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Park BS, Jeon H, Kim Y, Kwon H, Choi GE, Chi SG, Park HM, Lee H, Kim T. Polyamine and EIF5A hypusination downstream of c-Myc confers targeted therapy resistance in BRAF mutant melanoma. Mol Cancer 2024; 23:136. [PMID: 38965534 PMCID: PMC11223307 DOI: 10.1186/s12943-024-02031-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2024] [Accepted: 05/24/2024] [Indexed: 07/06/2024] Open
Abstract
BACKGROUND BRAF inhibitors are widely employed in the treatment of melanoma with the BRAF V600E mutation. However, the development of resistance compromises their therapeutic efficacy. Diverse genomic and transcriptomic alterations are found in BRAF inhibitor resistant melanoma, posing a pressing need for convergent, druggable target that reverse therapy resistant tumor with different resistance mechanisms. METHODS CRISPR-Cas9 screens were performed to identify novel target gene whose inhibition selectively targets A375VR, a BRAF V600E mutant cell line with acquired resistance to vemurafenib. Various in vitro and in vivo assays, including cell competition assay, water soluble tetrazolium (WST) assay, live-dead assay and xenograft assay were performed to confirm synergistic cell death. Liquid Chromatography-Mass Spectrometry analyses quantified polyamine biosynthesis and changes in proteome in vemurafenib resistant melanoma. EIF5A hypusination dependent protein translation and subsequent changes in mitochondrial biogenesis and activity were assayed by O-propargyl-puromycin labeling assay, mitotracker, mitoSOX labeling and seahorse assay. Bioinformatics analyses were used to identify the association of polyamine biosynthesis with BRAF inhibitor resistance and poor prognosis in melanoma patient cohorts. RESULTS We elucidate the role of polyamine biosynthesis and its regulatory mechanisms in promoting BRAF inhibitor resistance. Leveraging CRISPR-Cas9 screens, we identify AMD1 (S-adenosylmethionine decarboxylase 1), a critical enzyme for polyamine biosynthesis, as a druggable target whose inhibition reduces vemurafenib resistance. Metabolomic and proteomic analyses reveal that polyamine biosynthesis is upregulated in vemurafenib-resistant cancer, resulting in enhanced EIF5A hypusination, translation of mitochondrial proteins and oxidative phosphorylation. We also identify that sustained c-Myc levels in vemurafenib-resistant cancer are responsible for elevated polyamine biosynthesis. Inhibition of polyamine biosynthesis or c-Myc reversed vemurafenib resistance both in vitro cell line models and in vivo in a xenograft model. Polyamine biosynthesis signature is associated with poor prognosis and shorter progression free survival after BRAF/MAPK inhibitor treatment in melanoma cohorts, highlighting the clinical relevance of our findings. CONCLUSIONS Our findings delineate the molecular mechanisms involving polyamine-EIF5A hypusination-mitochondrial respiration pathway conferring BRAF inhibitor resistance in melanoma. These targets will serve as effective therapeutic targets that can maximize the therapeutic efficacy of existing BRAF inhibitors.
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Affiliation(s)
- Byung-Sun Park
- Medicinal Materials Research Center, Korea Institute of Science and Technology, 5 Hwarangro-14-Gil, SeongbukGu, Seoul, 02792, Republic of Korea
- Department of Life Sciences, Korea University, 145 AnamRo, SeongbukGu, Seoul, 02841, Republic of Korea
| | - Heeju Jeon
- Medicinal Materials Research Center, Korea Institute of Science and Technology, 5 Hwarangro-14-Gil, SeongbukGu, Seoul, 02792, Republic of Korea
- Department of Life Sciences, Korea University, 145 AnamRo, SeongbukGu, Seoul, 02841, Republic of Korea
| | - Yeonseo Kim
- Center for Advanced Biomolecular Recognition, Korea Institute of Science and Technology, 5 Hwarangro- 14-Gil, SeongbukGu, Seoul, 02792, Republic of Korea
| | - Haejin Kwon
- Advanced Analysis and Data Center, Korea Institute of Science and Technology, 5 Hwarangro-14-Gil, SeongbukGu, Seoul, 02792, Republic of Korea
| | - Ga-Eun Choi
- Medicinal Materials Research Center, Korea Institute of Science and Technology, 5 Hwarangro-14-Gil, SeongbukGu, Seoul, 02792, Republic of Korea
| | - Sung-Gil Chi
- Department of Life Sciences, Korea University, 145 AnamRo, SeongbukGu, Seoul, 02841, Republic of Korea
| | - Hyun-Mee Park
- Advanced Analysis and Data Center, Korea Institute of Science and Technology, 5 Hwarangro-14-Gil, SeongbukGu, Seoul, 02792, Republic of Korea
| | - Hyunbeom Lee
- Center for Advanced Biomolecular Recognition, Korea Institute of Science and Technology, 5 Hwarangro- 14-Gil, SeongbukGu, Seoul, 02792, Republic of Korea
| | - Tackhoon Kim
- Medicinal Materials Research Center, Korea Institute of Science and Technology, 5 Hwarangro-14-Gil, SeongbukGu, Seoul, 02792, Republic of Korea.
- Department of Life Sciences, Korea University, 145 AnamRo, SeongbukGu, Seoul, 02841, Republic of Korea.
- Division of Bio-Medical Science and Technology, Korea University of Science and Technology, 217 GajeongRo YuseongGu, Daejeon, 34113, Republic of Korea.
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Zong L, Cheng G, Zhao J, Zhuang X, Zheng Z, Liu Z, Song F. Inhibitory Effect of Ursolic Acid on the Migration and Invasion of Doxorubicin-Resistant Breast Cancer. Molecules 2022; 27:1282. [PMID: 35209071 PMCID: PMC8879026 DOI: 10.3390/molecules27041282] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2021] [Revised: 01/29/2022] [Accepted: 02/11/2022] [Indexed: 12/11/2022] Open
Abstract
The cause of death in most breast cancer patients is disease metastasis and the occurrence of multidrug resistance (MDR). Ornithine decarboxylase (ODC), which is involved into multiple pathways, is closely related to carcinogenesis and development. Ursolic acid (UA), a natural triterpenoid compound, has been shown to reverse the MDR characteristics of tumor cells. However, the effect of UA on the invasion and metastasis of tumor cells with MDR is not known. Therefore, we investigated the effects of UA on invasion and metastasis, ODC-related polyamine metabolism, and MAPK-Erk-VEGF/MMP-9 signaling pathways in a doxorubicin-resistant breast cancer cell (MCF-7/ADR) model. The obtained results showed that UA significantly inhibited the adhesion and migration of MCF-7/ADR cells, and had higher affinities with key active cavity residues of ODC compared to the known inhibitor di-fluoro-methyl-ornithine (DFMO). UA could downregulate ODC, phosphorylated Erk (P-Erk), VEGF, and matrix metalloproteinase-9 (MMP-9) activity. Meanwhile, UA significantly reduced the content of metabolites of the polyamine metabolism. Furthermore, UA increased the intracellular accumulation of Dox in MCF-7/ADR cells. Taken together, UA can inhibit against tumor progression during the treatment of breast cancer with Dox, and possibly modulate the Erk-VEGF/MMP-9 signaling pathways and polyamine metabolism by targeting ODC to exert these effects.
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Affiliation(s)
- Li Zong
- State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, China; (L.Z.); (G.C.); (J.Z.); (Z.Z.); (Z.L.)
- Jilin Province Key Laboratory of Chinese Medicine Chemistry and Mass Spectrometry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, China
| | - Guorong Cheng
- State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, China; (L.Z.); (G.C.); (J.Z.); (Z.Z.); (Z.L.)
- Jilin Province Key Laboratory of Chinese Medicine Chemistry and Mass Spectrometry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, China
| | - Jingwu Zhao
- State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, China; (L.Z.); (G.C.); (J.Z.); (Z.Z.); (Z.L.)
- Jilin Province Key Laboratory of Chinese Medicine Chemistry and Mass Spectrometry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, China
| | - Xiaoyu Zhuang
- Experiment Center for Science and Technology, Shanghai University of Traditional Chinese Medicine, Shanghai 201203, China
| | - Zhong Zheng
- State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, China; (L.Z.); (G.C.); (J.Z.); (Z.Z.); (Z.L.)
- Jilin Province Key Laboratory of Chinese Medicine Chemistry and Mass Spectrometry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, China
| | - Zhiqiang Liu
- State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, China; (L.Z.); (G.C.); (J.Z.); (Z.Z.); (Z.L.)
- Jilin Province Key Laboratory of Chinese Medicine Chemistry and Mass Spectrometry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, China
| | - Fengrui Song
- State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, China; (L.Z.); (G.C.); (J.Z.); (Z.Z.); (Z.L.)
- Jilin Province Key Laboratory of Chinese Medicine Chemistry and Mass Spectrometry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, China
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3
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Novita Sari I, Setiawan T, Seock Kim K, Toni Wijaya Y, Won Cho K, Young Kwon H. Metabolism and function of polyamines in cancer progression. Cancer Lett 2021; 519:91-104. [PMID: 34186159 DOI: 10.1016/j.canlet.2021.06.020] [Citation(s) in RCA: 45] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2021] [Revised: 06/11/2021] [Accepted: 06/22/2021] [Indexed: 01/18/2023]
Abstract
Polyamines are essential for the proliferation, differentiation, and development of eukaryotes. They include spermine, spermidine, and the diamine precursor putrescine, and are low-molecular-weight, organic polycations with more than two amino groups. Their intracellular concentrations are strictly maintained within a specific physiological range through several regulatory mechanisms in normal cells. In contrast, polyamine metabolism is dysregulated in many neoplastic states, including cancer. In various types of cancer, polyamine levels are elevated, and crosstalk occurs between polyamine metabolism and oncogenic pathways, such as mTOR and RAS pathways. Thus, polyamines might have potential as therapeutic targets in the prevention and treatment of cancer. The molecular mechanisms linking polyamine metabolism to carcinogenesis must be unraveled to develop novel inhibitors of polyamine metabolism. This overview describes the nature of polyamines, their association with carcinogenesis, the development of polyamine inhibitors and their potential, and the findings of clinical trials.
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Affiliation(s)
- Ita Novita Sari
- Department of Integrated Biomedical Science, Soonchunhyang University, Cheonan-si, 31151, Republic of Korea
| | - Tania Setiawan
- Department of Integrated Biomedical Science, Soonchunhyang University, Cheonan-si, 31151, Republic of Korea
| | - Kwang Seock Kim
- Soonchunhyang Institute of Medi-bio Science (SIMS), Soonchunhyang University, Cheonan-si, 31151, Republic of Korea
| | - Yoseph Toni Wijaya
- Department of Integrated Biomedical Science, Soonchunhyang University, Cheonan-si, 31151, Republic of Korea
| | - Kae Won Cho
- Department of Integrated Biomedical Science, Soonchunhyang University, Cheonan-si, 31151, Republic of Korea; Soonchunhyang Institute of Medi-bio Science (SIMS), Soonchunhyang University, Cheonan-si, 31151, Republic of Korea.
| | - Hyog Young Kwon
- Department of Integrated Biomedical Science, Soonchunhyang University, Cheonan-si, 31151, Republic of Korea; Soonchunhyang Institute of Medi-bio Science (SIMS), Soonchunhyang University, Cheonan-si, 31151, Republic of Korea.
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Li J, Meng Y, Wu X, Sun Y. Polyamines and related signaling pathways in cancer. Cancer Cell Int 2020; 20:539. [PMID: 33292222 PMCID: PMC7643453 DOI: 10.1186/s12935-020-01545-9] [Citation(s) in RCA: 57] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2020] [Accepted: 09/08/2020] [Indexed: 02/06/2023] Open
Abstract
Polyamines are aliphatic compounds with more than two amino groups that play various important roles in human cells. In cancer, polyamine metabolism dysfunction often occurs, and regulatory mechanisms of polyamine. This review summarizes the existing research on the metabolism and transport of polyamines to study the association of oncogenes and related signaling pathways with polyamines in tumor cells. Drugs that regulate enzymes have been developed for cancer treatment, and in the future, more attention should be paid to treatment strategies that simultaneously modulate polyamine metabolism and carcinogenic signaling pathways. In addition, the polyamine pathway is a potential target for cancer chemoprevention. As an irreversible suicide inhibitor of the ornithine decarboxylase (a vital enzyme of polyamine synthesis), Difluoro-methylornithine had been shown to have the chemoprevention effect on cancer. Therefore, we summarized and analyzed the chemoprophylaxis effect of the difluoromethylornithine in this systematic review.
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Affiliation(s)
- Jiajing Li
- Department of Otorhinolaryngology-Head and Neck Surgery, China-Japan Union Hospital, Jilin University, Changchun, Jilin Province, China.,Department of Pathophysiology, Prostate Diseases Prevention and Treatment Research Center, College of Basic Medical Science, Jilin University, Changchun, China
| | - Yan Meng
- Department of Pathophysiology, Prostate Diseases Prevention and Treatment Research Center, College of Basic Medical Science, Jilin University, Changchun, China
| | - Xiaolin Wu
- Department of Pathophysiology, Prostate Diseases Prevention and Treatment Research Center, College of Basic Medical Science, Jilin University, Changchun, China
| | - Yuxin Sun
- Department of Otorhinolaryngology-Head and Neck Surgery, China-Japan Union Hospital, Jilin University, Changchun, Jilin Province, China.
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5
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Polyamine Metabolism as a Therapeutic Target inHedgehog-Driven Basal Cell Carcinomaand Medulloblastoma. Cells 2019; 8:cells8020150. [PMID: 30754726 PMCID: PMC6406590 DOI: 10.3390/cells8020150] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2019] [Revised: 02/06/2019] [Accepted: 02/08/2019] [Indexed: 02/06/2023] Open
Abstract
Hedgehog (Hh) signaling is a critical developmental regulator and its aberrant activation,due to somatic or germline mutations of genes encoding pathway components, causes Basal CellCarcinoma (BCC) and medulloblastoma (MB). A growing effort has been devoted at theidentification of druggable vulnerabilities of the Hedgehog signaling, leading to the identificationof various compounds with variable efficacy and/or safety. Emerging evidence shows that anaberrant polyamine metabolism is a hallmark of Hh-dependent tumors and that itspharmacological inhibition elicits relevant therapeutic effects in clinical or preclinical models ofBCC and MB. We discuss here the current knowledge of polyamine metabolism, its role in cancerand the available targeting strategies. We review the literature about the connection betweenpolyamines and the Hedgehog signaling, and the potential therapeutic benefit of targetingpolyamine metabolism in two malignancies where Hh pathways play a well-established role: BCCand MB.
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6
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Smirnova OA, Bartosch B, Zakirova NF, Kochetkov SN, Ivanov AV. Polyamine Metabolism and Oxidative Protein Folding in the ER as ROS-Producing Systems Neglected in Virology. Int J Mol Sci 2018; 19:ijms19041219. [PMID: 29673197 PMCID: PMC5979612 DOI: 10.3390/ijms19041219] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2018] [Revised: 04/03/2018] [Accepted: 04/11/2018] [Indexed: 12/23/2022] Open
Abstract
Reactive oxygen species (ROS) are produced in various cell compartments by an array of enzymes and processes. An excess of ROS production can be hazardous for normal cell functioning, whereas at normal levels, ROS act as vital regulators of many signal transduction pathways and transcription factors. ROS production is affected by a wide range of viruses. However, to date, the impact of viral infections has been studied only in respect to selected ROS-generating enzymes. The role of several ROS-generating and -scavenging enzymes or cellular systems in viral infections has never been addressed. In this review, we focus on the roles of biogenic polyamines and oxidative protein folding in the endoplasmic reticulum (ER) and their interplay with viruses. Polyamines act as ROS scavengers, however, their catabolism is accompanied by H2O2 production. Hydrogen peroxide is also produced during oxidative protein folding, with ER oxidoreductin 1 (Ero1) being a major source of oxidative equivalents. In addition, Ero1 controls Ca2+ efflux from the ER in response to e.g., ER stress. Here, we briefly summarize the current knowledge on the physiological roles of biogenic polyamines and the role of Ero1 at the ER, and present available data on their interplay with viral infections.
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Affiliation(s)
- Olga A Smirnova
- Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, Vavilov str. 32, Moscow 119991, Russia.
| | - Birke Bartosch
- Cancer Research Center Lyon, INSERM U1052 and CNRS 5286, Lyon University, 69003 Lyon, France.
- DevWeCan Laboratories of Excellence Network (Labex), Lyon 69003, France.
| | - Natalia F Zakirova
- Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, Vavilov str. 32, Moscow 119991, Russia.
| | - Sergey N Kochetkov
- Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, Vavilov str. 32, Moscow 119991, Russia.
| | - Alexander V Ivanov
- Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, Vavilov str. 32, Moscow 119991, Russia.
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7
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Arruabarrena-Aristorena A, Zabala-Letona A, Carracedo A. Oil for the cancer engine: The cross-talk between oncogenic signaling and polyamine metabolism. SCIENCE ADVANCES 2018; 4:eaar2606. [PMID: 29376126 PMCID: PMC5783676 DOI: 10.1126/sciadv.aar2606] [Citation(s) in RCA: 65] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/19/2017] [Accepted: 12/28/2017] [Indexed: 05/09/2023]
Abstract
The study of metabolism has provided remarkable information about the biological basis and therapeutic weaknesses of cancer cells. Classic biochemistry established the importance of metabolic alterations in tumor biology and revealed the importance of various metabolite families to the tumorigenic process. We have evidence of the central role of polyamines, small polycatonic metabolites, in cell proliferation and cancer growth from these studies. However, how cancer cells activate this metabolic pathway and the molecular cues behind the oncogenic action of polyamines has remained largely obscure. In contrast to the view of metabolites as fuel (anabolic intermediates) for cancer cells, polyamines are better defined as the oil that lubricates the cancer engine because they affect the activity of biological processes. Modern research has brought back to the limelight this metabolic pathway, providing a strong link between genetic, metabolic, and signaling events in cancer. In this review, we enumerate and discuss current views of the regulation and activity of polyamine metabolism in tumor cell biology.
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Affiliation(s)
| | - Amaia Zabala-Letona
- CIC bioGUNE, Bizkaia Technology Park, 801A Building, 48160 Derio, Bizkaia, Spain
- CIBERONC Centro de Investigación Biomédica en Red de Cáncer, Avenida Monforte de Lemos, Madrid, Spain
| | - Arkaitz Carracedo
- CIC bioGUNE, Bizkaia Technology Park, 801A Building, 48160 Derio, Bizkaia, Spain
- CIBERONC Centro de Investigación Biomédica en Red de Cáncer, Avenida Monforte de Lemos, Madrid, Spain
- Ikerbasque, Basque Foundation for Science, 48011 Bilbao, Spain
- Biochemistry and Molecular Biology Department, University of the Basque Country (UPV/EHU), P.O. Box 644, E-48080 Bilbao, Spain
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8
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Kim DJ, Roh E, Lee MH, Oi N, Lim DY, Kim MO, Cho YY, Pugliese A, Shim JH, Chen H, Cho EJ, Kim JE, Kang SC, Paul S, Kang HE, Jung JW, Lee SY, Kim SH, Reddy K, Yeom YI, Bode AM, Dong Z. Herbacetin Is a Novel Allosteric Inhibitor of Ornithine Decarboxylase with Antitumor Activity. Cancer Res 2015; 76:1146-1157. [PMID: 26676750 DOI: 10.1158/0008-5472.can-15-0442] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2015] [Accepted: 10/28/2015] [Indexed: 11/16/2022]
Abstract
Ornithine decarboxylase (ODC) is a rate-limiting enzyme in the first step of polyamine biosynthesis that is associated with cell growth and tumor formation. Existing catalytic inhibitors of ODC have lacked efficacy in clinical testing or displayed unacceptable toxicity. In this study, we report the identification of an effective and nontoxic allosteric inhibitor of ODC. Using computer docking simulation and an in vitro ODC enzyme assay, we identified herbacetin, a natural compound found in flax and other plants, as a novel ODC inhibitor. Mechanistic investigations defined aspartate 44 in ODC as critical for binding. Herbacetin exhibited potent anticancer activity in colon cancer cell lines expressing high levels of ODC. Intraperitoneal or oral administration of herbacetin effectively suppressed HCT116 xenograft tumor growth and also reduced the number and size of polyps in a mouse model of APC-driven colon cancer (ApcMin/+). Unlike the well-established ODC inhibitor DFMO, herbacetin treatment was not associated with hearing loss. Taken together, our findings defined the natural product herbacetin as an allosteric inhibitor of ODC with chemopreventive and antitumor activity in preclinical models of colon cancer, prompting its further investigation in clinical trials.
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Affiliation(s)
- Dong Joon Kim
- The Hormel Institute, University of Minnesota, Austin, MN 55912, USA.,Biomedical Genomics Research Center, Korea Research Institute of Bioscience & Biotechnology (KRIBB), Daejeon, 305-806, Korea
| | - Eunmiri Roh
- The Hormel Institute, University of Minnesota, Austin, MN 55912, USA
| | - Mee-Hyun Lee
- The Hormel Institute, University of Minnesota, Austin, MN 55912, USA.,China-US Hormel Institute, Henan, 45008, China
| | - Naomi Oi
- The Hormel Institute, University of Minnesota, Austin, MN 55912, USA
| | - Do Young Lim
- The Hormel Institute, University of Minnesota, Austin, MN 55912, USA
| | - Myoung Ok Kim
- The Hormel Institute, University of Minnesota, Austin, MN 55912, USA.,Center for Laboratory Animal Resources, School of Animal Biotechnology, Kyungpook National University, Dae-gu, 700-842, Republic of Korea
| | - Young-Yeon Cho
- Department of Pharmacology, College of Pharmacy, The Catholic University of Korea, Bucheon 420-743, Republic of Korea
| | - Angelo Pugliese
- The Hormel Institute, University of Minnesota, Austin, MN 55912, USA
| | - Jung-Hyun Shim
- The Hormel Institute, University of Minnesota, Austin, MN 55912, USA.,College of Pharmacy, Mokpo National University, Muan-gun, Jeonnam 534-729, Republic of Korea
| | - Hanyong Chen
- The Hormel Institute, University of Minnesota, Austin, MN 55912, USA
| | - Eun Jin Cho
- The Hormel Institute, University of Minnesota, Austin, MN 55912, USA
| | - Jong-Eun Kim
- The Hormel Institute, University of Minnesota, Austin, MN 55912, USA
| | - Sun Chul Kang
- Department of Biotechnology, Daegu University, Kyoungsan, Kyoungbook 712-714, Republic of Korea
| | - Souren Paul
- Department of Biotechnology, Daegu University, Kyoungsan, Kyoungbook 712-714, Republic of Korea
| | - Hee Eun Kang
- Department of Pharmacology, College of Pharmacy, The Catholic University of Korea, Bucheon 420-743, Republic of Korea
| | - Ji Won Jung
- Department of Pharmacology, College of Pharmacy, The Catholic University of Korea, Bucheon 420-743, Republic of Korea
| | - Sung-Young Lee
- The Hormel Institute, University of Minnesota, Austin, MN 55912, USA
| | - Sung-Hyun Kim
- The Hormel Institute, University of Minnesota, Austin, MN 55912, USA.,Center for Laboratory Animal Resources, School of Animal Biotechnology, Kyungpook National University, Dae-gu, 700-842, Republic of Korea
| | - Kanamata Reddy
- The Hormel Institute, University of Minnesota, Austin, MN 55912, USA
| | - Young Il Yeom
- Biomedical Genomics Research Center, Korea Research Institute of Bioscience & Biotechnology (KRIBB), Daejeon, 305-806, Korea
| | - Ann M Bode
- The Hormel Institute, University of Minnesota, Austin, MN 55912, USA
| | - Zigang Dong
- The Hormel Institute, University of Minnesota, Austin, MN 55912, USA
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9
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Gupta ED, Pachauri M, Ghosh PC, Rajam MV. Targeting polyamine biosynthetic pathway through RNAi causes the abrogation of MCF 7 breast cancer cell line. Tumour Biol 2015; 37:1159-71. [DOI: 10.1007/s13277-015-3912-2] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2015] [Accepted: 08/06/2015] [Indexed: 12/31/2022] Open
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10
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Nowotarski SL, Feith DJ, Shantz LM. Skin Carcinogenesis Studies Using Mouse Models with Altered Polyamines. CANCER GROWTH AND METASTASIS 2015; 8:17-27. [PMID: 26380554 PMCID: PMC4558889 DOI: 10.4137/cgm.s21219] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/07/2015] [Revised: 06/30/2015] [Accepted: 07/01/2015] [Indexed: 12/16/2022]
Abstract
Nonmelanoma skin cancer (NMSC) is a major health concern worldwide. With increasing numbers in high-risk groups such as organ transplant recipients and patients taking photosensitizing medications, the incidence of NMSC continues to rise. Mouse models of NMSC allow us to better understand the molecular signaling cascades involved in skin tumor development in order to identify novel therapeutic strategies. Here we review the models designed to determine the role of the polyamines in NMSC development and maintenance. Elevated polyamines are absolutely required for tumor growth, and dysregulation of their biosynthetic and catabolic enzymes has been observed in NMSC. Studies using mice with genetic alterations in epidermal polyamines suggest that they play key roles in tumor promotion and epithelial cell survival pathways, and recent clinical trials indicate that pharmacological inhibitors of polyamine metabolism show promise in individuals at high risk for NMSC.
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Affiliation(s)
- Shannon L Nowotarski
- Department of Biochemistry, The Pennsylvania State University Berks College, Reading, PA, USA
| | - David J Feith
- University of Virginia Cancer Center and Department of Medicine, Hematology and Oncology, University of Virginia, Charlottesville, VA, USA
| | - Lisa M Shantz
- Department of Cellular and Molecular Physiology, The Pennsylvania State University College of Medicine, Hershey, PA, USA
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Abstract
Multiple molecular mechanisms are involved in the promotion of skin carcinogenesis. Induction of sustained proliferation and epidermal hyperplasia by direct activation of mitotic signaling pathways or indirectly in response to chronic wounding and/or inflammation, or due to a block in terminal differentiation or resistance to apoptosis is necessary to allow clonal expansion of initiated cells with DNA mutations to form skin tumors. The mitotic pathways include activation of epidermal growth factor receptor and Ras/Raf/mitogen-activated protein kinase signaling. Chronic inflammation results in inflammatory cell secretion of growth factors and cytokines such as tumor necrosis factor-α and interleukins, as well as production of reactive oxygen species, all of which can stimulate proliferation. Persistent activation of these pathways leads to tumor promotion.
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12
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Greene JM, Feugang JM, Pfeiffer KE, Stokes JV, Bowers SD, Ryan PL. L-Arginine enhances cell proliferation and reduces apoptosis in human endometrial RL95-2 cells. Reprod Biol Endocrinol 2013; 11:15. [PMID: 23442442 PMCID: PMC3598371 DOI: 10.1186/1477-7827-11-15] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/16/2012] [Accepted: 02/24/2013] [Indexed: 12/03/2022] Open
Abstract
BACKGROUND L-arginine is considered to be one of the most versatile amino acids due to the fact that it serves as a precursor for many important molecules in cellular physiology. When supplemented in the diet, L-arginine can increase the number of implantation sites in mice and rats, suggesting an effect at the level of the endometrium. To this end, this study determined the effect that L-arginine has on apoptosis and cell proliferation in human endometrial RL95-2 cells. RESULTS L-arginine at physiological (200 micromol/L) and supra-physiological (800 micromol/L) concentrations increased cell proliferation at days 2 and 4 post-treatment with a dose-dependent effect being observed on day 2. Additionally, inhibition of nitric oxide (NO) synthase and arginase, which are responsible for the conversion of L-arginine to NO and polyamines, respectively, reduced the proliferative effect of L-arginine. L-arginine also decreased the proportion of cells with TUNEL positive nuclei and increased the ratio of cells with healthy mitochondria compared to cells with a disrupted mitochondrial membrane potential, indicating that L-arginine prevents mitochondrial mediated apoptosis in endometrial RL95-2 cells. Furthermore, exposure to L-arginine did not affect total BAD protein expression; however, L-arginine increased the abundance of phosphorylated BAD protein. CONCLUSIONS In summary, L-arginine added to the culture media at physiological (200 micromol/L) and supraphysiological concentrations (800 micromol/L) enhanced endometrial RL95-2 cell proliferation through mechanisms mediated by NO and polyamine biosynthesis. In addition, L-arginine reduced endometrial RL95-2 mitochondrial mediated apoptosis through increased phosphorylation of BAD protein.
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Affiliation(s)
- Jonathan M Greene
- Department of Pathobiology and Population Medicine, Mississippi State University, Mississippi State, MS, USA
- Department of Animal and Dairy Sciences, Mississippi State University, Mississippi State, MS, USA
- Facility for Organismal and Cellular Imaging, Mississippi State University, Mississippi State, Mississippi, USA
| | - Jean M Feugang
- Department of Animal and Dairy Sciences, Mississippi State University, Mississippi State, MS, USA
- Facility for Organismal and Cellular Imaging, Mississippi State University, Mississippi State, Mississippi, USA
| | - Kathryn E Pfeiffer
- Department of Animal and Dairy Sciences, Mississippi State University, Mississippi State, MS, USA
| | - John V Stokes
- Department of Basic Sciences, Mississippi State University, Mississippi State, Mississippi, USA
| | - Susan D Bowers
- Department of Animal and Dairy Sciences, Mississippi State University, Mississippi State, MS, USA
- Facility for Organismal and Cellular Imaging, Mississippi State University, Mississippi State, Mississippi, USA
| | - Peter L Ryan
- Department of Pathobiology and Population Medicine, Mississippi State University, Mississippi State, MS, USA
- Department of Animal and Dairy Sciences, Mississippi State University, Mississippi State, MS, USA
- Facility for Organismal and Cellular Imaging, Mississippi State University, Mississippi State, Mississippi, USA
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13
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Gerhart J, Hayes C, Scheinfeld V, Chernick M, Gilmour S, George-Weinstein M. Myo/Nog cells in normal, wounded and tumor-bearing skin. Exp Dermatol 2012; 21:466-8. [PMID: 22621191 DOI: 10.1111/j.1600-0625.2012.01503.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Murine and human skin were examined for the presence of Myo/Nog cells that were originally discovered in the chick embryo by their expression of MyoD mRNA, noggin and the G8 antigen. Myo/Nog cells are the primary source of noggin in telogen hair follicles. They are scarce within the interfollicular dermis and absent in the epidermis. Within 24 h following epidermal abrasion, Myo/Nog cells increase in number in the follicles and appear in the wound. Myo/Nog cells are also recruited to the stroma of tumors formed from v-Ras-transformed keratinocytes (Ker/Ras). Human squamous cell carcinomas and malignant melanomas contain significantly more Myo/Nog cells than basal cell carcinomas. Myo/Nog cells are distinct from macrophages, granulocytes and cells expressing alpha smooth muscle actin in the tumor stroma. Myo/Nog cells may be modulators of skin homoeostasis and wound healing, and potential diagnostic and therapeutic targets in skin cancer.
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14
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Xu X, Liu Z, Fang M, Yu H, Liang X, Li X, Liu X, Chen C, Jia J. Helicobacter pylori CagA induces ornithine decarboxylase upregulation via Src/MEK/ERK/c-Myc pathway: implication for progression of gastric diseases. Exp Biol Med (Maywood) 2012; 237:435-41. [PMID: 22442341 DOI: 10.1258/ebm.2011.011199] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Helicobacter pylori (H. pylori) dysregulates the expression of various genes resulting in gastric precursor lesions and cancer. Meanwhile, ornithine decarboxylase (ODC) is a key enzyme that catalyzes the formation of polyamines which are critical for cell growth. So far, the possible regulation of ODC by H. pylori and its virulence factors, and the associated mechanism in gastric epithelial cells remains undefined. In the present study, we found that cellular ODC protein was upregulated by wild-type H. pylori infection and ectopic expression of a cytotoxin-associated gene A (CagA). As a negative control, there was no such effect by cagA-mutant H. pylori infection. Results of signal protein inhibitor treatment demonstrated that the Src, MEK (mitogen-activated protein kinase kinase) and ERK (extracellular signal-regulated kinase) pathway was involved. Moreover, when c-Myc was inhibited, the stimulatory effect of CagA on ODC expression was abolished. Clinically, a positive correlation between c-Myc and ODC expression was observed in patient-derived abnormal gastric tissues. These results implied that the Src/MEK/ERK/c-Myc pathway was required for CagA-mediated ODC induction. Finally, inhibition of ODC expression led to decreased foci formation of gastric epithelial cells before and after H. pylori infection, and ODC protein was over-expressed in precancerous gastric lesions and primary gastric cancer. Collectively, our findings provide new insights into the mechanism behind H. pylori-infection-associated gastric diseases.
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Affiliation(s)
- Xia Xu
- Department of Microbiology, Key Laboratory for Experimental Teratology of Chinese Ministry of Education, Shandong University, Jinan 250012, PR China
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15
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Olsen RR, Zetter BR. Evidence of a role for antizyme and antizyme inhibitor as regulators of human cancer. Mol Cancer Res 2011; 9:1285-93. [PMID: 21849468 DOI: 10.1158/1541-7786.mcr-11-0178] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Antizyme and its endogenous antizyme inhibitor have recently emerged as prominent regulators of cell growth, transformation, centrosome duplication, and tumorigenesis. Antizyme was originally isolated as a negative modulator of the enzyme ornithine decarboxylase (ODC), an essential component of the polyamine biosynthetic pathway. Antizyme binds ODC and facilitates proteasomal ODC degradation. Antizyme also facilitates degradation of a set of cell cycle regulatory proteins, including cyclin D1, Smad1, and Aurora A kinase, as well as Mps1, a protein that regulates centrosome duplication. Antizyme has been reported to function as a tumor suppressor and to negatively regulate tumor cell proliferation and transformation. Antizyme inhibitor binds to antizyme and suppresses its known functions, leading to increased polyamine synthesis, increased cell proliferation, and increased transformation and tumorigenesis. Gene array studies show antizyme inhibitor to be amplified in cancers of the ovary, breast, and prostate. In this review, we summarize the current literature on the role of antizyme and antizyme inhibitor in cancer, discuss how the ratio of antizyme to antizyme inhibitor can influence tumor growth, and suggest strategies to target this axis for tumor prevention and treatment.
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Affiliation(s)
- Rachelle R Olsen
- Vascular Biology Program, Department of Surgery, Children's Hospital Boston, MA, USA
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16
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Hayes CS, Defeo K, Dang H, Trempus CS, Morris RJ, Gilmour SK. A prolonged and exaggerated wound response with elevated ODC activity mimics early tumor development. Carcinogenesis 2011; 32:1340-8. [PMID: 21730362 DOI: 10.1093/carcin/bgr129] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Induction of ornithine decarboxylase (ODC), a key enzyme in polyamine biosynthesis, in ODC transgenic skin stimulates epidermal proliferation but not hyperplasia, activates underlying stromal cells and promotes skin tumorigenesis following a single subthreshold dose of a carcinogen. Because chronic wounds are a well-recognized risk factor for skin cancer, we investigated the response to a tissue remodeling event in normal skin that is abraded to remove only the epidermal layer in K6/ODC transgenic (follicular ODC expression) and in inducible ODCER transgenic mice (suprabasal ODC expression). When regenerative epidermal hyperplasia was resolved in normal littermates following abrasion, ODC transgenic mice exhibited progressive epidermal hyperplasia with formation of benign tumor growths and maintained an increased epidermal proliferation index and activation of translation-associated proteins at abrasion sites. The epidermal hyperplasia and tumor-like growth was accompanied by activation of underlying stromal cells and prolonged infiltration of inflammatory cells. Treatment with the anti-inflammatory agent dexamethasone did not reduce the high proliferative index in the regenerated epidermis but dramatically reduced the epidermal hyperplasia and prevented the wound-induced tumor growths in abraded ODCER skin. Treatment with α-difluoromethylornithine, a specific inhibitor of ODC activity, normalized the wound response in transgenic mice and decreased wound-induced inflammation if administered from the time of abrasion but not if initiated 4 days following abrasion. These results suggest a role for polyamines in prolonging wound-associated inflammation in addition to stimulating proliferation both of which are sufficient to sustain epidermal hyperplasia and benign tumor growth even in the absence of genetic damage.
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Affiliation(s)
- Candace S Hayes
- Lankenau Institute for Medical Research, Wynnewood, PA 19096, USA
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17
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Abstract
Polyamines are organic cations shown to control gene expression at the transcriptional, posttranscriptional, and translational levels. Multiple cellular oncogenic pathways are involved in regulation of transcription and translation of polyamine-metabolizing enzymes. As a consequence of genetic alterations, expression levels and activities of polyamine-metabolizing enzymes change rapidly during tumorigenesis resulting in high levels of polyamines in many human epithelial tumors. This review summarizes the mechanisms of polyamine regulation by canonical tumor suppressor genes and oncogenes, as well as the role of eukaryotic initiation factor 5A (EIF5A) in cancer. The importance of research utilizing pharmaceutical inhibitors and cancer chemopreventive strategies targeting the polyamine pathway is also discussed.
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Affiliation(s)
- Edwin A Paz
- Cancer Biology Interdisciplinary Graduate Program, Arizona Cancer Center, University of Arizona, Tucson, Arizona, USA
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18
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Culjkovic B, Tan K, Orolicki S, Amri A, Meloche S, Borden KLB. The eIF4E RNA regulon promotes the Akt signaling pathway. ACTA ACUST UNITED AC 2008; 181:51-63. [PMID: 18391071 PMCID: PMC2287285 DOI: 10.1083/jcb.200707018] [Citation(s) in RCA: 75] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Eukaryotic initiation factor 4E (eIF4E) promotes cellular proliferation and can rescue cells from apoptotic stimuli such as serum starvation. However, the mechanisms underlying apoptotic rescue are not well understood. In this study, we demonstrate that eIF4E overexpression leads to enhanced survival signaling through Akt and that eIF4E requires Akt1 to rescue serum-deprived fibroblasts. Furthermore, a mutant form of eIF4E (W73A), which is messenger RNA (mRNA) export competent but does not promote translation, rescues cells as readily as wild-type eIF4E. We show that eIF4E mediates Akt activation via up-regulation of Nijmegen breakage syndrome 1 (NBS1), a phosphoinositide-3 kinase–Akt pathway upstream activator. Additionally, eIF4E coordinately up-regulates the expression of downstream effectors of the Akt pathway, thereby amplifying Akt signaling effects. A negative regulator of eIF4E, the promyelocytic leukemia protein (PML), suppresses Akt activation and apoptotic rescue. These PML activities likely arise, at least in part, through its inhibition of eIF4E-mediated NBS1 mRNA export. In summary, eIF4E coordinately regulates gene expression to potentiate Akt activation, an activity required for apoptotic rescue.
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Affiliation(s)
- Biljana Culjkovic
- Institute for Research in Immunology and Cancer, Université de Montréal, Montréal, Québec H4M 1J6, Canada
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19
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Abstract
Studies over many years have suggested that increased polyamine synthesis may be necessary for neoplastic growth. This review summarizes recent work on the regulation of putrescine production both de novo and via the degradation of higher polyamines and provides a summary of studies using transgenic mice in which the levels of proteins that regulate these processes (L-ornithine decarboxylase, antizyme and spermidine/spermine-N(1)-acetyltransferase) are altered.
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Affiliation(s)
- A E Pegg
- Department of Cellular and Molecular Physiology, The Pennsylvania State University College of Medicine, Hershey, PA 17033, USA.
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20
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Shantz LM, Levin VA. Regulation of ornithine decarboxylase during oncogenic transformation: mechanisms and therapeutic potential. Amino Acids 2007; 33:213-23. [PMID: 17443268 DOI: 10.1007/s00726-007-0531-2] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2006] [Accepted: 02/01/2007] [Indexed: 01/10/2023]
Abstract
The activity of ornithine decarboxylase (ODC(1)), the first enzyme in polyamine biosynthesis, is induced during carcinogenesis by a variety of oncogenic stimuli. Intracellular levels of ODC and the polyamines are tightly controlled during normal cell growth, and regulation occurs at the levels of transcription, translation and protein degradation. Several known proto-oncogenic pathways appear to control ODC transcription and translation, and dysregulation of pathways downstream of ras and myc result in the constitutive elevation of ODC activity that occurs with oncogenesis. Inhibition of ODC activity reverts the transformation of cells in vitro and reduces tumor growth in several animal models, suggesting high levels of ODC are necessary for the maintenance of the transformed phenotype. The ODC irreversible inactivator DFMO has proven to be not only a valuable tool in the study of ODC in cancer, but also shows promise as a chemopreventive and chemotherapeutic agent in certain types of malignancies.
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Affiliation(s)
- L M Shantz
- Department of Cellular and Molecular Physiology, The Pennsylvania State University College of Medicine, Hershey, PA 17033, USA.
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21
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Gilmour SK. Polyamines and nonmelanoma skin cancer. Toxicol Appl Pharmacol 2006; 224:249-56. [PMID: 17234230 PMCID: PMC2098876 DOI: 10.1016/j.taap.2006.11.023] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2006] [Revised: 11/15/2006] [Accepted: 11/16/2006] [Indexed: 12/31/2022]
Abstract
Elevated levels of polyamines have long been associated with skin tumorigenesis. Tightly regulated metabolism of polyamines is critical for cell survival and normal skin homeostasis, and these controls are dysregulated in skin tumorigenesis. A key enzyme in polyamine biosynthesis, ornithine decarboxylase (ODC) is upregulated in skin tumors compared to normal skin. Use of transgenic mouse models has demonstrated that polyamines play an essential role in the early promotional phase of skin tumorigenesis. The formation of skin tumors in these transgenic mice is dependent upon polyamine biosynthesis, especially putrescine, since treatment with inhibitors of ODC activity blocks the formation of skin tumors and causes the rapid regression of existing tumors. Although the mechanism by which polyamines promote skin tumorigenesis are not well understood, elevated levels of polyamines have been shown to stimulate epidermal proliferation, alter keratinocyte differentiation status, increase neovascularization, and increase synthesis of extracellular matrix proteins in a manner similar to that seen in wound healing. It is becoming increasingly apparent that elevated polyamine levels activate not only epidermal cells but also underlying stromal cells in the skin to promote the development and progression of skin tumors. The inhibition of polyamine biosynthesis has potential to be an effective chemoprevention strategy for nonmelanoma skin cancer.
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Affiliation(s)
- Susan K Gilmour
- Lankenau Institute for Medical Research, 100 Lancaster Avenue, Wynnewood, PA 19096, USA.
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22
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Feith DJ, Origanti S, Shoop PL, Sass-Kuhn S, Shantz LM. Tumor suppressor activity of ODC antizyme in MEK-driven skin tumorigenesis. Carcinogenesis 2006; 27:1090-8. [PMID: 16400186 DOI: 10.1093/carcin/bgi343] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
To test the hypothesis that suppression of ornithine decarboxylase (ODC) activity blocks the promotion of target cells in the outer root sheath of the hair follicle initiated by Raf/MEK/ERK activation, we crossed mice overexpressing an activated MEK mutant in the skin (K14-MEK mice) with two transgenic lines overexpressing antizyme (AZ), which binds to ODC and targets it for degradation. K14-MEK mice develop spontaneous skin tumors without initiation or promotion. These mice on the ICR background were crossed with K5-AZ and K6-AZ mice on both the carcinogenesis-resistant C57BL/6 background and the sensitive DBA/2 background. Expression of AZ driven by either the K5 or K6 promoter along with K14-MEK dramatically delayed tumor incidence and reduced tumor multiplicity on both backgrounds compared with littermates expressing the MEK transgene alone. The effect was most remarkable in the MEK/K6-AZ mice from the ICR/D2 F1 cross, where double transgenic mice averaged less than one tumor per mouse for more than 8 weeks, while K14-MEK mice averaged over 13 tumors per mouse at this age. Putrescine was decreased in MEK/AZ tumors, while spermidine and spermine levels were unaffected, suggesting that the primary role played by AZ in this system is to inhibit putrescine accumulation. MEK/AZ tumors did not show evidence of apoptosis, but there was a 15-20% decrease in S-phase cells and a 40-60% decrease in mitotic cells in MEK/AZ tumors. These results indicate that the principal effect of AZ may be to slow cell growth primarily by increasing G2/M transit time.
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Affiliation(s)
- David J Feith
- Department of Cellular and Molecular Physiology, The Milton S. Hershey Medical Center, The Pennsylvania State University College of Medicine, Hershey, PA 17033, USA
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