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Enzler T, Nguyen A, Misleh J, Cline VJ, Johns M, Shumway N, Paulson S, Siegel R, Larson T, Messersmith W, Richards D, Chaves J, Pierce E, Zalupski M, Sahai V, Orr D, Ruste SA, Haun A, Kawabe T. A multicenter, randomized phase 2 study to establish combinations of CBP501, cisplatin and nivolumab for ≥3rd-line treatment of patients with advanced pancreatic adenocarcinoma. Eur J Cancer 2024; 201:113950. [PMID: 38422585 DOI: 10.1016/j.ejca.2024.113950] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2023] [Revised: 02/04/2024] [Accepted: 02/14/2024] [Indexed: 03/02/2024]
Abstract
BACKGROUND There is no standard of care for ≥ 3rd-line treatment of metastatic pancreatic adenocarcinoma (PDAC). CBP501 is a novel calmodulin-binding peptide that has been shown to enhance the influx of platinum agents into tumor cells and tumor immunogenicity. This study aimed to (1) confirm efficacy of CBP501/cisplatin/nivolumab for metastatic PDAC observed in a previous phase 1 study, (2) identify combinations that yield 35% 3-month progression-free survival rate (3MPFS) and (3) define the contribution of CBP501 to the effects of combination therapy. METHODS CBP501 16 or 25 mg/m2 (CBP(16) or CBP(25)) was combined with 60 mg/m2 cisplatin (CDDP) and 240 mg nivolumab (nivo), administered at 3-week intervals. Patients were randomized 1:1:1:1 to (1) CBP(25)/CDDP/nivo, (2) CBP(16)/CDDP/nivo, (3) CBP(25)/CDDP and (4) CDDP/nivo, with randomization stratified by ECOG PS and liver metastases. A Fleming two-stage design was used, yielding a one-sided type I error rate of 2.5% and 80% power when the true 3MPFS is 35%. RESULTS Among 36 patients, 3MPFS was 44.4% in arms 1 and 2, 11.1% in arm 3% and 33.3% in arm 4. Two patients achieved a partial response in arm 1 (ORR 22.2%; none in other arms). Median PFS and OS were 2.4, 2.1, 1.5 and 1.5 months and 6.3, 5.3, 3.7 and 4.9 months, respectively. Overall, all treatment combinations were well tolerated. Most treatment-related adverse events were grade 1-2. CONCLUSIONS The combination CBP(25)/(16)/CDDP/nivo demonstrated promising signs of efficacy and a manageable safety profile for the treatment of advanced PDAC. CLINICAL TRIAL REGISTRATION NCT04953962.
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Affiliation(s)
- T Enzler
- Rogel Cancer Center, University of Michigan Health, Ann Arbor, MI, USA.
| | - A Nguyen
- Comprehensive Cancer Centers of Nevada, Henderson, NV, USA
| | - J Misleh
- Medical Hematology Oncology Consultants PA, Newark, DE, USA
| | - V J Cline
- Texas Oncology - Austin Midtown, Austin, TX, USA
| | - M Johns
- Oncology Hematology Care Eastgate, Cincinnati, OH, USA
| | - N Shumway
- Texas Oncology-San Antonio Stone Oak, San Antonio, TX, USA
| | - S Paulson
- Texas Oncology - Baylor Charles A. Sammons Cancer Center, Dallas, TX, USA
| | - R Siegel
- Illinois Cancer Specialists, Arlington Heights, IL, USA
| | - T Larson
- Minnseota Oncology Hematology PA, Minneapolis, MN, USA
| | - W Messersmith
- University of Colorado Cancer Center, Aurora, CO, USA
| | - D Richards
- Texas Oncology - Northeast Texas Cancer and Research Institute, Tyler, TX, USA
| | - J Chaves
- Northwest Medical Specialties, PLLC, Tacoma, WA, USA
| | - E Pierce
- Ochsner MD Anderson Cancer Center, New Orleans, LA, USA
| | - M Zalupski
- Rogel Cancer Center, University of Michigan Health, Ann Arbor, MI, USA
| | - V Sahai
- Rogel Cancer Center, University of Michigan Health, Ann Arbor, MI, USA
| | - D Orr
- Mary Crowley Cancer Research, Dallas, TX, USA
| | - S A Ruste
- Medical Affairs, Veristat LLC, Toronto Canada
| | - A Haun
- Medical Affairs, Veristat LLC, Toronto Canada
| | - T Kawabe
- CanBas Co., Ltd., Numazu, Shizuoka, Japan
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Wu Y, Wu M, Zheng X, Yu H, Mao X, Jin Y, Wang Y, Pang A, Zhang J, Zeng S, Xu T, Chen Y, Zhang B, Lin N, Dai H, Wang Y, Yao X, Dong X, Huang W, Che J. Discovery of a potent and selective PARP1 degrader promoting cell cycle arrest via intercepting CDC25C-CDK1 axis for treating triple-negative breast cancer. Bioorg Chem 2024; 142:106952. [PMID: 37952486 DOI: 10.1016/j.bioorg.2023.106952] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2023] [Revised: 10/26/2023] [Accepted: 10/28/2023] [Indexed: 11/14/2023]
Abstract
PARP1 is a multifaceted component of DNA repair and chromatin remodeling, making it an effective therapeutic target for cancer therapy. The recently reported proteolytic targeting chimera (PROTAC) could effectively degrade PARP1 through the ubiquitin-proteasome pathway, expanding the therapeutic application of PARP1 blocking. In this study, a series of nitrogen heterocyclic PROTACs were designed and synthesized through ternary complex simulation analysis based on our previous work. Our efforts have resulted in a potent PARP1 degrader D6 (DC50 = 25.23 nM) with high selectivity due to nitrogen heterocyclic linker generating multiple interactions with the PARP1-CRBN PPI surface, specifically. Moreover, D6 exhibited strong cytotoxicity to triple negative breast cancer cell line MDA-MB-231 (IC50 = 1.04 µM). And the proteomic results showed that the antitumor mechanism of D6 was found that intensifies DNA damage by intercepting the CDC25C-CDK1 axis to halt cell cycle transition in triple-negative breast cancer cells. Furthermore, in vivo study, D6 showed a promising PK property with moderate oral absorption activity. And D6 could effectively inhibit tumor growth (TGI rate = 71.4 % at 40 mg/kg) without other signs of toxicity in MDA-MB-321 tumor-bearing mice. In summary, we have identified an original scaffold and potent PARP1 PROTAC that provided a novel intervention strategy for the treatment of triple-negative breast cancer.
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Affiliation(s)
- Yiquan Wu
- Hangzhou Institute of Innovative Medicine, Institute of Drug Discovery and Design, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou 310058, China
| | - Mingfei Wu
- Hangzhou Institute of Innovative Medicine, Institute of Drug Discovery and Design, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou 310058, China
| | - Xiaoli Zheng
- Key Laboratory of Novel Targets and Drug Study for Neural Repair of Zhejiang Province, School of Medicine, Hangzhou City University, Hangzhou 310058, China
| | - Hengyuan Yu
- Key Laboratory of Advanced Drug Delivery Systems of Zhejiang Province, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou 310058, China
| | - Xinfei Mao
- Hangzhou Institute of Innovative Medicine, Institute of Drug Discovery and Design, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou 310058, China
| | - Yuyuan Jin
- Key Laboratory of Neuropsychiatric Drug Research of Zhejiang Province, Hangzhou Medical College, Hangzhou 310058, China
| | - Yanhong Wang
- Department of Pharmacy, Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou 310009, Zhejiang, China
| | - Ao Pang
- Hangzhou Institute of Innovative Medicine, Institute of Drug Discovery and Design, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou 310058, China
| | - Jingyu Zhang
- Hangzhou Institute of Innovative Medicine, Institute of Drug Discovery and Design, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou 310058, China
| | - Shenxin Zeng
- Key Laboratory of Neuropsychiatric Drug Research of Zhejiang Province, Hangzhou Medical College, Hangzhou 310058, China
| | - Tengfei Xu
- Key Laboratory of Advanced Drug Delivery Systems of Zhejiang Province, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou 310058, China
| | - Yong Chen
- Key Laboratory of Advanced Drug Delivery Systems of Zhejiang Province, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou 310058, China
| | - Bo Zhang
- Department of Clinical Pharmacology, Key Laboratory of Clinical Cancer Pharmacology and Toxicology Research of Zhejiang Province, Affiliated Hangzhou First People's Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang 310006, China
| | - Nengming Lin
- Department of Clinical Pharmacology, Key Laboratory of Clinical Cancer Pharmacology and Toxicology Research of Zhejiang Province, Affiliated Hangzhou First People's Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang 310006, China
| | - Haibin Dai
- Department of Pharmacy, Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou 310009, Zhejiang, China
| | - Yuwei Wang
- Centre for Artificial Intelligence Driven Drug Discovery, Faculty of Applied Sciences, Macao Polytechnic University, Macau 999078, China
| | - Xiaojun Yao
- College of Pharmacy, Shaanxi University of Chinese Medicine, Xianyang 712046, China
| | - Xiaowu Dong
- Hangzhou Institute of Innovative Medicine, Institute of Drug Discovery and Design, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou 310058, China; Department of Pharmacy, Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou 310009, Zhejiang, China
| | - Wenhai Huang
- Key Laboratory of Neuropsychiatric Drug Research of Zhejiang Province, Hangzhou Medical College, Hangzhou 310058, China.
| | - Jinxin Che
- Hangzhou Institute of Innovative Medicine, Institute of Drug Discovery and Design, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou 310058, China.
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Oliveira AC, Santos M, Pinho M, Lopes CS. String/Cdc25 phosphatase is a suppressor of Tau-associated neurodegeneration. Dis Model Mech 2023; 16:286255. [PMID: 36601903 PMCID: PMC9903143 DOI: 10.1242/dmm.049693] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2022] [Accepted: 12/19/2022] [Indexed: 01/06/2023] Open
Abstract
Tau pathology is defined by the intracellular accumulation of abnormally phosphorylated Tau (MAPT) and is prevalent in several neurodegenerative disorders. The identification of modulators of Tau abnormal phosphorylation and aggregation is key to understanding disease progression and developing targeted therapeutic approaches. In this study, we identified String (Stg)/Cdc25 phosphatase as a suppressor of abnormal Tau phosphorylation and associated toxicity. Using a Drosophila model of tauopathy, we showed that Tau dephosphorylation by Stg/Cdc25 correlates with reduced Tau oligomerization, brain vacuolization and locomotor deficits in flies. Moreover, using a disease mimetic model, we provided evidence that Stg/Cdc25 reduces Tau phosphorylation levels independently of Tau aggregation status and delays neurodegeneration progression in the fly. These findings uncover a role for Stg/Cdc25 phosphatases as regulators of Tau biology that extends beyond their well-characterized function as cell-cycle regulators during cell proliferation, and indicate Stg/Cdc25-based approaches as promising entry points to target abnormal Tau phosphorylation.
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Affiliation(s)
- Andreia C. Oliveira
- Instituto de Investigação e Inovação em Saúde (i3S), Universidade do Porto, 4200-135 Porto, Portugal
- PhD Program in Molecular and Cell Biology, Instituto de Ciências Biomédicas Abel Salazar (ICBAS), Universidade do Porto, 4050-313 Porto, Portugal
- Instituto de Biologia Molecular e Celular (IBMC), Universidade do Porto, 4200-135 Porto, Portugal
| | - Madalena Santos
- Department of Anatomy, Unit for Multidisciplinary Research in Biomedicine (UMIB), ICBAS, Universidade do Porto, 4050-313 Porto, Portugal
- Laboratory for Integrative and Translational Research in Population Health (ITR), 4050-600 Porto, Portugal
- Department of Pathological, Cytological and Thanatological Anatomy, ESS|P.PORTO, 4200-072 Porto, Portugal
| | - Mafalda Pinho
- Instituto de Investigação e Inovação em Saúde (i3S), Universidade do Porto, 4200-135 Porto, Portugal
| | - Carla S. Lopes
- Instituto de Investigação e Inovação em Saúde (i3S), Universidade do Porto, 4200-135 Porto, Portugal
- Instituto de Biologia Molecular e Celular (IBMC), Universidade do Porto, 4200-135 Porto, Portugal
- Author for correspondence ()
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Ding N, Song X, Yu H, Wang J, Huang L, Zhou Y, He X. Mechanism of Exosomal LncRNA PART1 in Esophageal Cancer Angiogenesis by Targeting miR-302a-3p/CDC25A Axis. Technol Cancer Res Treat 2023; 22:15330338231184327. [PMID: 37386808 PMCID: PMC10333641 DOI: 10.1177/15330338231184327] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2022] [Revised: 05/16/2023] [Accepted: 06/05/2023] [Indexed: 07/01/2023] Open
Abstract
OBJECTIVE LncRNA PART1 has been confirmed related to multiple cancer bioactivities mediated with vascular endothelial growth factor signaling. Nevertheless, the role of LncRNA PART1 in esophageal cancer induced angiogenesis remains unclear. The present work focused on assessing LncRNA PART1 effects on esophageal cancer-induced angiogenesis and exploring possible mechanisms. METHODS Western blot and immunofluorescence were conducted for identifying EC9706 exosomes. MiR-302a-3p and LncRNA PART1 levels were assessed by real-time quantitative polymerase chain reaction. Cell Counting Kit-8, EdU, wound healing, transwell, and tubule information were adopted for detecting human umbilical vein endothelial cell viability, proliferation, migration, invasion, and tubule information, respectively. Starbase software and dual-luciferase reporter were conducted for predicting and judging the expression interrelation of LncRNA PART1 and its potential target-miR-302a-3p. The same methods were carried out for verifying the inhibiting influences of miR-302a-3p upregulation and its potential target-cell division cycle 25 A. RESULTS LncRNA PART1 levels were upregulated and related to the overall survival of patients in esophageal cancer. EC9706-Exos accelerated human umbilical vein endothelial cell proliferation, migration, invasion, and tubule formation via LncRNA PART1. LncRNA PART1 served as a sponge of miR-302a-3p, then miR-302a-3p targeted cell division cycle 25 A, and EC9706-Exos accelerated human umbilical vein endothelial cell angiogenesis via LncRNA PART1/ miR-302a-3p/cell division cycle 25 A axis. CONCLUSION EC9706-Exos accelerates human umbilical vein endothelial cell angiogenesis via LncRNA PART1/miR-302a-3p/ cell division cycle 25 A axis, indicating EC9706-Exos may act as a promoter of angiogenesis. Our research will contribute to clarify the mechanism of tumor angiogenesis.
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Affiliation(s)
- Naixin Ding
- Department of Radiotherapy, Jiangsu
Cancer Hospital & Jiangsu Institute of Cancer Research & The Affiliated
Cancer Hospital of Nanjing Medical University, Nanjing, China
| | - Xue Song
- Department of Radiotherapy, Jiangsu
Cancer Hospital & Jiangsu Institute of Cancer Research & The Affiliated
Cancer Hospital of Nanjing Medical University, Nanjing, China
| | - Hongliang Yu
- Department of Radiotherapy, Jiangsu
Cancer Hospital & Jiangsu Institute of Cancer Research & The Affiliated
Cancer Hospital of Nanjing Medical University, Nanjing, China
| | - Jie Wang
- Department of Tumor Biobank, Jiangsu
Cancer Hospital & Jiangsu Institute of Cancer Research & The Affiliated
Cancer Hospital of Nanjing Medical University, Nanjing, China
| | - Lei Huang
- Department of Radiotherapy, Jiangsu
Cancer Hospital & Jiangsu Institute of Cancer Research & The Affiliated
Cancer Hospital of Nanjing Medical University, Nanjing, China
| | - Yiqin Zhou
- Department of Radiotherapy, Jiangsu
Cancer Hospital & Jiangsu Institute of Cancer Research & The Affiliated
Cancer Hospital of Nanjing Medical University, Nanjing, China
| | - Xia He
- Department of Radiotherapy, Jiangsu
Cancer Hospital & Jiangsu Institute of Cancer Research & The Affiliated
Cancer Hospital of Nanjing Medical University, Nanjing, China
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Xu J, Li D, Lu Y, Zheng TY. Aβ monomers protect lens epithelial cells against oxidative stress by upregulating CDC25B. Free Radic Biol Med 2021; 175:161-170. [PMID: 34478836 DOI: 10.1016/j.freeradbiomed.2021.08.242] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/24/2021] [Revised: 08/27/2021] [Accepted: 08/30/2021] [Indexed: 12/30/2022]
Abstract
Our previous studies showed high β-amyloid (Aβ) expression levels in the nuclei of the lens epithelial cells (LECs) of healthy subjects and revealed that Aβ monomers could protect LECs from oxidative damage. Here, we further explored the mechanism by which Aβ monomers act as transcription factors to regulate the oxidative stress of LECs through high-throughput studies. First, we compared the Aβ-binding sites in the lens epithelia (LE) of age-related cataract patients with those in the LE of healthy donors via chromatin immunoprecipitation-sequencing (ChIP-seq), and we identified comparable numbers (1648 and 1445, respectively) of Aβ peaks. Then, the KEGG tool was used for gene function enrichment analysis of these genes, which were more highly enriched in healthy LE. Combining the literature review with these KEGG analysis results, in the current study, we chose four target genes related to oxidative stress, namely, CDC25B, SOS2, CTNNA1 and Cox6a1. Then, ChIP-PCR assays, dual-luciferase reporter assays, real-time PCR and Western blotting were performed to validate the regulatory effects of Aβ on these targets. Our data suggested that Aβ monomers could upregulate the mRNA and protein expression levels of CDC25B in LECs. We also confirmed that Aβ monomers could activate the Akt/Nrf2 pathway in a CDC25B-dependent manner by knockdown experiments in cultured LECs. Furthermore, we performed functional verification of the CDC25B-mediated protective effects of Aβ monomers against oxidative stress. We observed that Aβ monomers significantly improved the antioxidant capacity (the GSH level, SOD activity and total antioxidant capacity) and decreased the oxidative stress (the ROS and MDA levels) of LECs, while CDC25B knockdown decreased the antioxidant effects of Aβ, disrupting redox homeostasis. Therefore, we propose that Aβ monomers activate the Akt/Nrf2 pathway by upregulating CDC25B expression, increase various downstream antioxidant enzyme levels, maintain peroxidation-antioxidant homeostasis in LECs, and prevent the cell damage caused by oxidative stress.
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Affiliation(s)
- Jie Xu
- Department of Ophthalmology, Eye and ENT Hospital, Fudan University, 83 Fenyang Rd., Shanghai 200031, China; Eye Institute, Eye and ENT Hospital, Fudan University, 83 Fenyang Rd., Shanghai 200031, China; Key Laboratory of Myopia, Ministry of Health, 83 Fenyang Rd., Shanghai 200031, China; Shanghai Key Laboratory of Visual Impairment and Restoration, 83 Fenyang Rd., Shanghai 200031, China
| | - Dan Li
- Department of Ophthalmology, Eye and ENT Hospital, Fudan University, 83 Fenyang Rd., Shanghai 200031, China; Eye Institute, Eye and ENT Hospital, Fudan University, 83 Fenyang Rd., Shanghai 200031, China; Key Laboratory of Myopia, Ministry of Health, 83 Fenyang Rd., Shanghai 200031, China; Shanghai Key Laboratory of Visual Impairment and Restoration, 83 Fenyang Rd., Shanghai 200031, China
| | - Yi Lu
- Department of Ophthalmology, Eye and ENT Hospital, Fudan University, 83 Fenyang Rd., Shanghai 200031, China; Eye Institute, Eye and ENT Hospital, Fudan University, 83 Fenyang Rd., Shanghai 200031, China; Key Laboratory of Myopia, Ministry of Health, 83 Fenyang Rd., Shanghai 200031, China; Shanghai Key Laboratory of Visual Impairment and Restoration, 83 Fenyang Rd., Shanghai 200031, China.
| | - Tian-Yu Zheng
- Department of Ophthalmology, Eye and ENT Hospital, Fudan University, 83 Fenyang Rd., Shanghai 200031, China; Eye Institute, Eye and ENT Hospital, Fudan University, 83 Fenyang Rd., Shanghai 200031, China; Key Laboratory of Myopia, Ministry of Health, 83 Fenyang Rd., Shanghai 200031, China; Shanghai Key Laboratory of Visual Impairment and Restoration, 83 Fenyang Rd., Shanghai 200031, China.
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Lam CW, Fong NC, Chan TYC, Lau KC, Ling TK, Mak DWY, Cheng X, Law CY. Centrosome-associated CDC25B is a novel disease-causing gene for a syndrome with cataracts, dilated cardiomyopathy, and multiple endocrinopathies. Clin Chim Acta 2020; 504:81-87. [PMID: 32027886 DOI: 10.1016/j.cca.2020.01.017] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2019] [Revised: 01/07/2020] [Accepted: 01/17/2020] [Indexed: 11/16/2022]
Abstract
We describe a unique Chinese girl who presented with intrauterine growth retardation, delayed development, bilateral cataracts, hypothyroidism, growth hormone deficiency, and juvenile dilated cardiomyopathy. She was born to consanguineous parents with a history of one fetal and one infantile death in the family. She died from cardiac failure at the age of 12. In the pursuit of a diagnosis, the family was referred to the Clinics for Rare Diseases Referral and the University of Hong Kong Undiagnosed Disease Program. Whole-exome sequencing analysis revealed a homozygous non-sense variant, NM_021873:c.313G > T (p.Glu105*), in the CDC25B gene, a key regulator of the cell cycle. This variant was located in a region of homozygosity of 25 Mb on chromosome 20. Her parents and two asymptomatic sisters were confirmed to be carriers and one brother did not carry the variant. This is the first report of a natural human knockout of the CDC25B gene. Multiple endocrinopathies and fatal juvenile dilated cardiomyopathy suggests the potential for unfavorable complications in oncology patients receiving CDC25B inhibitors as an emerging targeted therapy.
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Affiliation(s)
- Ching-Wan Lam
- Department of Pathology, The University of Hong Kong, Queen Mary Hospital, Hong Kong, China.
| | - Nai-Chung Fong
- Department of Paediatrics & Adolescent Medicine, Princess Margaret Hospital, Hong Kong, China
| | | | - Kwai-Cheung Lau
- Department of Pathology, Princess Margaret Hospital, Hong Kong, China
| | - Tsz-Ki Ling
- Division of Chemical Pathology, Department of Pathology, Queen Mary Hospital, Hong Kong, China
| | - Daniel Wai-Yau Mak
- Department of Paediatrics & Adolescent Medicine, Princess Margaret Hospital, Hong Kong, China
| | - Xinqi Cheng
- Department of Clinical Laboratory, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences, Beijing 100730, China
| | - Chun-Yiu Law
- Division of Chemical Pathology, Department of Pathology, Queen Mary Hospital, Hong Kong, China
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朱 星, 杨 嘉, 张 恩, 乔 炜, 李 学. [Bioinformatic analysis of direct protein targets of aspirin against human breast cancer proliferation]. Nan Fang Yi Ke Da Xue Xue Bao 2019; 39:1141-1148. [PMID: 31801720 PMCID: PMC6867953 DOI: 10.12122/j.issn.1673-4254.2019.10.02] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Received: 04/11/2019] [Indexed: 01/05/2023]
Abstract
OBJECTIVE To explore the molecular mechanism underlying the inhibitory effects of aspirin against human breast cancer cell proliferation through bioinformatics analysis. METHODS Drug Bank 5.1.3 was searched to identify direct protein targets (DPTs) of aspirin, and the protein-protein interaction (PPI) network of the DPTs was constructed online using STRING and the signaling pathways involved were identified. The genetic alterations of 6 DPTs associated with human breast cancer was analyzed and visualized by cBio Portal and OncoPrint, respectively. The transcriptomic data of breast cancer and normal tissues were downloaded from TCGA database, and the overexpressed genes were analyzed by DECenter. The intersection between the genes associated with the DPTs obtained by STRING analysis and the differentially over-expressed genes in TCGA was determined to confirm the candidate DPTs as a potential target of aspirin, and GO functional enrichment analysis was performed using Gene Ontology. The potential targets of aspirin against the proliferation of human breast cancer cells were verified by Western blotting. RESULTS Eleven DPTs of aspirin were identified. KEGG pathway enrichment indicated that 6 genes (EDNRA, IKBKB, NFKB2, NFKBIA, PTGS2 and TP53) were associated with the occurrence and development of cancer. A total of 10 220 differentially expressed genes were identified from the TCGA database, and among them 4 genes (CDC25C, TPX2, CDC20, PLK1) were found to be the potential targets for aspirin. These genes were involved mostly in the regulation of cell cycle and cell division. Western blotting showed that aspirin could down-regulate the expression levels of several pivotal proteins that regulated cell cycle and cell division, including CDC25C, TPX2, CDC20 and PLK1. CONCLUSIONS CDC25C, TPX2, CDC20 and PLK1 may be potential targets for aspirin to inhibit the proliferation of human breast cancer cells, by affecting the progress of cell cycle and cell division.
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Affiliation(s)
- 星枚 朱
- 陕西中医药大学药学院药理学教研室,陕西 咸阳 712046Department of Pharmacology, Shaanxi University of Chinese Medicine, Xianyang 712046, China
- 陕西省中医药管理局中药药效机制与物质基础重点研究室,陕西 咸阳 712046Key Laboratory of Pharmacodynamics and Material Basis of Chinese Medicine of Shaanxi Administration of Traditional Chinese Medicine, Xianyang 712046, China
- 陕西省中药基础与新药研究重点实验室,陕西 咸阳 712046Shaanxi Key Laboratory of Traditional Medicine Foundation and New Drug Research, Xianyang 712046, China
| | - 嘉妮 杨
- 陕西中医药大学药学院药理学教研室,陕西 咸阳 712046Department of Pharmacology, Shaanxi University of Chinese Medicine, Xianyang 712046, China
- 陕西省中医药管理局中药药效机制与物质基础重点研究室,陕西 咸阳 712046Key Laboratory of Pharmacodynamics and Material Basis of Chinese Medicine of Shaanxi Administration of Traditional Chinese Medicine, Xianyang 712046, China
- 陕西省中药基础与新药研究重点实验室,陕西 咸阳 712046Shaanxi Key Laboratory of Traditional Medicine Foundation and New Drug Research, Xianyang 712046, China
| | - 恩户 张
- 陕西中医药大学药学院药理学教研室,陕西 咸阳 712046Department of Pharmacology, Shaanxi University of Chinese Medicine, Xianyang 712046, China
- 陕西省中医药管理局中药药效机制与物质基础重点研究室,陕西 咸阳 712046Key Laboratory of Pharmacodynamics and Material Basis of Chinese Medicine of Shaanxi Administration of Traditional Chinese Medicine, Xianyang 712046, China
| | - 炜 乔
- 中国兵器工业五二一医院,陕西 西安 710065Department of Gastroenterology, 521 Hospital of Norinco Group, Shaanxi, Xi'an, 710065, China
| | - 学军 李
- 北京大学医学部药理学系,北京 100191School of Basic Medicine, Peking University Health Science Center, Beijing, 100191, China
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Silva VC, Cassimeris L. Stathmin and microtubules regulate mitotic entry in HeLa cells by controlling activation of both Aurora kinase A and Plk1. Mol Biol Cell 2013; 24:3819-31. [PMID: 24152729 PMCID: PMC3861079 DOI: 10.1091/mbc.e13-02-0108] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2013] [Revised: 09/18/2013] [Accepted: 10/16/2013] [Indexed: 12/11/2022] Open
Abstract
Depletion of stathmin, a microtubule (MT) destabilizer, delays mitotic entry by ∼4 h in HeLa cells. Stathmin depletion reduced the activity of CDC25 and its upstream activators, Aurora A and Plk1. Chemical inhibition of both Aurora A and Plk1 was sufficient to delay mitotic entry by 4 h, while inhibiting either kinase alone did not cause a delay. Aurora A and Plk1 are likely regulated downstream of stathmin, because the combination of stathmin knockdown and inhibition of Aurora A and Plk1 was not additive and again delayed mitotic entry by 4 h. Aurora A localization to the centrosome required MTs, while stathmin depletion spread its localization beyond that of γ-tubulin, indicating an MT-dependent regulation of Aurora A activation. Plk1 was inhibited by excess stathmin, detected in in vitro assays and cells overexpressing stathmin-cyan fluorescent protein. Recruitment of Plk1 to the centrosome was delayed in stathmin-depleted cells, independent of MTs. It has been shown that depolymerizing MTs with nocodazole abrogates the stathmin-depletion induced cell cycle delay; in this study, depolymerization with nocodazole restored Plk1 activity to near normal levels, demonstrating that MTs also contribute to Plk1 activation. These data demonstrate that stathmin regulates mitotic entry, partially via MTs, to control localization and activation of both Aurora A and Plk1.
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Affiliation(s)
- Victoria C. Silva
- Department of Biological Sciences, Lehigh University, Bethlehem, PA 18015
| | - Lynne Cassimeris
- Department of Biological Sciences, Lehigh University, Bethlehem, PA 18015
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9
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Shima H. [Development of diagnostic and therapeutic modalities for cancer by targeting protein phosphatases]. Rinsho Byori 2012; 60:1145-1147. [PMID: 23971138] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
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10
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Abstract
Vertebrate oocytes are maintained in meiotic arrest for prolonged periods of time before undergoing oocyte maturation in preparation for fertilization. Cyclic AMP (cAMP) signaling plays a crucial role in maintaining meiotic arrest, which is released by a species-specific hormonal signal. Evidence in both frog and mouse argues that meiotic arrest is maintained by a constitutively active G-protein coupled receptor (GPCR) leading to high cAMP levels. Because activated GPCRs are typically targeted for endocytosis as part of the signal desensitization pathway, we were interested in determining the role of trafficking at the cell membrane in maintaining meiotic arrest. Here we show that blocking exocytosis, using a dominant-negative SNAP25 mutant in Xenopus oocytes, releases meiotic arrest independently of progesterone. Oocyte maturation in response to the exocytic block induces the MAPK and Cdc25C signaling cascades, leading to MPF activation, germinal vesicle breakdown and arrest at metaphase of meiosis II with a normal bipolar spindle. It thus replicates all tested aspects of physiological maturation. Furthermore, inhibiting clathrin-mediated endocytosis hinders the effectiveness of progesterone in releasing meiotic arrest. These data show that vesicular traffic at the cell membrane is crucial in maintaining meiotic arrest in vertebrates, and support the argument for active recycling of a constitutively active GPCR at the cell membrane.
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Affiliation(s)
- Wassim El-Jouni
- Department of Physiology and Biophysics, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA
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11
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Abstract
SummaryIn amphibian oocytes meiosis, the transition from G2to M phase is regulated by the maturation promoting factor (MPF), a complex of the cyclin-dependent kinase p34/cdc2 and cyclin B. In immature oocytes there is an inactive complex (pre-MPF), in which cdc2 is phosphorylated on both Thr-161 and Thr-14/Tyr-15 residues. The dephosphorylation of Thr-14/Tyr-15 is necessary for the start of MPF activation and it is induced by the activation of cdc25 phosphatase. Late, to complete the activation, a small amount of active MPF induces an auto-amplification loop of MPF stimulation (MPF amplification). Dehydroleucodine (DhL) is a sesquiterpenic lactone that inhibits mammalian cell proliferation in G2. We asked whether DhL interferes with MPF activation. For this question, the effect of DhL (up to 30 μM) on the resumption of meiosis was evaluated, and visualized by germinal vesicle break down (GVBD), ofBufo arenarumoocytes inducedin vitroby either: (i) removing follicle cells; (ii) progesterone stimulation; (iii) VG-content injection; or (iv) injection of mature cytoplasm. The results show that DhL induced GVBD inhibition, in a dose-dependent manner, in spontaneous and progesterone-induced oocyte maturation. Nevertheless, DhL at the doses assayed had no effect on GVBD induced by mature cytoplasm injection, but exerted an inhibitory effect on GVBD induced by GV content. On the basis of these results, we interpreted that DhL does not inhibit MPF amplification and that the target of DhL is any event in the early stages of the cdc25 activation cascade.
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Affiliation(s)
- G Sánchez Toranzo
- Departamento de Biología del Desarrollo, Chacabuco, San Miguel de Tucumán, Argentina
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12
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Dhankher OP, Rosen BP, McKinney EC, Meagher RB. Hyperaccumulation of arsenic in the shoots of Arabidopsis silenced for arsenate reductase (ACR2). Proc Natl Acad Sci U S A 2006; 103:5413-8. [PMID: 16567632 PMCID: PMC1459369 DOI: 10.1073/pnas.0509770102] [Citation(s) in RCA: 210] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2005] [Indexed: 11/18/2022] Open
Abstract
Endogenous plant arsenate reductase (ACR) activity converts arsenate to arsenite in roots, immobilizing arsenic below ground. By blocking this activity, we hoped to construct plants that would mobilize more arsenate aboveground. We have identified a single gene in the Arabidopsis thaliana genome, ACR2, with moderate sequence homology to yeast arsenate reductase. Expression of ACR2 cDNA in Escherichia coli complemented the arsenate-resistant and arsenate-sensitive phenotypes of various bacterial ars operon mutants. RNA interference reduced ACR2 protein expression in Arabidopsis to as low as 2% of wild-type levels. The various knockdown plant lines were more sensitive to high concentrations of arsenate, but not arsenite, than wild type. The knockdown lines accumulated 10- to 16-fold more arsenic in shoots (350-500 ppm) and retained less arsenic in roots than wild type, when grown on arsenate medium with <8 ppm arsenic. Reducing expression of ACR2 homologs in tree, shrub, and grass species should play a vital role in the phytoremediation of environmental arsenic contamination.
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Affiliation(s)
| | - Barry P. Rosen
- Department of Biochemistry and Molecular Biology, Wayne State University, Detroit, MI 48201
| | | | - Richard B. Meagher
- *Department of Genetics, University of Georgia, Athens, GA 30602-7223; and
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13
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Barth H, Klingler M, Aktories K, Kinzel V. Clostridium botulinum C2 toxin delays entry into mitosis and activation of p34cdc2 kinase and cdc25-C phosphatase in HeLa cells. Infect Immun 1999; 67:5083-90. [PMID: 10496881 PMCID: PMC96856 DOI: 10.1128/iai.67.10.5083-5090.1999] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The Clostridium botulinum C2 toxin ADP-ribosylates monomeric actin, thereby inducing disassembly of actin filaments, alteration of focal adhesions, and rounding of cells. After treatment with C2 toxin, cells stop to proliferate but remain viable for about 2 days. In view of reported correlations between the structure of the actin cytoskeleton and cell cycle transition, the effects of C2 toxin on the G(2)/M phase transition of the cell division cycle were studied. Since C2 toxin delayed entry into mitosis in HeLa cells, those enzymes which control entry into mitosis, the cyclin-dependent protein kinase mitosis-promoting factor (MPF) and the phosphatase cdc25-C were examined after treatment of synchronized cells with C2 toxin. MPF is composed of the regulatory cyclin B and the enzymatic p34cdc2 kinase subunits. For its activation at the G2/M border, p34cdc2 needs to be associated with cyclin B and additionally dephosphorylated at Tyr-15 by the specific phosphatase cdc25-C. Treatment of synchronized cells in S or G2 phase with C. botulinum C2 toxin prevented p34cdc2 protein kinase activation by inhibiting its tyrosine dephosphorylation at the G2/M border. Furthermore, the activity of cdc25-C phosphatase was decreased after treatment of cells with C2 toxin. Our results suggest that the prevented activation of the mitotic inducers p34cdc2 kinase and cdc25-C phosphatase represents the final downstream events in the action of C2 toxin resulting in a G(2) phase cell cycle delay in synchronized HeLa cells.
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Affiliation(s)
- H Barth
- Institut für Pharmakologie und Toxikologie der Albert-Ludwigs-Universität Freiburg, D-79104 Freiburg, Germany.
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14
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Yao Y, Slosberg ED, Wang L, Hibshoosh H, Zhang YJ, Xing WQ, Santella RM, Weinstein IB. Increased susceptibility to carcinogen-induced mammary tumors in MMTV-Cdc25B transgenic mice. Oncogene 1999; 18:5159-66. [PMID: 10498865 DOI: 10.1038/sj.onc.1202908] [Citation(s) in RCA: 63] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Cdc25 phosphatases activate cyclin-dependent kinases (Cdks) by dephosphorylating critical phospho-tyrosine and phospho-threonine residues on these proteins. Several types of studies indicate that Cdc25s can enhance cell proliferation and oncogenesis. Furthermore, overexpression of Cdc25A and/or B have been detected in several types of primary human cancers, including breast cancers. To further assess the oncogenic capacity of Cdc25B in vivo, we have generated transgenic mice that overexpress Cdc25B in the mammary epithelium, driven by the MMTV - LTR promoter. Although these mice are grossly normal for up to 18 months, the ectopic expression of Cdc25B in their mammary glands increases the susceptibility of these mice to induction of mammary tumors by the carcinogen 9,10-dimethyl-1, 2-benzanthracene (DMBA).
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MESH Headings
- 9,10-Dimethyl-1,2-benzanthracene/toxicity
- Animals
- Carcinogens/toxicity
- Cell Cycle Proteins/biosynthesis
- Cell Cycle Proteins/genetics
- Cell Cycle Proteins/physiology
- Epithelial Cells/enzymology
- Gene Expression Regulation, Viral
- Genetic Predisposition to Disease
- Isoenzymes/genetics
- Mammary Neoplasms, Experimental/chemically induced
- Mammary Neoplasms, Experimental/enzymology
- Mammary Neoplasms, Experimental/genetics
- Mammary Tumor Virus, Mouse/genetics
- Mice
- Mice, Inbred CBA
- Mice, Transgenic
- Phosphoprotein Phosphatases/biosynthesis
- Phosphoprotein Phosphatases/genetics
- Phosphoprotein Phosphatases/physiology
- Phosphorylation
- Protein Processing, Post-Translational
- Recombinant Fusion Proteins/biosynthesis
- Recombinant Fusion Proteins/genetics
- Recombinant Fusion Proteins/physiology
- Terminal Repeat Sequences
- Transgenes
- cdc25 Phosphatases
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Affiliation(s)
- Y Yao
- Herbert Irving Comprehensive Cancer Center, College of Physicians and Surgeons, Columbia University, 701 West 168th Street, New York, NY 10032, USA
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15
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Blomberg I, Hoffmann I. Ectopic expression of Cdc25A accelerates the G(1)/S transition and leads to premature activation of cyclin E- and cyclin A-dependent kinases. Mol Cell Biol 1999; 19:6183-94. [PMID: 10454565 PMCID: PMC84557 DOI: 10.1128/mcb.19.9.6183] [Citation(s) in RCA: 224] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Human Cdc25 phosphatases play important roles in cell cycle regulation by removing inhibitory phosphates from tyrosine and threonine residues of cyclin-dependent kinases. Three human Cdc25 isoforms, A, B, and C, have been discovered. Cdc25B and Cdc25C play crucial roles at the G(2)/M transition. In the present study, we have investigated the function of human Cdc25A phosphatase. Cell lines that express human Cdc25A in an inducible manner have been generated. Ectopic expression of Cdc25A accelerates the G(1)/S-phase transition, indicating that Cdc25A controls an event(s) that is rate limiting for entry into S phase. Furthermore, we carried out a detailed analysis of the expression and activation of human Cdc25A. Activation of endogenous Cdc25A occurs during late G(1) phase and increases in S and G(2) phases. We further demonstrate that Cdc25A is activated at the same time as cyclin E- and cyclin A-dependent kinases. In vitro, Cdc25A dephosphorylates and activates the cyclin-Cdk complexes that are active during G(1). Overexpression of Cdc25A in the inducible system, however, leads to a premature activation of both cyclin E-Cdk2 and cyclin A-Cdk2 complexes, while no effect of cyclin D-dependent kinases is observed. Furthermore, Cdc25A overexpression induces a tyrosine dephosphorylation of Cdk2. These results suggest that Cdc25A is an important regulator of the G(1)/S-phase transition and that cyclin E- and cyclin A-dependent kinases act as direct targets.
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Affiliation(s)
- I Blomberg
- Forschungsschwerpunkt Angewandte Tumorvirologie (F0400), Deutsches Krebsforschungszentrum, D-69120 Heidelberg, Germany
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16
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Abstract
We have shown previously that a peptide, MPG, derived from the hydrophobic fusion peptide of HIV-1 gp41 and the hydrophilic nuclear localisation sequence of SV40 large T antigen, can be used as a powerful tool for the delivery of oligonucleotides into cultured cells. Now we extend the potential of MPG to the delivery of nucleic acids into cultured cells. In vitro, MPG interacts strongly with nucleic acids, most likely forming a peptide cage around them, which stabilises and protects them from degradation in cell culture media. MPG is non-cytotoxic, insensitive to serum and efficiently delivers plasmids into several different cell lines in only 1 h. Moreover, MPG enables complete expression of the gene products encoded by the plasmids it delivers into cultured cells. Finally, we have investigated the potential of MPG as an efficient delivery agent for gene therapy, by attempting to deliver antisense nucleic acids targeting an essential cell cycle gene. MPG efficiently delivered a plasmid expressing the full-length antisense cDNA of human cdc25C, which consequently successfully reduced cdc25C expression levels and promoted a block to cell cycle progression. Based on our results, we conclude that MPG is a potent delivery agent for the generalised delivery of nucleic acids as well as of oligonucleotides into cultured cells and believe that its contribution to the development of new gene therapy strategies could be of prime interest.
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Affiliation(s)
- M C Morris
- Centre de Recherches de Biochimie Macromoleculaire, UPR-1086 CNRS, 1919 Route de Mende, 34293 Montpellier Cedex 5, France
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17
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Vigo E, Müller H, Prosperini E, Hateboer G, Cartwright P, Moroni MC, Helin K. CDC25A phosphatase is a target of E2F and is required for efficient E2F-induced S phase. Mol Cell Biol 1999; 19:6379-95. [PMID: 10454584 PMCID: PMC84608 DOI: 10.1128/mcb.19.9.6379] [Citation(s) in RCA: 259] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/1999] [Accepted: 06/14/1999] [Indexed: 11/20/2022] Open
Abstract
Functional inactivation of the pRB pathway is a very frequent event in human cancer, resulting in deregulated activity of the E2F transcription factors. To understand the functional role of the E2Fs in cell proliferation, we have developed cell lines expressing E2F-1, E2F-2, and E2F-3 fused to the estrogen receptor ligand binding domain (ER). In this study, we demonstrated that activation of all three E2Fs could relieve the mitogen requirement for entry into S phase in Rat1 fibroblasts and that E2F activity leads to a shortening of the G(0)-G(1) phase of the cell cycle by 6 to 7 h. In contrast to the current assumption that E2F-1 is the only E2F capable of inducing apoptosis, we showed that deregulated E2F-2 and E2F-3 activities also result in apoptosis. Using the ERE2F-expressing cell lines, we demonstrated that several genes containing E2F DNA binding sites are efficiently induced by the E2Fs in the absence of protein synthesis. Furthermore, CDC25A is defined as a novel E2F target whose expression can be directly regulated by E2F-1. Data showing that CDC25A is an essential target for E2F-1, since its activity is required for efficient induction of S phase by E2F-1, are provided. Finally, our results show that expression of two E2F target genes, namely CDC25A and cyclin E, is sufficient to induce entry into S phase in quiescent fibroblasts. Taken together, our results provide an important step in defining how E2F activity leads to deregulated proliferation.
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Affiliation(s)
- E Vigo
- Department of Experimental Oncology, European Institute of Oncology, 20141 Milan, Italy
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18
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Abstract
In mammalian cells the Cdc25 family of dual-specificity phosphatases has three distinct isoforms, termed A, B, and C, which are thought to play discrete roles in cell-cycle control. In this paper we report the cloning of Xenopus Cdc25A and demonstrate its developmental regulation and key role in embryonic cell-cycle control. Northern and Western blot analyses show that Cdc25A is absent in oocytes, and synthesis begins within 30 min after fertilization. The protein product is localized in the nucleus in interphase and accumulates continuously until the midblastula transition (MBT), after which it is degraded. Upon injection into newly fertilized eggs, wild-type Cdc25A shortened the cell cycle and accelerated the timing of cleavage, whereas embryos injected with phosphatase-dead Cdc25A displayed a dose-dependent increase in the length of the cell cycle and a slower rate of cleavage. In contrast, injection of the phosphatase-dead Cdc25C isoform had no effect. Western blotting with an antibody specific for phosphorylated tyr15 in Cdc2/Cdk2 revealed a cycle of phosphorylation/dephosphorylation in each cell cycle in control embryos, and in embryos injected with phosphatase-dead Cdc25A there was a twofold increase in the level of p-tyr in Cdc2/Cdk2. Consistent with this, the levels of cyclin B/Cdc2 and cyclin E/Cdk2 histone H1 kinase activity were both reduced by approximately 50% after phosphatase-dead Cdc25A injection. The phosphatase-dead Cdc25A could be recovered in a complex with both Cdks, suggesting that it acts in a dominant-negative fashion. These results indicate that periodic phosphorylation of Cdc2/Cdk2 on tyr15 occurs in each pre-MBT cell cycle, and dephosphorylation of Cdc2/Cdk2 by Cdc25A controls at least in part the length of the cell cycle and the timing of cleavage in pre-MBT embryos. The disappearance of Cdc25A after the MBT may underlie in part the lengthening of the cell cycle at that time.
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Affiliation(s)
- S H Kim
- Department of Pharmacology, University of Colorado School of Medicine, Denver, Colorado, 80262, USA
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19
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Abstract
Cdc25 A and B are dual-specificity phosphatases which have been implicated in neoplastic transformation. Although Cdc25A and Cdc25B have been found to be over-expressed in many cancer cell lines and primary tumors, the physiological roles of Cdc25A and B in vivo are largely undefined. To investigate the roles of these proteins in the oncogenic transformation of the mammary gland we used the mouse mammary tumor virus (MMTV) promoter to target over-expression of the Cdc25B transgene in the mammary glands of transgenic mouse lines. Here we report that the over-expression of Cdc25B enhances the proliferation of mammary epithelial cells resulting in the formation of precocious alveolar hyperplasia. At the molecular level, marked increases in cyclin D1 protein have been found in transgenic mammary epithelial cells. The accelerated growth rate of the mammary epithelial cells could also be attributed to the increased levels of cyclin E/cdk2 activity. In addition, a pronounced decrease in apoptosis was also observed during the involution of mammary gland. The reduction of apoptosis during involution correlated well with the reduced expression of c-myc and p53, both of which have been implicated in apoptosis. Taken together, our results clearly indicate that the deregulated expression of Cdc25B generates mammary gland hyperplasia.
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Affiliation(s)
- Z Q Ma
- Department of Cell Biology, Baylor College of Medicine, One Baylor Plaza, Houston, Texas, TX 77030, USA
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20
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Karlsson C, Katich S, Hagting A, Hoffmann I, Pines J. Cdc25B and Cdc25C differ markedly in their properties as initiators of mitosis. J Cell Biol 1999; 146:573-84. [PMID: 10444066 PMCID: PMC2150562 DOI: 10.1083/jcb.146.3.573] [Citation(s) in RCA: 130] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/1999] [Accepted: 06/24/1999] [Indexed: 11/22/2022] Open
Abstract
We have used time-lapse fluorescence microscopy to study the properties of the Cdc25B and Cdc25C phosphatases that have both been implicated as initiators of mitosis in human cells. To differentiate between the functions of the two proteins, we have microinjected expression constructs encoding Cdc25B or Cdc25C or their GFP-chimeras into synchronized tissue culture cells. This assay allows us to express the proteins at defined points in the cell cycle. We have followed the microinjected cells by time-lapse microscopy, in the presence or absence of DNA synthesis inhibitors, and assayed whether they enter mitosis prematurely or at the correct time. We find that overexpressing Cdc25B alone rapidly causes S phase and G2 phase cells to enter mitosis, whether or not DNA replication is complete, whereas overexpressing Cdc25C does not cause premature mitosis. Overexpressing Cdc25C together with cyclin B1 does shorten the G2 phase and can override the unreplicated DNA checkpoint, but much less efficiently than overexpressing Cdc25B. These results suggest that Cdc25B and Cdc25C do not respond identically to the same cell cycle checkpoints. This difference may be related to the differential localization of the proteins; Cdc25C is nuclear throughout interphase, whereas Cdc25B is nuclear in the G1 phase and cytoplasmic in the S and G2 phases. We have found that the change in subcellular localization of Cdc25B is due to nuclear export and that this is dependent on cyclin B1. Our data suggest that although both Cdc25B and Cdc25C can promote mitosis, they are likely to have distinct roles in the controlling the initiation of mitosis.
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Affiliation(s)
| | - Stephanie Katich
- FS 6 Angewandte Tumorvirologie (F0400), Deutsches Krebsforschungszentrum, 69120 Heidelberg, Germany
| | - Anja Hagting
- Wellcome/CRC Institute, Cambridge CB2 1QR United Kingdom
| | - Ingrid Hoffmann
- FS 6 Angewandte Tumorvirologie (F0400), Deutsches Krebsforschungszentrum, 69120 Heidelberg, Germany
| | - Jonathon Pines
- Wellcome/CRC Institute, Cambridge CB2 1QR United Kingdom
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21
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Abstract
When renal epithelial cells are exposed to epidermal growth factor-transforming growth factor-beta1 (EGF-TGF-beta1) the typical EGF-mediated hyperplastic growth response is converted to a hypertrophic growth response. Hypertrophy in this setting involves cell entrance into G(1), but arrest of cell cycle progression at the G(1)/S interface. Late G(1) arrest is mediated by retaining retinoblastoma protein (pRB) in its active, hypophosphorylated state. The present studies examine the mechanism by which pRB is retained in its active state. The results demonstrate that TGF-beta1-mediated conversion of hyperplasia to hypertrophy involves preventing activation of cdk2/cyclin E kinase but has no effect on cdk4(6)/cyclin D kinase activity. Preventing activation of cyclin E kinase is associated with 1) decreased abundance of cdk2/cyclin E complexes and 2) retention of p57(Kip2) in formed cdk2/cyclin E complexes. The development of hypertrophy does not involve regulation of either cdk2, cyclin E, or cdc25A protein abundances, or the abundance of p27(Kip1) or p21 in formed complexes.
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Affiliation(s)
- B Liu
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas 75235-8856, USA
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22
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Mulvihill DP, Petersen J, Ohkura H, Glover DM, Hagan IM. Plo1 kinase recruitment to the spindle pole body and its role in cell division in Schizosaccharomyces pombe. Mol Biol Cell 1999; 10:2771-85. [PMID: 10436027 PMCID: PMC25513 DOI: 10.1091/mbc.10.8.2771] [Citation(s) in RCA: 126] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Polo kinases execute multiple roles during cell division. The fission yeast polo related kinase Plo1 is required to assemble the mitotic spindle, the prophase actin ring that predicts the site for cytokinesis and for septation after the completion of mitosis (Ohkura et al., 1995; Bahler et al., 1998). We show that Plo1 associates with the mitotic but not interphase spindle pole body (SPB). SPB association of Plo1 is the earliest fission yeast mitotic event recorded to date. SPB association is strong from mitotic commitment to early anaphase B, after which the Plo1 signal becomes very weak and finally disappears upon spindle breakdown. SPB association of Plo1 requires mitosis-promoting factor (MPF) activity, whereas its disassociation requires the activity of the anaphase-promoting complex. The stf1.1 mutation bypasses the usual requirement for the MPF activator Cdc25 (Hudson et al., 1990). Significantly, Plo1 associates inappropriately with the interphase SPB of stf1.1 cells. These data are consistent with the emerging theme from many systems that polo kinases participate in the regulation of MPF to determine the timing of commitment to mitosis and may indicate that pole association is a key aspect of Plo1 function. Plo1 does not associate with the SPB when septation is inappropriately driven by deregulation of the Spg1 pathway and remains SPB associated if septation occurs in the presence of a spindle. Thus, neither Plo1 recruitment to nor its departure from the SPB are required for septation; however, overexpression of plo1+ activates the Spg1 pathway and causes transient Cdc7 recruitment to the SPB and multiple rounds of septation.
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Affiliation(s)
- D P Mulvihill
- School of Biological Sciences, University of Manchester, Manchester M13 9PT, United Kingdom
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23
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Forrest AR, McCormack AK, DeSouza CP, Sinnamon JM, Tonks ID, Hayward NK, Ellem KA, Gabrielli BG. Multiple splicing variants of cdc25B regulate G2/M progression. Biochem Biophys Res Commun 1999; 260:510-5. [PMID: 10403798 DOI: 10.1006/bbrc.1999.0870] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Progression through G2 phase into mitosis is regulated by the activation of the mitotic cyclin/cdk complexes, which are in turn activated cdc25B and cdc25C phosphatases. Here we report that alternate splicing produces at least five variants of cdc25B, although only cdc25B2 and cdc25B3 are detectable as proteins. Analysis of these two variants shows that cdc25B2 is expressed at lower levels relative to cdc25B3 in all cell lines tested, and the expression of both increased markedly during G2 and mitosis. Overexpression of the catalytically inactive version of either cdc25B variant produced a G2 arrest implicating both in regulating G2/M progression.
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Affiliation(s)
- A R Forrest
- Joint Oncology Program, Queensland Institute of Medical Research, Queensland, Brisbane, 4029, Australia
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24
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Xia K, Lee RS, Narsimhan RP, Mukhopadhyay NK, Neel BG, Roberts TM. Tyrosine phosphorylation of the proto-oncoprotein Raf-1 is regulated by Raf-1 itself and the phosphatase Cdc25A. Mol Cell Biol 1999; 19:4819-24. [PMID: 10373531 PMCID: PMC84280 DOI: 10.1128/mcb.19.7.4819] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
There is a growing body of evidence demonstrating that Raf-1 is phosphorylated on tyrosines upon stimulation of a variety of receptors. Although detection of Raf-1 tyrosine phosphorylation has remained elusive, genetic analyses have demonstrated it to be important for Raf-1 activation. Here we report new findings which indicate that Raf-1 tyrosine phosphorylation is regulated in vivo. In both a mammalian and baculovirus expression system, a kinase-inactive allele of Raf-1 was found to be tyrosine phosphorylated at levels much greater than that of wild-type Raf-1. The level of tyrosine phosphate on Raf-1 was markedly increased upon treatment with phosphatase inhibitors either before or after cell lysis. Cdc25A was found to dephosphorylate Raf-1 on tyrosines that resulted in a significant decrease in Raf-1 kinase activity. In NIH 3T3 cells, coexpression of wild-type Raf-1 and phosphatase-inactive Cdc25A led to a marked increase in Raf-1 tyrosine phosphorylation in response to platelet-derived growth factor. These data suggest that the tyrosine phosphorylation of Raf-1 is regulated not only by itself but also by Cdc25A.
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Affiliation(s)
- K Xia
- Dana-Farber Cancer Institute, Harvard Medical School, Boston, Massachusetts 02115, USA
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25
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Jayaram HN, Cooney DA, Grusch M, Krupitza G. Consequences of IMP dehydrogenase inhibition, and its relationship to cancer and apoptosis. Curr Med Chem 1999; 6:561-74. [PMID: 10390601] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/13/2023]
Abstract
Inosine 5 -monophosphate dehydrogenase (IMPDH) is a rate-limiting enzyme for the synthesis of GTP and dGTP. Two isoforms of IMPDH have been identified. IMPDH Type I is ubiquitous and predominantly present in normal cells, whereas IMPDH Type II is predominant in malignant cells. IMPDH plays an important role in the expression of cellular genes, such as p53, c-myc and Ki-ras. IMPDH activity is transformation and progression linked in cancer cells. IMPDH inhibitors, tiazofurin, selenazofurin, and benzamide riboside share similar mechanism of action and are metabolized to their respective NAD analogues to exert antitumor activity. Tiazofurin exhibits clinical responses in patients with acute myeloid leukemia and chronic myeloid leukemia in blast crisis. These responses relate to the level of the NAD analogue formed in the leukemic cells. Resistance to tiazofurin and related IMPDH inhibitors relate mainly to a decrease in NMN adenylyltransferase activity. IMPDH inhbitors induce apoptosis. IMPDH inhitors are valuable probes for examining biochemical functions of GTP as they selectively reduce guanylate concentration. Incomplete depletion of cellular GTP level seems to down-regulate G-protein function, thereby inhibit cell growth or induce apoptosis. Inosine 5'-monophosphate dehydrogenase (IMPDH, EC 1.1.1.205) catalyzes the dehydrogenation of IMP to XMP utilizing NAD as the proton acceptor. Studies have demonstrated that IMPDH is a rate-limiting step in the de novo synthesis of guanylates, including GTP and dGTP. The importance of IMPDH is central because dGTP is required for the DNA synthesis and GTP plays a major role not only for the cellular activity but also for cellular regulation. Two isoforms of IMPDH have been demonstrated. IMPDH Type I is ubiquitous and predominately present in normal cells, whereas the IMPDH Type II enzyme is predominant in malignant cells. Although guanylates could be salvaged from guanine by the enzyme hypoxanthine-guanine phosphoribosyltransferase (EC 2.4.2.8), the level of circulating guanine is low in dividing cells and this route is probably insufficient to satisfy the needs of guanylates in the cells.
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Affiliation(s)
- H N Jayaram
- Department of Biochemistry and Molecular Biology and Laboratory for Experimental Oncology, Indiana University School of Medicine, 699 West St., Indianapolis, IN 46202-5119, USA
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26
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Abstract
The novel synthetic retinoid 6-[3-(1-adamantyl)-4-hydroxyphenyl]-2-naphthalene carboxylic acid (CD437) has been recently identified to be a potent inducer of apoptosis in human non-small cell lung carcinoma (NSCLC) cells through a nuclear retinoic acid receptor independent mechanism. To approach the mechanism by which CD437 induces apoptosis in NSCLC cells, we investigated the involvement of c-Myc in CD437-induced apoptosis. CD437 (1 microM) up-regulated the expression of c-Myc and of its downstream target genes ornithine decarboxylase (ODC) and cdc25A in all three NSCLC cell lines (i.e., H460, SK-MES-1 and H1792) used. These effects were correlated with cellular susceptibilities to induction of apoptosis by CD437. Furthermore, CD437-induced apoptosis could be blocked by the ODC inhibitor difluoromethylornithine, the caspase inhibitors Z-VAD FMK and Z-DEVD FMK, and c-Myc antisense oligodeoxynucleotide, respectively. These data indicate that c-Myc gene plays an important role in mediating CD437-induced apoptosis in human NSCLC cells.
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Affiliation(s)
- S Y Sun
- Department of Thoracic/Head and Neck Medical Oncology, The University of Texas MD Anderson Cancer Center, Houston 77030, USA
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27
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Chen X, Prywes R. Serum-induced expression of the cdc25A gene by relief of E2F-mediated repression. Mol Cell Biol 1999; 19:4695-702. [PMID: 10373518 PMCID: PMC84267 DOI: 10.1128/mcb.19.7.4695] [Citation(s) in RCA: 70] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/1998] [Accepted: 04/21/1999] [Indexed: 11/20/2022] Open
Abstract
The cdc25A gene encodes a tyrosine phosphatase which activates cyclin-dependent kinase activity in the G1 phase of the cell cycle. cdc25A RNA levels are induced from 3 to 6 h after serum induction of serum-starved NIH 3T3 cells, suggesting that the cdc25A gene is a delayed-early gene. Analysis of cdc25A promoter constructs showed that the cdc25A promoter is sufficient for serum induction. Surprisingly for a gene expressed in early to mid-G1, serum induction of the promoter requires an E2F site at position -62 in the promoter. Deletion or point mutation of the E2F site resulted in activation of expression in serum-starved cells and no further induction by serum treatment. E2F factors were found to bind to the cdc25A E2F site along with the retinoblastoma protein (Rb) family members p130 and p107. A shift in mobility of the E2F-p107 complex in extracts of cells induced for 6 h correlated with induction of cdc25A expression. These results suggest that serum induction of cdc25A expression is mediated by inactivation of p107 or p130, both of which repress transcription when bound to the promoter through E2F.
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Affiliation(s)
- X Chen
- Department of Biological Sciences, Columbia University, New York, New York 10027, USA
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28
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Mochizuki T, Kitanaka C, Noguchi K, Muramatsu T, Asai A, Kuchino Y. Physical and functional interactions between Pim-1 kinase and Cdc25A phosphatase. Implications for the Pim-1-mediated activation of the c-Myc signaling pathway. J Biol Chem 1999; 274:18659-66. [PMID: 10373478 DOI: 10.1074/jbc.274.26.18659] [Citation(s) in RCA: 188] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The pim-1 oncogene encodes a serine/threonine kinase (Pim-1) involved in the transduction of cytokine-triggered mitogenic signals. Pim-1 is unique in that it closely cooperates with c-Myc not only in oncogenesis, but also in apoptosis induction. However, the molecular basis of Pim-1 function remains poorly understood, largely because the downstream effector molecule(s) for Pim-1 kinase has not been identified. Here we provide several lines of evidence that Cdc25A cell cycle phosphatase, a direct transcriptional target for c-Myc, is a substrate for Pim-1 kinase and functions as an effector for Pim-1. We found that Pim-1 physically interacts with Cdc25A both in vitro and in vivo and phosphorylates Cdc25A. We also observed that Pim-1-mediated phosphorylation of Cdc25A increases its phosphatase activity. In addition, wild-type Pim-1, but not kinase-inactive Pim-1, enhanced Cdc25A-mediated cellular transformation and apoptosis. Our results indicate that Cdc25A might be a key molecule that links Pim-1 and c-Myc and that also ties Pim-1-mediated mitogenic signals to cell cycle machinery.
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Affiliation(s)
- T Mochizuki
- Biophysics Division, National Cancer Center Research Institute, 5-1-1 Tsukiji, Chuo-ku, Tokyo 104-0045, Japan
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29
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Lu SL, Kawabata M, Imamura T, Miyazono K, Yuasa Y. Two divergent signaling pathways for TGF-beta separated by a mutation of its type II receptor gene. Biochem Biophys Res Commun 1999; 259:385-90. [PMID: 10362519 DOI: 10.1006/bbrc.1999.0788] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Transforming growth factor beta (TGF-beta) can inhibit epithelial cell growth and induce extracellular matrix formation through signal transduction via its two receptors and its downstream intracellular Smad proteins. We recently reported a germline mutation, i.e., substitution of methionine for threonine at codon 315 in the kinase subdomain IV, of the TGF-beta type II receptor gene in a kindred of hereditary nonpolyposis colorectal cancer without microsatellite instability and found that the mutant receptor abolished the signal transduction for growth inhibition by TGF-beta. In this study, we performed further functional analysis of this mutant receptor. The results showed that, in contrast to its failure to mediate growth inhibition by TGF-beta, the mutant receptor still retained the ability to induce one of the extracellular matrix proteins, plasminogen activator inhibitor type 1, upon TGF-beta treatment. However, coincident with its failure to mediate growth inhibition by TGF-beta, the mutant receptor failed to transcriptionally upregulate one of the cyclin-dependent kinase inhibitors, p15(INK4B), in response to TGF-beta. These data suggest that threonine 315 of the TGF-beta type II receptor is dispensable for extracellular matrix protein production, but is essential for the growth inhibition by TGF-beta, and that the lack of growth inhibition due to the mutant receptor is possibly mediated through its failure to upregulate p15(INK4B).
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Affiliation(s)
- S L Lu
- Department of Hygiene and Oncology, Tokyo Medical and Dental University School of Medicine, 1-5-45 Yushima, Tokyo, Bunkyo-ku, 113-8519, Japan
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30
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Abstract
We have designed, synthesized and purified a 51 amino acid peptide derived from an essential domain of human cdc25C phosphatase. In vivo, differential phosphorylation of this domain regulates either the induction of mitotic processes, or the checkpoint arrest of eukaryotic cells in response to DNA damage. Peptide synthesis was achieved using the stepwise Fmoc strategy and resulted in an important yield of highly pure peptide. The final peptide was identified by amino acid analysis, electrospray mass spectrometry and nuclear magnetic resonance, which revealed that one of the two methionines within the peptide was oxidized into its sulphoxide derivative We investigated whether this 51 amino acid peptide folded into secondary structures in solution by circular dichroism and observed the formation of alpha helices in TFE. Finally, we verified that this peptide could bind to its biologically relevant 14-3-3 partner in vitro by fluorescence spectroscopy.
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Affiliation(s)
- M C Morris
- CRBM, CNRS-UPR 1086, Montpellier, France
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31
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Dalal SN, Schweitzer CM, Gan J, DeCaprio JA. Cytoplasmic localization of human cdc25C during interphase requires an intact 14-3-3 binding site. Mol Cell Biol 1999; 19:4465-79. [PMID: 10330186 PMCID: PMC104405 DOI: 10.1128/mcb.19.6.4465] [Citation(s) in RCA: 213] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
cdc25C induces mitosis by activating the cdc2-cyclin B complex. The intracellular localization of cyclin B1 is regulated in a cell cycle-specific manner, and its entry into the nucleus may be required for the initiation of mitosis. To determine the cellular localization of cdc25C, monoclonal antibodies specific for cdc25C were developed and used to demonstrate that in human cells, cdc25C is retained in the cytoplasm during interphase. A deletion analysis identified a 58-amino-acid region (amino acids 201 to 258) in cdc25C that was required for the cytoplasmic localization of cdc25C. This region contained a specific binding site for 14-3-3 proteins, and mutations in cdc25C that disrupted 14-3-3 binding also disrupted the cytoplasmic localization of cdc25C during interphase. cdc25C proteins that do not contain a binding site for 14-3-3 proteins showed a pancellular localization and an increased ability to induce premature chromosome condensation. The cytoplasmic localization of cdc25C was not altered by gamma irradiation or treatment with the nuclear export inhibitor leptomycin B. These results suggest that 14-3-3 proteins may negatively regulate cdc25C function by sequestering cdc25C in the cytoplasm.
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Affiliation(s)
- S N Dalal
- Dana-Farber Cancer Institute and Harvard Medical School, Boston, Massachusetts 02115, USA
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32
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Kang SH, Bang YJ, Jong HS, Seo JY, Kim NK, Kim SJ. Rapid induction of p21WAF1 but delayed down-regulation of Cdc25A in the TGF-beta-induced cell cycle arrest of gastric carcinoma cells. Br J Cancer 1999; 80:1144-9. [PMID: 10376964 PMCID: PMC2362369 DOI: 10.1038/sj.bjc.6690478] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Transforming growth factor-beta (TGF-beta) is a multifunctional polypeptide that inhibits cellular proliferation in most epithelial cells. cdk4 and several cyclin-dependent kinase (cdk) inhibitors (p15INK4B, p21WAF1/Cip1 and p27Kip1) have been implicated in the TGF-beta-induced cell cycle arrest. More recently, down-regulation of Cdc25A, a cdk activator, was additionally suggested as a mechanism underlying growth inhibition by TGF-beta. The existence of diverse cellular mediators of TGF-beta, however, raises the question of whether their involvement might occur in a redundant manner or coordinately in a certain cell type. Using two TGF-beta-sensitive gastric carcinoma cell lines (SNU-16 and -620), we addressed the contributory roles of several cdk inhibitors, and of cdk4 and Cdc25A, in TGF-beta-induced cell cycle arrest by comparing their temporal expression pattern in response to TGF-beta. Among the cdk inhibitors examined, p21 mRNA was most rapidly (in less than 1 h) and prominently induced by TGF-beta. In contrast, p15 mRNA was more slowly induced than p21 in SNU-620 cells, and not expressed in SNU-16 cells harbouring homozygous deletion of p15. Western blotting results confirmed the rapid increase of p21, while opposite patterns of p27 expression were observed in the two cell lines. The down-regulation of Cdc25A mRNA occurred, but was more delayed than that of p15 or p21. Until G1 arrest was established, changes in the protein levels of both Cdc25A and cdk4 were marginal. Co-immunoprecipitation with anti-cdk4 antibody showed that induced p21 associates with cdk4 and that its kinase activity is reduced by TGF-beta, which kinetically correlates closely with G1 arrest following TGF-beta treatment of both cell lines. These results suggest that in certain human epithelial cells, p21 may play an early role in TGF-beta-induced cell cycle arrest, and its cooperation with other cdk inhibitors is different depending on cell type. Delayed down-regulation of Cdc25A and cdk4 may contribute to cell adaptation to the quiescent state in the two gastric carcinoma cell lines studied.
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Affiliation(s)
- S H Kang
- Cancer Research Center, Seoul National University College of Medicine, Korea
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33
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Naeger LK, Goodwin EC, Hwang ES, DeFilippis RA, Zhang H, DiMaio D. Bovine papillomavirus E2 protein activates a complex growth-inhibitory program in p53-negative HT-3 cervical carcinoma cells that includes repression of cyclin A and cdc25A phosphatase genes and accumulation of hypophosphorylated retinoblastoma protein. Cell Growth Differ 1999; 10:413-22. [PMID: 10392903] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Indexed: 02/13/2023]
Abstract
The bovine papillomavirus E2 protein can inhibit the proliferation of HT-3 cells, a p53-negative cervical carcinoma cell line containing integrated human papillomavirus type 30 DNA. Here, we analyzed HT-3 cells to explore the mechanism of p53-independent E2-mediated growth inhibition. Expression of the E2 protein repressed expression of the endogenous human papillomavirus type 30 E6/E7 genes. This was accompanied by hypophosphorylation and increased accumulation of p105Rb and repression of E2F1 expression. The E2 protein also caused reduced cyclin-dependent kinase (cdk) 2 activity, but this did not appear to be due to increased expression of cdk inhibitors. Rather, expression of cyclin A, which regulates cdk2 activity, and the cdc25A and cdc25B phosphatases, which are thought to activate cdk2, was significantly reduced at both the RNA and protein levels in response to E2 expression. The E2 protein reduced expression of cdc25A and cdc25B in both HT-3 and HeLa cells, but not in cells that were not growth-inhibited by the E2 protein. E2 point mutants unable to inhibit cell growth did not repress cdc25A and cdc25B expression, nor did the cell cycle inhibitors hydroxyurea and mimosine. Based on these results and the known properties of cell cycle components, we propose a model to account for E2-induced growth inhibition of cervical carcinoma cell lines.
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Affiliation(s)
- L K Naeger
- Department of Genetics, Yale University School of Medicine, New Haven, Connecticut 06510, USA
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34
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Sangfelt O, Erickson S, Castro J, Heiden T, Gustafsson A, Einhorn S, Grandér D. Molecular mechanisms underlying interferon-alpha-induced G0/G1 arrest: CKI-mediated regulation of G1 Cdk-complexes and activation of pocket proteins. Oncogene 1999; 18:2798-810. [PMID: 10362250 DOI: 10.1038/sj.onc.1202609] [Citation(s) in RCA: 106] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
One prominent effect of IFNs is their cell growth-inhibitory activity. The mechanism behind this inhibition of proliferation is still not fully understood. In this study, the effect of IFN-alpha treatment on cell cycle progression has been analysed in three lymphoid cell lines, Daudi, U-266 and H9. Examination of the growth-arrested cell populations shows that Daudi cells accumulate in a G0-like state, whereas U-266 cells arrest later in G1. H9 cells are completely resistant to IFN-alpha's cell growth-inhibitory effects. The G0/G1-phase arrest is preceded by a rapid induction of the cyclin-dependent kinase inhibitors (CKIs), p21 and p15. In parallel, the activities of the G1 Cdks are significantly reduced. In addition to p21/p15 induction, IFN-alpha regulates the expression of another CKI, p27, presumably by a post-transcriptional mechanism. In the G1 Cdk-complexes, there is first an increased binding of p21 and p15 to their respective kinases. At longer exposure times, when Cdk-bound p15 and p21 decline, p27 starts to accumulate. Furthermore, we found that IFN-alpha not only suppresses the phosphorylation of pRb, but also alters the phosphorylation and expression of the other pocket proteins p130 and p107. These data suggest that induction of p21/p15 is involved in the primary IFN-alpha response inhibiting G1 Cdk activity, whereas increased p27 expression is part of a second set of events which keep these Cdks in their inactive form. Moreover, elevated levels of p27 correlated with a dissociation of cyclin E/Cdk2-p130 or p107 complexes to yield cyclin E/Cdk2-p27 complexes. In resistant H9 cells, which possess a homozygous deletion of the p15/p16 genes and lack p21 protein expression, IFN-alpha causes no detectable changes in p27 expression and, furthermore, no effects are observed on either pocket proteins in this cell line. Taken together, these data suggest that the early decline in G1 Cdk activity, subsequent changes in phosphorylation of pocket proteins, and G1/G0 arrest following IFN-alpha treatment, is not primarily due to loss of the G1 kinase components, but result from the inhibitory action of CKIs on these complexes.
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Affiliation(s)
- O Sangfelt
- Department of Oncology/Pathology, Karolinska Hospital and Institute, Stockholm, Sweden
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35
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Abstract
The G2-M checkpoint in the cell cycle is identified with a set of phosphorylation-dephosphorylation (PD) cycles involving Cdc25 and the maturation-promoting factor (MPF); these PD cycles are coupled in a way that generates an instability. This instability arises out of a transcritical bifurcation which could be exploited by the G2 DNA damage checkpoint pathway in order to arrest or delay entry into mitosis. The coupling between PD cycles involving Wee1 and MPF does not lead to an instability and therefore Wee1 may not be a crucial target of the checkpoint pathway. A set of PD cycles exhibiting transcritical bifurcation also possesses the integrative ability of a checkpoint for 'checking' that prerequisites are satisfied prior to the next cell cycle event. Such a set of coupled PD cycles is suggested to be a core mechanism of cell cycle checkpoints.
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Affiliation(s)
- B D Aguda
- Department of Chemistry and Biochemistry, Laurentian University, Sudbury, Ontario, Canada
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36
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Abstract
Mitosis in most Drosophila cells is triggered by brief bursts of transcription of string (stg), a Cdc25-type phosphatase that activates the mitotic kinase, Cdk1 (Cdc2). To understand how string transcription is regulated, we analyzed the expression of string-lacZ reporter genes covering approximately 40 kb of the string locus. We also tested protein coding fragments of the string locus of 6 kb to 31.6 kb for their ability to complement loss of string function in embryos and imaginal discs. A plethora of cis-acting elements spread over >30 kb control string transcription in different cells and tissue types. Regulatory elements specific to subsets of epidermal cells, mesoderm, trachea and nurse cells were identified, but the majority of the string locus appears to be devoted to controlling cell proliferation during neurogenesis. Consistent with this, compact promotor-proximal sequences are sufficient for string function during imaginal disc growth, but additional distal elements are required for the development of neural structures in the eye, wing, leg and notum. We suggest that, during evolution, cell-type-specific control elements were acquired by a simple growth-regulated promoter as a means of coordinating cell division with developmental processes, particularly neurogenesis.
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Affiliation(s)
- D A Lehman
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, WA 98109, USA
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37
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Abstract
Binding of 14-3-3 proteins near the nuclear localization sequence of Xenopus Cdc25 suppresses its ability to induce entry into mitosis. We have examined the intracellular localization of green fluorescent protein (GFP)-tagged wild-type Cdc25 or a mutant (S287A) that cannot bind 14-3-3 proteins. Upon coexpression with Myc-14-3-3epsilon, GFP-Cdc25-WT was predominantly cytoplasmic, whereas GFP-Cdc25-S287A was exclusively nuclear. Leptomycin B, an inhibitor of nuclear export, elicited a prompt redistribution of GFP-Cdc25-WT to the nucleus. Mutagenesis experiments demonstrated that Cdc25 contains multiple nuclear export sequences. These studies indicate that the binding of 14-3-3 proteins and nuclear export regulate the intracellular localization of Cdc25.
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Affiliation(s)
- A Kumagai
- Division of Biology 216-76, Howard Hughes Medical Institute, California Institute of Technology, Pasadena, California 91125, USA
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38
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Abstract
Cells exposed to inhibitors of DNA synthesis or suffering DNA damage are arrested or delayed in interphase through the action of checkpoint controls. If the arrested cell is exposed to caffeine, relatively normal cell cycle progression is resumed and, as observed in checkpoint control mutants, loss of checkpoint control activity is associated with a reduction in cell viability. To address the mechanism of caffeine's action on cell progression, fission yeast mutants that take up caffeine but are not sensitized to hydroxyurea (HU) by caffeine were selected. Mutants 788 and 1176 are point mutants of rhp6, the fission yeast homolog of the budding yeast RAD6 gene. Mutant rhp6-788 is slightly HU sensitive, radiosensitive, and exhibits normal checkpoint responses to HU, radiation, or inactivation of DNA ligase. However, the addition of caffeine does not override the associated cell cycle blocks. Both point and deletion mutations show synthetic lethality at room temperature with temperature-sensitive mutations in cyclin B (cdc13-117) or the phosphatase cdc25 (cdc25-22). These observations suggest that the rhp6 gene product, a ubiquitin-conjugating enzyme required for DNA damage repair, promotes entry to mitosis in response to caffeine treatment.
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Affiliation(s)
- R Rowley
- Department of Radiation Oncology, University of Utah Medical Center, Salt Lake City, Utah 84132, USA.
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39
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Abstract
The dual specificity phosphatase and oncogene Cdc25B has been implicated in the G2/M cell cycle checkpoint, but the mode by which it is regulated remains poorly understood. Regional subcellular redistribution of proteins represents a unique potential regulatory mechanism. Thus, we examined in live cells the subcellular localization characteristics of Cdc25B2 and Cdc25B3 fused to green fluorescent protein. Cdc25B2 partitioned primarily in the cytoplasm during G1 and progressively migrated to the nucleus as cells transited from S to G2/M phase. In contrast, Cdc25B3 maintained a homogeneously staining diffuse phenotype irrespective of cell cycle phase. Treatment of the Cdc25B2-green fluorescent protein stable transfectants with vanadate inhibited the cell cycle dependency of intracellular distribution, while okadaic acid had little effect except in G1, suggesting regulation by at least one phosphorylation-dependent pathway. The DNA topoisomerase II poison and DNA damaging agent, etoposide, inhibited nuclear localization of Cdc25B2 in S phase, possibly by invoking a sequestration cascade. Thus, differences in the spatial distribution of Cdc25B subtypes exist within cells and the 41 amino acid insert in the N-terminus of the Cdc25B3 splice variant encodes an important inhibitory determinant for such regulation. The subcellular redistribution of Cdc25B2 could be functionally important for G2/M checkpoint regulation.
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Affiliation(s)
- E S Woo
- Department of Pharmacology, University of Pittsburgh Cancer Institute, University of Pittsburgh, Pennsylvania 15261, USA
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40
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Abstract
Increasing evidence indicates that the control of cell proliferation and apoptosis are linked. The c-myc proto-oncogene is induced early after cell-cycle entry in vascular smooth muscle cells (VSMCs) in vitro and after arterial injury and regulates both cell proliferation and apoptosis. Although both proliferation and apoptosis are likely to be mediated via transcriptional activation of target genes, few c-myc targets have been identified. Therefore, the recent identification that cdc25A, a cell-cycle phosphatase involved in G1 progression, is transcriptionally activated by c-myc and regulates c-myc-induced apoptosis has suggested that cdc25A may be the principal mediator of c-myc in VSMCs. We examined cdc25A regulation of c-myc-induced proliferation and apoptosis by expressing cdc25A or antisense cdc25A in primary rat VSMCs or in VSMCs expressing deregulated c-myc or adenovirus E1A. Ectopic c-myc increased cdc25A expression, but cdc25A was still responsive to serum components, which indicated that c-myc alone is not the main determinant of cdc25A expression. Antisense cdc25A inhibited c-myc-induced proliferation and apoptosis; however, drug and metabolic blocks indicated that this effect was limited to G1. Ectopic cdc25A augmented the proproliferative and proapoptotic action of c-myc but did not increase cell proliferation or apoptosis in the absence of ectopic c-myc. In contrast, E1A/E2F-induced apoptosis was independent of cdc25A. We conclude that cdc25A expression modulates the ability of c-myc to induce apoptosis in G1. However, cdc25A alone does not induce apoptosis and cannot substitute for c-myc in VSMCs. Additional targets of c-myc are therefore involved in apoptosis of both G1 and post-G1 VSMCs.
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Affiliation(s)
- K Macdonald
- Department of Medicine, Addenbrooke's Hospital, Cambridge, UK
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41
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Yang J, Winkler K, Yoshida M, Kornbluth S. Maintenance of G2 arrest in the Xenopus oocyte: a role for 14-3-3-mediated inhibition of Cdc25 nuclear import. EMBO J 1999; 18:2174-83. [PMID: 10205171 PMCID: PMC1171301 DOI: 10.1093/emboj/18.8.2174] [Citation(s) in RCA: 186] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Cdc2-cyclin B1 in the G2-arrested Xenopus oocyte is held inactive by phosphorylation of Cdc2 at two negative regulatory sites, Thr14 and Tyr15. Upon treatment with progesterone, these sites are dephosphorylated by the dual specificity phosphatase, Cdc25, leading to Cdc2-cyclin B1 activation. Whereas maintenance of the G2 arrest depends upon preventing Cdc25-induced Cdc2 dephosphorylation, the mechanisms responsible for keeping Cdc25 in check in these cells have not yet been described. Here we report that Cdc25 in the G2-arrested oocyte is bound to 14-3-3 proteins and that progesterone treatment abrogates this binding. We demonstrate that Cdc25, apparently statically localized in the cytoplasm, is actually capable of shuttling in and out of the oocyte nucleus. Binding of 14-3-3 protein markedly reduces the nuclear import rate of Cdc25, allowing nuclear export mediated by a nuclear export sequence present in the N-terminus of Cdc25 to predominate. If 14-3-3 binding to Cdc25 is prevented while nuclear export is inhibited, the coordinate nuclear accumulation of Cdc25 and Cdc2-cyclin B1 facilitates their mutual activation, thereby promoting oocyte maturation.
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Affiliation(s)
- J Yang
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, C366 LSRC, Research Drive, Box 3686, Durham, NC 27710, USA
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42
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Hinchcliffe EH, Thompson EA, Miller FJ, Yang J, Sluder G. Nucleo-cytoplasmic interactions that control nuclear envelope breakdown and entry into mitosis in the sea urchin zygote. J Cell Sci 1999; 112 ( Pt 8):1139-48. [PMID: 10085249 DOI: 10.1242/jcs.112.8.1139] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
In sea urchin zygotes and mammalian cells nuclear envelope breakdown (NEB) is not driven simply by a rise in cytoplasmic cyclin dependent kinase 1-cyclin B (Cdk1-B) activity; the checkpoint monitoring DNA synthesis can prevent NEB in the face of mitotic levels of Cdk1-B. Using sea urchin zygotes we investigated whether this checkpoint prevents NEB by restricting import of regulatory proteins into the nucleus. We find that cyclin B1-GFP accumulates in nuclei that cannot complete DNA synthesis and do not break down. Thus, this checkpoint limits NEB downstream of both the cytoplasmic activation and nuclear accumulation of Cdk1-B1. In separate experiments we fertilize sea urchin eggs with sperm whose DNA has been covalently cross-linked to inhibit replication. When the pronuclei fuse, the resulting zygote nucleus does not break down for >180 minutes (equivalent to three cell cycles), even though Cdk1-B activity rises to greater than mitotic levels. If pronuclear fusion is prevented, then the female pronucleus breaks down at the normal time (average 68 minutes) and the male pronucleus with cross-linked DNA breaks down 16 minutes later. This male pronucleus has a functional checkpoint because it does not break down for >120 minutes if the female pronucleus is removed just prior to NEB. These results reveal the existence of an activity released by the female pronucleus upon its breakdown, that overrides the checkpoint in the male pronucleus and induces NEB. Microinjecting wheat germ agglutinin into binucleate zygotes reveals that this activity involves molecules that must be actively translocated into the male pronucleus.
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Affiliation(s)
- E H Hinchcliffe
- Department of Cell Biology, University of Massachusetts Medical School, Worcester, MA 01605, USA
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43
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Abstract
In the fission yeast Schizosaccharomyces pombe, the protein kinase Cds1 is activated by the S-M replication checkpoint that prevents mitosis when DNA is incompletely replicated. Cds1 is proposed to regulate Wee1 and Mik1, two tyrosine kinases that inhibit the mitotic kinase Cdc2. Here, we present evidence from in vivo and in vitro studies, which indicates that Cds1 also inhibits Cdc25, the phosphatase that activates Cdc2. In an in vivo assay that measures the rate at which Cdc25 catalyzes mitosis, Cds1 contributed to a mitotic delay imposed by the S-M replication checkpoint. Cds1 also inhibited Cdc25-dependent activation of Cdc2 in vitro. Chk1, a protein kinase that is required for the G2-M damage checkpoint that prevents mitosis while DNA is being repaired, also inhibited Cdc25 in the in vitro assay. In vitro, Cds1 and Chk1 phosphorylated Cdc25 predominantly on serine-99. The Cdc25 alanine-99 mutation partially impaired the S-M replication and G2-M damage checkpoints in vivo. Thus, Cds1 and Chk1 seem to act in different checkpoint responses to regulate Cdc25 by similar mechanisms.
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Affiliation(s)
- B Furnari
- Departments of Molecular Biology and Cell Biology, The Scripps Research Institute, La Jolla, California 92037, USA
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Abstract
We postulate that genes involved in the control of cell proliferation are important determinants of melanoma growth and/or transformation. Using Western blot analysis, we compared the expression of nine key cell cycle regulators in metastatic melanomas with that in benign acquired naevi. Among the cyclin-dependent kinases (CDKs) examined, CDK2 was consistently and significantly overexpressed (three- to eight-fold) in metastatic melanomas compared with naevi. CDK1 and CDK4 exhibited no significant difference in expression between benign naevi and metastatic melanomas. CDK6 expression was variable, with four out of 10 metastatic melanomas showing higher expression than naevi. All the cyclins examined, especially cyclins A and D, were expressed more in metastatic melanomas than in naevi. Cyclin E was not detected in benign naevi, but was easily detectable in most of the metastatic melanomas. In addition, there was significantly greater expression of CDC25A, a tyrosine phosphatase that activates CDK kinases, in the metastatic melanomas. Over-expression of CDK2, CDK6, CDC25A and cyclin A was confirmed in melanoma cell lines. These cell cycle regulators may play an important role in melanoma growth and/or transformation.
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Affiliation(s)
- L Tang
- Department of Medicine, Vancouver Hospital and Health Sciences Center, BC, Canada
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45
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Abstract
Fission yeast cells tolerate the total absence of the cdc25 mitotic inducer in two cases, either in cdc2-3w or in wee1 genetic backgrounds. In the cdc2-3w cdc25Delta double mutant, the rate-limiting step leading to mitosis is reaching a critical size. However, the size control of this mutant operates in late G2, which is different from wild-type (WT) cells. This fact suggests that in WT the rate-limiting molecular process during the G2 timer is the Tyr15 dephosphorylation of cdc2, for which the cdc25 phosphatase (together with its back-up, pyp3) is dependent. In the wee1-50 cdc25Delta mutant, the population splits into different clusters, all lacking mitotic size control. This strain maintains size homeostasis by a novel method, which is random movement of the cells from one cluster to another in the successive generations. These cells should normally have a ‘minimal cycle’, a ‘timer’ with short G1 and G2 phases. However, very often the cells abort mitosis, possibly at an early event and return back to early G2, thus lengthening their cycles. The inability of these cells to start anaphase might be caused by the absence of the main mitotic regulators (wee1 and cdc25) and the improper regulation of their back-up copies (mik1 and pyp3, respectively).
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Affiliation(s)
- A Sveiczer
- Department of Agricultural Chemical Technology, Technical University of Budapest, Szt. Gellert ter 4, Hungary.
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46
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Abstract
The CDC25 dual specificity phosphatase is a universal cell cycle regulator. The evolutionary conservation of this enzyme from yeast to man bears witness to its major role in the control of cyclin-dependent kinases (CDK) activity that are central regulators of the cell cycle machinery. CDC25 phosphatase both dephosphorylates and activates CDKs. Three human CDC25s have been identified. CDC25A is involved in the control of G1/S, and CDC25C at G2/M throught the activation of CDK 1-cyclin B. The exact function of CDC25B however remains elusive. We have found that CDC25B is degraded by the proteasome pathway in vitro and in vivo. This degradation is dependent upon phosphorylation by the CDK1-cyclin A complex, but not by CDK1-cyclin B. Together with the observations of others made in yeast and mammals, our results suggest that CDC25B might act as a 'mitotic starter' triggering the activation of an auto-amplification loop before being degraded.
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Affiliation(s)
- C Cans
- Institut de Pharmacologie et de Biologie Structurale du CNRS and Université Paul Sabatier, Toulouse, France
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Patel R, Holt M, Philipova R, Moss S, Schulman H, Hidaka H, Whitaker M. Calcium/calmodulin-dependent phosphorylation and activation of human Cdc25-C at the G2/M phase transition in HeLa cells. J Biol Chem 1999; 274:7958-68. [PMID: 10075693 DOI: 10.1074/jbc.274.12.7958] [Citation(s) in RCA: 105] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The human tyrosine phosphatase (p54(cdc25-c)) is activated by phosphorylation at mitosis entry. The phosphorylated p54(cdc25-c) in turn activates the p34-cyclin B protein kinase and triggers mitosis. Although the active p34-cyclin B protein kinase can itself phosphorylate and activate p54(cdc25-c), we have investigated the possibility that other kinases may initially trigger the phosphorylation and activation of p54(cdc25-c). We have examined the effects of the calcium/calmodulin-dependent protein kinase (CaM kinase II) on p54(cdc25-c). Our in vitro experiments show that CaM kinase II can phosphorylate p54(cdc25-c) and increase its phosphatase activity by 2.5-3-fold. Treatment of a synchronous population of HeLa cells with KN-93 (a water-soluble inhibitor of CaM kinase II) or the microinjection of AC3-I (a specific peptide inhibitor of CaM kinase II) results in a cell cycle block in G2 phase. In the KN-93-arrested cells, p54(cdc25-c) is not phosphorylated, p34(cdc2) remains tyrosine phosphorylated, and there is no increase in histone H1 kinase activity. Our data suggest that a calcium-calmodulin-dependent step may be involved in the initial activation of p54(cdc25-c).
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Affiliation(s)
- R Patel
- Department of Biochemistry, University of Leicester, University Road, Leicester, United Kingdom LE1 7RH
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48
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Abstract
A hallmark of neoplastic transformation by DNA tumor viruses is the deregulation of cell cycle genes. At least in some genes, this deregulation appears to be due to the oncoprotein-mediated disruption of complexes between E2F and pocket proteins and the ensuing generation of transcriptionally active free E2F. In the present study, we have analysed the effect of the SV40 large T oncoprotein (SV-LT) on the function of a different cell cycle-regulated transcriptional repressor, CDF, which is the principal regulator of the cdc25C, cyclin A and cdc2 genes. As shown by genomic footprinting of sorted G1 and G2 cell populations, transformation by SV-LT completely abrogated protection of the CDF binding site (CDE-CHR) in the cdc25C promoter. In agreement with this observation, expression of the SV-LT in fibroblasts led to a dramatic up-regulation of the cdc25C promoter in cells synchronized in G0. These findings indicate that the oncoprotein-mediated dissociation of the CDF repressor protein from its cognate DNA-binding site is a major mechanism in virus-induced transcriptional deregulation.
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Affiliation(s)
- J Zwicker
- Institut für Molekularbiologie und Tumorforschung, Philipps-Universität Marburg, Germany
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49
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Abstract
Chk1 kinase, a DNA damage/replication G2 checkpoint kinase, has recently been shown to phosphorylate and inhibit Cdc25C, a Cdc2 Tyr-15 phosphatase, thereby directly linking the G2 checkpoint to negative regulation of Cdc2. Immature Xenopus oocytes are arrested naturally at the first meiotic prophase (prophase I) or the late G2 phase, with sustained Cdc2 Tyr-15 phosphorylation. Here we have cloned a Xenopus homolog of Chk1, determined its developmental expression, and examined its possible role in prophase I arrest of oocytes. Xenopus Chk1 protein is expressed at approximately constant levels throughout oocyte maturation and early embryogenesis. Overexpression of wild-type Chk1 in oocytes prevents the release from prophase I arrest by progesterone. Conversely, specific inhibition of endogenous Chk1 either by overexpression of a dominant-negative Chk1 mutant or by injection of a neutralizing anti-Chk1 antibody facilitates prophase I release by progesterone. Moreover, when ectopically expressed in oocytes, a Chk1-nonphosphorylatable Cdc25C mutant alone can induce prophase I release much more efficiently than wild-type Cdc25C; if endogenous Chk1 function is inhibited, however, even wild-type Cdc25C can induce the release very efficiently. These results suggest strongly that Chk1 is involved in physiological prophase I arrest of Xenopus oocytes via the direct phosphorylation and inhibition of Cdc25C. We discuss the possibility that Chk1 might function either as a G2 checkpoint kinase or as an ordinary cell cycle regulator in prophase-I-arrested oocytes.
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Affiliation(s)
- N Nakajo
- Faculty of Science, Kyushu University, Hakozaki 6-10-1, Fukuoka, 812-8581, Japan
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Pályi I, Vincze B, Lovas S, Mezö I, Pató J, Kálnay A, Turi G, Gaál D, Mihalik R, Péter I, Teplán I, Murphy RF. Gonadotropin-releasing hormone analogue conjugates with strong selective antitumor activity. Proc Natl Acad Sci U S A 1999; 96:2361-6. [PMID: 10051647 PMCID: PMC26789 DOI: 10.1073/pnas.96.5.2361] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Conjugation of gonadotropin-releasing hormone (GnRH) analogues GnRH-III, MI-1544, and MI-1892 through lysyl side chains and a tetrapeptide spacer, Gly-Phe-Leu-Gly (X) to a copolymer, poly(N-vinylpyrrolidone-co-maleic acid) (P) caused increased antiproliferative activity toward MCF-7 and MDA-MB-231 breast, PC3 and LNCaP prostate, and Ishikawa endometrial cancer cell lines in culture and against tumor development by xenografts of the breast cancer cells in immunodeficient mice. MCF-7 cells treated with P-X-1544 and P-X-1892 displayed characteristic signs of apoptosis, including vacuoles in the cytoplasm, rounding up, apoptotic bodies, bleb formation, and DNA fragmentation. Conjugates, but not free peptides, inhibited cdc25 phosphatase and caused accumulation of Ishikawa and PC3 cells in the G2/M phase of the cell cycle after 24 h at lower doses and in the G1 and G2 phases after 48 h. Since P-X-peptides appear to be internalized, the increased cytotoxicity of the conjugates is attributed to protection of peptides from proteolysis, enhanced interaction of the peptides with the GnRH receptors, and/or internalization of P-X-peptide receptor complexes so that P can exert toxic effects inside, possibly by inhibiting enzymes involved in the cell cycle. The additional specificity of P-X-peptides compared with free peptides for direct antiproliferative effects on the cancer cells but not for interactions in the pituitary indicates the therapeutic potential of the conjugates.
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Affiliation(s)
- I Pályi
- National Institute of Oncology, Budapest, H-1525, P.O. Box 21, Hungary.
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