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Chen B, Dai Q, Zhang Q, Yan P, Wang A, Qu L, Jin Y, Zhang D. The relationship among occupational irradiation, DNA methylation status, and oxidative damage in interventional physicians. Medicine (Baltimore) 2019; 98:e17373. [PMID: 31574886 PMCID: PMC6775365 DOI: 10.1097/md.0000000000017373] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Ionizing radiation can induce deoxyribonucleic acid (DNA) methylation pattern change, and ionizing radiation-induced oxidative damage may also affect DNA methylation status. However, the influence of low-dose ionizing radiation, such as occupational radiation exposure, on DNA methylation is still controversial.By investigating the relationship between occupational radiation exposure and DNA methylation changes, we evaluated whether radiation-induced oxidative damage was related to DNA methylation alterations and then determined the relationship among occupational radiation level, DNA methylation status, and oxidative damage in interventional physicians.The study population included 117 interventional physicians and 117 controls. We measured global methylation levels of peripheral blood leukocyte DNA and expression level of DNA methyltransferase (Dnmts) and homocysteine (Hcy) in serum to assess the DNA methylation status of the body. We measured 8-hydroxy-2'-deoxyguanosine (8-OHDG) and 4-hydroxynonenal (4-HNE) levels as indices of oxidative damage. Relevance analysis between multiple indices can reflect the relationship among occupational radiation exposure, DNA methylation changes, and oxidative damage in interventional physicians.The expression levels of Dnmts, 4-HNE, and 8-OHDG in interventional physicians were higher than those in controls, while there was no statistical difference in total DNA methylation rate and expression of Hcy between interventional physicians and controls. Total cumulative personal dose equivalent in interventional physicians was positively correlated with the expression levels of Dnmts, 8-OHDG, and 4-HNE. The expression levels of 8-OHDG in interventional physicians were negatively correlated with global DNA methylation levels and positively correlated with the expression levels of Hcy.Occupational radiation exposure of interventional physicians has a certain effect on the expression of related enzymes in the process of DNA methylation, while ionizing radiation-induced oxidative damage also has a certain effect on DNA methylation. However, there was no evidence that dose burden of occupational exposure was associated to changes of DNA methylation status of interventional physicians, since it is rather unclear which differences are observed among the effects produced by radiation exposure and oxidative damage.
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Affiliation(s)
- Bin Chen
- Department of Radiology, HwaMei Hospital, University of Chinese Academy of Sciences
| | - Qi Dai
- Department of Radiology, HwaMei Hospital, University of Chinese Academy of Sciences
| | - Qun Zhang
- Department of Environmental and Occupational Health, Ningbo Municipal Center for Disease Control and Prevention, Ningbo, Zhejiang, China
| | - Peng Yan
- Department of Environmental and Occupational Health, Ningbo Municipal Center for Disease Control and Prevention, Ningbo, Zhejiang, China
| | - Aihong Wang
- Department of Environmental and Occupational Health, Ningbo Municipal Center for Disease Control and Prevention, Ningbo, Zhejiang, China
| | - Linyan Qu
- Department of Environmental and Occupational Health, Ningbo Municipal Center for Disease Control and Prevention, Ningbo, Zhejiang, China
| | - Yinhua Jin
- Department of Radiology, HwaMei Hospital, University of Chinese Academy of Sciences
| | - Dandan Zhang
- Department of Environmental and Occupational Health, Ningbo Municipal Center for Disease Control and Prevention, Ningbo, Zhejiang, China
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Illamola SM, Echaabi AK, Mazeron C, Deshayes S, Loriot MA, Pallet N. Development and validation of a UPLC-UV method for the quantification of thiopurine methyltransferase enzyme activity in human erythrocytes. J Chromatogr B Analyt Technol Biomed Life Sci 2019; 1113:91-97. [PMID: 30901734 DOI: 10.1016/j.jchromb.2019.03.014] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2018] [Revised: 02/13/2019] [Accepted: 03/13/2019] [Indexed: 01/07/2023]
Abstract
Thiopurines are drugs widely used for the treatment of autoimmune conditions, inflammatory bowel disease or acute lymphoblastic leukemia. Determination of thiopurine methyltransferase activity (TPMT), a major determinant of thiopurines toxicity, has been suggested before implementing thiopurine treatment. An ultraperformance liquid chromatography (UPLC) method was developed and validated for the quantification of TPMT enzyme activity based on the conversion of 6-mercaptopurine (6-MP) to 6-methylmercaptopurine (6-MMP) using S-adenosyl-L-methionine (SAM) as methyl donor in red blood cell lysates (RBC). This method was improved from a previous laborious high performance liquid chromatography (HPLC) method, using a lower volume of injection and with a shorter runtime. After incubation and protein precipitation 6-MMP was separated on a HSS-T3 (2.1 × 50 mm, 1.8 μm) column and monitored by UV detection (290 nm). A change on the organic solvent used to dissolve 6-MP resulted in a reduction of interference by endogenous or non-enzymatic methylated 6-MMP. A full validation of the 6-MMP assay was performed according to the FDA and EMA guidelines. The method was linear from 0.125 to 2 nmol/mL, with acceptable values of accuracy and precision. The method was applied in 106 patients treated with thiopurines whose TPMT activity was previously quantified by HPLC. Evaluation through Bland-Altman plot showed that TPMT activities were in agreement between both methods.
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Affiliation(s)
- S M Illamola
- Service de Biochimie, Hôpital Européen Georges Pompidou, Assistance Publique-Hôpitaux de Paris, Paris, France.
| | - A K Echaabi
- Service de Biochimie, Hôpital Européen Georges Pompidou, Assistance Publique-Hôpitaux de Paris, Paris, France
| | - C Mazeron
- Service de Biochimie, Hôpital Européen Georges Pompidou, Assistance Publique-Hôpitaux de Paris, Paris, France
| | - S Deshayes
- Service de Biochimie, Hôpital Européen Georges Pompidou, Assistance Publique-Hôpitaux de Paris, Paris, France
| | - M A Loriot
- Service de Biochimie, Hôpital Européen Georges Pompidou, Assistance Publique-Hôpitaux de Paris, Paris, France; INSERM U1147, Centre Universitaire des Saints Pères, Paris, France; Université Paris Descartes, Paris, France
| | - N Pallet
- Service de Biochimie, Hôpital Européen Georges Pompidou, Assistance Publique-Hôpitaux de Paris, Paris, France; INSERM U1147, Centre Universitaire des Saints Pères, Paris, France; Université Paris Descartes, Paris, France; Service de Néphrologie, Hôpital Européen Georges Pompidou, Assistance Publique-Hôpitaux de Paris, Paris, France
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Ghobadi F, Vaisi-Raygani A, Bahrehmand F, Tanhapour M, Kiani A, Rahimi Z, Pourmotabbed T. Genetic Variants of Pre-microRNAs A-499G(rs3746444) and T-196a2C(rs11614913) with Ulcerative Colitis (UC) and Investigated with Thiopurine-S-Methyltransferase (TPMT) Activity. Clin Lab 2017; 63:1683-1690. [PMID: 29035443 DOI: 10.7754/clin.lab.2017.170502] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
BACKGROUND Abnormal expression and different splicing of miRNAs are involved in several human inflammatory disorders. It has been suggested that gene variants of miRNAs may be associated with increased risk of ulcerative colitis (UC). We aimed to evaluate the association of two SNPs (miRNA-A-499G(rs3746444) and miRNA-T196a2C(rs11614913)) with the risk of UC and monitor their effect on thiopurine-S-methyltransferase (TPMT) activity in Kurdish population of Iran. METHODS This case-control study was performed on 210 UC patients and 212 healthy individuals. Genotyping assay was performed using PCR-RFLP and the TPMT-activity was measured via non-extraction-HPLC method. RESULTS We found that the existence of GG genotypes and G allele of miRNA-A-499G SNPs significantly increased the risk of UC by 1.76 and 1.32 times, respectively. The distribution of GG genotype (23.8% vs. 16%, χ2 = 4.2, p = 0.041) and G allele (46.4% vs. 39.4%, χ2 = 4, p = 0.046) of miRNA-A-499G, were significantly higher in UC patients compared to control group. Our results indicate that miRNA SNPs (miRNA-T-196a2C and miRNA-A-499G) have no significant effect on TPMT activity of studied population. CONCLUSIONS Our results, for the first time, demonstrate that the GG genotype and G allele of miRNA-A-499G significantly increase the risk of UC. However, miRNA SNPs showed no significant effect on TPMT activity in studied population.
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Chapdelaine A, Mansour AM, Troyanov Y, Williamson DR, Doré M. Metabolite monitoring to guide thiopurine therapy in systemic autoimmune diseases. Clin Rheumatol 2017; 36:1341-1348. [PMID: 28130685 DOI: 10.1007/s10067-017-3554-4] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2016] [Revised: 12/22/2016] [Accepted: 01/18/2017] [Indexed: 02/06/2023]
Abstract
6-Thioguanine nucleotide (6-TGN) is the active metabolite of thiopurine drugs azathioprine and 6-mercaptopurine. 6-Methylmercaptopurine (6-MMP) is an inactive and potentially hepatotoxic metabolite. A subgroup of patients (shunters) preferentially produce 6-MMP instead of 6-TGN, therefore displaying thiopurine resistance and risk for hepatotoxicity. Outside inflammatory bowel disease literature, few data exist regarding individualized thiopurine therapy based on metabolite monitoring. This study sought to describe metabolite monitoring in patients receiving weight-based thiopurine for systemic autoimmune diseases. Patients were enrolled using a laboratory database, and data were retrospectively collected. The correlation between the highest thiopurine dose (mg/kg) and the 6-TGN concentration (pmol/8 × 108 erythrocytes) was estimated with Pearson's correlation coefficient. Seventy-one patients with various systemic autoimmune conditions were enrolled. The correlation between the thiopurine dose and the 6-TGN level was weak for the overall patient sample (r = 0.201, p = 0.092) and for the subgroup of non-shunters (r = 0.278, p = 0.053). Subjects with 6-MMP levels >5700 pmol/8 × 108 erythrocytes had more hepatic cytolysis compared to subjects with 6-MMP <5700, OR = 4.36 (CI 95% 1.18-16.13, p = 0.027). Twenty-two patients (31%) were identified as shunters. Six shunters developed hepatotoxicity, five of which had 6-MMP concentration >5700. Eleven non-shunters had hepatotoxicity, one of which had 6-MMP >5700. Thiopurine metabolite monitoring shows wide variability in 6-TGN levels among patients treated with weight-based thiopurine for systemic autoimmune diseases. Thirty-one percent of the patients in our series fulfilled the shunter definition. Thiopurine metabolite monitoring and dose adjustment to improve maintenance of remission and avoid hepatotoxicity should be studied prospectively.
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Affiliation(s)
- Aurélie Chapdelaine
- Department of Medicine, Hôpital du Sacré-Cœur de Montréal, 5400 Gouin Ouest, Montréal, Québec, H4J 1C5, Canada.
| | - Anne-Marie Mansour
- Department of Medicine, Hôpital du Sacré-Cœur de Montréal, 5400 Gouin Ouest, Montréal, Québec, H4J 1C5, Canada
- Faculty of Medicine, Université de Montréal, 5400 Gouin Ouest, Montréal, Québec, H4J 1C5, Canada
| | - Yves Troyanov
- Department of Medicine, Hôpital du Sacré-Cœur de Montréal, 5400 Gouin Ouest, Montréal, Québec, H4J 1C5, Canada
| | - David R Williamson
- Department of Pharmacy, Hôpital du Sacré-Cœur de Montréal, 5400 Gouin Ouest, Montréal, Québec, H4J 1C5, Canada
- Faculty of Pharmacy, Université de Montréal, 5400 Gouin Ouest, Montréal, Québec, H4J 1C5, Canada
| | - Maxime Doré
- Department of Pharmacy, Hôpital du Sacré-Cœur de Montréal, 5400 Gouin Ouest, Montréal, Québec, H4J 1C5, Canada
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Abstract
Background: We have developed a new thiopurine S-methyltransferase (TPMT) phenotyping method that measures TPMT activity in whole blood. To evaluate this assay, we compared it with conventional TPMT phenotyping, which uses a red blood cell (RBC) lysate and genotyping for analysis of common TPMT mutations. Methods: Whole-blood and RBC lysates were prepared from 402 patients' samples received for routine analysis. The TPMT activity of lysates was determined using 6-thioguanine as substrate with high-performance liquid chromatographic (HPLC) analysis and fluorimetric detection. DNA was extracted from buffy coats using phenol-chloroform extraction. A multiplex amplification refractory mutation system (ARMS) strategy was used to screen for the common TPMT mutations TPMT*2 and TPMT*3 (TPMT*3A, TPMT*3C and TPMT*3D). Results: TPMT activities were higher in the whole-blood (mean TPMT activity 51 nmol 6-MTG/gHb/h) compared with the RBC lysate (37 nmol 6-MTG/gHb/h). Overall, concordance with TPMT genotypic analysis was 97% for both the new whole-blood and standard RBC lysate methods. Between low TPMT activity and heterozygotes, both phenotypic methods gave a concordance of 79%. Conclusion: Using multiplex ARMS testing for TPMT*2 and 3*C mutations to define the cut-off between low and normal TPMT activity, we have demonstrated that the new whole-blood TPMT phenotyping method performs as well as the conventional RBC lysate assay. This new method overcomes the need to prepare a RBC lysate, a process which is time consuming and increases analytical variation. The resulting assay is better suited to a regional or national TPMT phenotyping service.
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Affiliation(s)
- Loretta Ford
- Clinical Biochemistry Department, City Hospital, Birmingham, UK.
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Ford LT, Cooper SC, Lewis MJV, Berg JD. Reference intervals for thiopurine S-methyltransferase activity in red blood cells using 6-thioguanine as substrate and rapid non-extraction liquid chromatography. Ann Clin Biochem 2016; 41:303-8. [PMID: 15298742 DOI: 10.1258/0004563041201617] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Background: Although widely used, thiopurine drugs have a narrow therapeutic index and treatment can result in life-threatening toxicity, the basis being pharmacogenetic variation in thiopurine metabolism by thiopurine S-methyltransferase (TPMT). We recently developed a modified phenotyping assay to determine TPMT activity in red blood cells. Here we describe improvements to the method and establish reference intervals in a large prospective study. Methods: A modified enzyme assay for TPMT activity is reported. It uses 6-thioguanine as substrate with heat treatment of the incubate to stop the reaction and precipitate protein prior to high-performance liquid chromatographic (HPLC) analysis. Measurement of the reaction product, 6-methylthioguanine (6-MTG), uses HPLC with fluorimetric detection. Results: The assay shows excellent characteristics, with clear discrimination of patients who are deficient in TPMT activity (< 5 nmol 6-MTG per g Hb per h) from heterozygotes (5-24 nmol 6-MTG per g Hb per h) and patients with normal activity (>25 nmol 6-MTG per g Hb per h). Conclusion: A modified TPMT assay is described which is suited for routine analysis in a regional centre. The method overcomes the need for extraction and has speeded up the chromatographic determination of 6-MTG, enabling large numbers of samples to be analysed. A prospective study of 1000 individuals has established the distribution of TPMT activity using the assay.
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Affiliation(s)
- Loretta T Ford
- Clinical Biochemistry Department, City Hospital, Sandwell and West Birmingham Hospitals NHS Trust, Birmingham, B18 7QH, UK
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Emmungil H, Durusoy R, Kalfa M, Yargucu Zihni F, Özmen M, Keser G, Gücenmez S, Yilmaz Z, Aksu K. Plasma thiopurine S-methyltransferase levels and azathioprine-related adverse events in patients with Behçet's disease. Clin Exp Rheumatol 2015; 33:S40-S45. [PMID: 25936353] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2014] [Accepted: 02/04/2015] [Indexed: 06/04/2023]
Abstract
OBJECTIVES Thiopurine S-methyltransferase (TPMT) is the key enzyme inactivating azathioprine (AZA), an immunosuppressive agent commonly used for treating inflammatory diseases including Behçet's disease (BD), systemic lupus erythematosus (SLE) and systemic vasculitis. Low TPMT levels facilitate occurrence of AZA-related adverse effects. We investigated TPMT levels in patients with BD, compared to healthy controls and patients with SLE or systemic vasculitis. METHODS This cross-sectional study included 101 BD (77 using AZA), 74 SLE (35 using AZA), and 44 vasculitis (18 using AZA) patients and 101 healthy controls. Plasma TPMT levels were measured using ELISA. Student's t- and Kruskal-Wallis tests were used to compare TPMT levels according to possible risk factors. Receiver operating characteristic (ROC) analysis was used to determine whether a cut-off TPMT level could be found to predict AZA-related adverse effects. RESULTS Plasma TPMT levels (mean± SD ng/mL) in BD (22.80±13.81) were comparable with healthy controls (22.71±13.49), but significantly lower than in SLE group (29.37±11.39) (p<0.001). TPMT levels in 130 patients receiving AZA were similar to the rest of the group. AZA-related adverse effects were identified in only 8 patients (5 with BD and 3 with SLE). TPMT levels were significantly lower in those 8 patients (14.08±9.49 vs. 25.62±12.68) (p=0.013), besides a cut-off value for predicting adverse effects was determined for the BD group with ROC analysis (area under the curve: 0.813). CONCLUSIONS This is the first study to evaluate TPMT activity in a Turkish adult population. Although low plasma TPMT level is not the only factor determining AZA toxicity, a TPMT cut-off value may help to predict AZA-related adverse effects in BD.
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Affiliation(s)
- Hakan Emmungil
- Department of Internal Medicine, Division of Rheumatology, Koç University Hospital, Istanbul, Turkey.
| | - Raika Durusoy
- Department of Public, Health Ege University School of Medicine, Izmir, Turkey
| | - Melike Kalfa
- Department of Internal Medicine, Division of Rheumatology, Acıbadem University, Istanbul, Turkey
| | - Figen Yargucu Zihni
- Department of Internal Medicine, Division of Rheumatology, Ege University School of Medicine, Izmir, Turkey
| | - Mustafa Özmen
- Clinic of Internal Medicine, Division of Rheumatology, Ataturk Research and Training Hospital, Izmir, Turkey
| | - Gökhan Keser
- Department of Internal Medicine, Division of Rheumatology, Ege University School of Medicine, Izmir, Turkey
| | - Sercan Gücenmez
- Department of Internal Medicine, Division of Rheumatology, Ege University School of Medicine, Izmir, Turkey
| | - Zevcet Yilmaz
- Department of Internal Medicine, Division of Rheumatology, Tepecik Research and Training Hospital, Izmir, Turkey
| | - Kenan Aksu
- Department of Internal Medicine, Division of Rheumatology, Ege University School of Medicine, Izmir, Turkey
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Wong DR, Pierik M, Seinen ML, van Bodegraven AA, Gilissen LPL, Bus P, Bakker JA, Masclee AAM, Neef C, Engels LGJB, Hooymans PM. The pharmacokinetic effect of adalimumab on thiopurine metabolism in Crohn's disease patients. J Crohns Colitis 2014; 8:120-8. [PMID: 23932783 DOI: 10.1016/j.crohns.2013.07.004] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/17/2013] [Revised: 07/01/2013] [Accepted: 07/09/2013] [Indexed: 12/26/2022]
Abstract
BACKGROUND AND AIMS A drug interaction between infliximab and azathioprine has previously been reported in Crohn's disease patients: the concentration of the main active thiopurine metabolites, the 6-thioguanine nucleotides (6-TGN), increased 1-3 weeks after the first infliximab infusion by 50% compared to baseline. The aim of this prospective study was to determine the effect of adalimumab on thiopurine metabolism in Crohn's disease patients, evaluated by 6-TGN and 6-methylmercaptopurine ribonucleotides (6-MMPR) concentration measurement. METHODS Crohn's disease patients on azathioprine or mercaptopurine maintenance therapy starting with concomitant adalimumab treatment were included. 6-TGN and 6-MMPR concentrations were determined before initiation of adalimumab and after 2, 4, 6 and 12 weeks of combination therapy. The activity of three essential enzymes involving thiopurine metabolism, thiopurine S-methyltransferase (TPMT), hypoxanthine-guanine phosphoribosyl transferase (HGPRT) and inosine-triphosphate pyrophosphatase (ITPase), was evaluated at baseline and week 4. Clinical outcome was evaluated by the Crohn's disease activity index and C-reactive protein concentrations at baseline, week 4 and week 12. RESULTS Twelve Crohn's disease patients were analyzed. During the follow-up period of 12 weeks the median 6-TGN and 6-MMPR concentrations did not significantly change compared to baseline. TPMT, ITPase and HGPRT enzyme activity did not change either after 4 weeks. In two patients (17%) myelotoxicity was observed within 2-4 weeks, in whom both low therapeutic 6-TGN and 6-MMPR concentrations were found. CONCLUSIONS In this study in Crohn's disease patients no pharmacokinetic interaction was shown between adalimumab and the conventional thiopurines, azathioprine and mercaptopurine.
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Affiliation(s)
- D R Wong
- Department of Clinical Pharmacy & Toxicology, Orbis Medical Centre, Sittard, The Netherlands.
| | - M Pierik
- Department of Gastroenterology and Hepatology, University Hospital Maastricht, Maastricht, The Netherlands
| | - M L Seinen
- Department of Gastroenterology and Hepatology, VU University Medical Centre, Amsterdam, The Netherlands
| | - A A van Bodegraven
- Department of Gastroenterology and Hepatology, VU University Medical Centre, Amsterdam, The Netherlands
| | - L P L Gilissen
- Department of Gastroenterology and Hepatology, Catharina Hospital, Eindhoven, The Netherlands
| | - P Bus
- Department of Gastroenterology, Laurentius Hospital, Roermond, The Netherlands
| | - J A Bakker
- Department of Clinical Chemistry and Laboratory Medicine, Leiden University Medical Centre, Leiden, The Netherlands
| | - A A M Masclee
- Department of Gastroenterology and Hepatology, University Hospital Maastricht, Maastricht, The Netherlands
| | - C Neef
- Department of Clinical Pharmacy & Toxicology, University Hospital Maastricht, Maastricht, The Netherlands; Department of Toxicology, Maastricht University, CAPHRI School for Public Health and Primary Care, Maastricht, The Netherlands
| | - L G J B Engels
- Department of Gastroenterology, Orbis Medical Centre, Sittard, The Netherlands
| | - P M Hooymans
- Department of Clinical Pharmacy & Toxicology, Orbis Medical Centre, Sittard, The Netherlands
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Abstract
Thiopurine methyltransferase (TPMT) is the main enzyme responsible for inactivating toxic products of azathioprine (AZA) metabolism. Patients with homozygous deficiency of this enzyme have no enzyme activity and ideally should not be given AZA. Patients with heterozygous deficiency have 50% of enzyme activity and have been shown to respond well and tolerate half a standard dose. We describe a patient with homozygous deficiency of TPMT who developed life threatening neutropenic sepsis, and advocate that all patients should be tested for TPMT activity prior to starting AZA therapy.
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Seinen ML, van Bodegraven AA, van Kuilenburg ABP, de Boer NKH. High TPMT activity as a risk factor for severe myelosuppression during thiopurine therapy. Neth J Med 2013; 71:222. [PMID: 23723121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
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González-Lama Y, Gisbert JP. Letter: TPMT - not all that glitters is gold. Aliment Pharmacol Ther 2012; 36:208-9; author reply 209-10. [PMID: 22703467 DOI: 10.1111/j.1365-2036.2012.05148.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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Chrzanowska M, Kuehn M, Januszkiewicz-Lewandowska D, Kurzawski M, Droździk M. Thiopurine S-methyltransferase phenotype-genotype correlation in children with acute lymphoblastic leukemia. Acta Pol Pharm 2012; 69:405-410. [PMID: 22594254] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Thiopurine S-methyltransferase (TPMT) is an enzyme that catalyzes the S-methylation of thiopurine drugs such as 6-mercaptopurine, 6-thioguanine, and azathioprine. TPMT activity exhibits an interindividual variability mainly as a result of genetic polymorphism. Patients with intermediate or deficient TPMT activity are at risk for toxicity after receiving standard doses of thiopurine drugs. The aim of this study was to determine the TPMT genotype and phenotype (activity) and investigate the correlation between TPMT genotype and enzyme activity in 43 Polish children receiving 6-MP during maintenance therapy in course of acute lymphoblastic leukemia (ALL), in 16 children with ALL at diagnosis and 39 healthy controls. TPMT activity was measured in RBC by HPLC method. Patients were genotyped for TPMT *2, *3A and *3C variant allelesusing PCR-RFLP and allele-specific PCR methods. In the group of children with ALL during maintenance therapy, median TPMT activity (29.3 nmol 6-mMP g(-1) Hb h(-1)) was significantly higher compared to the group of children with ALL at diagnosis (20.6 nmol 6-mMP g(-1) Hb h(-1), p = 0.0028), as well as to the control group (22.8 nmol 6-mMP g(-1) Hb h(-1), p = 0.0002). Percentages of individuals heterozygous for TPMT variant allele in respective groups were: 9.3, 6.2 and 15.5% (p > 0.05). In all the study groups heterozygous patients manifested a significantly lower TPMT activity as compared to the wild type homozygotes (16.7 +/- 2.1 vs. 31.2 +/- 6.8 nmol 6-mMP g(-1) Hb h(-1), p = 0.002, in children during maintenance therapy, 11.9 +/- 2.7 vs. 24.6 +/- 9.5, p = 0.0003, in the combined group of children with ALL at diagnosis and controls). The results present that commencement of the thiopurine therapy caused an increase in the TPMT activity in RBCs by approximately 20%. All patients heterozygous for the TPMT variant allele revealed decreased TPMT activity compared to TPMT wild-type patients. Since decreased TPMT activity is associated with higher risk for toxicity after receiving standard doses of thiopurine drugs, pretreatment determination of TPMT status, with phenotypic or genetic assay, should be performed routinely, also in Poland.
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Affiliation(s)
- Maria Chrzanowska
- Department of Physical Pharmacy and Pharmacokinetics, University of Medical Sciences, Swiecickiego 6, 60-781 Poznań, Poland
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Fargher EA, Tricker K, Newman W, Elliott R, Roberts SA, Shaffer JL, Bruce I, Payne K. Current use of pharmacogenetic testing: a national survey of thiopurine methyltransferase testing prior to azathioprine prescription. J Clin Pharm Ther 2007; 32:187-95. [PMID: 17381669 DOI: 10.1111/j.1365-2710.2007.00805.x] [Citation(s) in RCA: 90] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
BACKGROUND Azathioprine is an immunosuppressant prescribed for the treatment of inflammatory conditions and after organ transplantation. Risk of neutropaenia has limited the effective use of azathioprine (AZA) and driven requirements for careful monitoring and blood tests. Thiopurine methyltransferase (TPMT) is a genetically moderated key enzyme involved in the metabolism of AZA that can be used to stratify individuals into different levels of risk of developing neutropaenia. Two techniques can be used to measure TPMT status: enzyme-level testing (phenotype testing) and DNA based testing (genotype testing). OBJECTIVE To identify the current uptake of TPMT enzyme-level testing, TPMT genotype testing, and, the role of guidelines; to inform the prescribing and monitoring of AZA. METHOD A survey was mailed to a consultant dermatologist, gastroenterologist, and rheumatologist at every NHS Hospital Trust in England. The survey comprised mainly closed questions exploring: use of AZA and monitoring; use of TPMT enzyme-level testing and genotype testing; and, the role of guidelines to guide prescribing practice. RESULTS A 70% (n=287) response rate was obtained. The majority of respondents reported prescribing AZA (99%, n=283). Prescribing and monitoring patterns differed between individual respondents and between the three disciplines. TPMT enzyme-level testing was reportedly used by 67% (n=189) of respondents, but this differed by discipline (dermatologists 94%, gastroenterologists 60%, rheumatologists 47%). In 91% of cases enzyme-level testing was carried out prior to prescribing AZA. Genotype testing is not typically available to NHS clinicians but 15 clinicians (six dermatologists, six gastroenterologists, three rheumatologists) reported using it. Most consultants (82%) reported using guidelines to inform their AZA prescribing and monitoring (dermatologists 81%, gastroenterologists 75%, rheumatologists 94%). CONCLUSION Two-thirds of the consultants surveyed in England are using TPMT enzyme-level testing, prior to AZA treatment. Uptake differs between specialities. High uptake of TPMT enzyme-level testing by dermatologists, compared with gastroenterologists and rheumatologists, may reflect national guidelines advocating its use prior to AZA. Uptake of enzyme-level testing may alter in other specialties as other guidelines are developed.
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Affiliation(s)
- E A Fargher
- North West Genetics Knowledge Park (Nowgen), Manchester, UK
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Reinshagen M, Schütz E, Armstrong VW, Behrens C, von Tirpitz C, Stallmach A, Herfarth H, Stein J, Bias P, Adler G, Shipkova M, Kruis W, Oellerich M, von Ahsen N. 6-Thioguanine Nucleotide–Adapted Azathioprine Therapy Does Not Lead to Higher Remission Rates Than Standard Therapy in Chronic Active Crohn Disease: Results from a Randomized, Controlled, Open Trial. Clin Chem 2007; 53:1306-14. [PMID: 17495015 DOI: 10.1373/clinchem.2007.086215] [Citation(s) in RCA: 84] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Abstract
Background: A prospective randomized trial in patients with Crohn disease studied whether 6-thioguanine nucleotide (6-TGN) concentration–adapted azathioprine (AZA) therapy is clinically superior to a standard dose of 2.5 mg/kg/day AZA.
Methods: After 2 weeks of standard therapy, patients (n = 71) were randomized into standard (n = 32) or adapted-dose (n = 25) groups; 14 patients dropped out before randomization. In the adapted group, the AZA dose was adjusted to maintain 6-TGN concentrations between 250 and 400 pmol/8 × 108 erythrocytes (Ery). Response criteria were the number of patients in remission after 16 weeks without steroids (primary) and remission after 24 weeks, frequency of side effects, and quality of life (secondary).
Results: After 16 weeks, 14 of 32 (43.8%) patients in the standard group vs 11 of 25 (44%) in the adapted group were in remission without steroids (intent-to-treat analysis). After 24 weeks, 43.8% vs 40% were in remission. No significant differences were found concerning quality of life, disease activity, 6-TGN concentrations, AZA dose, or dropouts due to side effects. Sixty-six patients had a wild-type thiopurine S-methyltransferase (TPMT) genotype, with TPMT activities of 8 to 20 nmol/(mL Ery × h). Five patients (dropouts after randomization) were heterozygous, with TPMT activities <8 nmol/(mL Ery × h). 6-Methyl mercaptopurine (6-MMP) concentrations >5700 pmol/8 × 108 Ery were not associated with hepatotoxicity.
Conclusion: Standard and adapted dosing with the provided dosing scheme led to identical 6-TGN concentrations and remission rates. Adapted dosing had no apparent clinical benefit for patients with TPMT activity between 8 and 20 nmol/(mL Ery × h). Additionally, 6-MMP monitoring had no predictive value for hepatotoxicity.
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Affiliation(s)
- Max Reinshagen
- Department of Medicine I, Klinikum Braunschweig, Braunschweig, Germany.
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Gisbert JP, Gomollón F, Cara C, Luna M, González-Lama Y, Pajares JM, Maté J, Guijarro LG. Thiopurine methyltransferase activity in Spain: a study of 14,545 patients. Dig Dis Sci 2007; 52:1262-9. [PMID: 17334911 DOI: 10.1007/s10620-006-9119-z] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/07/2005] [Accepted: 10/28/2005] [Indexed: 12/20/2022]
Abstract
We sought to assess the activity of thiopurine methyltransferase (TPMT) in 14,545 Spanish patients with different diseases amenable to treatment with azathioprine/6-mercaptopurine (6-MP), and to evaluate the proportion of patients with low TPMT activity and therefore a higher risk of myelotoxicity with these drugs. TPMT activity in red blood cells (RBCs) was measured by a radiochemical method. The association between several clinical variables and TPMT activity was assessed by multiple linear regression. We included 14,545 patients: autoimmune hepatitis (n=359 patients), inflammatory bowel disease (n=7,046), multiple sclerosis (n = 814), myasthenia gravis (n=344), pemphigus (n=133), and other diseases (n=5,849). Mean TPMT activity was 20.1 +/- 6 U/mL, but differed depending on the disease (P<.001). TPMT distribution was low (<5) in 0.5%; intermediate (5.0-13.7) in 11.9%; or high (>or=13.8) in 87.6%. Only when TPMT activity was considered separately in each disease did it reveal a normal distribution. In the multivariate analysis, gender, hematocrit, and treatment with 5-aminosalicylates/steroids/azathioprine/6-MP statistically influenced TPMT activity, although, probably, in a clinically irrelevant manner. This study shows, in a large sample of 14,545 patients, that 0.5% had low TPMT activity, indicating a higher risk of myelotoxicity with azathioprine/6-MP, a figure similar or slightly higher than that reported in other areas. Nevertheless, the trimodal distribution of TPMT activity varied depending on disease, and the proportion of patients with low activity values ranged from 0-0.8%. The drugs prescribed for the treatment of autoimmune diseases, including azathioprine/6-MP, modified TPMT activity, but the magnitude of this effect was very small and the differences found are probably irrelevant from the clinical point of view.
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Affiliation(s)
- Javier P Gisbert
- Servicio de Aparato Digestivo, Hospital Universitario de la Princesa, Universidad Autónoma, Playa de Mojácar 29, Urb, Bonanza, 28669, Boadilla del Monte, Madrid, Spain.
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Payne K, Newman W, Fargher E, Tricker K, Bruce IN, Ollier WER. TPMT testing in rheumatology: any better than routine monitoring? Rheumatology (Oxford) 2007; 46:727-9. [PMID: 17255139 DOI: 10.1093/rheumatology/kel427] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
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Gisbert JP, Niño P, Rodrigo L, Cara C, Guijarro LG. Thiopurine methyltransferase (TPMT) activity and adverse effects of azathioprine in inflammatory bowel disease: long-term follow-up study of 394 patients. Am J Gastroenterol 2006; 101:2769-76. [PMID: 17026564 DOI: 10.1111/j.1572-0241.2006.00843.x] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
AIM To prospectively evaluate whether a relationship between thiopurine methyltransferase (TPMT) activity and incidence of adverse effects (especially myelotoxicity) exists, in a long-term follow-up study of a large group of patients with inflammatory bowel disease treated with azathioprine. METHODS TPMT activity in red blood cells (RBC) was measured by a radiochemical method in 394 consecutive patients with Crohn's disease (238) or ulcerative colitis (156) starting treatment with azathioprine. The relationship among several variables and TPMT values was assessed, and the correlation between such levels and the incidence of adverse effects was evaluated. RESULTS Mean TPMT value was 18.6 +/- 4 U/mL RBCs (range 9.4-33.7). No patient had low levels (<5), 7.1% had intermediate levels (5-13.7), and 92.9% had high levels (>13.8). Differences (P < 0.001) were demonstrated in TPMT activity depending on the type of inflammatory bowel disease, but not on the remaining variables (including treatment with 5-aminosalycilates). Adverse effects were reported in 74 patients (18.8%), the most frequent being gastrointestinal intolerance (9.1%) and myelotoxicity (4.3%). No patient having adverse effects had low TPMT levels. However, mean TPMT activity was lower in those with adverse effects (16.6 +/- 3 vs 19.1 +/- 4 U/mL, P < 0.001). Moreover, the probability of suffering myelotoxicity in the high TPMT group was only 3.5%, compared with 14.3% in the TPMT intermediate group (95% CI = 1.37-14.9; OR = 4.5). CONCLUSIONS The strategy of determining TPMT activity in all patients prior to initiating treatment with azathioprine could help to minimize the risk of myelotoxicity, as patients with intermediate TPMT activity had fourfold more risk than high TPMT activity patients.
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Affiliation(s)
- Javier P Gisbert
- Gastroenterology Unit, Hospital Universitario de la Princesa, Universidad Autónoma, Madrid, Spain
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Abstract
OBJECTIVES We evaluated how our use of thiopurines was altered by determination of thiopurine methyltransferase (TPMT) level and drug dose adjustment guided by a 6-mercaptopurine metabolite assay. We further examined whether these resulted in better selection of the drug dose, improved control of disease, and decreased corticosteroid use in pediatric inflammatory bowel disease (IBD). PATIENTS AND METHODS This is a retrospective review of 101 pediatric patients with IBD receiving a stable dose of azathioprine (AZA) for 4 months or longer. The study group (n = 64) consisted of patients who received AZA and had metabolite levels measured. The comparison group (n = 37) consisted of patients who were receiving AZA before the availability of metabolite measurement. The TPMT level was measured in study group patients before starting AZA. RESULTS Patients with normal TPMT level received a higher starting dose of AZA than in patients who were heterozygous for TPMT deficiency (1.7 vs 0.9 mg/[kg x d], P < 0.0001). Study group patients received a higher starting dose (1.6 vs 1.2 mg/[kg x d], P = 0.001) and a higher final dose of AZA (2.4 vs 1.7 mg/[kg x d], P < 0.0001) compared with patients in the comparison group. These patients also had more dose adjustments (0.8 vs 0.4 mg/kg, P < 0.002). The number of disease exacerbations per patient per year was 55% less in the study group (95% CI, 17%-76%, P < 0.0001). The study group patients received less prednisone (P < 0.0001) and had lower disease activity scores (P < 0.05). There was no difference between groups in infliximab use or surgery rate. CONCLUSIONS Azathioprine dose adjustment using a 6-mercaptopurine metabolite assay was associated with use of higher doses, improved control of disease and decreased corticosteroid use in pediatric patients with IBD.
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Affiliation(s)
- Sanjoy Banerjee
- Children's Hospital of Iowa, Department of Pediatric Gastroenterology, Iowa City, Iowa, USA
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Ma XL, Wu MY, Hu YM, Zu P, Li ZG. [Relationships between thiopurine methyltransferase gene polymorphisms and its enzymatic activity]. Zhonghua Zhong Liu Za Zhi 2006; 28:456-9. [PMID: 17152495] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
OBJECTIVE To investigate the relationship between the thiopurine methytransferase (TPMT) gene polymorphisms and its enzymatic activity, and to clarify the significance of TPMT activity and gene polymorphisms on individualized therapy with thiopurines. METHODS The TPMT activity and gene polymorphisms were determined in an unrelated population of 250 Chinese healthy blood donors, 100 cords blood and 280 patients with acute leukemia. The TPMT genotyping assay was based on polymerase chain reaction (PCR), restriction digestion of PCR products, denaturing high-performance liquid chromatography (DHPLC) and SNaPshot sequencing and direct DNA sequencing in the TPMT exon 5 (G238C), TPMT exon7 (G460A) and TPMTexon10 (A719G). Erythrocyte TPMT activity was measured by high-performance liquid chromatography (HPLC). RESULTS The frequency of TPMT polymorphism in 250 Chinese healthy blood donors, 100 cords blood and 280 patients with acute leukemia was low (3.5%), and all the varied alleles were TPMT* 3C (exon 10A719G). All of them were TPMT* 1/TPMT* 3C heterozygote. The TPMT activity was between 6 and 12 U. The activity in 95.1% was more than 12 U (13 - 32 U), while the activity in others (4.9%) was 6 - 12 U. TPMT activity and genotype were concordant. Of 630 subjects evaluated, TPMT activity of heterozygous individuals in Chinese healthy blood donors, cords blood and acute leukemia patients were 9.1 U, 9.3 U and 9.07 U, respectively, significantly lower than that in general population (17.6 U, 17.67 U and 18.6 U, respectively). In the samples analyzed, ten subjects with heterozygous phenotypes (6/15 acute leukemia children and 4/16 healthy blood donors and cords blood) did not have TPMT* 2, TPMT* 3A or TPMT* 3C. Therefore, other factors may affect on TPMT activity. CONCLUSION TPMT gene polymorphisms and its activity were concordant. The heterozygotes had low TPMT activity. Therefore, detection of TPMT genotype and its activity is useful. These findings hold a promise of improving the safety and efficacy of thiopurines therapy.
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Affiliation(s)
- Xiao-Li Ma
- Beijing children's Hospital, Capital University of Medical Sciences, Beijing 100045, China.
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Abstract
Thiopurine methyltransferase deficiency has been associated with intolerance to azathioprine. Our goals were to assess the frequency of enzyme deficiency in autoimmune hepatitis and correlate deficiency states with azathioprine intolerance. Eighty-six patients receiving azathioprine (50-150 mg daily) were evaluated for enzyme activity and azathioprine-related complications. Their findings were compared to 89 similarly treated but untested patients. Thirteen patients (15%) had low thiopurine methyltransferase levels (11.4+/- 0.9 U/ml RBC; range, 3.5-14.9 U/ml RBC). Azathioprine intolerance occurred as commonly in patients with normal or above normal enzyme levels as in patients with below normal levels (12% versus 15%, p = 0.7). Patients treated without enzyme testing had the same frequency of complications (9% versus 13%, p = 0.5) as tested patients. We conclude that routine screening of blood thiopurine methyltransferase levels has a low yield for identifying individual patients at risk for azathioprine toxicity during conventional low dose therapy for autoimmune hepatitis.
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Affiliation(s)
- Albert J Czaja
- Division of Gastroenterology and Hepatology, Mayo Clinic College of Medicine, Rochester, Minnesota 55905, USA.
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Gearry RB, Barclay ML, Roberts RL, Harraway J, Zhang M, Pike LS, George PM, Florkowski CM. Thiopurine methyltransferase and 6-thioguanine nucleotide measurement: early experience of use in clinical practice. Intern Med J 2006; 35:580-5. [PMID: 16207256 DOI: 10.1111/j.1445-5994.2005.00904.x] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
BACKGROUND Azathioprine and 6-mercaptopurine (6-MP) are well established for the treatment of inflammatory bowel disease (IBD). Assessing thiopurine methyltransferase (TPMT) status has been recommended to reduce the risk of serious toxicity. Measuring red blood cell (RBC) 6-thioguanine nucleotide (6-TGN) concentrations has been recommended for dose adjustment. AIM To describe the results of measuring TPMT activity and genotype, and 6-TGN concentration in New Zealand. METHODS Canterbury Health Laboratories provided these analyses for New Zealand. Those with low TPMT activity also underwent genotyping. All results were collated and analysed descriptively. 6-TGN concentrations were correlated with the dose of thiopurine when known. RESULTS TPMT enzyme activity (range 1-22 U/mL) from 574 patients showed a trimodal distribution. Genotyping results matched this distribution with only mild overlap between (*1/*1) homozygote and (*1/*3) heterozygote groups. One patient without TPMT measurement before therapy had life-threatening neutropenia and was later found to have (*3/*3) genotype. TPMT analysis probably prevented two further such cases. Of 884 6-TGN concentrations (range 0-1434 pmol/10(8) RBC), 41, 39 and 20% were within, below, and above the therapeutic range of 235-450 pmol/10(8) RBC, respectively. Leucopenia was seen in some patients with high 6-TGN. 6-MMP concentrations in 177 patients with low 6-TGN suggested non-compliance in 31, underdosing in 130, and preferential metabolism of 6-MP to 6-methylmercaptopurine in 16. There was poor correlation between azathioprine dose and 6-TGN concentration (r(2) = 0.002), supporting 6-TGN monitoring. CONCLUSIONS Measurement of TPMT enzyme activity and 6-TGN concentration has been well-integrated into clinical practice. These tests should reduce the risk of toxicity and improve efficacy with thiopurines in patients with IBD.
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Affiliation(s)
- R B Gearry
- Department of Medicine, Christchurch School of Medicine and Health Sciences, New Zealand.
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Bierau J, Bakker JA, Lindhout M, van Gennip AH. Determination of ITPase activity in erythrocyte lysates obtained for determination of TPMT activity. Nucleosides Nucleotides Nucleic Acids 2006; 25:1129-32. [PMID: 17065077 DOI: 10.1080/15257770600894253] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
The indication for the determination of both thiopurine methyltransferase (TPMT) and inosine triphosphate pyrophosphohydrolase is identical (i.e., adverse drug reactions toward mercaptopurines). Therefore, we tested whether or not our standard procedure to prepare erythrocyte lysates for measurement of TPMT activity, which includes treatment with Chelex 100 (a chelating resin), was suitable for the measurement of ITPase activity. It also was tested to see if ITPase activity differs in EDTA and Heparin anti-coagulated blood samples. We found that there was no difference between the ITPase activity in erythrocyte lysates prepared from EDTA or Heparin anti-coagulated blood. Treatment with a chelating resin or omission of magnesium from the assay procedure resulted in decreased and nearly absent ITPase activity, respectively. We conclude that untreated erythrocyte lysates obtained for determination of TPMT activity are suitable for determination of ITPase activity. However, after treatment with Chelex 100 the erythrocyte lysates become unsuitable for determination of ITPase activity.
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Affiliation(s)
- J Bierau
- Laboratory of Biochemical Genetics, Department of Clinical Genetics, Maastricht University Hospital, Maastricht, The Netherlands.
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Roessler M, Rollinger W, Palme S, Hagmann ML, Berndt P, Engel AM, Schneidinger B, Pfeffer M, Andres H, Karl J, Bodenmüller H, Rüschoff J, Henkel T, Rohr G, Rossol S, Rösch W, Langen H, Zolg W, Tacke M. Identification of nicotinamide N-methyltransferase as a novel serum tumor marker for colorectal cancer. Clin Cancer Res 2005; 11:6550-7. [PMID: 16166432 DOI: 10.1158/1078-0432.ccr-05-0983] [Citation(s) in RCA: 157] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
PURPOSE The goal of this study was to identify and validate novel serum markers of human colorectal cancer as potential candidates for noninvasive detection of early colorectal neoplasm. EXPERIMENTAL DESIGN Employing two-dimensional gel electrophoresis and mass spectrometry, we analyzed 16 matched colorectal cancer and adjacent normal tissue samples. Proteins found to be elevated in cancer tissue were further validated by generating antibodies which were used for immunoblotting of tissue samples and for the development of highly sensitive immunoassays for assessment of serum samples. RESULTS In total, 735 different proteins were identified in colon tissue. Strong elevation in colorectal cancer for five proteins was confirmed by immunoblot analysis: transforming growth factor-beta induced protein ig-h3 (betaIG-H3), nicotinamide N-methyltransferase (NNMT), nucleoside diphosphate kinase A (nm23-H1), purine nucleoside phosphorylase (PNPH), and mannose-6-phosphate receptor binding protein 1 (M6P1). Elevated levels of NNMT, which is not predicted to be secreted but is known as a cytoplasmic protein, were found in serum from patients with colorectal cancer. Employing a receiver-operating characteristic curve based on the measurement of 109 patients with colorectal cancer and 317 healthy controls, we obtained an area under the curve of 0.84 for NNMT, which was superior to the established tumor marker carcinoembryogenic antigen with an area under the curve of 0.78. CONCLUSIONS It is proposed that NNMT serum levels may have significance in the early detection and in the management of patients with colorectal cancer.
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Affiliation(s)
- Markus Roessler
- Centralized Diagnostics, Roche Diagnostics GmbH, Penzberg, Germany
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Gisbert JP, Gomollón F, Cara C, Luna M, González-Lama Y, Pajares JM, Maté J, Guijarro LG. Actividad de la tiopurina metiltransferasa en la enfermedad inflamatoria intestinal. Un estudio en 7.046 pacientes españoles. Med Clin (Barc) 2005; 125:281-5. [PMID: 16159550 DOI: 10.1157/13078420] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
BACKGROUND AND OBJECTIVE Our objective was to assess the activity of thiopurine methyltransferase (TPMT) in a very large number of Spanish patients with inflammatory bowel disease (IBD), to evaluate the influence of several variables (including azathioprine or 6-mercaptopurine) on that activity, and to know the proportion of patients with low TPMT activity and therefore high risk of myelotoxicity when treated with these drugs. PATIENTS AND METHOD TPMT activity in red blood cells (RBCs) was measured by a radiochemical method. The association between several variables and TPMT values was assessed by multiple lineal regression. RESULTS 7046 patients were included (mean age: 37 years; 53% males): 70% with Crohn's disease, 22% with ulcerative colitis, and 8% with indeterminate colitis. Mean TPMT value was 20 (6) U/ml RBCs (minimum 0 and maximum 46). TPMT activity distribution was as follows: low levels (< 5 U/ml), 0.5%; intermediate (5-13.7), 11.1%; and high (> or = 13.8), 88.4%. TPMT values did not follow a normal distribution (p < 0.001). In the univariate study, statistically significant differences (p < 0.001), yet of doubtly clinical significance because its minimal magnitude, were demonstrated in TPMT values depending on age, sex, type of disease, and treatment with azathioprine/6-mercaptopurine. In the multivariate study, the variables associated with TPMT activity were: sex, treatment with 5-aminosalicylates, steroids and azathioprine/6-mercaptopurine. CONCLUSIONS This study shows that 0.5% of the Spanish patients with IBD have low TPMT activity (< 5 U/ml RBCs), a figure similar to that reported in other countries, these patients being at higher risk of myelotoxicity when treated with azathioprine or 6-mercaptopurine. The drugs usually prescribed for the treatment of IBD, including 5-aminosalicylates and azathioprine/6-mercaptopurine, do not seem to modify in a clinically relevant manner TPMT activity.
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Affiliation(s)
- Javier P Gisbert
- Servicio de Aparato Digestivo, Hospital Universitario de la Princesa, Universidad Autónoma, Madrid, Spain.
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Domènech Morral E, Gassull Duro MA. Actividad eritrocitaria de tiopurina metiltransferasa y tratamiento con tiopurinas en la enfermedad inflamatoria intestinal. Med Clin (Barc) 2005; 125:293-4. [PMID: 16159553 DOI: 10.1157/13078429] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Khalil MN, Erb N, Khalil PN, Escherich G, Janka-Schaub GE. Interference free and simplyfied liquid chromatography-based determination of thiopurine S-methyltransferase activity in erythrocytes. J Chromatogr B Analyt Technol Biomed Life Sci 2005; 821:105-11. [PMID: 15897017 DOI: 10.1016/j.jchromb.2005.04.028] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2004] [Revised: 04/26/2005] [Accepted: 04/28/2005] [Indexed: 10/25/2022]
Abstract
The determination of the thiopurine S-methyltransferase activity (TPMT; EC 2.1.1.67) has become an important issue during thiopurine therapy due to its known genetic polymorphism resulting in a wide range of TPMT activity. Therefore, the standard thiopurine drug regimen is associated with increased hematopoetic toxicity in patients with low or absent TPMT activity, whereas patients with high activity may be insufficiently treated. However, presently available methods are labour intensive and time consuming and tend towards too high or too low enzyme activity due to their methodological approach. The use of instable substrate solutions (6-MP or 6-TG), organic solvents like dimethyl sulfoxide and too high substrate and co-substrate saturation concentrations contribute to this phenomenon. We therefore, established an optimized and fast isocratic HPLC linked TPMT assay based on the enzymatic methylation of mercaptopurine or thioguanine in RBC lysates with S-adenosyl-l-methionine as methyl donor. Unspecific non-enzymatic methylation was not detectable. The recovery of 6-methyl-mercaptopurine was 97-102%, the intra- and interday variation between 1.0 and 5.0%, respectively. The assay dispenses with a time consuming extraction procedure with organic solvents, a heating step, and a gradient elution and is therefore, favourable for clinical routine application. The TPMT activity was measured in 62 untreated children with acute lymphoblastic leucemia at the time of diagnosis (activity = 34.0+/-10.6 nmol/g Hb/h, range: 11.5-55.4 nmol/g Hb/h) and in 12 adult healthy volunteers (62.8+/-7.7 nmol/g Hb/h, range: 48-82 nmol/g Hb/h) reflecting the wide measurable TPMT activity found in erythrocytes.
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Affiliation(s)
- Maurice N Khalil
- Clinic of Paediatric Haematology and Oncology, University Medical Center Hamburg-Eppendorf, D-20251 Hamburg, Germany
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Affiliation(s)
- I C Roberts-Thomson
- Dept. of Gastroenterology and Hepatology, The Queen Elizabeth Hospital, Woodville South, SA, Australia
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Hindorf U, Peterson C, Almer S. Assessment of thiopurine methyltransferase and metabolite formation during thiopurine therapy: results from a large Swedish patient population. Ther Drug Monit 2005; 26:673-8. [PMID: 15570193 DOI: 10.1097/00007691-200412000-00014] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
This study examined thiopurine methyltransferase (TPMT) and the relationship to thioguanine nucleotides (TGN) and methylthioinosine monophosphate (meTIMP) in a large Swedish patient population. The current hypothesis is that the cytotoxic effects of thiopurine drugs are mediated by the incorporation of TGN into DNA. The authors assayed the TPMT activity in red blood cells from 1151 subjects and the concentrations of TGN (n = 602) and meTIMP (n = 593) from patients treated with thiopurine drugs. The TPMT frequency distribution in both adults and children showed some differences from what had been found in unselected general populations. Children had lower median TPMT activity than adults (12.0 versus 12.9 U/mL RBC; P < 0.001). Relative differences in both TGN formation [medians: normal TPMT, 1.3; intermediate TPMT, 3.3; low TPMT, 47.9 pmol/8 x 10(8) RBC per mg azathioprine (AZA); P < 0.001] and meTIMP formation (medians: normal TPMT, 13; intermediate TPMT, 7.3; low TPMT, 0 pmol/8 x 10(8) RBC per mg AZA; P = 0.001) per 1 mg administered drug were noted among the 3 TPMT activity groups. Women formed higher concentrations of both TGN (1.5 versus 1.3 pmol/8 x 10(8) RBC per mg AZA; P = 0.01) and meTIMP (14.4 versus 10.7 pmol/8 x 10(8) RBC per mg AZA; P = 0.01) than men did. There was a significant correlation between the AZA dose and the meTIMP concentrations (r = 0.45; P < 0.001). Furthermore, dose alterations made in subjects with normal TPMT (n = 84) and intermediate TPMT (n = 22) activity resulted in more pronounced increases in TGN concentrations (170 versus 30 pmol/8 x 10(8) RBC; P < 0.001) in intermediate TPMT activity, whereas in normal TPMT activity changes in meTIMP concentrations were more pronounced (1.3 versus 0 nmol/8 x 10(8) RBC; P < 0.001). In normal TPMT activity both metabolites increased in a dose-dependent fashion, whereas in intermediate TPMT activity only TGN concentrations increased. The results of this study demonstrate the dynamic nature of thiopurine metabolism and its importance for thiopurine dosing.
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Affiliation(s)
- Ulf Hindorf
- Division of Gastroenterology, Department of Internal Medicine, University Hospital, Lund, Sweden.
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Abstract
Determination of thiopurine S-methyltransferase (TPMT) activity prior to starting azathioprine therapy is used to identify individuals with low or deficient TPMT activities who are at risk of severe complications and even death This case describes a patient treated with azathioprine without prior knowledge of TPMT status. Pancytopaenia developed over several months and at this point TPMT activity was determined and found to be low at 16 nmol 6-methyl thioguanine (6-MTG)/g Hb/h, which is within the reference interval associated with heterozygosity for TPMT mutant alleles. On repeating the TPMT measurement 3 months later, the TPMT activity was 2 nmol 6-MTG/g Hb/h, consistent with deficient TPMT activity (homozygosity for TPMT mutant alleles), suggesting the patient is at high risk of myelosuppression if treated with thiopurine drugs. Retrospectively, it was found that the patient had received transfusions of red blood cell and platelets 6 days before TPMT activity was first measured. This case underlines the importance of determining TPMT activity status prior to azathioprine treatment, rather than taking a dose incrementation approach. It also highlights the caution that must be taken in interpreting TPMT activity in patients who have recently been transfused.
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Affiliation(s)
- Loretta Ford
- Clinical Biochemistry Department, City Hospital, Birmingham B18 7QH, UK
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Schaeffeler E, Fischer C, Brockmeier D, Wernet D, Moerike K, Eichelbaum M, Zanger UM, Schwab M. Comprehensive analysis of thiopurine S-methyltransferase phenotype-genotype correlation in a large population of German-Caucasians and identification of novel TPMT variants. ACTA ACUST UNITED AC 2005; 14:407-17. [PMID: 15226673 DOI: 10.1097/01.fpc.0000114745.08559.db] [Citation(s) in RCA: 285] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
The thiopurine S-methyltransferase (TPMT) genetic polymorphism has a significant clinical impact on the toxicity of thiopurine drugs. It has been proposed that the identification of patients who are at high risk for developing toxicity on the basis of genotyping could be used to individualize drug treatment. In the present study, phenotype-genotype correlation of 1214 healthy blood donors was investigated to determine the accuracy of genotyping for correct prediction of different TPMT phenotypes. In addition, the influence of gender, age, nicotine and caffeine intake was examined. TPMT red blood cell activity was measured in all samples and genotype was determined for the TPMT alleles *2 and *3. Discordant cases between phenotype and genotype were systematically sequenced. A clearly defined trimodal frequency distribution of TPMT activity was found with 0.6% deficient, 9.9% intermediate and 89.5% normal to high methylators. The frequencies of the mutant alleles were 4.4% (*3A), 0.4% (*3C) and 0.2% (*2). All seven TPMT deficient subjects were homozygous or compound heterozygous carriers for these alleles. In 17 individuals with intermediate TPMT activity discordant to TPMT genotype, four novel variants were identified leading to amino acid changes (K119T, Q42E, R163H, G71R). Taking these new variants into consideration, the overall concordance rate between TPMT genetics and phenotypes was 98.4%. Specificity, sensitivity and the positive and negative predictive power of the genotyping test were estimated to be higher than 90%. Thus, the results of this study provide a solid basis to predict TPMT phenotype in a Northern European Caucasian population by molecular diagnostics.
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Affiliation(s)
- Elke Schaeffeler
- Dr Margarete Fischer-Bosch Institute of Clinical Pharmacology, Stuttgart, Germany
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Okada Y, Nakamura K, Kodama T, Ueki K, Tsukada Y, Maezawa A, Tsukamoto N, Nojima Y, Ishizaki T, Horiuchi R, Yamamoto K. Thiopurine Methyltransferase Genotype and Phenotype Status in Japanese Patients with Systemic Lupus Erythematosus. Biol Pharm Bull 2005; 28:2117-9. [PMID: 16272700 DOI: 10.1248/bpb.28.2117] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We investigated the genotypic status of thiopurine methyltransferase (TPMT) polymorphism to evaluate the possible risk of the toxicity of azathioprine (AZA) in 68 patients with systemic lupus erythematosus (SLE). The allele frequency of TPMT mutation in the SLE group (2.9%) was higher than that in 174 Japanese healthy volunteers (1.1%), although it did not reach statistically significant difference (p=0.23). The mean value of TPMT activities in 51 subjects with TPMT*1/*1 was 40% higher than that of 4 subjects with TPMT*1/*3C in SLE group (18.1+/-6.1 nmol/h/ml packed red blood cells (pRBC) versus 13.2+/-3.2 nmol/h/ml pRBC; p=0.11). Two out of 4 SLE patients with TPMT*1/*3C had been treated with AZA, and one patient showed a leucopenia. The TPMT genotyping before AZA treatment is recommended for Japanese SLE patient group to avoid the AZA-induced adverse events, although detection of the patient with low TPMT activity by genotyping is still imperfect.
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Affiliation(s)
- Yuko Okada
- Department of Clinical Pharmacology, Gunma University Graduate School of Medicine, Japan
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Abstract
BACKGROUND The immunosuppressive effects of thiopurine drugs are mainly mediated through their intracellular metabolism into active 6-thioguanine nucleotide (6-TGN) metabolites, which are incorporated into DNA. Erythrocyte 6-TGN (E-6TGN) levels have been proposed as an instrument for monitoring treatment. The aim of the study was to use erythrocyte E-6TGN, methylated mercaptopurine (MeMP) metabolites, and thiopurine methyltransferase (TPMT) measurements in a clinical setting to determine the clinical outcome in relation to thiopurine metabolism. METHODS Fifty-five adult patients with inflammatory bowel disease were included in a prospective study and followed for 6 months. Metabolite levels were measured and correlated to outcome and AZA/6-MP dose. RESULTS The E-6TGN level was significantly related to the TPMT genotype (P = 0.008). Patients in disease remission had higher E-6TGN levels than patients with disease activity both at baseline (P < 0.05) and after 6 months (P = 0.02). Active disease was more frequent among subjects with E-6TGN < or = 125 nmol/mmol Hb at baseline (P = 0.04), but not at 6 months. AZA/6-MP drug dose was positively correlated to E-MeMP levels (r = 0.48; P < 0.001) and E-MeMP/E-6TGN ratio (r = 0.41; P = 0.002). Dose changes were positively correlated with the changes in E-MeMP levels (P = 0.01) and E-MeMP/E-6TGN ratio (P = 0.03). CONCLUSIONS E-6TGN level was the only factor in this study related to disease activity, while there was no relationship between AZA/6-MP dose and E-6TGN levels. This finding illustrates the clinical usefulness of E-6TGN monitoring in the evaluation of treatment intensity.
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Affiliation(s)
- U Hindorf
- Section of Gastroenterology, Department of Internal Medicine, Blekinge Hospital, Karlskrona, Sweden.
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Kubota T, Nishida A, Takeuchi K, Iida T, Yokota H, Higashi K, Nakahara K, Hanai H, Iga T. Frequency distribution of thiopurine S-methyltransferase activity in red blood cells of a healthy Japanese population. Ther Drug Monit 2004; 26:319-21. [PMID: 15167635 DOI: 10.1097/00007691-200406000-00017] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Thiopurine S-methyltransferase (TPMT), which exhibits a genetic polymorphism, plays an important role in the metabolism of thiopurine drugs such as mercaptopurine, thioguanine, and azathioprine. To determine the frequency distribution of TPMT activity in 157 Japanese subjects with different TPMT genotypes, ie, TPMT*1/*1 and TPMT*1/*3, the authors measured levels of 6-methylmercaptopurine formed from 6-mercaptopurine in red blood cells lysates by HPLC. The TPMT activities in our Japanese subjects ranged from 11.0 to 42.6 pmol/h/mgHb. Although the mean value of TPMT activities in 6 subjects with TPMT*1/*3C (20.3 +/- 8.1 pmol/h/mgHb) was 25% lower than that in 151 subjects with TPMT*1/*1 (27.0 +/- 5.1 pmol/h/mgHb), there was overlap. The ranges of TPMT activity in subjects with TPMT*1/*1 and those with TPMT*1/*3C were similar. The median values in TPMT*1/*3C and TPMT*1/*1 individuals were 20.1 (11.0-31.2) and 26.8 pmol/h/mgHb (15.7-42.7), respectively (Mann-Whitney U-test: median difference 6.7 pmol/h/mgHb, 95% CI 0-25.5, P < 0.05). This observation may have relevance for the use of 6-mercaptopurine and azathioprine as therapeutic agents in Japanese patients.
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Affiliation(s)
- Takahiro Kubota
- Department of Pharmacy, University of Tokyo Hospital, Faculty of Medicine, Tokyo, Japan.
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Ganiere-Monteil C, Medard Y, Lejus C, Bruneau B, Pineau A, Fenneteau O, Bourin M, Jacqz-Aigrain E. Phenotype and genotype for thiopurine methyltransferase activity in the French Caucasian population: impact of age. Eur J Clin Pharmacol 2004; 60:89-96. [PMID: 15022030 DOI: 10.1007/s00228-004-0732-5] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2003] [Accepted: 01/16/2004] [Indexed: 10/26/2022]
Abstract
OBJECTIVE Thiopurine drugs are commonly used in pediatric patients for the treatment of acute leukemia, organ transplantation and inflammatory diseases. They are catabolized by the cytosolic thiopurine methyltransferase (TPMT), which is subject to a genetic polymorphism. In children, enzyme activities are immature at birth and developmental patterns vary widely from one enzyme to another. The present study was undertaken to evaluate erythrocyte TPMT activity and the correlation between genotype and phenotype in different age groups from birth to adolescence and adulthood. METHODS The study included 304 healthy adult blood donors, 147 children and 18 neonates (cord bloods). TPMT activity was measured by liquid chromatography, and genotype was determined using a polymerase chain reaction reverse dot-blot analysis identifying the predominant TPMT mutant alleles (TPMT*3A, TPMT*3B, TPMT*3C, TPMT*2). RESULTS There was no significant difference in TPMT activity between cord bloods ( n=18) and children ( n=147) (17.48+/-4.04 versus 18.62+/-4.14 respectively, P=0.424). However, TPMT was significantly lower in children than in adults (19.34+/-4.09) ( P=0.033). In the whole population, there were 91.9% homozygous wild type, 7.9% heterozygous mutants and 0.2% homozygous mutants. The frequency of mutant alleles was 3.0% for TPMT*3A, 0.7% for TPMT*2 and 0.4% for TPMT*3C. CONCLUSION No impact of child development on TPMT activity could be evidenced, suggesting that TPMT activity is already mature at birth. The difference between children and adults was low with reduced clinical impact expected. When individual TPMT activity was compared with genotype, there was an overlapping region where subjects (4.5%, 12 adults, 9 children) were either homozygous wild type or heterozygous, with a TPMT activity below the antimode value. This result highlighted the importance of measuring TPMT activity to detect all patients at risk of thiopurine toxicity.
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Shipkova M, Niedmann PD, Armstrong VW, Oellerich M, Wieland E. Determination of Thiopurine Methyltransferase Activity in Isolated Human Erythrocytes Does Not Reflect Putative in Vivo Enzyme Inhibition by Sulfasalazine. Clin Chem 2004; 50:438-41. [PMID: 14752016 DOI: 10.1373/clinchem.2003.026096] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Maria Shipkova
- Central Institute for Clinical Chemistry and Laboratory Medicine, Klinikum Stuttgart, Germany.
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Affiliation(s)
- Nanda M Verhoeven
- Department of Child Neurology, VU University Medical Center, De Boelelaan 1117, 1081 HV Amsterdam, The Netherlands.
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Ford LT, Berg JD. Determination of thiopurine S-methyltransferase activity in erythrocytes using 6-thioguanine as substrate and a non-extraction liquid chromatographic technique. J Chromatogr B Analyt Technol Biomed Life Sci 2003; 798:111-5. [PMID: 14630365 DOI: 10.1016/j.jchromb.2003.09.017] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
A non-extraction high-performance liquid chromatographic (HPLC) method has been developed for the determination of 6-methylthioguanine (6-MTG), as part of the determination of thiopurine S-methyltransferase activity (TPMT) in erythrocytes. Erythrocyte lysate is added to a glass vial containing substrates and incubation buffer, which is then sealed for the rest of the analysis. Enzyme incubation, sample preparation, and analysis are then undertaken without further sample-handling steps. The need for a solvent extraction step has been overcome by heating the incubate to 85 degrees C to stop the enzyme reaction. The heat inactivation step precipitates protein which upon centrifugation forms a thin film in the bottom of the glass vial enabling the supernatant to be injected directly onto the HPLC system. The assay shows excellent precision and recovery with a within-batch imprecision giving a co-efficient of variation of 2.9% (mean=41.5 nmol 6-MTG/gHb/h, n=10) and 5.1% (mean=12.6 nmol 6-MTG/g Hb/h, n=10). The between-batch imprecision gives a co-efficient of variation of 8.2% (mean=11.1 nmol 6-MTG/gHb/h, n=11) and 7.3% (mean=41.0 nmol 6-MTG/gHb/h, n=16). Determination of the TPMT activity in 120 people shows a range of enzyme activity of 11.3-63.8 nmol 6-MTG/gHb/h with a mean and median activity of 34.8 and 34.2 nmol 6-MTG/gHb/h, respectively. TPMT is increasingly used in clinical practice to ensure optimisation of treatment with thioguanine drugs. This direct HPLC method minimises sample-handling, reduces inherent imprecision, the possibility of laboratory error and with the potential for further automation, makes it ideal for use in a regional referral laboratory.
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Affiliation(s)
- Loretta Theresa Ford
- Clinical Biochemistry Department, City Hospital, Dudley Road, Birmingham B18 7QH, UK
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Abstract
Azathioprine (AZA) is widely used in the management of rheumatological diseases. Despite its efficacy, AZA can often cause bone marrow suppression, notably leucopenia, which has been recorded in up to 17% of patients taking AZA for rheumatoid arthritis, though this can be considered clinically significant in about 3% overall. Severe myelosuppression, associated with abnormal AZA metabolism, is linked to the thiopurine methyltransferase (TPMT) genetic polymorphism. TPMT status can be assessed prior to AZA treatment by measuring enzyme activity or genotyping techniques. Analysis of recent data suggests that by optimizing the AZA dose on the basis of TPMT status testing (with a substantial reduction in dose for patients homozygous for mutant TPMT alleles), a reduction in drug-induced morbidity and cost savings can be made by avoiding hospitalization and rescue therapy for leucopenic events. In this article we review the pharmacogenetic and clinical implications of the TPMT polymorphism, emphasizing its relevance to rheumatologists managing diseases with AZA.
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Affiliation(s)
- G P R Clunie
- Rheumatology Department, Ipswich Hospital NHS Trust, Ipswich, UK.
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Indjova D, Shipkova M, Atanasova S, Niedmann PD, Armstrong VW, Svinarov D, Oellerich M. Determination of Thiopurine Methyltransferase Phenotype in Isolated Human Erythrocytes Using a New Simple Nonradioactive HPLC Method. Ther Drug Monit 2003; 25:637-44. [PMID: 14508388 DOI: 10.1097/00007691-200310000-00014] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Genetic polymorphism of the S-methylation pathway catalyzed by thiopurine methyltransferase (TPMT) is responsible for variation in the metabolism, toxicity, and therapeutic efficacy of thiopurine drugs. This paper describe a new simple, nonradioactive HPLC method for determination of TPMT activity in isolated erythrocytes (Ery), based on the conversion of 6-mercaptopurine (pH 7.5, 37 degrees C) to 6-methylmercaptopurine (6-MMP) using S-adenosyl-l-methionine as methyl donor. The incubation step was stopped by a mixture of trichloroacetic acid/acetonitrile containing the internal standard 4-aminoacetophenone. 6-MMP was quantified by absorbance at 290 nm after chromatographic separation on a Zorbax SB-Phenyl column (5 microm, 4.6 x 250 mm) using mobile phases (flow rate 1.1 mL/min) consisting of acetonitrile, phosphate buffer pH 3.0, triethylamine, and dithiothreitol. The assay was linear up to 50 nmol/(mL Ery. h), and the detection limit was 0.3 nmol/(mL Ery. h). The extraction efficiency of 6-MMP was 95-103% (n = 3), and its analytic recovery ranged between 98.3% and 101.8% (n = 12). The within-day imprecision using pooled human erythrocytes (n = 12) was 4.4% at a TPMT activity of 14.3 nmol/(mL Ery.h) and 4.9% at 6.5 nmol/(mL Ery.h). The between-day imprecision (n = 12) was 6.8% and 7.5% nmol/(mL Ery.h), respectively. A very good agreement was found between TPMT activity determined with this method (y) and a widely used radiochemical procedure (x) (r = 0.94; n = 130; y = 0.502 + 0.946x; P < 0.05). Genotype analysis of all individuals with TPMT activity under 12.5 nmol/(mL Ery.h) revealed a genotype/phenotype concordance of 86%. The new HPLC method for determination of TPMT activity in Ery is a simple, rapid, and reliable nonradioactive procedure that can be successfully used for both research and routine clinical analysis.
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Affiliation(s)
- Dessislava Indjova
- Department of Clinical Laboratory, Medical University Sofia, Sofia, Bulgaria.
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Lindqvist M, Almer S, Peterson C, Söderkvist P. Real-time RT-PCR methodology for quantification of thiopurine methyltransferase gene expression. Eur J Clin Pharmacol 2003; 59:207-11. [PMID: 12819840 DOI: 10.1007/s00228-003-0617-z] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2002] [Accepted: 04/16/2003] [Indexed: 11/27/2022]
Abstract
OBJECTIVE The aim of the present study was to develop a real-time reverse-transcription polymerase chain reaction (RT-PCR) methodology for the quantification of thiopurine methyltransferase (TPMT) gene expression in whole blood and compare it with the TPMT enzyme activity measured in red blood cells. METHODS TPMT gene expression was quantified relative to the housekeeping gene cyclophilin (huCYC) and expressed as a TPMT/huCYC ratio. TPMT activity in red blood cells was determined by measuring the formation rate of 6-(14)C-methylmercaptopurine from 6-MP using S-adenosyl-L-((14)C-methyl)-methionine as methyl donor. Thirty-nine individuals were included in the study. A cut-off value of 9 U/ml pRBC was used to distinguish intermediate TPMT enzyme activity from high TPMT enzyme activity. RESULTS Sequencing of the real-time RT-PCR amplicon proved that the method was specific for the TPMT cDNA, without co-amplification of the highly similar TPMT processed pseudogene. The intra-assay coefficients of variation (CVs), as determined by the threshold cycle, were 0.7% for TPMT and 0.5% for huCYC. The interassay CVs were 1.5% for TPMT and 4.0% for huCYC. The intra- and interassay CVs, as determined by the TPMT/huCYC ratio, were 8.6% and 25%, respectively. There was a statistically significant correlation between TPMT enzyme activity and mRNA level in blood cells from individuals with an enzyme activity above 9 U/ml pRBC (r(s)=0.66, P=0.0001). However, we did not find any statistically significant correlation in individuals with lower enzyme activity or when analysing the whole population. CONCLUSION We present a specific and robust real-time RT-PCR method for quantifying TPMT gene expression. The method may be used for studies on TPMT gene regulation.
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Affiliation(s)
- Malin Lindqvist
- Department of Medicine and Care, Division of Clinical Pharmacology, Faculty of Health Sciences, Linköping University, 58185 Linköping, Sweden.
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Affiliation(s)
- A Qasim
- Gastroenterolgy Department, AMNCH, Tallaght, Dublin 24, Ireland
| | - J Seery
- Gastroenterolgy Department, AMNCH, Tallaght, Dublin 24, Ireland
| | - M Buckley
- Gastroenterolgy Department, AMNCH, Tallaght, Dublin 24, Ireland
| | - C O Morain
- Gastroenterolgy Department, AMNCH, Tallaght, Dublin 24, Ireland
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Schwab M, Herrlinger K, Schaeffeler E, Stange EF. [Therapy of chronic inflammatory bowel diseases with azathioprine, 6-mercaptopurine and 6-thioguanine. Clinico-pharmacologic aspects]. Dtsch Med Wochenschr 2003; 128:378-85. [PMID: 12594624 DOI: 10.1055/s-2003-37378] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Affiliation(s)
- M Schwab
- Dr. Margarete Fischer-Bosch Institut für Klinische Pharmakologie, Stuttgart
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Steventon GB, Waring RH, Williams AC. An Investigation into the Inter-Relationships of Sulphur Xeno- Biotransformation Pathways in Parkinson's and Motor Neurone Diseases. ACTA ACUST UNITED AC 2003; 19:223-40. [PMID: 14768972 DOI: 10.1515/dmdi.2003.19.4.223] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
The role of defective 'sulphur xenobiotic' biotransformations in the aetiology of Parkinson's and motor neurone diseases has been in the literature for over a decade. Problems in the S-oxidation of aliphatic thioethers, sulphation of phenolic compounds and the S-methylation of aliphatic sulphydryl groups have all been reported. These reports have also been consistent in observing that only a 'significant minority' of patients express these problems in sulphur biotransformation pathways. However, no investigation has yet reported on the incidence of these three defective pathways in control invididuals and in patients with Parkinson's and motor neurone disease. This investigation has found that: 1. Forty percent of patients with Parkinson's and motor neurone disease have a defect in the S-oxidation of S-carboxymethyl-L-cysteine compared to 4% of controls. 2. 35-40% of patients with Parkinson's and motor neurone disease have a defect in the sulphation of paracetamol compared to 4% of controls. 3. 60% of patients with motor neurone disease have a high capacity for the S-methylation of 2-mercaptoethanol compared to 4% of controls. 4. 38% of patients with Parkinson's disease have a low capacity for the S-methylation of 2-mercaptoethanol compared to 4% of controls. 5. There is no correlation between the S-oxidation phenotype, low paracetamol sulphation phenotype and low or high S-methylation phenotype in controls or patients with Parkinson's or motor neurone disease. 6. The number of controls that expressed one of the aberrant phenotypes was 4% compared to 38% of the patients with Parkinson's disease and 47% of the patients with motor neurone disease. 7. The number of controls that expressed two of the aberrant phenotypes was 0% compared to 18% of the patients with Parkinson's disease and 19% of those with motor neurone disease. 8. No controls or patients with Parkinson's disease or motor neurone disease expressed all three of the aberrant phenotypes. The results indicate that the three xeno-biotransformation pathways are under separate genetic control in the three population groups studied and that patients with Parkinson's and motor neurone disease do not have a widespread defect in their sulphur xenobiochemistry capacity.
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Affiliation(s)
- Glyn B Steventon
- Department of Pharmacy, School of Health and Life Sciences, King's College London, UK.
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48
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Keizer-Garritsen JJ, Brouwer C, Lambooy LHJ, Ter Riet P, Bökkerink JPM, Trijbels FJM, De Abreu RA. Measurement of thiopurine S-methyltransferase activity in human blood samples based on high-performance liquid chromatography: reference values in erythrocytes from children. Ann Clin Biochem 2003; 40:86-93. [PMID: 12542916 DOI: 10.1258/000456303321016222] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
BACKGROUND Monitoring 6-thiopurine S-methyltransferase (TPMT; EC 2.1.1.67) activity is especially important when patients are treated with 6-thiopurine drugs, since severe bone marrow toxicity may be induced if patients have deficient TPMT activity. METHODS We have developed a method based on high-performance liquid chromatography (HPLC) for the measurement of TPMT activity in various cell types: erythrocytes (RBC), human peripheral blood mononuclear cells (pMNC) and human malignant lymphoblasts (Molt-F4). The enzymatic activity is measured by the amount of 6-methylmercaptopurine formed, using 6-mercaptopurine (6MP) as substrate and S-adenosylmethionine as co-substrate. RESULTS The K(m) values calculated for 6MP were 0.54 (RBC), 0.85 (pMNC) and 0.65 (Molt-F4 cells) mmol/L. The K(m) values for S-adenosylmethionine were 11.9 (RBC), 16.4 (pMNC) and 6.65 (Molt-F4 cells) micro mol/L. The assay variation was 8.2-17%. TPMT activity was determined in a control group of 103 children and young adults (44 female, 59 male). The values observed were (mean +/- standard deviation): female children and young adults, 15.1 +/- 4.8 pmol/10(7) cells per h (n = 44); male children and young adults, 15.8 +/- 6.4 pmol/10(7) cells per h (n = 59). No gender or age differences were found. CONCLUSION The HPLC-based method enables the rapid screening of TPMT activities in large groups of patients treated with 6-thiopurines.
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Affiliation(s)
- Jenneke J Keizer-Garritsen
- Center for Pediatric Oncology, SE Netherlands, Department of Pediatrics, University Medical Center St Radboud, PO Box 9101, 6500 HB Nijmegen, The Netherlands
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Ansari A, Hassan C, Duley J, Marinaki A, Shobowale-Bakre EM, Seed P, Meenan J, Yim A, Sanderson J. Thiopurine methyltransferase activity and the use of azathioprine in inflammatory bowel disease. Aliment Pharmacol Ther 2002; 16:1743-50. [PMID: 12269967 DOI: 10.1046/j.1365-2036.2002.01353.x] [Citation(s) in RCA: 148] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
BACKGROUND Azathioprine therapy is discontinued in one-third of patients with inflammatory bowel disease because of toxicity or a lack of clinical response. Patients with thiopurine methyltransferase (TPMT) deficiency are intolerant to azathioprine, whilst carriers are at increased risk of side-effects. AIM To evaluate the importance of TPMT activity in the management of azathioprine therapy in inflammatory bowel disease. METHODS Clinical response, adverse effects and haematological parameters were determined and correlated with TPMT enzyme activity and genotype in 106 patients with inflammatory bowel disease. RESULTS Ninety-six patients had high TPMT activity, and 10 had intermediate activity. Nineteen patients (18%) were intolerant to azathioprine. Fifteen (16%) of those with high TPMT activity were intolerant, compared with five (50%) with intermediate activity [odds ratio (OR), 5.4; 95% confidence interval (CI), 1.5-19.8]. Complete remission was achieved in 63% of cases, and complete or partial remission in 79%. Interestingly, very high TPMT activity (> 14 units/mL red blood cells) was significantly associated with non-response, irrespective of the time on azathioprine (OR, 0.21; 95% CI, 0.07-0.68). TPMT gene mutations correlated with TPMT activity. CONCLUSIONS Inflammatory bowel disease patients with intermediate TPMT activity have an increased risk of azathioprine toxicity. Conversely, very high TPMT activity predicts treatment failure. TPMT genotype predicted TPMT phenotype in this study.
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Affiliation(s)
- A Ansari
- Department of Public Health Medicine, GKT School of Medicine, London, UK
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Murphy LA, Atherton D. A retrospective evaluation of azathioprine in severe childhood atopic eczema, using thiopurine methyltransferase levels to exclude patients at high risk of myelosuppression. Br J Dermatol 2002; 147:308-15. [PMID: 12174104 DOI: 10.1046/j.1365-2133.2002.04922.x] [Citation(s) in RCA: 101] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
BACKGROUND Atopic eczema is a chronic inflammatory skin disease, which in most children can be adequately controlled using topical therapy. However, in a small number of children it is necessary to use systemic treatments to gain an acceptable level of disease control. OBJECTIVES To evaluate azathioprine as a treatment for severe atopic eczema in children, and the value of pretreatment thiopurine methyltransferase (TPMT) levels in the identification of patients at high risk of myelosuppression. METHODS Between January 1997 and May 2000, 91 children had erythrocyte TPMT assays with the intention of treating their atopic eczema with azathioprine. This study is based on retrospective examination of data taken from the hospital notes of these children, who had attended Great Ormond Street Hospital for Children and St John's Institute of Dermatology, London. RESULTS The distribution of TPMT values corresponded closely to that previously described in adults. Forty-eight children were commenced on treatment with azathioprine. Twenty-eight had an excellent response to treatment, 13 had a good response and seven had a poor response. No patient developed neutropenia. CONCLUSIONS Azathioprine may prove a very valuable treatment for severe atopic eczema in children. We consider its short-term adverse effect profile in children with normal TPMT activity to have been entirely acceptable with our treatment protocol. As result, we now feel confident to initiate therapy at dose levels of 2.5-3.5 mg kg(-1) in those with a normal TPMT level, and to reduce the frequency with which we undertake tests of bone marrow and liver function.
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Affiliation(s)
- L-A Murphy
- Department of Dermatology, Great Ormond Street Hospital for Children NHS Trust, London WC1N 3JH, UK
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