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Chiorean EG, Von Hoff DD, Reni M, Arena FP, Infante JR, Bathini VG, Wood TE, Mainwaring PN, Muldoon RT, Clingan PR, Kunzmann V, Ramanathan RK, Tabernero J, Goldstein D, McGovern D, Lu B, Ko A. CA19-9 decrease at 8 weeks as a predictor of overall survival in a randomized phase III trial (MPACT) of weekly nab-paclitaxel plus gemcitabine versus gemcitabine alone in patients with metastatic pancreatic cancer. Ann Oncol 2016; 27:654-60. [PMID: 26802160 PMCID: PMC4803454 DOI: 10.1093/annonc/mdw006] [Citation(s) in RCA: 73] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2015] [Accepted: 12/23/2015] [Indexed: 12/17/2022] Open
Abstract
Any CA19-9 decline at week 8 and radiologic response by week 8 each predicted longer OS in both treatment arms. In the nab-P + Gem arm, the higher proportion of patients with week 8 CA19-9 decrease [82% (206/252); median OS 13.2 months] than a RECIST-defined response [16% (40/252); median OS 13.7 months] suggests that CA19-9 decline is a predictor of OS applicable to a larger population. Background A phase I/II study and subsequent phase III study (MPACT) reported significant correlations between CA19-9 decreases and prolonged overall survival (OS) with nab-paclitaxel plus gemcitabine (nab-P + Gem) treatment for metastatic pancreatic cancer (MPC). CA19-9 changes at week 8 and potential associations with efficacy were investigated as part of an exploratory analysis in the MPACT trial. Patients and methods Untreated patients with MPC (N = 861) received nab-P + Gem or Gem alone. CA19-9 was evaluated at baseline and every 8 weeks. Results Patients with baseline and week-8 CA19-9 measurements were analyzed (nab-P + Gem: 252; Gem: 202). In an analysis pooling the treatments, patients with any CA19-9 decline (80%) versus those without (20%) had improved OS (median 11.1 versus 8.0 months; P = 0.005). In the nab-P + Gem arm, patients with (n = 206) versus without (n = 46) any CA19-9 decrease at week 8 had a confirmed overall response rate (ORR) of 40% versus 13%, and a median OS of 13.2 versus 8.3 months (P = 0.001), respectively. In the Gem-alone arm, patients with (n = 159) versus without (n = 43) CA19-9 decrease at week 8 had a confirmed ORR of 15% versus 5%, and a median OS of 9.4 versus 7.1 months (P = 0.404), respectively. In the nab-P + Gem and Gem-alone arms, by week 8, 16% (40/252) and 6% (13/202) of patients, respectively, had an unconfirmed radiologic response (median OS 13.7 and 14.7 months, respectively), and 79% and 84% of patients, respectively, had stable disease (SD) (median OS 11.1 and 9 months, respectively). Patients with SD and any CA19-9 decrease (158/199 and 133/170) had a median OS of 13.2 and 9.4 months, respectively. Conclusion This analysis demonstrated that, in patients with MPC, any CA19-9 decrease at week 8 can be an early marker for chemotherapy efficacy, including in those patients with SD. CA19-9 decrease identified more patients with survival benefit than radiologic response by week 8.
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Lee MS, Jeong MH, Lee HW, Han HJ, Ko A, Hewitt SM, Kim JH, Chun KH, Chung JY, Lee C, Cho H, Song J. PI3K/AKT activation induces PTEN ubiquitination and destabilization accelerating tumourigenesis. Nat Commun 2015; 6:7769. [PMID: 26183061 PMCID: PMC4518267 DOI: 10.1038/ncomms8769] [Citation(s) in RCA: 117] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2015] [Accepted: 06/08/2015] [Indexed: 12/16/2022] Open
Abstract
The activity of the phosphatase and tensin homologue (PTEN) is known to be suppressed via post-translational modification. However, the mechanism and physiological significance by which post-translational modifications lead to PTEN suppression remain unclear. Here we demonstrate that PTEN destabilization is induced by EGFR- or oncogenic PI3K mutation-mediated AKT activation in cervical cancer. EGFR/PI3K/AKT-mediated ubiquitination and degradation of PTEN are dependent on the MKRN1 E3 ligase. These processes require the stabilization of MKRN1 via AKT-mediated phosphorylation. In cervical cancer patients with high levels of pAKT and MKRN1 expression, PTEN protein levels are low and correlate with a low 5-year survival rate. Taken together, our results demonstrate that PI3K/AKT signals enforce positive-feedback regulation by suppressing PTEN function. Mutations and post-translational modifications of the PI3K/AKT pathway inhibitor PTEN are a feature of many cancers, but these have not been associated with cervical cancer. Here, the authors identify a PI3K/AKT-mediated ubiquitination degradation pathway of PTEN that occurs in patients with cervical cancer.
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McEneny J, Henry S, Fogarty M, Ko A, Ingle L, Young I, Cleland J. Inflammation and peroxidation of HDL are increased in subjects with chronic heart failure. Atherosclerosis 2015. [DOI: 10.1016/j.atherosclerosis.2015.04.380] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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Fidelman N, Kerlan R, Taylor A, Kolli K, Kohi M, Hawkins R, Pampaloni M, Atreya C, Bergsland E, Kelley R, Ko A, Korn W, Van Loon K, Luan J, McWhirter R, Johanson C, Venook A. Radioembolization with 490Y glass microspheres for the treatment of unresectable metastatic liver disease from chemotherapy-refractory gastrointestinal cancers: final report of a prospective pilot study. J Vasc Interv Radiol 2015. [DOI: 10.1016/j.jvir.2014.12.511] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
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Ko A, Maslowski A, Jaffe W, Visser A. Rotablation in the treatment of patients with heavily calcified coronary artery disease. Heart Lung Circ 2015. [DOI: 10.1016/j.hlc.2015.04.131] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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Hirsh V, Page R, Ko A, Renshler M, Socinski M. Analysis of Predictive Factors in a Phase 3 Trial of Nab-Paclitaxel (nab-P) Plus Carboplatin (C) as First-Line Therapy for Patients (Pts) With Advanced Non-Small Cell Lung Cancer (NSCLC). Int J Radiat Oncol Biol Phys 2014. [DOI: 10.1016/j.ijrobp.2014.08.228] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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Hirsh V, Owen S, Ko A, Renschler M, Socinski M. Analysis of Outcomes in Diabetic Patients in a Phase 3 Trial of Nab-Paclitaxel (nab-P) Plus Carboplatin (C) in the First-Line Treatment of Advanced Non-Small Cell Lung Cancer (NSCLC). Int J Radiat Oncol Biol Phys 2014. [DOI: 10.1016/j.ijrobp.2014.08.176] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Baek MH, Suk H, Jung P, Ko A, Han WS, Lee SW, Park JY, Kim D, Kim JH, Kim YM, Kim YT, Nam JH. Feasibility and Safety of Laparoscopic Surgery for Obese Korean Women with Endometrial Cancer: Long-Term Results at a Single Institution. J Minim Invasive Gynecol 2014. [DOI: 10.1016/j.jmig.2014.08.612] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Cortes J, Ji X, Lin F, Whiting S, Ko A, Bravo M, Fandi A, Botteman M. Mean Overall Survival (Os) and Quality-Adjusted Time Without Symptoms or Toxicity (Q-Twist) of Nanoparticle Albumin-Bound Paclitaxel (Nab-P) Vs Conventional Solvent-Based Paclitaxel (Sb-P) in Metastatic Breast Cancer. Ann Oncol 2014. [DOI: 10.1093/annonc/mdu329.19] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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Spigel D, Ko A, Ong T, West H, Kim E, Reynolds C. Abound.Sqm: a Phase 3 Randomized Study of Maintenance Nab-Paclitaxel (Nab-P) After Induction Therapy with Nab-P Plus Carboplatin (C) in Patients (Pts) with Squamous Cell (Scc) Non-Small Cell Lung Cancer (Nsclc). Ann Oncol 2014. [DOI: 10.1093/annonc/mdu348.26] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Wilke H, Clingan P, Ananda S, Kurteva G, Suuroja T, Folprecht G, Beny A, Pastorelli D, Cesas A, Toganel C, Bodoky G, Lipatov O, Limon M, Cunningham D, Cummins S, Wainberg Z, Ko A, Emig M, Chandrawansa K, Van Cutsem E. Rainbow: A Global, Phase 3, Double-Blind Study of Ramucirumab Plus Paclitaxel Versus Placebo Plus Paclitaxel in the Treatment of Gastric Cancer Following Disease Progression: Western Population Subgroup. Ann Oncol 2014. [DOI: 10.1093/annonc/mdu193.6] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
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Deutsch E, Ko A, Perfettini J. 56: Impact of tumor autophagy on solid tumors response to IR; role of the tumor stroma. Radiother Oncol 2014. [DOI: 10.1016/s0167-8140(15)34077-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Ko A, Kanehisa A, Martins I, Senovilla L, Chargari C, Dugue D, Mariño G, Kepp O, Michaud M, Perfettini JL, Kroemer G, Deutsch E. Autophagy inhibition radiosensitizes in vitro, yet reduces radioresponses in vivo due to deficient immunogenic signalling. Cell Death Differ 2014; 21:92-9. [PMID: 24037090 PMCID: PMC3857616 DOI: 10.1038/cdd.2013.124] [Citation(s) in RCA: 163] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2013] [Revised: 07/03/2013] [Accepted: 07/10/2013] [Indexed: 12/15/2022] Open
Abstract
Clinical oncology heavily relies on the use of radiotherapy, which often leads to merely transient responses that are followed by local or distant relapse. The molecular mechanisms explaining radioresistance are largely elusive. Here, we identified a dual role of autophagy in the response of cancer cells to ionizing radiation. On one hand, we observed that the depletion of essential autophagy-relevant gene products, such as ATG5 and Beclin 1, increased the sensitivity of human or mouse cancer cell lines to irradiation, both in vitro (where autophagy inhibition increased radiation-induced cell death and decreased clonogenic survival) and in vivo, after transplantation of the cell lines into immunodeficient mice (where autophagy inhibition potentiated the tumour growth-inhibitory effect of radiotherapy). On the other hand, when tumour proficient or deficient for autophagy were implanted in immunocompetent mice, it turned out that defective autophagy reduced the efficacy of radiotherapy. Indeed, radiotherapy elicited an anti-cancer immune response that was dependent on autophagy-induced ATP release from stressed or dying tumour cells and was characterized by dense lymphocyte infiltration of the tumour bed. Intratumoural injection of an ecto-ATPase inhibitor restored the immune infiltration of autophagy-deficient tumours post radiotherapy and improved the growth-inhibitory effect of ionizing irradiation. Altogether, our results reveal that beyond its cytoprotective function, autophagy confers immunogenic properties to tumours, hence amplifying the efficacy of radiotherapy in an immunocompetent context. This has far-reaching implications for the development of pharmacological radiosensitizers.
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Korenaga T, Ko A, Shimada K. Low-Temperature Rh-Catalyzed Asymmetric 1,4-Addition of Arylboronic Acids to α,β-Unsaturated Carbonyl Compounds. J Org Chem 2013; 78:9975-80. [DOI: 10.1021/jo4014707] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Lee EW, Kim JH, Ahn YH, Seo J, Ko A, Jeong M, Kim SJ, Ro JY, Park KM, Lee HW, Park EJ, Chun KH, Song J. Ubiquitination and degradation of the FADD adaptor protein regulate death receptor-mediated apoptosis and necroptosis. Nat Commun 2012; 3:978. [PMID: 22864571 DOI: 10.1038/ncomms1981] [Citation(s) in RCA: 90] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2011] [Accepted: 06/28/2012] [Indexed: 12/15/2022] Open
Abstract
Fas-associated protein with death domain (FADD) is a pivotal component of death receptor-mediated extrinsic apoptosis and necroptosis. Here we show that FADD is regulated by Makorin Ring Finger Protein 1 (MKRN1) E3 ligase-mediated ubiquitination and proteasomal degradation. MKRN1 knockdown results in FADD protein stabilization and formation of the rapid death-inducing signalling complex, which causes hypersensitivity to extrinsic apoptosis by facilitating caspase-8 and caspase-3 cleavage in response to death signals. We also show that MKRN1 and FADD are involved in the regulation of necrosome formation and necroptosis upon caspase inhibition. Downregulation of MKRN1 results in severe defects of tumour growth upon tumour necrosis factor-related apoptosis-inducing ligand treatment in a xenograft model using MDA-MB-231 breast cancer cells. Suppression of tumour growth by MKRN1 depletion is relieved by simultaneous FADD knockdown. Our data reveal a novel mechanism by which fas-associated protein with death domain is regulated via an ubiquitination-induced degradation pathway.
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Ko A, Shin JY, Seo J, Lee KD, Lee EW, Lee MS, Lee HW, Choi IJ, Jeong JS, Chun KH, Song J. Acceleration of gastric tumorigenesis through MKRN1-mediated posttranslational regulation of p14ARF. J Natl Cancer Inst 2012; 104:1660-72. [PMID: 23104211 PMCID: PMC3490844 DOI: 10.1093/jnci/djs424] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Background We investigated whether Makorin ring finger protein 1 (MKRN1), an E3 ligase, affects p14ARF-associated cellular senescence and tumorigenesis by posttranslational modification in gastric tumorigenesis. Methods A link between MKRN1 and ARF was examined in MKRN1 null mouse embryonic fibroblasts (MEFs) and in human fibroblasts and gastric cancer cells by silencing MKRN1 using small interfering RNA (siRNA) and short hairpin RNA (shRNA). Ubiquitination and proteasomal degradation assays were used to assess p14ARF degradation associated with MKRN1. MKRN1 and p14ARF expression levels were analyzed with immunohistochemistry in malignant and normal tissues from gastric cancer patients and with χ2 tests. The tumor growth of gastric cancer cells stably expressing MKRN1 shRNA, p14ARF shRNA, or both was examined in mouse xenograft models (n = 4–6) and analyzed with unpaired t tests. All statistical tests were two-sided. Results MKRN1 knockout MEFs exhibited premature senescence and growth retardation with increased p19ARF protein expression. Similar results were obtained for human fibroblasts or gastric cancer cell lines by MKRN1 knockdown. Biochemical analyses confirmed that MKRN1 targets p14ARF for ubiquitination and subsequent proteasome-dependent degradation. A statistically significant association was shown between MKRN1 overexpression and p14ARF underexpression (P = .016). Xenograft analyses using p53-functional AGS or -dysfunctional SNU601 cells displayed statistically significant tumor growth retardation by silencing MKRN1, which was reversed under depletion of p14ARF (AGS cells, MKRN1 knockdown tumors vs MKRN1 and p14ARF knockdown tumors: 164.6 vs 464.8mm3, difference = 300.2mm3, 95% CI = 189.1 to 411.3mm3, P < .001). Conclusions We demonstrated that MKRN1 functions as a novel E3 ligase of p14ARF and that it potentially regulates cellular senescence and tumorigenesis in gastric cancer.
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Hornung T, Ko A, Tüting T, Bieber T, Wenzel J. Efficacy of low-dose methotrexate in the treatment of dermatomyositis skin lesions. Clin Exp Dermatol 2011; 37:139-42. [DOI: 10.1111/j.1365-2230.2011.04188.x] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Korenaga T, Ko A, Uotani K, Tanaka Y, Sakai T. Synthesis and Application of 2,6-Bis(trifluoromethyl)-4-pyridyl Phosphanes: The Most Electron-Poor Aryl Phosphanes with Moderate Bulkiness. Angew Chem Int Ed Engl 2011; 50:10703-7. [DOI: 10.1002/anie.201104588] [Citation(s) in RCA: 66] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2011] [Indexed: 11/11/2022]
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Korenaga T, Ko A, Uotani K, Tanaka Y, Sakai T. Synthesis and Application of 2,6-Bis(trifluoromethyl)-4-pyridyl Phosphanes: The Most Electron-Poor Aryl Phosphanes with Moderate Bulkiness. Angew Chem Int Ed Engl 2011. [DOI: 10.1002/ange.201104588] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Carvalho M, Claudio S, Boaventura E, Ribeiro G, Quintana M, Nobre A, Diggle P, Reis M, Ko A. P2-506 Influence of climate on the incidence of urban leptospirosis. Br J Soc Med 2011. [DOI: 10.1136/jech.2011.142976m.33] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
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Kraus VB, Burnett B, Coindreau J, Cottrell S, Eyre D, Gendreau M, Gardiner J, Garnero P, Hardin J, Henrotin Y, Heinegård D, Ko A, Lohmander LS, Matthews G, Menetski J, Moskowitz R, Persiani S, Poole AR, Rousseau JC, Todman M. Application of biomarkers in the development of drugs intended for the treatment of osteoarthritis. Osteoarthritis Cartilage 2011; 19:515-42. [PMID: 21396468 PMCID: PMC3568396 DOI: 10.1016/j.joca.2010.08.019] [Citation(s) in RCA: 220] [Impact Index Per Article: 16.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/22/2010] [Revised: 08/21/2010] [Accepted: 08/28/2010] [Indexed: 02/02/2023]
Abstract
OBJECTIVE Osteoarthritis (OA) is a chronic and slowly progressive disease for which biomarkers may be able to provide a more rapid indication of therapeutic responses to therapy than is currently available; this could accelerate and facilitate OA drug discovery and development programs. The goal of this document is to provide a summary and guide to the application of in vitro (biochemical and other soluble) biomarkers in the development of drugs for OA and to outline and stimulate a research agenda that will further this goal. METHODS The Biomarkers Working Group representing experts in the field of OA biomarker research from both academia and industry developed this consensus document between 2007 and 2009 at the behest of the Osteoarthritis Research Society International Federal Drug Administration initiative (OARSI FDA initiative). RESULTS This document summarizes definitions and classification systems for biomarkers, the current outcome measures used in OA clinical trials, applications and potential utility of biomarkers for development of OA therapeutics, the current state of qualification of OA-related biomarkers, pathways for biomarker qualification, critical needs to advance the use of biomarkers for drug development, recommendations regarding practices and clinical trials, and a research agenda to advance the science of OA-related biomarkers. CONCLUSIONS Although many OA-related biomarkers are currently available they exist in various states of qualification and validation. The biomarkers that are likely to have the earliest beneficial impact on clinical trials fall into two general categories, those that will allow targeting of subjects most likely to either respond and/or progress (prognostic value) within a reasonable and manageable time frame for a clinical study (for instance within 1-2 years for an OA trial), and those that provide early feedback for preclinical decision-making and for trial organizers that a drug is having the desired biochemical effect. As in vitro biomarkers are increasingly investigated in the context of specific drug treatments, advances in the field can be expected that will lead to rapid expansion of the list of available biomarkers with increasing understanding of the molecular processes that they represent.
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Lönnies M, Hoffmann B, Bock E, Hertel S, Viehmann A, Jöckel K, Pannier F, Ko A, Berboth G, Rabe E. Assoziation sozioökonomischer Faktoren mit Inzidenz und Progression chronischer phlebologischer Erkrankungen. DAS GESUNDHEITSWESEN 2010. [DOI: 10.1055/s-0030-1266451] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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Korenaga T, Abe K, Ko A, Maenishi R, Sakai T. Ligand Electronic Effect on Reductive Elimination of Biphenyl from cis-[Pt(Ph)2(diphosphine)] Complexes Bearing Electron-Poor Diphosphine: Correlation Study between Experimental and Theoretical Results. Organometallics 2010. [DOI: 10.1021/om100073j] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Oh W, Lee EW, Lee D, Yang MR, Ko A, Yoon CH, Lee HW, Bae YS, Choi CY, Song J. Hdm2 negatively regulates telomerase activity by functioning as an E3 ligase of hTERT. Oncogene 2010; 29:4101-12. [PMID: 20453884 DOI: 10.1038/onc.2010.160] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
In this study, we identified posttranslational regulation of human telomerase reverse-transcriptase (hTERT) by the E3 ligase Hdm2. The telomerase activity generated by exogenous hTERT in U2OS cells was reduced on adriamycin treatment. The overexpressed levels of hTERT were also decreased under the same conditions. These processes were reversed by treatment with a proteasome inhibitor or depletion of Hdm2. Furthermore, intrinsic telomerase activity was increased in HCT116 cells with ablation of Hdm2. Immunoprecipitation analyses showed that hTERT and Hdm2 bound to each other in multiple domains. Ubiquitination analyses showed that Hdm2 could polyubiquitinate hTERT principally at the N-terminus, which was further degraded in a proteasome-dependent manner. An hTERT mutant with all five lysine residues at the N-terminus of hTERT that mutated to arginine became resistant to Hdm2-mediated ubiquitination and degradation. In U2OS cells, depletion of Hdm2 or addition of the Hdm2-resistant hTERT mutant strengthened the cellular protective effects against apoptosis. Similar results were obtained with the Hdm2-stable H1299 cell line. These observations indicate that Hdm2 is an E3 ligase of hTERT.
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Rabe E, Pannier F, Ko A, Berboth G, Hoffmann B, Hertel S. Incidence of Varicose Veins, Chronic Venous Insufficiency, and Progression of the Disease in the Bonn Vein Study II. J Vasc Surg 2010. [DOI: 10.1016/j.jvs.2009.11.014] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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