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Johar D, Elmehrath AO, Khalil RM, Elberry MH, Zaky S, Shalabi SA, Bernstein LH. Protein networks linking Warburg and reverse Warburg effects to cancer cell metabolism. Biofactors 2021; 47:713-728. [PMID: 34453457 DOI: 10.1002/biof.1768] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/04/2021] [Accepted: 06/22/2021] [Indexed: 12/11/2022]
Abstract
It was 80 years after the Otto Warburg discovery of aerobic glycolysis, a major hallmark in the understanding of cancer. The Warburg effect is the preference of cancer cell for glycolysis that produces lactate even when sufficient oxygen is provided. "reverse Warburg effect" refers to the interstitial tissue communications with adjacent epithelium, that in the process of carcinogenesis, is needed to be explored. Among these cell-cell communications, the contact between epithelial cells; between epithelial cells and matrix; and between fibroblasts and inflammatory cells in the underlying matrix. Cancer involves dysregulation of Warburg and reverse Warburg cellular metabolic pathways. How these gene and protein-based regulatory mechanisms have functioned has been the basis for this review. The importance of the Warburg in oxidative phosphorylation suppression, with increased glycolysis in cancer growth and proliferation is emphasized. Studies that are directed at pathways that would be expected to shift cell metabolism to an increased oxidation and to a decrease in glycolysis are emphasized. Key enzymes required for oxidative phosphorylation, and affect the inhibition of fatty acid metabolism and glutamine dependence are conferred. The findings are of special interest to cancer pharmacotherapy. Studies described in this review are concerned with the effects of therapeutic modalities that are intimately related to the Warburg effect. These interactions described may be helpful as adjuvant therapy in controlling the process of proliferation and metastasis.
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Affiliation(s)
- Dina Johar
- Department of Biochemistry and Nutrition, Faculty of Women for Arts, Sciences and Education, Ain Shams University, Heliopolis, Cairo, Egypt
| | | | - Rania M Khalil
- Department of Biochemistry, Pharmacy College, Delta University for Science and Technology, Gamasa, Egypt
| | - Mostafa H Elberry
- Virology and Immunology Unit, Cancer Biology Department, National Cancer Institute, Cairo University, Cairo, Egypt
| | - Samy Zaky
- Hepatogastroenterology and Infectious Diseases, Faculty of Medicine, Al-Azhar University, Cairo, Egypt
| | - Samy A Shalabi
- Pathology Department, Faculty of Medicine, Cairo University, Cairo, Egypt
- Consultant Pathologist, Kuwait, Kuwait
| | - Larry H Bernstein
- Emeritus Prof. Department of Pathology, Yale University, Connecticut, USA
- Triplex Consulting Pharmaceuticals, 54 Firethorn Lane Northampton, MA 01060, USA
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2
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Fuchs J, Cheblal A, Gasser SM. Underappreciated Roles of DNA Polymerase δ in Replication Stress Survival. Trends Genet 2021; 37:476-487. [PMID: 33608117 DOI: 10.1016/j.tig.2020.12.003] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2020] [Revised: 12/11/2020] [Accepted: 12/14/2020] [Indexed: 01/06/2023]
Abstract
Recent structural analysis of Fe-S centers in replication proteins and insights into the structure and function of DNA polymerase δ (DNA Pol δ) subunits have shed light on the key role played by this polymerase at replication forks under stress. The sequencing of cancer genomes reveals multiple point mutations that compromise the activity of POLD1, the DNA Pol δ catalytic subunit, whereas the loci encoding the accessory subunits POLD2 and POLD3 are amplified in a very high proportion of human tumors. Consistently, DNA Pol δ is key for the survival of replication stress and is involved in multiple long-patch repair pathways. Synthetic lethality arises from compromising the function and availability of the noncatalytic subunits of DNA Pol δ under conditions of replication stress, opening the door to novel therapies.
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Affiliation(s)
- Jeannette Fuchs
- Friedrich Miescher Institute for Biomedical Research, Maulbeerstrasse 66, CH-4058 Basel, Switzerland
| | - Anais Cheblal
- Friedrich Miescher Institute for Biomedical Research, Maulbeerstrasse 66, CH-4058 Basel, Switzerland; Faculty of Sciences, University of Basel, Klingelbergstrasse 90, CH-4056 Basel, Switzerland
| | - Susan M Gasser
- Friedrich Miescher Institute for Biomedical Research, Maulbeerstrasse 66, CH-4058 Basel, Switzerland; Faculty of Sciences, University of Basel, Klingelbergstrasse 90, CH-4056 Basel, Switzerland.
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3
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Chen CW, Li Y, Hu S, Zhou W, Meng Y, Li Z, Zhang Y, Sun J, Bo Z, DePamphilis ML, Yen Y, Han Z, Zhu W. DHS (trans-4,4'-dihydroxystilbene) suppresses DNA replication and tumor growth by inhibiting RRM2 (ribonucleotide reductase regulatory subunit M2). Oncogene 2018; 38:2364-2379. [PMID: 30518875 PMCID: PMC6705423 DOI: 10.1038/s41388-018-0584-6] [Citation(s) in RCA: 41] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2018] [Revised: 08/29/2018] [Accepted: 09/27/2018] [Indexed: 01/06/2023]
Abstract
DNA replication machinery is responsible for accurate and efficient duplication of the chromosome. Since inhibition of DNA replication can lead to replication fork stalling, resulting in DNA damage and apoptotic death, inhibitors of DNA replication are commonly used in cancer chemotherapy. Ribonucleotide reductase (RNR) is the rate-limiting enzyme in the biosynthesis of deoxyribonucleoside triphosphates (dNTPs) that are essential for DNA replication and DNA damage repair. Gemcitabine, a nucleotide analog that inhibits RNR, has been used to treat various cancers. However, patients often develop resistance to this drug during treatment. Thus, new drugs that inhibit RNR are needed to be developed. In this study, we identified a synthetic analog of resveratrol (3,5,4’-trihydroxy-trans-stilbene), termed DHS (trans-4,4’-dihydroxystilbene), that acts as a potent inhibitor of DNA replication. Molecular docking analysis identified the RRM2 (ribonucleotide reductase regulatory subunit M2) of RNR as a direct target of DHS. At the molecular level, DHS induced cyclin F-mediated down-regulation of RRM2 by the proteasome. Thus, treatment of cells with DHS reduced RNR activity and consequently decreased synthesis of dNTPs with concomitant inhibition of DNA replication, arrest of cells at S-phase, DNA damage, and finally apoptosis. In mouse models of tumor xenografts, DHS was efficacious against pancreatic, ovarian, and colorectal cancer cells. Moreover, DHS overcame both gemcitabine resistance in pancreatic cancer and cisplatin resistance in ovarian cancer. Thus, DHS is a novel anti-cancer agent that targets RRM2 with therapeutic potential either alone or in combination with other agents to arrest cancer development.
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Affiliation(s)
- Chi-Wei Chen
- Department of Biochemistry and Molecular Medicine, The George Washington University School of Medicine and Health Sciences, Washington, DC, USA.,GW Cancer Center, The George Washington University, Washington, DC, USA
| | - Yongming Li
- Department of Biochemistry and Molecular Medicine, The George Washington University School of Medicine and Health Sciences, Washington, DC, USA.,College of Basic Medical Sciences, Dalian Medical University, Dalian, China
| | - Shuya Hu
- City of Hope National Medical Center, Duarte, CA, USA
| | - Wei Zhou
- Department of Biochemistry and Molecular Medicine, The George Washington University School of Medicine and Health Sciences, Washington, DC, USA.,GW Cancer Center, The George Washington University, Washington, DC, USA.,Department of Colorectal Surgery, Sir Run Run Shaw Hospital, School of Medicine, Zhejiang University, Hangzhou, China
| | - Yunxiao Meng
- Department of Biochemistry and Molecular Medicine, The George Washington University School of Medicine and Health Sciences, Washington, DC, USA.,GW Cancer Center, The George Washington University, Washington, DC, USA
| | - Zongzhu Li
- Department of Biochemistry and Molecular Medicine, The George Washington University School of Medicine and Health Sciences, Washington, DC, USA.,GW Cancer Center, The George Washington University, Washington, DC, USA
| | - Yi Zhang
- Department of Biochemistry and Molecular Medicine, The George Washington University School of Medicine and Health Sciences, Washington, DC, USA.,GW Cancer Center, The George Washington University, Washington, DC, USA
| | - Jing Sun
- Department of Biochemistry and Molecular Medicine, The George Washington University School of Medicine and Health Sciences, Washington, DC, USA.,GW Cancer Center, The George Washington University, Washington, DC, USA
| | - Zhou Bo
- State Key Laboratory of Applied Organic Chemistry, Lanzhou University, Lanzhou, China
| | | | - Yun Yen
- City of Hope National Medical Center, Duarte, CA, USA
| | - Zhiyong Han
- Department of Medical Sciences, Hackensack Meridian School of Medicine at Seton Hall University, South Orange, NJ, USA.
| | - Wenge Zhu
- Department of Biochemistry and Molecular Medicine, The George Washington University School of Medicine and Health Sciences, Washington, DC, USA. .,GW Cancer Center, The George Washington University, Washington, DC, USA.
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4
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Qu J, Sun W, Zhong J, Lv H, Zhu M, Xu J, Jin N, Xie Z, Tan M, Lin SH, Geng M, Ding J, Huang M. Phosphoglycerate mutase 1 regulates dNTP pool and promotes homologous recombination repair in cancer cells. J Cell Biol 2017; 216:409-424. [PMID: 28122957 PMCID: PMC5294784 DOI: 10.1083/jcb.201607008] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2016] [Revised: 11/02/2016] [Accepted: 01/17/2017] [Indexed: 02/04/2023] Open
Abstract
Phosphoglycerate mutase 1 (PGAM1) regulates metabolism in cancer cells. Qu et al. show that PGAM1 maintains the intracellular dNTP pool, promotes the stability of CTBP-interacting protein, and is required for homologous recombination repair. PGAM1 inhibition sensitizes BRCA1/2-proficient breast cancer to PARP inhibitors. Glycolytic enzymes are known to play pivotal roles in cancer cell survival, yet their molecular mechanisms remain poorly understood. Phosphoglycerate mutase 1 (PGAM1) is an important glycolytic enzyme that coordinates glycolysis, pentose phosphate pathway, and serine biosynthesis in cancer cells. Herein, we report that PGAM1 is required for homologous recombination (HR) repair of DNA double-strand breaks (DSBs) caused by DNA-damaging agents. Mechanistically, PGAM1 facilitates DSB end resection by regulating the stability of CTBP-interacting protein (CtIP). Knockdown of PGAM1 in cancer cells accelerates CtIP degradation through deprivation of the intracellular deoxyribonucleotide triphosphate pool and associated activation of the p53/p73 pathway. Enzymatic inhibition of PGAM1 decreases CtIP protein levels, impairs HR repair, and hence sensitizes BRCA1/2-proficient breast cancer to poly(ADP-ribose) polymerase (PARP) inhibitors. Together, this study identifies a metabolically dependent function of PGAM1 in promoting HR repair and reveals a potential therapeutic opportunity for PGAM1 inhibitors in combination with PARP inhibitors.
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Affiliation(s)
- Jia Qu
- State Key Laboratory of Pharmaceutical Biotechnology, School of Life Sciences, Nanjing University, Nanjing 210023, China.,State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China
| | - Wenyi Sun
- State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China
| | - Jie Zhong
- Department of Biochemistry and Molecular Cell Biology, Shanghai Key Laboratory for Tumor Microenvironment and Inflammation, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, China
| | - Hao Lv
- State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China
| | - Mingrui Zhu
- State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China
| | - Jun Xu
- State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China
| | - Nan Jin
- State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China
| | - Zuoquan Xie
- State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China
| | - Minjia Tan
- State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China
| | - Shu-Hai Lin
- Department of Biochemistry and Molecular Cell Biology, Shanghai Key Laboratory for Tumor Microenvironment and Inflammation, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, China
| | - Meiyu Geng
- State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China
| | - Jian Ding
- State Key Laboratory of Pharmaceutical Biotechnology, School of Life Sciences, Nanjing University, Nanjing 210023, China .,State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China
| | - Min Huang
- State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China
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5
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Oldemeyer S, Franz S, Wenzel S, Essen LO, Mittag M, Kottke T. Essential Role of an Unusually Long-lived Tyrosyl Radical in the Response to Red Light of the Animal-like Cryptochrome aCRY. J Biol Chem 2016; 291:14062-14071. [PMID: 27189948 DOI: 10.1074/jbc.m116.726976] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2016] [Indexed: 11/06/2022] Open
Abstract
Cryptochromes constitute a group of flavin-binding blue light receptors in bacteria, fungi, plants, and insects. Recently, the response of cryptochromes to light was extended to nearly the entire visible spectral region on the basis of the activity of the animal-like cryptochrome aCRY in the green alga Chlamydomonas reinhardtii This finding was explained by the absorption of red light by the flavin neutral radical as the dark state of the receptor, which then forms the anionic fully reduced state. In this study, time-resolved UV-visible spectroscopy on the full-length aCRY revealed an unusually long-lived tyrosyl radical with a lifetime of 2.6 s, which is present already 1 μs after red light illumination of the flavin radical. Mutational studies disclosed the tyrosine 373 close to the surface to form the long-lived radical and to be essential for photoreduction. This residue is conserved exclusively in the sequences of other putative aCRY proteins distinguishing them from conventional (6-4) photolyases. Size exclusion chromatography showed the full-length aCRY to be a dimer in the dark at 0.5 mm injected concentration with the C-terminal extension as the dimerization site. Upon illumination, partial oligomerization was observed via disulfide bridge formation at cysteine 482 in close proximity to tyrosine 373. The lack of any light response in the C-terminal extension as evidenced by FTIR spectroscopy differentiates aCRY from plant and Drosophila cryptochromes. These findings imply that aCRY might have evolved a different signaling mechanism via a light-triggered redox cascade culminating in photooxidation of a yet unknown substrate or binding partner.
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Affiliation(s)
- Sabine Oldemeyer
- Physical and Biophysical Chemistry, Department of Chemistry, Bielefeld University, Universitätsstr. 25, 33615 Bielefeld
| | - Sophie Franz
- Structural Biochemistry, Department of Chemistry, Philipps University Marburg, Hans-Meerwein Straβe 4, 35039 Marburg
| | - Sandra Wenzel
- Institute of General Botany and Plant Physiology, Friedrich Schiller University, Am Planetarium 1, 07743 Jena, Germany
| | - Lars-Oliver Essen
- Structural Biochemistry, Department of Chemistry, Philipps University Marburg, Hans-Meerwein Straβe 4, 35039 Marburg
| | - Maria Mittag
- Institute of General Botany and Plant Physiology, Friedrich Schiller University, Am Planetarium 1, 07743 Jena, Germany
| | - Tilman Kottke
- Physical and Biophysical Chemistry, Department of Chemistry, Bielefeld University, Universitätsstr. 25, 33615 Bielefeld,.
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6
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Kirschbaum MH, Frankel P, Synold TW, Xie Z, Yen Y, Popplewell L, Chen R, Aljitawi O, Tuscano JM, Chan KK, Newman EM. A phase I pharmacodynamic study of GTI-2040, an antisense oligonucleotide against ribonuclotide reductase, in acute leukemias: a California Cancer Consortium study. Leuk Lymphoma 2016; 57:2307-14. [PMID: 26895565 DOI: 10.3109/10428194.2016.1146947] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
We performed a phase I study of GTI-2040, an antisense oligonucleotide against ribonucleotide reductase mRNA, on a novel dosing schedule of days 1-4 and 15-18 by continuous infusion to examine efficacy and tolerability in patients with leukemia. A dose of 11 mg/kg/d was safely reached. Dose-limiting toxicities (DLTs) at the higher levels included elevated troponin I and liver function enzymes. There were no objective responses to GTI-2040 in this study; 7/24 patients were able to complete the predetermined three infusion cycles. Pharmacokinetic and pharmacodynamic studies were performed, indicating a trend towards increasing intracellular drug levels and decreasing RRM2 gene expression with increasing doses. This dose schedule may be considered if appropriate combinations are identified in preclinical studies.
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Affiliation(s)
| | - Paul Frankel
- a City of Hope Comprehensive Cancer Center , Duarte , CA , USA
| | | | - Zhiliang Xie
- b Ohio State University Comprehensive Cancer Center , Columbus , OH , USA
| | - Yun Yen
- a City of Hope Comprehensive Cancer Center , Duarte , CA , USA
| | | | - Robert Chen
- a City of Hope Comprehensive Cancer Center , Duarte , CA , USA
| | - Omar Aljitawi
- a City of Hope Comprehensive Cancer Center , Duarte , CA , USA
| | - Joseph M Tuscano
- c Davis Comprehensive Cancer Center, University of California , Sacramento , CA , USA
| | - Kenneth K Chan
- b Ohio State University Comprehensive Cancer Center , Columbus , OH , USA
| | - Edward M Newman
- a City of Hope Comprehensive Cancer Center , Duarte , CA , USA
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7
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IWAMOTO KAZUKI, NAKASHIRO KOHICHI, TANAKA HIROSHI, TOKUZEN NORIHIKO, HAMAKAWA HIROYUKI. Ribonucleotide reductase M2 is a promising molecular target for the treatment of oral squamous cell carcinoma. Int J Oncol 2015; 46:1971-7. [DOI: 10.3892/ijo.2015.2912] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2014] [Accepted: 01/30/2015] [Indexed: 11/06/2022] Open
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8
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Han P, Lin ZR, Xu LH, Zhong Q, Zhu XF, Liang FY, Cai Q, Huang XM, Zeng MS. Ribonucleotide reductase M2 subunit expression and prognostic value in nasopharyngeal carcinoma. Mol Med Rep 2015; 12:401-9. [PMID: 25695839 DOI: 10.3892/mmr.2015.3360] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2014] [Accepted: 12/17/2014] [Indexed: 11/06/2022] Open
Abstract
The ribonucleotide reductase M2 subunit (RRM2) modulates the enzymatic activity of ribonucleotide reductase, and is involved in tumor progression. Recently, high levels of RRM2 expression were reported to correlate with poor survival outcomes in patients with colorectal and bladder cancer. However, changes in RRM2 expression in nasopharyngeal carcinoma (NPC), and its effect on the prognosis of this disease remain unknown. The aim of the present study was to analyze the expression of RRM2 in NPC cell lines, and to identify whether RRM2 may serve as a biomarker with which to assess the prognosis of NPC. The present study found that RRM2 expression was higher in NPC cell lines and tissue samples than in noncancerous nasopharyngeal epithelial cell lines and noncancerous tissues, as shown by reverse transcription-quantitative polymerase chain reaction analysis, western blotting and immunohistochemistry staining. Kaplan-Meier survival analysis demonstrated that patients with higher RRM2 expression levels had poorer disease-free survival outcomes than those with lower expression levels of RRM2. Univariate analysis showed that a lower survival rate was significantly associated with high RRM2 expression levels [hazard ratio (HR), 6.424; 95% confidence interval (CI), 2.381-17.333; P<0.001]. Multivariate analysis indicated that RRM2 expression is an independent prognostic factor for patients with NPC (HR, 3.461; 95 % CI, 1.204-9.949; P=0.021). Overexpression of RRM2 led to increased cell proliferation, colony formation, migration and invasion in vivo. These results suggest that high levels of RRM2 expression may be a useful predictor for survival in patients with NPC and may serve as a novel prognostic indicator for these individuals.
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Affiliation(s)
- Ping Han
- Department of Otolaryngology-Head and Neck Surgery, Sun Yat-sen Memorial Hospital, Sun Yat-sen University, Guangzhou, Guangdong 510120, P.R. China
| | - Zhi-Rui Lin
- Sun Yat-sen University Cancer Center, State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Guangzhou, Guangdong 510060, P.R. China
| | - Li-Hua Xu
- Sun Yat-sen University Cancer Center, State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Guangzhou, Guangdong 510060, P.R. China
| | - Qian Zhong
- Sun Yat-sen University Cancer Center, State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Guangzhou, Guangdong 510060, P.R. China
| | - Xiao-Fen Zhu
- Department of Otolaryngology-Head and Neck Surgery, Huizhou First Hospital, Huizhou, Guangdong 516000, P.R. China
| | - Fa-Ya Liang
- Department of Otolaryngology-Head and Neck Surgery, Sun Yat-sen Memorial Hospital, Sun Yat-sen University, Guangzhou, Guangdong 510120, P.R. China
| | - Qian Cai
- Department of Otolaryngology-Head and Neck Surgery, Sun Yat-sen Memorial Hospital, Sun Yat-sen University, Guangzhou, Guangdong 510120, P.R. China
| | - Xiao-Ming Huang
- Department of Otolaryngology-Head and Neck Surgery, Sun Yat-sen Memorial Hospital, Sun Yat-sen University, Guangzhou, Guangdong 510120, P.R. China
| | - Mu-Sheng Zeng
- Sun Yat-sen University Cancer Center, State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Guangzhou, Guangdong 510060, P.R. China
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9
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Taricani L, Shanahan F, Malinao MC, Beaumont M, Parry D. A functional approach reveals a genetic and physical interaction between ribonucleotide reductase and CHK1 in mammalian cells. PLoS One 2014; 9:e111714. [PMID: 25375241 PMCID: PMC4222937 DOI: 10.1371/journal.pone.0111714] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2014] [Accepted: 10/07/2014] [Indexed: 11/30/2022] Open
Abstract
Ribonucleotide reductase (RNR) enzyme is composed of the homodimeric RRM1 and RRM2 subunits, which together form a heterotetramic active enzyme that catalyzes the de novo reduction of ribonucleotides to generate deoxyribonucleotides (dNTPs), which are required for DNA replication and DNA repair processes. In this study, we show that ablation of RRM1 and RRM2 by siRNA induces G1/S phase arrest, phosphorylation of Chk1 on Ser345 and phosphorylation of γ-H2AX on S139. Combinatorial ablation of RRM1 or RRM2 and Chk1 causes a dramatic accumulation of γ-H2AX, a marker of double-strand DNA breaks, suggesting that activation of Chk1 in this context is essential for suppression of DNA damage. Significantly, we demonstrate for the first time that Chk1 and RNR subunits co-immunoprecipitate from native cell extracts. These functional genomic studies suggest that RNR is a critical mediator of replication checkpoint activation.
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Affiliation(s)
- Lorena Taricani
- Merck Research Laboratories, Palo Alto, California, United States of America
| | - Frances Shanahan
- Merck Research Laboratories, Palo Alto, California, United States of America
| | | | - Maribel Beaumont
- Merck Research Laboratories, Palo Alto, California, United States of America
| | - David Parry
- Merck Research Laboratories, Palo Alto, California, United States of America
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10
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Labroli MA, Dwyer MP, Shen R, Popovici-Muller J, Pu Q, Wyss D, McCoy M, Barrett D, Davis N, Seghezzi W, Shanahan F, Taricani L, Beaumont M, Malinao MC, Parry D, Guzi TJ. The identification of novel 5'-amino gemcitabine analogs as potent RRM1 inhibitors. Bioorg Med Chem 2014; 22:2303-10. [PMID: 24588962 DOI: 10.1016/j.bmc.2014.02.007] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2013] [Revised: 01/29/2014] [Accepted: 02/07/2014] [Indexed: 11/25/2022]
Abstract
The ribonucleotide reductase (RNR) enzyme is a heteromer of RRM1 and RRM2 subunits. The active enzyme catalyzes de novo reduction of ribonucleotides to generate deoxyribonucleotides (dNTPs), which are required for DNA replication and DNA repair processes. Complexity in the generation of physiologically relevant, active RRM1/RRM2 heterodimers was perceived as limiting to the identification of selective RRM1 inhibitors by high-throughput screening of compound libraries and led us to seek alternative methods to identify lead series. In short, we found that gemcitabine, as its diphosphate metabolite, represents one of the few described active site inhibitors of RRM1. We herein describe the identification of novel 5'-amino gemcitabine analogs as potent RRM1 inhibitors through in-cell phenotypic screening.
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Affiliation(s)
- Marc A Labroli
- Merck Research Laboratories, 2000 Galloping Hill Road, Kenilworth, NJ 07033, USA.
| | - Michael P Dwyer
- Merck Research Laboratories, PO Box 2000, Rahway, NJ 07065, USA
| | - Ruichao Shen
- Merck Research Laboratories, 33 Avenue Louis Pasteur, BMB-3, Boston, MA 02115, USA
| | | | - Qinglin Pu
- Merck Research Laboratories, 33 Avenue Louis Pasteur, BMB-3, Boston, MA 02115, USA
| | - Daniel Wyss
- Merck Research Laboratories, 2000 Galloping Hill Road, Kenilworth, NJ 07033, USA
| | - Mark McCoy
- Merck Research Laboratories, 2000 Galloping Hill Road, Kenilworth, NJ 07033, USA
| | - Dianah Barrett
- Merck Research Laboratories, 2000 Galloping Hill Road, Kenilworth, NJ 07033, USA
| | - Nicole Davis
- Merck Research Laboratories, 901 South California Avenue, Palo Alto, CA 94304, USA
| | - Wolfgang Seghezzi
- Merck Research Laboratories, 901 South California Avenue, Palo Alto, CA 94304, USA
| | - Frances Shanahan
- Merck Research Laboratories, 901 South California Avenue, Palo Alto, CA 94304, USA
| | - Lorena Taricani
- Merck Research Laboratories, 901 South California Avenue, Palo Alto, CA 94304, USA
| | - Maribel Beaumont
- Merck Research Laboratories, 901 South California Avenue, Palo Alto, CA 94304, USA
| | | | - David Parry
- Merck Research Laboratories, 901 South California Avenue, Palo Alto, CA 94304, USA
| | - Timothy J Guzi
- Merck Research Laboratories, 33 Avenue Louis Pasteur, BMB-3, Boston, MA 02115, USA
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11
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Chen X, Xu Z, Zhang L, Liu H, Liu X, Lou M, Zhu L, Huang B, Yang CG, Zhu W, Shao J. The conserved Lys-95 charged residue cluster is critical for the homodimerization and enzyme activity of human ribonucleotide reductase small subunit M2. J Biol Chem 2013; 289:909-20. [PMID: 24253041 DOI: 10.1074/jbc.m113.524546] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Ribonucleotide reductase (RR) catalyzes the reduction of ribonucleotides to deoxyribonucleotides for DNA synthesis. Human RR small subunit M2 exists in a homodimer form. However, the importance of the dimer form to the enzyme and the related mechanism remain unclear. In this study, we tried to identify the interfacial residues that may mediate the assembly of M2 homodimer by computational alanine scanning based on the x-ray crystal structure. Co-immunoprecipitation, size exclusion chromatography, and RR activity assays showed that the K95E mutation in M2 resulted in dimer disassembly and enzyme activity inhibition. In comparison, the charge-exchanging double mutation of K95E and E98K recovered the dimerization and activity. Structural comparisons suggested that a conserved cluster of charged residues, including Lys-95, Glu-98, Glu-105, and Glu-174, at the interface may function as an ionic lock for M2 homodimer. Although the measurements of the radical and iron contents showed that the monomer (the K95E mutant) was capable of generating the diiron and tyrosyl radical cofactor, co-immunoprecipitation and competitive enzyme inhibition assays indicated that the disassembly of M2 dimer reduced its interaction with the large subunit M1. In addition, the immunofluorescent and fusion protein-fluorescent imaging analyses showed that the dissociation of M2 dimer altered its subcellular localization. Finally, the transfection of the wild-type M2 but not the K95E mutant rescued the G1/S phase cell cycle arrest and cell growth inhibition caused by the siRNA knockdown of M2. Thus, the conserved Lys-95 charged residue cluster is critical for human RR M2 homodimerization, which is indispensable to constitute an active holoenzyme and function in cells.
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Affiliation(s)
- Xinhuan Chen
- From the Department of Pathology and Pathophysiology, Zhejiang University School of Medicine, Hangzhou 310058, China
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Expression of RRM1 and RRM2 as a novel prognostic marker in advanced non-small cell lung cancer receiving chemotherapy. Tumour Biol 2013; 35:1899-906. [DOI: 10.1007/s13277-013-1255-4] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2013] [Accepted: 09/25/2013] [Indexed: 10/26/2022] Open
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13
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Small Interfering RNA (siRNA)-Mediated Silencing of the M2 Subunit of Ribonucleotide Reductase. Int J Gynecol Cancer 2013; 23:659-66. [DOI: 10.1097/igc.0b013e318287e2b3] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
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14
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Chao J, Synold TW, Morgan RJ, Kunos C, Longmate J, Lenz HJ, Lim D, Shibata S, Chung V, Stoller RG, Belani CP, Gandara DR, McNamara M, Gitlitz BJ, Lau DH, Ramalingam SS, Davies A, Espinoza-Delgado I, Newman EM, Yen Y. A phase I and pharmacokinetic study of oral 3-aminopyridine-2-carboxaldehyde thiosemicarbazone (3-AP, NSC #663249) in the treatment of advanced-stage solid cancers: a California Cancer Consortium Study. Cancer Chemother Pharmacol 2011; 69:835-43. [PMID: 22105720 DOI: 10.1007/s00280-011-1779-5] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2011] [Accepted: 11/07/2011] [Indexed: 10/15/2022]
Abstract
BACKGROUND 3-Aminopyridine-2-carboxaldehyde thiosemicarbazone (3-AP) is a novel small-molecule ribonucleotide reductase inhibitor. This study was designed to estimate the maximum tolerated dose (MTD) and oral bioavailability of 3-AP in patients with advanced-stage solid tumors. METHODS Twenty patients received one dose of intravenous and subsequent cycles of oral 3-AP following a 3 + 3 patient dose escalation. Intravenous 3-AP was administered to every patient at a fixed dose of 100 mg over a 2-h infusion 1 week prior to the first oral cycle. Oral 3-AP was administered every 12 h for 5 consecutive doses on days 1-3, days 8-10, and days 15-17 of every 28-day cycle. 3-AP was started at 50 mg with a planned dose escalation to 100, 150, and 200 mg. Dose-limiting toxicities (DLT) and bioavailability were evaluated. RESULTS Twenty patients were enrolled. For dose level 1 (50 mg), the second of three treated patients had a DLT of grade 3 hypertension. In the dose level 1 expansion cohort, three patients had no DLTs. No further DLTs were encountered during escalation until the 200-mg dose was reached. At the 200 mg 3-AP dose level, two treated patients had DLTs of grade 3 hypoxia. One additional DLT of grade 4 febrile neutropenia was subsequently observed at the de-escalated 150 mg dose. One DLT in 6 evaluable patients established the MTD as 150 mg per dose on this dosing schedule. Responses in the form of stable disease occurred in 5 (25%) of 20 patients. The oral bioavailability of 3-AP was 67 ± 29% and was consistent with the finding that the MTD by the oral route was 33% higher than by the intravenous route. CONCLUSIONS Oral 3-AP is well tolerated and has an MTD similar to its intravenous form after accounting for the oral bioavailability. Oral 3-AP is associated with a modest clinical benefit rate of 25% in our treated patient population with advanced solid tumors.
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Affiliation(s)
- Joseph Chao
- City of Hope Medical Center, Building room 4117, 1500 East Duarte Road, 91010, Duarte, CA, USA
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Morikawa T, Maeda D, Kume H, Homma Y, Fukayama M. Ribonucleotide reductase M2 subunit is a novel diagnostic marker and a potential therapeutic target in bladder cancer. Histopathology 2011; 57:885-92. [PMID: 21166702 DOI: 10.1111/j.1365-2559.2010.03725.x] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
AIMS To examine the immunohistochemical expression and function of ribonucleotide reductase M2 subunit (RRM2), a gemcitabine-related molecule, in bladder cancer. METHODS AND RESULTS One hundred and seventeen bladder specimens on a tissue microarray were immunostained for RRM2. Positive RRM2 staining was observed in none of 14 examples of non-neoplastic urothelium, none of four low-grade urothelial carcinoma (UC), 69 of 83 (83%) high-grade UC, three of three (100%) squamous cell carcinoma and 12 of 13 (92%) lymph node metastasis of UC. RRM2 overexpression was associated significantly with muscularis propria invasion in UC patients who had undergone radical cystectomy (P=0.005). Immunohistochemistry for RRM2 was then applied to small biopsy specimens of 15 cystitis with reactive atypia cases and 25 urothelial carcinoma in-situ (CIS) cases. Positive RRM2 staining was found in one of 15 (6.7%) cystitis with reactive atypia cases and in 24 of 25 (96%) CIS cases. Finally, UM-UC-3 bladder cancer cells were transfected with RRM2 siRNAs and cell growth was evaluated. Knockdown of RRM2 protein markedly inhibited cell growth. CONCLUSIONS We have shown frequent overexpression of RRM2 protein and its possible role in bladder cancer. Our results suggest that RRM2 is a novel diagnostic marker and a potential therapeutic target in bladder cancer.
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Affiliation(s)
- Teppei Morikawa
- Department of Pathology, Graduate School of Medicine, University of Tokyo, Tokyo, Japan.
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Yokoyama K, Uhlin U, Stubbe J. A hot oxidant, 3-NO2Y122 radical, unmasks conformational gating in ribonucleotide reductase. J Am Chem Soc 2010; 132:15368-79. [PMID: 20929229 PMCID: PMC3005585 DOI: 10.1021/ja1069344] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Escherichia coli ribonucleotide reductase is an α2β2 complex that catalyzes the conversion of nucleotides to deoxynucleotides and requires a diferric-tyrosyl radical (Y(•)) cofactor to initiate catalysis. The initiation process requires long-range proton-coupled electron transfer (PCET) over 35 Å between the two subunits by a specific pathway (Y(122)(•)→W(48)→Y(356) within β to Y(731)→Y(730)→C(439) within α). The rate-limiting step in nucleotide reduction is the conformational gating of the PCET process, which masks the chemistry of radical propagation. 3-Nitrotyrosine (NO(2)Y) has recently been incorporated site-specifically in place of Y(122) in β2. The protein as isolated contained a diferric cluster but no nitrotyrosyl radical (NO(2)Y(•)) and was inactive. In the present paper we show that incubation of apo-Y(122)NO(2)Y-β2 with Fe(2+) and O(2) generates a diferric-NO(2)Y(•) that has a half-life of 40 s at 25 °C. Sequential mixing experiments, in which the cofactor is assembled to 1.2 NO(2)Y(•)/β2 and then mixed with α2, CDP, and ATP, have been analyzed by stopped-flow absorption spectroscopy, rapid freeze quench EPR spectroscopy, and rapid chemical quench methods. These studies have, for the first time, unmasked the conformational gating. They reveal that the NO(2)Y(•) is reduced to the nitrotyrosinate with biphasic kinetics (283 and 67 s(-1)), that dCDP is produced at 107 s(-1), and that a new Y(•) is produced at 97 s(-1). Studies with pathway mutants suggest that the new Y(•) is predominantly located at 356 in β2. In consideration of these data and the crystal structure of Y(122)NO(2)Y-β2, a mechanism for PCET uncoupling in NO(2)Y(•)-RNR is proposed.
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Affiliation(s)
- Kenichi Yokoyama
- Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139–4307
| | - Ulla Uhlin
- Department of Molecular Biology, Swedish University of Agricultural Science, Uppsala Biomedical Center, Box 590, SE-75124 Uppsala, Sweden
| | - JoAnne Stubbe
- Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139–4307
- Department of Biology, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139–4307
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Morikawa T, Hino R, Uozaki H, Maeda D, Ushiku T, Shinozaki A, Sakatani T, Fukayama M. Expression of ribonucleotide reductase M2 subunit in gastric cancer and effects of RRM2 inhibition in vitro. Hum Pathol 2010; 41:1742-8. [PMID: 20825972 DOI: 10.1016/j.humpath.2010.06.001] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/13/2010] [Revised: 05/31/2010] [Accepted: 06/03/2010] [Indexed: 12/12/2022]
Abstract
Ribonucleotide reductase M2 subunit is one of two subunits that constitute ribonucleotide reductase, the enzyme that catalyzes the conversion of ribonucleotide 5'-diphosphates into 2'-deoxyribonucleotides, which are required for DNA synthesis. This study was conducted to investigate the roles of ribonucleotide reductase M2 subunit in gastric cancer. The expression of ribonucleotide reductase M2 subunit protein was examined by immunohistochemistry. In normal gastric mucosa, ribonucleotide reductase M2 subunit expression was restricted to the neck regions of gastric pits and no expression was observed in the surface epithelium. Among 112 gastric cancer tissues, ribonucleotide reductase M2 subunit overexpression (≥10% cancer cells stained) was observed in 72 cases (64.3%). Ribonucleotide reductase M2 subunit overexpression was significantly associated with male sex (P = .015), presence of muscularis propria invasion (P = .020), presence of Epstein-Barr virus (P = .045), expression of survivin (P = .0014), and DNA methyltransferase 1 (P = .043), but not with age, histology, tumor size, lymph node metastasis or expression of phosphatase and tensin homolog, phosphorylated signal transducer, and activator of transcription 3 or p53. Suppression of ribonucleotide reductase M2 subunit synthesis, using small interfering RNA, inhibited the growth of 3 gastric cancer cell lines, MKN-1, MKN-7, and SNU-719. Our data suggest that ribonucleotide reductase M2 subunit overexpression could be associated with the gastric cancer progression and that suppression of its function is a potential therapeutic strategy in gastric cancer.
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Affiliation(s)
- Teppei Morikawa
- Department of Pathology, Graduate School of Medicine, the University of Tokyo, Tokyo, Japan
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Shibata SI, Doroshow JH, Frankel P, Synold TW, Yen Y, Gandara DR, Lenz HJ, Chow WA, Leong LA, Lim D, Margolin KA, Morgan RJ, Somlo G, Newman EM. Phase I trial of GTI-2040, oxaliplatin, and capecitabine in the treatment of advanced metastatic solid tumors: a California Cancer Consortium Study. Cancer Chemother Pharmacol 2009; 64:1149-55. [PMID: 19322566 PMCID: PMC3046108 DOI: 10.1007/s00280-009-0977-x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2008] [Accepted: 03/03/2009] [Indexed: 12/27/2022]
Abstract
BACKGROUND GTI-2040 is a 20-mer antisense oligonucleotide targeting the mRNA of ribonucleotide reductase M2. It was combined with oxaliplatin and capecitabine in a phase I trial in patients with advance solid tumors based on previous studies demonstrating potentiation of chemotherapy with ribonucleotide reductase inhibitors. METHODS Patients at least 18 years of age with advanced incurable solid tumors and normal organ function as well as a Karnofsky performance status of > or =60% were eligible. One prior chemotherapy regimen for advanced disease or relapse within 12 months of adjuvant chemotherapy was required. Patients could have received prior fluoropyrimidines, including capecitabine, but not oxaliplatin. Treatment cycles were 21 days. In each cycle, GTI-2040 was given as a continuous intravenous infusion over 14 days, oxaliplatin as a 2-h intravenous infusion on day 1, and capecitabine orally twice a day for 14 days. In cycle 1 only, oxaliplatin and capecitabine were started on day 2 to allow ribonucleotide reductase mRNA levels to be measured with and without oxaliplatin and capecitabine. Doses were escalated in cohorts of three patients using a standard 3 + 3 design until the maximum tolerated dose was established, defined as no more than one first-cycle dose-limiting toxicity among six patients treated at a given dose level. RESULTS The maximum tolerated dose was estimated to be the combination of GTI-2040 3 mg/kg per day for 14 days, capecitabine 600 mg/m(2) twice daily for 14 days, and oxaliplatin 100 mg/m(2) every 21 days. Dose-limiting toxicities were hematologic. GTI-2040 pharmacokinetics, obtained at steady-state on days 7 and 14, showed the high inter-patient variability previously reported. Two of six patients had stable disease at the maximum tolerated dose and one patient, with heavily pre-treated non-small cell lung cancer, had a partial response at a higher dose level. In samples from a limited number of patients, there was no clear decrease in ribonucleotide reductase expression in peripheral blood mononuclear cells during treatment. CONCLUSION A combination of GTI-2040, capecitabine and oxaliplatin is feasible in patients with advanced solid tumors.
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Affiliation(s)
- Stephen I Shibata
- Department of Medical Oncology, City of Hope Comprehensive Cancer Center, 1500 E. Duarte Road, Duarte, CA 91010, USA.
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Evaluation of mRNA by Q-RTPCR and protein expression by AQUA of the M2 subunit of ribonucleotide reductase (RRM2) in human tumors. Cancer Chemother Pharmacol 2008; 64:79-86. [PMID: 18941749 DOI: 10.1007/s00280-008-0845-0] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2008] [Accepted: 09/23/2008] [Indexed: 10/21/2022]
Abstract
PURPOSE The purpose of this study was to evaluate baseline RRM2 protein and gene expression in tumors of patients receiving 3-AP. METHODS Tumor blocks from patients enrolled in phase I and II clinical studies using 3-AP, were evaluated for RRM2 gene and protein expression by quantitative real time polymerase chain reaction (Q-RTPCR) and automated quantitative analysis (AQUA). RESULTS Esophageal and gastric cancers overexpressed RRM2 protein when compared to prostate cancer (Z-score, 0.68 +/- 0.94 SD, vs 0.41 +/- 0.84 SD, respectively; p = 0.04). Esophageal and gastric cancers also overexpressed RRM2 mRNA when compared to prostate cancer (relative gene expression 2.56 +/- 1.49 SD, vs 0.29 +/- 0.20 SD, respectively; p = 0.02). Protein and gene expression were moderately associated (Spearman's rank correlation = 0.30; p = 0.12). CONCLUSION RRM2 gene and protein expression varies by tumor type.
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Ribonucleotide reductase subunits M1 and M2 mRNA expression levels and clinical outcome of lung adenocarcinoma patients treated with docetaxel/gemcitabine. Br J Cancer 2008; 98:1710-5. [PMID: 18414411 PMCID: PMC2391126 DOI: 10.1038/sj.bjc.6604344] [Citation(s) in RCA: 88] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Ribonucleotide reductase subunits M1 (RRM1) and M2 (RRM2) are involved in the metabolism of gemcitabine (2′,2′-difluorodeoxycytidine), which is used for the treatment of nonsmall cell lung cancer. The mRNA expression of RRM1 and RRM2 in tumours from lung adenocarcinoma patients treated with docetaxel/gemcitabine was assessed and the results correlated with clinical outcome. RMM1 and RMM2 mRNA levels were determined by quantitative real-time PCR in primary tumours of previously untreated patients with advanced lung adenocarcinoma who were subsequently treated with docetaxel/gemcitabine. Amplification was successful in 42 (79%) of 53 enrolled patients. Low levels of RRM2 mRNA were associated with response to treatment (P< 0.001). Patients with the lowest expression levels of RRM1 had a significantly longer time to progression (P=0.044) and overall survival (P=0.02) than patients with the highest levels. Patients with low levels of both RRM1 and RRM2 had a significantly higher response rate (60 vs 14.2%; P=0.049), time to progression (9.9 vs 2.3 months; P=0.003) and overall survival (15.4 vs 3.6; P=0.031) than patients with high levels of both RRM1 and RRM2. Ribonucleotide reductase subunit M1 and RRM2 mRNA expression in lung adenocarcinoma tumours is associated with clinical outcome to docetaxel/gemcitabine. Prospective studies are warranted to evaluate the role of these markers in tailoring chemotherapy.
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Avolio TM, Lee Y, Feng N, Xiong K, Jin H, Wang M, Vassilakos A, Wright J, Young A. RNA interference targeting the R2 subunit of ribonucleotide reductase inhibits growth of tumor cells in vitro and in vivo. Anticancer Drugs 2007; 18:377-88. [PMID: 17351390 DOI: 10.1097/cad.0b013e328013c04f] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
RNA interference, a posttranscriptional gene-silencing mechanism, has received considerable attention for its potential as a new therapeutic strategy to treat human diseases and conditions including cancer. Various studies have supported a role for the R2 subunit of ribonucleotide reductase in cancer progression and metastasis. Short interfering siRNA 1284 was designed to target R2. In vitro studies, in which three different human tumor cell lines (A498, HT-29 and A2058) were transfected with short interfering siRNA 1284, demonstrate sequence-specific down-regulation of R2, which coincides with a decrease in cell proliferation, and cell cycle inhibition. In vivo studies with xenograft mouse models, generated from the same tumor cell lines, indicate that treatment with short interfering siRNA 1284 leads to inhibition of tumor growth and this effect was found to be dose dependent. Taken together, these results suggest that short interfering siRNA 1284, targeting R2, has great potential to serve as a therapeutic agent towards the treatment of human cancers.
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Duxbury MS, Whang EE. RRM2 induces NF-kappaB-dependent MMP-9 activation and enhances cellular invasiveness. Biochem Biophys Res Commun 2006; 354:190-6. [PMID: 17222798 DOI: 10.1016/j.bbrc.2006.12.177] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2006] [Accepted: 12/21/2006] [Indexed: 02/07/2023]
Abstract
Ribonucleotide reductase is a dimeric enzyme that catalyzes conversion of ribonucleotide 5'-diphosphates to their 2'-deoxynucleotide forms, a rate-limiting step in the production of 2'-deoxyribonucleoside 5'-triphosphates required for DNA synthesis. The ribonucleotide reductase M2 subunit (RRM2) is a determinant of malignant cellular behavior in a range of human cancers. We examined the effect of RRM2 overexpression on pancreatic adenocarcinoma cellular invasiveness and nuclear factor-kappaB (NF-kappaB) transcription factor activity. RRM2 overexpression increases pancreatic adenocarcinoma cellular invasiveness and MMP-9 expression in a NF-kappaB-dependent manner. RNA interference (RNAi)-mediated silencing of RRM2 expression attenuates cellular invasiveness and NF-kappaB activity. NF-kappaB is a key mediator of the invasive phenotypic changes induced by RRM2 overexpression.
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Affiliation(s)
- Mark S Duxbury
- Department of Surgery, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115, USA
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Stubbe J. Ribonucleotide reductases. ADVANCES IN ENZYMOLOGY AND RELATED AREAS OF MOLECULAR BIOLOGY 2006; 63:349-419. [PMID: 2407066 DOI: 10.1002/9780470123096.ch6] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Affiliation(s)
- J Stubbe
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge 02139
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Jiang ZG, Lebowitz MS, Ghanbari HA. Neuroprotective activity of 3-aminopyridine-2-carboxaldehyde thiosemicarbazone (PAN-811), a cancer therapeutic agent. CNS DRUG REVIEWS 2006; 12:77-90. [PMID: 16834759 PMCID: PMC6741723 DOI: 10.1111/j.1527-3458.2006.00077.x] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
3-aminopyridine-2-carboxaldehyde thiosemicarbazone (3-AP) is a highly-hydrophobic small molecule that was originally developed for cancer therapy (Triapine, Vion Pharmaceuticals) due to its ability to inhibit ribonucleotide reductase, a key enzyme required for DNA synthesis. 3-AP has a high affinity for divalent cations, chelating the Fe(2+) at the R2 subunit of the enzyme and inhibiting formation of a tyrosyl radical essential for ribonucleotide reduction. We have demonstrated that 3-AP is also a potent neuroprotectant (as such, it is referred to as "PAN-811"). In vitro it completely blocks ischemic neurotoxicity at a concentration of 0.5 microM (EC(50) approximate, equals 0.35 microM) and hypoxic toxicity at 1.2 microM (EC(50) approximate, equals 0.75 microM). Full protection of primary cortical and striatal neurons can be achieved with 3-AP when it is added to the medium at up to six hours after an ischemic insult. 3-AP also suppresses cell death induced by neurotoxic agents, including staurosporine, veratridine and glutamate, indicating activity against a central target(s) in the neurodegenerative process. 3-AP acts via neutralization of two important intracellular effectors of excitatory neurotoxicity; calcium and free radicals. Its reported ability to elevate anti-apoptotic proteins is likely to be a consequence of the suppression of excessive intracellular free calcium. In a rat model of transient ischemia, a single bolus delivery of 3-AP 1 h after the initiation of ischemic attack reduced infarct volume by 59% when administered i.c.v. (50 mug per rat) and by 35% when administered i.v. (1 mg/kg). In Phase I clinical trials in cancer therapy 3-AP had no cardiovascular, CNS or other major adverse effects. Thus, 3-AP has a high potential for development as a novel, potent neuroprotectant for the treatment of neurodegenerative diseases.
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Affiliation(s)
- Zhi-Gang Jiang
- Neurodegenerative Diseases, Panacea Pharmaceuticals, Inc., Gaithersburg, Maryland 20877, USA.
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Abstract
Muscle cells grow by proliferation and protein accumulation. During the initial stages of development the participation of nerves is not always required. Myoblasts and satellite cells proliferate, fusing to form myotubes which further differentiate to muscle fibers. Myotubes and muscle fibers grow by protein accumulation and fusion with other myogenic cells. Muscle fibers finally reach a quasi-steady state which is then maintained for a long period. The mechanism of maintenance is not well understood. However, it is clear that protein metabolism plays a paramount role. The role played by satellite cells in the maintenance of muscle fibers is not known. Growth and maintenance of muscle cells are under the influence of various tissues and substances. Among them are Tf and the motor nerve, the former being the main object of this review and essential for both DNA and protein synthesis. Two sources of Tf have been proposed, i.e., the motor nerve and the tissue fluid. The first proposal is that the nervous trophic influence on muscle cells is mediated by Tf which is released from the nerve terminals. In this model, the sole source of Tf which is donated to muscle cells should be the nerve, and Tf should not be provided for muscle fiber at sites other than the synaptic region; otherwise, denervation atrophy would not occur, since Tf provided from TfR located at another site would cancel the effect of denervation. The second proposal is that Tf is provided from tissue fluid. This implies that an adequate amount of Tf is transferred from serum to tissue fluid; in this case TfR may be distributed over the entire surface of the cells. The trophic effects of the motor neuron have been studied in vivo, but its effects of myoblast proliferation have not been determined. There are few experiments on its effects on myotubes. Most work has been made on muscle fibers, where innervation is absolutely required for their maintenance. Without it, muscle fibers atrophy, although they do not degenerate. In contrast, almost all the work on Tf has been performed in vitro. Its effects on myoblast proliferation and myotube growth and maintenance have been established; myotubes degenerate following Tf removal. But its effects on mature muscle fibers in vivo are not well understood. Muscle fibers possess TfR all over on their cell surface and contain a variety of Fe-binding proteins, such as myoglobin. It is entirely plausible that muscle fibers require an amount of Tf, and that this is provided by TfR scattered on the cell surface.(ABSTRACT TRUNCATED AT 400 WORDS)
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Woldman I, Reither H, Kattinger A, Hornykiewicz O, Pifl C. Dopamine inhibits cell growth and cell cycle by blocking ribonucleotide reductase. Neuropharmacology 2005; 48:525-37. [PMID: 15755480 DOI: 10.1016/j.neuropharm.2004.11.013] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2004] [Revised: 10/15/2004] [Accepted: 11/27/2004] [Indexed: 01/08/2023]
Abstract
Dopamine (DA) is a classical neurotransmitter modulating various brain functions by acting on its specific receptors. In addition, DA is a reactive molecule that has been implicated in neurodegeneration, especially in Parkinson's disease. Here we show that DA inhibited cell growth of dopamine transporter transfected cells by intracellularly blocking cell cycle progression. To pinpoint the site of this effect, we measured DNA distribution and 5-bromo-2'-deoxyuridine (BrdU) incorporation, as well as the levels of the key cell cycle proteins. DA increased number of cells with a G1 DNA content, decreased BrdU incorporation and simultaneously increased cyclin A but had no effect on cyclin D2, D3, E, nor on cdk4 and p21. These results narrowed down the DA effect to the beginning of S phase, suggesting inhibition of the ribonucleotide reductase, an enzyme essential for DNA synthesis. Indeed, measurement of enzyme activity in situ revealed that DA, within 1h of addition to cells labelled with [3H]cytidine, strongly reduced the cell content of [3H]2'-deoxycytidine 5'-triphophate. The time course of this DA effect preceded the cell cycle progression. This novel molecular mechanism of intracellular DA action independent of plasmamembrane receptors may be involved in processes controlling the development and survival of brain dopaminergic neurons.
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Affiliation(s)
- Irina Woldman
- Center for Brain Research, Medical University of Vienna, Spitalgasse 4, A-1090 Vienna, Austria
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Duxbury MS, Ito H, Benoit E, Zinner MJ, Ashley SW, Whang EE. RETRACTED: Retrovirally mediated RNA interference targeting the M2 subunit of ribonucleotide reductase: A novel therapeutic strategy in pancreatic cancer. Surgery 2004; 136:261-9. [PMID: 15300189 DOI: 10.1016/j.surg.2004.04.029] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
This article has been retracted: please see Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy). This article has been retracted at the request of the Editors-in-Chief, because an investigation by Harvard Medical School and the Brigham and Women’s Hospital has concluded that Figure 1A is invalid and no underlying research data are available to resolve the discrepancies or validate the reported results.
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Affiliation(s)
- Mark S Duxbury
- Department of Surgery, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115, USA
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Lin ZP, Belcourt MF, Cory JG, Sartorelli AC. Stable suppression of the R2 subunit of ribonucleotide reductase by R2-targeted short interference RNA sensitizes p53(-/-) HCT-116 colon cancer cells to DNA-damaging agents and ribonucleotide reductase inhibitors. J Biol Chem 2004; 279:27030-8. [PMID: 15096505 DOI: 10.1074/jbc.m402056200] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Ribonucleotide reductase catalyzes the production of deoxyribonucleoside diphosphates, the precursors of deoxyribonucleoside triphosphates for DNA synthesis. Mammalian ribonucleotide reductase (RNR) is a tetramer consisting of two non-identical homodimers, R1 and either R2 or p53R2, which are considered to be involved in DNA replication and repair, respectively. We have demonstrated that DNA damage by doxorubicin and cisplatin caused a steady elevation of the R2 protein in p53(-/-) HCT-116 human colon carcinoma cells but induced degradation of the protein in p53(+/+) cells. To evaluate the involvement of R2 in response to DNA damage, p53(-/-) HCT-116 cells were stably transfected with an expression vector transcribing short hairpin/short interference RNA directed against R2 mRNA. Stably transfected clones exhibited a pronounced reduction of the R2 protein with no change in the cellular growth rate. Furthermore, short interference RNA-mediated reduction of the R2 protein caused a marked increase in sensitivity to the DNA-damaging agent cisplatin as well as to the RNR inhibitors Triapine and hydroxyurea. Ectopic expression of p53R2 partially reversed the cytotoxicity of cisplatin but not that of RNR inhibitors to R2 knockdown cells. The increase in sensitivity to cisplatin and RNR inhibitors was correlated with the suppression of dATP and dGTP levels caused by stable expression of R2-targeted short interference RNA. These results indicated that DNA damage resulted in elevated levels of the R2 protein and dNTPs and, consequently, enhanced the survival of p53(-/-) HCT-116 cells. The findings provide evidence that R2-RNR can be employed to supply dNTPs for the repair of DNA damage in cells with an impaired p53-dependent induction of p53R2.
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Affiliation(s)
- Z Ping Lin
- Department of Pharmacology and Cancer Center, Yale University School of Medicine, New Haven, Connecticut 06520, USA
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Duxbury MS, Ito H, Zinner MJ, Ashley SW, Whang EE. RNA interference targeting the M2 subunit of ribonucleotide reductase enhances pancreatic adenocarcinoma chemosensitivity to gemcitabine. Oncogene 2004; 23:1539-48. [PMID: 14661056 DOI: 10.1038/sj.onc.1207272] [Citation(s) in RCA: 191] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Ribonucleotide reductase is emerging as an important determinant of gemcitabine chemoresistance in human cancers. Activity of this enzyme, which catalyses conversion of ribonucleotide 5'-diphosphates to their 2'-deoxynucleotides, is modulated by levels of its M2 subunit (RRM2). Here we show that RRM2 overexpression is associated with gemcitabine chemoresistance in pancreatic adenocarcinoma cells, and that suppression of RRM2 expression using RNA interference mediated by small interfering RNA (siRNA) enhances gemcitabine-induced cytotoxicity in vitro. We demonstrate the ability of systemically administered RRM2 siRNA to suppress tumoral RRM2 expression in an orthotopic xenograft model of pancreatic adenocarcinoma. Synergism between RRM2 siRNA and gemcitabine results in markedly suppressed tumor growth, increased tumor apoptosis and inhibition of metastasis. Our findings confirm the importance of RRM2 in pancreatic adenocarcinoma gemcitabine chemoresistance. This is the first demonstration that systemic delivery of siRNA-based therapy can enhance the efficacy of an anticancer nucleoside analog.
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Affiliation(s)
- Mark S Duxbury
- Department of Surgery, Brigham and Women's Hospital, Harvard Medical School, 75 Francis Street, Boston, Massachusetts, USA
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Stubbe J, Nocera DG, Yee CS, Chang MCY. Radical initiation in the class I ribonucleotide reductase: long-range proton-coupled electron transfer? Chem Rev 2003; 103:2167-201. [PMID: 12797828 DOI: 10.1021/cr020421u] [Citation(s) in RCA: 666] [Impact Index Per Article: 31.7] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- JoAnne Stubbe
- Department of Chemistry, 77 Massachusetts Avenue, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139-4307, USA.
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Vée S, Lafanechère L, Fisher D, Wehland J, Job D, Picard A. Evidence for a role of the (alpha)-tubulin C terminus in the regulation of cyclin B synthesis in developing oocytes. J Cell Sci 2001; 114:887-98. [PMID: 11181172 DOI: 10.1242/jcs.114.5.887] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Microinjected mAb YL1/2, an (alpha)-tubulin antibody specific for the tyrosinated form of the protein, blocks the cell cycle in developing oocytes. Here, we have investigated the mechanism involved in the mAb effect. Both developing starfish and Xenopus oocytes were injected with two different (alpha)-tubulin C terminus antibodies. The injected antibodies blocked cell entry into mitosis through specific inhibition of cyclin B synthesis. The antibody effect was independent of the presence or absence of polymerized microtubules and was mimicked by injected synthetic peptides corresponding to the tyrosinated (alpha)-tubulin C terminus, whereas peptides lacking the terminal tyrosine were ineffective. These results indicate that tyrosinated (alpha)-tubulin, or another protein sharing the same C-terminal epitope, is involved in specific regulation of cyclin B synthesis in developing oocytes.
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Affiliation(s)
- S Vée
- Laboratoire Arago, BP 44, Banyuls sur mer F-66651 cedex, France
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33
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Takada S, Shibata T, Hiraoka Y, Masuda H. Identification of ribonucleotide reductase protein R1 as an activator of microtubule nucleation in Xenopus egg mitotic extracts. Mol Biol Cell 2000; 11:4173-87. [PMID: 11102516 PMCID: PMC15065 DOI: 10.1091/mbc.11.12.4173] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Microtubule nucleation on the centrosome and the fungal equivalent, the spindle pole body (SPB), is activated at the onset of mitosis. We previously reported that mitotic extracts prepared from Xenopus unfertilized eggs convert the interphase SPB of fission yeast into a competent state for microtubule nucleation. In this study, we have purified an 85-kDa SPB activator from the extracts and identified it as the ribonucleotide reductase large subunit R1. We further confirmed that recombinant mouse R1 protein was also effective for SPB activation. On the other hand, another essential subunit of ribonucleotide reductase, R2 protein, was not required for SPB activation. SPB activation by R1 protein was suppressed in the presence of anti-R1 antibodies or a partial oligopeptide of R1; the oligopeptide also inhibited aster formation on Xenopus sperm centrosomes. In accordance, R1 was detected in animal centrosomes by immunofluorescence and immunoblotting with anti-R1 antibodies. In addition, recombinant mouse R1 protein bound to gamma- and alpha/beta-tubulin in vitro. These results suggest that R1 is a bifunctional protein that acts on both ribonucleotide reduction and centrosome/SPB activation.
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Affiliation(s)
- S Takada
- Cellular and Molecular Biology Laboratory, RIKEN (The Institute of Physical and Chemical Research), Wako, Saitama 351-0198, Japan
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Jong AY, Yu K, Zhou B, Frgala T, Reynolds CP, Yen Y. A simple and sensitive ribonucleotide reductase assay. J Biomed Sci 2000; 5:62-8. [PMID: 9570515 DOI: 10.1007/bf02253357] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Ribonucleotide reductase (RR) is a key regulatory enzyme in the DNA synthesis pathway and is the target of the cancer chemotherapeutic agent hydroxyurea. The study of RR is significantly hindered by the tedious and labor-intensive nature of enzymatic assay. In this report, we present a novel RR assay in which detection of the deoxyribonucleotides produced by RR occurs via coupling to the DNA polymerase reaction, and is enhanced by using RNase to degrade endogenous RNA. Cell extracts from various cell lines were treated with RNase and then reacted with ATP and radioactive ribonucleotide diphosphate as the substrate. Incorporation of the radioactive substrate [14C]CDP into DNA was linear over 30 min and was linear with the amount of extract, which provided RR activity. The reaction was inhibited by hydroxyurea and required Mg2+ and ATP, suggesting that the assay is specific to RR activity. While RR activities determined by our method and by a conventional method were comparable, this novel method proved to be simpler, faster, more sensitive and less expensive. In addition, assay of the RR activity for multiple samples can easily be performed simultaneously. It is superior to other RR assays in all aspects.
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Affiliation(s)
- A Y Jong
- Department of Pediatrics, Childrens Hospital of Los Angeles and the University of Southern California School of Medicine, 90027, USA. ajong%
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Chabes A, Thelander L. Controlled protein degradation regulates ribonucleotide reductase activity in proliferating mammalian cells during the normal cell cycle and in response to DNA damage and replication blocks. J Biol Chem 2000; 275:17747-53. [PMID: 10747958 DOI: 10.1074/jbc.m000799200] [Citation(s) in RCA: 125] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Ribonucleotide reductase (RNR) plays a central role in the formation and control of the optimal levels of deoxyribonucleoside triphosphates, which are required for DNA replication and DNA repair processes. Mammalian RNRs are composed of two nonidentical subunits, proteins R1 and R2. The levels of the limiting R2 protein control overall RNR activity during the mammalian cell cycle, being undetectable in G(1) phase and increasing in S phase. We show that in proliferating mammalian cells, the transcription of the R2 gene, once activated in the beginning of S phase, reaches its maximum 6-7 h later and then declines. Surprisingly, DNA damage and replication blocks neither increase nor prolong the R2 promoter activity in S phase. Instead, the cell cycle activity of the mammalian enzyme is controlled by an S phase/DNA damage-specific stabilization of the R2 protein, which is effective until cells pass into mitosis.
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Affiliation(s)
- A Chabes
- Department of Medical Biosciences, Medical Biochemistry, Umeå University, SE-901 87 Umeå, Sweden.
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36
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Finch RA, Liu M, Grill SP, Rose WC, Loomis R, Vasquez KM, Cheng Y, Sartorelli AC. Triapine (3-aminopyridine-2-carboxaldehyde- thiosemicarbazone): A potent inhibitor of ribonucleotide reductase activity with broad spectrum antitumor activity. Biochem Pharmacol 2000; 59:983-91. [PMID: 10692563 DOI: 10.1016/s0006-2952(99)00419-0] [Citation(s) in RCA: 292] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
Previous studies from our laboratories have shown that (a) Triapine() is a potent inhibitor of ribonucleotide reductase activity and (b) hydroxyurea-resistant L1210 leukemia cells are fully sensitive to Triapine. In an analogous manner, Triapine was similarly active against the wild-type and a hydroxyurea-resistant subline of the human KB nasopharyngeal carcinoma. Triapine was active in vivo against the L1210 leukemia over a broad range of dosages and was curative for some mice. This agent also caused pronounced inhibition of the growth of the murine M109 lung carcinoma and human A2780 ovarian carcinoma xenografts in mice. Optimum anticancer activity required twice daily dosing due to the duration of inhibition of DNA synthesis which lasted about 10 hr in L1210 cells treated with Triapine in vivo. DNA synthesis in normal mouse tissues (i.e. duodenum and bone marrow) uniformly recovered faster than that in L1210 leukemia cells, demonstrating a pharmacological basis for the therapeutic index of this agent. Triapine was more potent than hydroxyurea in inhibiting DNA synthesis in L1210 cells in vivo, and the effects of Triapine were more pronounced. In addition, the duration of the inhibition of DNA synthesis in leukemia cells from mice treated with Triapine was considerably longer than in those from animals treated with hydroxyurea. Combination of Triapine with various classes of agents that damage DNA (e.g. etoposide, cisplatin, doxorubicin, and 1-acetyl-1,2-bis(methylsulfonyl)-2-(2-chloroethyl)hydrazine) resulted in synergistic inhibition of the L1210 leukemia, producing long-term survivors of tumor-bearing mice treated with several dosage levels of the combinations, whereas no enhancement of survival was found when Triapine was combined with gemcitabine or cytosine arabinoside. The findings demonstrate the superiority of Triapine over hydroxyurea as an anticancer agent and further suggest that prevention by Triapine of repair of DNA lesions created by agents that damage DNA may result in efficacious drug combinations for the treatment of cancer.
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Affiliation(s)
- R A Finch
- Department of Pharmacology, Cancer Center, Yale University School of Medicine, New Haven, CT, USA
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37
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Chen S, Zhou B, He F, Yen Y. Inhibition of human cancer cell growth by inducible expression of human ribonucleotide reductase antisense cDNA. ANTISENSE & NUCLEIC ACID DRUG DEVELOPMENT 2000; 10:111-6. [PMID: 10805162 DOI: 10.1089/oli.1.2000.10.111] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Ribonucleotide reductase (RR) is a rate-limiting enzyme in DNA synthesis and repair. The enzyme consists of two dissimilar subunits, M1 and M2. It is known that the M2 subunit plays a role in tumorgenicity and metastasis. In this study, we transfected human oropharyngeal KB cancer cells with human RR M1 and M2 antisense cDNA expressed by an inducible vector system. The transfectants were double-selected with hygromycin and G418. The clones, designated KB-M1AS, KB-M2AS and KB-CAT, represented transfectant clones that contained M1 antisense cDNA, M2 antisense cDNA, and a CAT reporter gene, respectively. In a colony-forming assay, colony formation for the KB-M2AS clone decreased approximately 50% when M2 antisense mRNA expression was induced by isopropylthiogalactose (IPTG). However, the KB-M1AS clone revealed no significant inhibition under IPTG induction. RR enzyme activity, as measured by 14CDP reduction assay, revealed a 30% decrease in the IPTG-induced KB-M2AS clone relative to non-IPTG-induced samples at 144 hours. As shown by Northern blot, expression of the M2 antisense mRNA showed peaks at 48 hours and 144 hours after induction by IPTG. M2 antisense mRNA expression induced by IPTG was 33-fold greater than the uninduced control at 144 hours. Western blot analysis showed that the M2 subunit protein level decreased in the KB-M2AS clone beginning at 72 hours after induction and continued to decrease to 50% of the uninduced control at 144 hours, then showed a slight recovery at 168 hours. In conclusion, M2 antisense mRNA expression by an inducible system can effectively decrease RR M2 protein expression, reduce enzyme activity, and inhibit growth. Furthermore, this approach can be employed in future antisense investigations.
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Affiliation(s)
- S Chen
- Cancer Center, Veterans General Hospital, National Yang-Ming University Taipei, Taiwan, ROC
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38
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Chabes A, Domkin V, Larsson G, Liu A, Graslund A, Wijmenga S, Thelander L. Yeast ribonucleotide reductase has a heterodimeric iron-radical-containing subunit. Proc Natl Acad Sci U S A 2000; 97:2474-9. [PMID: 10716984 PMCID: PMC15953 DOI: 10.1073/pnas.97.6.2474] [Citation(s) in RCA: 76] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Ribonucleotide reductase (RNR) catalyzes the de novo synthesis of deoxyribonucleotides. Eukaryotes have an alpha(2)beta(2) form of RNR consisting of two homodimeric subunits, proteins R1 (alpha(2)) and R2 (beta(2)). The R1 protein is the business end of the enzyme containing the active site and the binding sites for allosteric effectors. The R2 protein is a radical storage device containing an iron center-generated tyrosyl free radical. Previous work has identified an RNR protein in yeast, Rnr4p, which is homologous to other R2 proteins but lacks a number of conserved amino acid residues involved in iron binding. Using highly purified recombinant yeast RNR proteins, we demonstrate that the crucial role of Rnr4p (beta') is to fold correctly and stabilize the radical-storing Rnr2p by forming a stable 1:1 Rnr2p/Rnr4p complex. This complex sediments at 5.6 S as a betabeta' heterodimer in a sucrose gradient. In the presence of Rnr1p, both polypeptides of the Rnr2p/Rnr4p heterodimer cosediment at 9.7 S as expected for an alpha(2)betabeta' heterotetramer, where Rnr4p plays an important role in the interaction between the alpha(2) and the betabeta ' subunits. The specific activity of the Rnr2p complexed with Rnr4p is 2,250 nmol deoxycytidine 5'-diphosphate formed per min per mg, whereas the homodimer of Rnr2p shows no activity. This difference in activity may be a consequence of the different conformations of the inactive homodimeric Rnr2p and the active Rnr4p-bound form, as shown by CD spectroscopy. Taken together, our results show that the Rnr2p/Rnr4p heterodimer is the active form of the yeast RNR small subunit.
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Affiliation(s)
- A Chabes
- Department of Medical Biosciences, Medical Biochemistry, Umeå University, SE-901 87 Umeå, Sweden.
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39
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Park JB, Levine M. Characterization of the promoter of the human ribonucleotide reductase R2 gene. Biochem Biophys Res Commun 2000; 267:651-7. [PMID: 10631117 DOI: 10.1006/bbrc.1999.1980] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We describe here cloning and characterization of the promoter region of the human ribonucleotide reductase R2 gene. Primer extension and sequence data indicated that two different transcripts were produced via using two different promoter regions. Promoter activity of the 5' flanking region of the first transcript was approximately 100-fold higher than controls, and that of the second transcript was approximately 30-fold higher than controls. Particularly, the proximal region of the first transcript, -125 to +1 bp, was responsible for approximately a 50-fold increase in promoter activity, compared to controls. This region had three CCAAT sequences, each of which contributed similarly to promoter activity. When all three CCAAT sequences were mutated, promoter activity declined 80%. In addition, the promoter region -125 to +1 bp was responsible for cell-cycle-specific expression. These data provided essential information concerning regulatory mechanisms of cell-cycle-specific expression of human ribonucleotide reductase R2.
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Affiliation(s)
- J B Park
- Phytonutrients Laboratory, BHNRC/ARS/USDA, Building 307, Room 313, Beltsville, Maryland 20705, USA
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40
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Wong WS, McLean AE. Effects of phenolic antioxidants and flavonoids on DNA synthesis in rat liver, spleen, and testis in vitro. Toxicology 1999; 139:243-53. [PMID: 10647924 DOI: 10.1016/s0300-483x(99)00136-5] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Paracetamol (acetaminophen) and hydroxyurea were found to inhibit DNA synthesis in a dose-dependent manner in tissue slices in vitro, with little effect on protein synthesis. Considerable variation in the sensitivity of the different tissues was also observed with an order of least sensitive to most sensitive tissue of liver < testis < spleen. The phenolic antioxidant properties of paracetamol are thought to be the mechanism by which paracetamol inhibits DNA synthesis, which led us to study other phenolic antioxidant molecules and flavonoids for specific inhibition of DNA synthesis. (+)-catechin, m-aminophenol, p-aminophenol and p-cresol all displayed a highly specific inhibition of DNA synthesis. Quercetin displayed a preferential inhibition of DNA synthesis but a significant level of inhibition of protein synthesis was also seen. Nordihydroguaiaretic acid (NDGA) and n-propyl gallate showed preferential inhibition of DNA synthesis at the lower doses tested, but at higher doses showed significant inhibition of protein synthesis, presumably because of cytotoxicity. Caffeic acid and naringenin did not display any specific inhibition of DNA synthesis as protein synthesis was equally inhibited at all doses tested. This study demonstrates that certain phenolic antioxidants can inhibit DNA synthesis specifically but this is not a property shared by all phenolic antioxidants; and that these inhibitors show considerable variation in effectiveness between different tissues.
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Affiliation(s)
- W S Wong
- Laboratory of Toxicology, Centre for Clinical Pharmacology and Toxicology, University College London Medical School, The Rayne Institute, UK
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41
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Finch RA, Liu MC, Cory AH, Cory JG, Sartorelli AC. Triapine (3-aminopyridine-2-carboxaldehyde thiosemicarbazone; 3-AP): an inhibitor of ribonucleotide reductase with antineoplastic activity. ADVANCES IN ENZYME REGULATION 1999; 39:3-12. [PMID: 10470363 DOI: 10.1016/s0065-2571(98)00017-x] [Citation(s) in RCA: 180] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The enzyme RR catalyzes the conversion of ribonucleoside diphosphates to their deoxyribonucleotide counterparts. RR is critical for the generation of the cytosine, adenine, and guanine deoxyribonucleotide 5'-triphosphate building blocks of DNA, which are present in cells as exceedingly small intracellular pools. Therefore, interference with the function of RR might well result in an agent with significant antineoplastic activity, particularly against rapidly proliferating tumor cells. HUr is the only inhibitor of RR in clinical usage; this agent, however, is a relatively poor inhibitor of the enzyme and has a short serum half-life. Consequently, HUr is a relatively weak anticancer agent. In an effort to develop a more potent inhibitor of RR with utility as an anticancer agent, we have synthesized 3-AP and demonstrated (a) potent inhibition of L1210 leukemia cells in vitro, (b) curative capacity for mice bearing the L1210 leukemia, (c) marked inhibition of RR, and (d) sensitivity of HUr-resistant cells to 3-AP. These findings collectively demonstrate the clinical potential of 3-AP as an antineoplastic agent.
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Affiliation(s)
- R A Finch
- Department of Pharmacology, Yale University School of Medicine, New Haven CT 06520, USA
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42
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Hendricks SP, Mathews CK. Differential effects of hydroxyurea upon deoxyribonucleoside triphosphate pools, analyzed with vaccinia virus ribonucleotide reductase. J Biol Chem 1998; 273:29519-23. [PMID: 9792659 DOI: 10.1074/jbc.273.45.29519] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Hydroxyurea inhibits DNA synthesis by destroying the catalytically essential free radical of class I ribonucleoside diphosphate (rNDP) reductase, thereby blocking the de novo synthesis of deoxyribonucleotides. In mammalian cells, including those infected by vaccinia virus, hydroxyurea treatment causes a differential depletion of the four deoxyribonucleoside triphosphate pools, suggesting that the activities of rNDP reductase are differentially sensitive to hydroxyurea. In the presence of different substrates and allosteric modifiers, we measured rates of free radical destruction in the vaccinia virus-coded rNDP reductase, by following absorbance at 417 nm as a function of time after hydroxyurea addition. Also, we followed enzyme activity directly, by using a recently developed assay that allows simultaneous monitoring of the four activities, in the presence of substrates and effectors at concentrations that approximate the intracellular environment. We found the primary determinant of radical loss to be not the ensemble of allosteric ligands bound but the activity of the enzyme. Nucleoside triphosphate effectors accelerated radical decay, compared with rates seen with the free enzyme. Adding substrate to the holoenzyme, under conditions where the enzymatic reaction is proceeding, further accelerated radical decay. Alternative models are discussed, to account for selective depletion of purine nucleotide pools by hydroxyurea.
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Affiliation(s)
- S P Hendricks
- Department of Biochemistry and Biophysics, Oregon State University, Corvallis, Oregon 97331-7305, USA
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43
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Gao WY, Zhou BS, Johns DG, Mitsuya H, Yen Y. Role of the M2 subunit of ribonucleotide reductase in regulation by hydroxyurea of the activity of the anti-HIV-1 agent 2',3'-dideoxyinosine. Biochem Pharmacol 1998; 56:105-12. [PMID: 9698094 DOI: 10.1016/s0006-2952(98)00127-0] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The ribonucleotide reductase inhibitor hydroxyurea exhibits potent synergism, even at low, non-cytotoxic concentrations, with the anti-HIV-1 dideoxynucleoside 2',3'-dideoxyinosine, bringing about failure of HIV DNA synthesis and, thus, of HIV replication. To elucidate the incompletely defined role of hydroxyurea in the hydroxyurea/dideoxyinosine interaction and, in particular, to identify the reasons for the unusual selective inhibitory action of the combination on retroviral rather than on cellular DNA synthesis, we prepared specific cDNA probes to determine the effects of low-level hydroxyurea on mammalian cell ribonucleotide reductase M1 and M2 subunit mRNA, while simultaneously quantitating the effects of the drug on cell cycle and on deoxynucleoside triphosphate pools. While dTTP, dCTP, and dGTP pools changed little or even increased in the presence of low-level hydroxyurea, there took place a rapid and specific inhibition of M2-subunit-catalyzed generation of dATP, with consequent slowing of cellular DNA synthesis and prolongation of S phase. However, the latter effect, in turn, resulted in increased M2 subunit mRNA transcription (a process blocked in Go/G1-phase cells, with full-length functional M2 transcripts being generated only during S phase) and, hence, in a return to normal levels of dATP and to a normal rate of cellular DNA synthesis. Because of this self-regulating mechanism, hydroxyurea-induced host-cell toxicity was obviated under conditions where HIV DNA synthesis, a process sensitive to both dATP depletion and the chain-terminating properties of the other inhibitory component of the combination (ddATP derived from dideoxyinosine), was unable to recover.
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Affiliation(s)
- W Y Gao
- Experimental Retrovirology Section, Medicine Branch, Division of Clinical Sciences, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA.
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Zhou BS, Ker R, Ho R, Yu J, Zhao YR, Shih J, Yen Y. Determination of deoxyribonucleoside triphosphate pool sizes in ribonucleotide reductase cDNA transfected human KB cells. Biochem Pharmacol 1998; 55:1657-65. [PMID: 9634002 DOI: 10.1016/s0006-2952(98)00042-2] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Ribonucleotide reductase (RR) is a rate-limiting enzyme in DNA synthesis, which is responsible for controlling deoxyribonucleoside triphosphate (dNTP) pool size. It has been shown that transfection of RR M2 cDNA in human KB cells (M2-D clone) results in overexpression for the M2 subunit and resistance to hydroxyurea (HU). In this study, dNTP pool assays were performed to measure the pool sizes in six cell lines: two controls, three transfectants, and drug-induced HU-resistant (HUR) cells. Total dNTP levels among the six cell lines rose in the following order: KB wild-type, KB vector-only transfectant, M1 cDNA transfectant, M2 cDNA transfectant, M1/M2 cDNA transfectant, and HU-induced resistant clone. The dCTP levels of the cells mimicked the total dNTP pools on a smaller scale. The significant increases in the dCTP pool sizes of the M2-D, X-D, and HUR clones were proportional to their respective increases in RR activity. Relative to all other transfectants, the M1-D clone demonstrated lower dCTP levels but increased dATP pools. The M1-D clone demonstrated a significant resistance to dNTP inhibition of RR activity compared with the control KB wild-type cells. In contrast, a profound inhibition of dCTP and a decreased sensitivity to dATP inhibition was observed in M2-D, X-D, and HUR clones. In summary, M2 cDNA transfectants and HUR clones had increased RR activity as well as expanded dNTP pools, particularly dCTP, when compared with wild-type KB cells. These data provide evidence for the intertwined relationship between RR activity and dNTP pools.
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Affiliation(s)
- B S Zhou
- City of Hope National Medical Center, Duarte, CA 91010-3000, USA
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Wadler S, Horowitz R, Zhang HY, Schwartz EL. Effects of perturbations of pools of deoxyribonucleoside triphosphates on expression of ribonucleotide reductase, a G1/S transition state enzyme, in p53-mutated cells. Biochem Pharmacol 1998; 55:1353-60. [PMID: 10076525 DOI: 10.1016/s0006-2952(97)00641-2] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Effects of drug treatment with antimetabolites on a human colon cancer cell line, SW480, were studied. Cells were treated with 10 microM of 5-fluorouracil (5FU), an inhibitor of pyrimidine synthesis, or 1000 microM of hydroxyurea (HU), an inhibitor of both purine and pyrimidine syntheses, or the combination. Recombinant alpha-2a-interferon (IFN), 500 U/mL, also was employed, as this augments the effects of both antimetabolites in vitro and in vivo. The predominant effect of this combination was to block cells in early S phase as measured by 5-bromo-2'-deoxyuridine (BrdUrd) incorporation. By 24 hr, 86% of the cells had accumulated in S phase, but failed to progress to G2/M. This was accompanied by an early, rapid decline in all four deoxyribonucleoside triphosphates (dNTPs) by 38-86% at 4-24 hr. Despite these effects, expression of the G1/S transition state enzyme, ribonucleotide reductase (RR), increased at 24 hr as measured by a 3 to 5-fold increase in mRNA levels for the M2 subunit, in the absence of a measurable effect on protein levels. The rise in levels of RR mRNA and the continued progression of cells into S phase were associated with a synergistic inhibition of cell cycle proliferation resulting from treatment with the three-drug combination. This suggests that in the presence of antimetabolite-induced depletion of dNTPs, SW480 cells, which lack a normal p53 gene, will proceed into S phase, and that this is associated with a rise in expression of the G1/S transition state enzyme, RR. Cells arrested in S phase by a p53-independent mechanism will undergo a synergistic enhancement of cell death.
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Affiliation(s)
- S Wadler
- Albert Einstein Cancer Center, Bronx, NY, USA
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Dormeyer M, Schöneck R, Dittmar GA, Krauth-Siegel RL. Cloning, sequencing and expression of ribonucleotide reductase R2 from Trypanosoma brucei. FEBS Lett 1997; 414:449-53. [PMID: 9315738 DOI: 10.1016/s0014-5793(97)01036-3] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Ribonucleotide reductase (RR) is an attractive drug target molecule. The gene of the R2 protein of Trypanosoma brucei RR (nrd B) has been cloned. It encodes a protein of 337 residues which shows about 60% identity with other eukaryotic R2 proteins. All residues which bind the iron center, the tyrosyl radical or are supposed to participate in the radical transfer are conserved in the trypanosomal protein sequence. Overexpression of the gene in E. coli resulted in 2-5 mg pure R2 protein from 100 ml bacterial cell culture. Northern blot analysis revealed a transcript of 1.85 kb in bloodstream and procyclic forms of the parasite.
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Affiliation(s)
- M Dormeyer
- Biochemie-Zentrum Heidelberg, Ruprecht-Karls-Universität, Germany
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Klinga-Levan K, Helou K, Issa R, Szpirer C, Szpirer J, Levan G. Mapping of the ribonucleotide reductase genes (Rrm1, Rrm2) in the rat. Mamm Genome 1997; 8:47-9. [PMID: 9021149 DOI: 10.1007/s003359900346] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Affiliation(s)
- K Klinga-Levan
- Department of Genetics, Göteborg University, Lundberg Laboratory, Sweden
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Cooper CE, Lynagh GR, Hoyes KP, Hider RC, Cammack R, Porter JB. The relationship of intracellular iron chelation to the inhibition and regeneration of human ribonucleotide reductase. J Biol Chem 1996; 271:20291-9. [PMID: 8702762 DOI: 10.1074/jbc.271.34.20291] [Citation(s) in RCA: 130] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
The depletion of cellular iron can lead to the inhibition of ribonucleotide reductase, preventing new DNA synthesis and hence inhibiting cell proliferation. Electron paramagnetic resonance (EPR) spectroscopy has been used to examine simultaneously for the first time the relationship between chelation of intracellular iron and the rate of removal and regeneration of the tyrosyl radical of ribonucleotide reductase within intact human leukemia K562 cells. The different physiochemical characteristics of relatively hydrophobic low molecular weight bidentate hydroxypyridinone chelators and the higher molecular weight hexadentate ferrioxamine have been exploited to elucidate these interactions further. The base-line concentration of EPR-detectable mononuclear nonheme iron complexes was 3.15 =/- 1.05 microM, rising on incubation with chelators more rapidly with hydroxypyridinones than with desferrioxamine. Hydroxypyridinones also removed the tyrosyl radical more rapidly, apparently as a consequence of depletion of the intracellular iron pools necessary to regenerate the active enzyme and compatible with their reportedly greater cell toxicity. The radical decay rate is consistent with previous models, suggesting that iron is spontaneously removed from mammalian ribonucleotide reductase. Upon removal of extracellular chelator the regeneration of the tyrosyl radical was significantly faster for hydroxypyridinones than for desferrioxamine, consistent with their differential effects on cell cycle synchronization.
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Affiliation(s)
- C E Cooper
- Department of Biological and Chemical Sciences, University of Essex, Colchester CO4 3SQ, United Kingdom
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Ingemarson R, Thelander L. A kinetic study on the influence of nucleoside triphosphate effectors on subunit interaction in mouse ribonucleotide reductase. Biochemistry 1996; 35:8603-9. [PMID: 8679622 DOI: 10.1021/bi960184n] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
For enzymatic activity, mouse ribonucleotide reductase must form a heterodimeric complex composed of homodimeric R1 and R2 proteins. Both substrate specificity and overall activity are regulated by the allosteric effectors ATP, dATP, dTTP, and dGTP, which bind to two different sites found on R1, the activity site and the substrate specificity site. We have used biosensor technique to directly observe the effects of these nucleotides on R1/R2 interactions. In the absence of effectors, positive cooperativity was observed with a Hill coefficient of 1.8 and a KD of 0.5 microM. In the presence of dTTP or dGTP, there was no cooperativity and subunit interaction was observed at a much lower R1 concentration. The highest R1/R2 affinity was in the presence of dATP or ATP with KDs of 0.05-0.1 microM. In all experiments, the molar stoichiometry between the subunits was close to 1:1. Our data support a model whereby binding of any of the effectors to the substrate specificity site promotes formation of the R1 dimer, which we believe is prerequisite for binding to the R2 dimer. Additional binding of either ATP (a positive effector) or dATP (a negative effector) to the activity site further increases R1/R2 association. We propose that binding of ATP or dATP to the activity site controls enzyme activity, not by changing the aggregation state of the R1/R2 proteins as proposed earlier, but rather by locally influencing the long range electron transport between the catalytic site of R1 and the tyrosyl free radical of R2.
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Affiliation(s)
- R Ingemarson
- Department of Medical Biochemistry and Biophysics, Umeå University, Sweden.
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Cory JG, Downes DL, Cory AH. Differences in the properties of mammalian ribonucleotide reductase toward its substrates. ADVANCES IN ENZYME REGULATION 1996; 36:3-15. [PMID: 8869737 DOI: 10.1016/0065-2571(95)00008-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
These studies, using three different reagents, show that the substrate properties of ribonucleotide reductase are specific but can be variable depending upon the nature of the interaction of the reagent with the holoenzyme or the individual subunit. Etheno-CDP, which acts as a competitive inhibitor with respect to CDP, interacts with the active site of the holoenzyme. This interaction was the result of rather tight structural requirements as epsilon-ADP did not result in a similar level of inhibition of either CDP or ADP reductase activities. The YL 1/2 antibody which binds very tightly to the NHI subunit has a much greater effect on CDP reductase activity than ADP reductase activity. The nonapeptide that corresponds to the C-terminus amino acid sequence of the NHI subunit and which binds to the EB subunit and aborts the formation of the NHI-EB active complex has a greater effect on ADP reductase activity than on CDP reductase activity. The use of reagents such as these can be helpful in dissecting the subtle but important differences in the substrate properties of mammalian ribonucleotide reductase.
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Affiliation(s)
- J G Cory
- Department of Biochemistry, East Carolina University, School of Medicine, Greenville, NC 27858, USA
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