oncology, Children's Clinic, Jena University Hospital, Jena, Germany.,Research Center Lobeda, Jena University Hospital, Jena, Germany
| | - Kanstantsin Siniuk
- Leibniz Institute On Aging - Fritz Lipmann Institute (FLI), Jena, Germany
| | - Sabine Becker
- Department of Pediatric Hematology and Oncology, Children's Clinic, Jena University Hospital, Jena, Germany.,Research Center Lobeda, Jena University Hospital, Jena, Germany
| | - René Thierbach
- Department of Human Nutrition, Institute of Nutrition, Friedrich Schiller University Jena, Jena, Germany
| | - James F Beck
- Department of Pediatric Hematology and Oncology, Children's Clinic, Jena University Hospital, Jena, Germany
| | - Jürgen Sonnemann
- Department of Pediatric Hematology and Oncology, Children's Clinic, Jena University Hospital, Jena, Germany. .,Research Center Lobeda, Jena University Hospital, Jena, Germany. .,Klinik Für Kinder- Und Jugendmedizin, Universitätsklinikum Jena, Am Klinikum 1, 07747, Jena, Germany.
| | - Zhao-Qi Wang
- Leibniz Institute On Aging - Fritz Lipmann Institute (FLI), Jena, Germany.,Faculty of Biology and Pharmacy, Friedrich Schiller University of Jena, Jena, Germany
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13
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Yu W, Liu J, Yu Y, Zhang V, Clausen D, Kelly J, Wolkenberg S, Beshore D, Duffy JL, Chung CC, Myers RW, Klein DJ, Fells J, Holloway K, Wu J, Wu G, Howell BJ, Barnard RJ, Kozlowski J. Discovery of ethyl ketone-based HDACs 1, 2, and 3 selective inhibitors for HIV latency reactivation. Bioorg Med Chem Lett 2020; 30:127197. [DOI: 10.1016/j.bmcl.2020.127197] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2020] [Revised: 04/10/2020] [Accepted: 04/12/2020] [Indexed: 11/17/2022]
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14
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Bresciani A, Ontoria JM, Biancofiore I, Cellucci A, Ciammaichella A, Di Marco A, Ferrigno F, Francone A, Malancona S, Monteagudo E, Nizi E, Pace P, Ponzi S, Rossetti I, Veneziano M, Summa V, Harper S. Improved Selective Class I HDAC and Novel Selective HDAC3 Inhibitors: Beyond Hydroxamic Acids and Benzamides. ACS Med Chem Lett 2019; 10:481-486. [PMID: 30996783 DOI: 10.1021/acsmedchemlett.8b00517] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2018] [Accepted: 11/27/2018] [Indexed: 12/11/2022] Open
Abstract
The application of class I HDAC inhibitors as cancer therapies is well established, but more recently their development for nononcological indications has increased. We report here on the generation of improved class I selective human HDAC inhibitors based on an ethylketone zinc binding group (ZBG) in place of the hydroxamic acid that features the majority of HDAC inhibitors. We also describe a novel set of HDAC3 isoform selective inhibitors that show stronger potency and selectivity than the most commonly used HDAC3 selective tool compound RGFP966. These compounds are again based on an alternative ZBG with respect to the ortho-anilide that is featured in HDAC3 selective compounds reported to date.
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Affiliation(s)
- Alberto Bresciani
- IRBM Science Park, Via Pontina km 30,600, 00071 Pomezia, Rome, Italy
| | - Jesus M. Ontoria
- IRBM Science Park, Via Pontina km 30,600, 00071 Pomezia, Rome, Italy
| | | | | | | | - Annalise Di Marco
- IRBM Science Park, Via Pontina km 30,600, 00071 Pomezia, Rome, Italy
| | - Federica Ferrigno
- IRBM Science Park, Via Pontina km 30,600, 00071 Pomezia, Rome, Italy
| | | | - Savina Malancona
- IRBM Science Park, Via Pontina km 30,600, 00071 Pomezia, Rome, Italy
| | - Edith Monteagudo
- IRBM Science Park, Via Pontina km 30,600, 00071 Pomezia, Rome, Italy
| | - Emanuela Nizi
- IRBM Science Park, Via Pontina km 30,600, 00071 Pomezia, Rome, Italy
| | - Paola Pace
- IRBM Science Park, Via Pontina km 30,600, 00071 Pomezia, Rome, Italy
| | - Simona Ponzi
- IRBM Science Park, Via Pontina km 30,600, 00071 Pomezia, Rome, Italy
| | - Ilaria Rossetti
- IRBM Science Park, Via Pontina km 30,600, 00071 Pomezia, Rome, Italy
| | - Maria Veneziano
- IRBM Science Park, Via Pontina km 30,600, 00071 Pomezia, Rome, Italy
| | - Vincenzo Summa
- IRBM Science Park, Via Pontina km 30,600, 00071 Pomezia, Rome, Italy
| | - Steven Harper
- IRBM Science Park, Via Pontina km 30,600, 00071 Pomezia, Rome, Italy
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15
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Loss of Wilms tumor 1 protein is a marker for apoptosis in response to replicative stress in leukemic cells. Arch Toxicol 2018; 92:2119-2135. [PMID: 29589053 DOI: 10.1007/s00204-018-2202-3] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2018] [Accepted: 03/22/2018] [Indexed: 02/08/2023]
Abstract
A remaining expression of the transcription factor Wilms tumor 1 (WT1) after cytotoxic chemotherapy indicates remaining leukemic clones in patients. We determined the regulation and relevance of WT1 in leukemic cells exposed to replicative stress and DNA damage. To induce these conditions, we used the clinically relevant chemotherapeutics hydroxyurea and doxorubicin. We additionally treated cells with the pro-apoptotic kinase inhibitor staurosporine. Our data show that these agents promote apoptosis to a variable extent in a panel of 12 leukemic cell lines and that caspases cleave WT1 during apoptosis. A chemical inhibition of caspases as well as an overexpression of mitochondrial, anti-apoptotic BCL2 family proteins significantly reduces the processing of WT1 and cell death in hydroxyurea-sensitive acute promyelocytic leukemia cells. Although the reduction of WT1 correlates with the pharmacological efficiency of chemotherapeutics in various leukemic cells, the elimination of WT1 by different strategies of RNA interference (RNAi) does not lead to changes in the cell cycle of chronic myeloid leukemia K562 cells. RNAi against WT1 does also not increase the extent of apoptosis and the accumulation of γH2AX in K562 cells exposed to hydroxyurea. Likewise, a targeted genetic depletion of WT1 in primary oviduct cells does not increase the levels of γH2AX. Our findings position WT1 as a downstream target of the apoptotic process that occurs in response to cytotoxic forms of replicative stress and DNA damage.
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