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Kakuta Y, Kinouchi Y, Shimosegawa T. Pharmacogenetics of thiopurines for inflammatory bowel disease in East Asia: prospects for clinical application of NUDT15 genotyping. J Gastroenterol 2018; 53:172-180. [PMID: 29192347 PMCID: PMC5846876 DOI: 10.1007/s00535-017-1416-0] [Citation(s) in RCA: 60] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/19/2017] [Accepted: 11/19/2017] [Indexed: 02/06/2023]
Abstract
The thiopurine drugs 6-mercaptopurine (6-MP) and azathiopurine (AZA) are widely used to treat inflammatory bowel disease. However, the incidence of adverse reactions is high, particularly in Asia, and the mechanisms of toxicity in Asian populations remain unclear. Thiopurine S-methyltransferase (TPMT) is a well-known enzyme that inactivates AZA or 6-MP through methylation and is one of the few pharmacogenetic predictors used in clinical settings in Western countries. Individuals carrying TPMT-deficient genetic variants require reduced drug doses, but this treatment modification is are not applicable to East Asian populations. Several genes code thiopurine-metabolizing enzymes, including TPMT, multidrug-resistance protein 4, and inosine triphosphatase. These genes have been studied as candidate pharmacogenetic markers; however, it remains unclear why Asian populations seem to be more intolerant than other ethnic groups to a full dose of thiopurines. A genome-wide association approach to identify Asian-specific pharmacogenetic markers in Korean patients with Crohn's disease revealed that a non-synonymous single nucelotide polymorphism in nucleoside diphosphate-linked moiety X-type motif 15 (NUDT15) which causes p.Arg139Cys was strongly associated with thiopurine-induced early leukopenia. Six common haplotypes of NUDT15 were reported, and five variants showed medium-to-low enzyme activities, compared with the wild haplotype. NUDT15 hydrolyzes the thiopurine active metabolites 6-thio-GTP and 6-thio-dGTP; variants of NUDT15 had lower enzyme activities, causing higher levels of thiopurine active metabolites, resulting in thiopurine-induced leukopenia. In clinical application, NUDT15 genotyping is a good candidate for predicting thiopurine toxicity in East Asian populations. However, the association of NUDT15 diplotypes with thiopurine toxicity remains unclear. Further analyses with large cohorts to confirm the clinical effects of each haplotype are planned.
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Affiliation(s)
- Yoichi Kakuta
- Division of Gastroenterology, Tohoku University Graduate School of Medicine, 1-1 Seiryo, Aoba, Sendai, 980-8574 Japan
| | - Yoshitaka Kinouchi
- Institute for Excellent in Higher Education, Tohoku University, Sendai, Japan
| | - Tooru Shimosegawa
- Division of Gastroenterology, Tohoku University Graduate School of Medicine, 1-1 Seiryo, Aoba, Sendai, 980-8574 Japan
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Hoang PTV, Ambroise J, Dekairelle AF, Durant JF, Butoescu V, Chi VLD, Huynh N, Nguyen TB, Robert A, Vermylen C, Gala JL. Comparative pharmacogenetic analysis of risk polymorphisms in Caucasian and Vietnamese children with acute lymphoblastic leukemia: prediction of therapeutic outcome? Br J Clin Pharmacol 2015; 79:429-40. [PMID: 25099492 DOI: 10.1111/bcp.12481] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2013] [Accepted: 08/04/2014] [Indexed: 01/10/2023] Open
Abstract
AIMS Acute lymphoblastic leukemia (ALL) is the most common of all paediatric cancers. Aside from predisposing to ALL, polymorphisms could also be associated with poor outcome. Indeed, genetic variations involved in drug metabolism could, at least partially, be responsible for heterogeneous responses to standardized leukemia treatments, hence requiring more personalized therapy. The aims of this study were to (a) to determine the prevalence of seven common genetic polymorphisms including those that affect the folate and/or thiopurine metabolic pathways, i.e. cyclin D1 (CCND1-G870A), γ-glutamyl hydrolase (GGH-C452T), methylenetetrahydrofolate reductase (MTHFR-C677T and MTHFR-A1298C), thymidylate synthase promoter (TYMS-TSER), thiopurine methyltransferase (TPMT*3A and TPMT*3C) and inosine triphosphate pyrophosphatase (ITPA-C94A), in Caucasian (n = 94, age < 20) and Vietnamese (n = 141, age < 16 years) childhood ALL and (b) to assess the impact of a multilocus genetic risk score (MGRS) on relapse-free survival (RFS) using a Cox proportional-hazards regression model. RESULTS The prevalence of MTHFR-677TT genotype was significantly higher in Caucasians (P = 0.008), in contrast to the prevalence of TYMS-TSER*3R/3R and ITPA-94AA/AC genotypes which were significantly higher in Vietnamese (P < 0.001 and P = 0.02, respectively). Compared with children with a low MGRS (≤ 3), those with a high MGRS (≥ 4) were 2.06 (95% CI = 1.01, 4.22; P = 0.04) times more likely to relapse. Adding MGRS into a multivariate Cox regression model with race/ethnicity and four clinical variables improved the predictive accuracy of the model (AUC from 0.682 to 0.709 at 24 months). CONCLUSION Including MGRS into a clinical model improved the predictive accuracy of short and medium term prognosis, hence confirming the association between well determined pharmacogenotypes and outcome of paediatric ALL. Whether variants on other genes associated with folate metabolism can substantially improve the predictive value of current MGRS is not known but deserves further evaluation.
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Affiliation(s)
- Phuong Thu Vu Hoang
- Centre de Technologies Moléculaires Appliquées (CTMA), Institut de Recherche Expérimentale et Clinique (IREC), Université catholique de Louvain (UCL), Brussels, Belgium; Service d'hématologie et oncologie pédiatrique, Cliniques universitaires Saint-Luc, Université catholique de Louvain (UCL), Brussels, Belgium; Pham Ngoc Thach University of Medecin, Ho Chi Minh city, Vietnam; Blood Transfusion and Hematology Hospital, Ho Chi Minh city, Vietnam
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Abstract
The drug-metabolizing enzyme thiopurine methyltransferase (TPMT) has become one of the best examples of pharmacogenomics to be translated into routine clinical practice. TPMT metabolizes the thiopurines 6-mercaptopurine, 6-thioguanine, and azathioprine, drugs that are widely used for treatment of acute leukemias, inflammatory bowel diseases, and other disorders of immune regulation. Since the discovery of genetic polymorphisms in the TPMT gene, many sequence variants that cause a decreased enzyme activity have been identified and characterized. Increasingly, to optimize dose, pretreatment determination of TPMT status before commencing thiopurine therapy is now routine in many countries. Novel TPMT sequence variants are currently numbered sequentially using PubMed as a source of information; however, this has caused some problems as exemplified by two instances in which authors' articles appeared on PubMed at the same time, resulting in the same allele numbers given to different polymorphisms. Hence, there is an urgent need to establish an order and consensus to the numbering of known and novel TPMT sequence variants. To address this problem, a TPMT nomenclature committee was formed in 2010, to define the nomenclature and numbering of novel variants for the TPMT gene. A website (http://www.imh.liu.se/tpmtalleles) serves as a platform for this work. Researchers are encouraged to submit novel TPMT alleles to the committee for designation and reservation of unique allele numbers. The committee has decided to renumber two alleles: nucleotide position 106 (G>A) from TPMT*24 to TPMT*30 and position 611 (T>C, rs79901429) from TPMT*28 to TPMT*31. Nomenclature for all other known alleles remains unchanged.
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Influences of thiopurine methyltransferase genotype and activity on thiopurine-induced leukopenia in Korean patients with inflammatory bowel disease: a retrospective cohort study. J Clin Gastroenterol 2010; 44:e242-8. [PMID: 20308917 DOI: 10.1097/mcg.0b013e3181d6baf5] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
BACKGROUND AND AIM Myelotoxicity has been shown to be very common in Korean patients with inflammatory bowel disease (IBD) during azathioprine (AZA) or 6-mercaptopurine (6-MP) treatment. The purpose of this study was to investigate the relative risk of the thiopurine methyltransferase (TPMT) and inosine triphosphate pyrophosphatase (ITPA) genotypes and TPMT activity for the development of leukopenia in Korean IBD patients during AZA/6-MP treatment. METHODS We retrospectively analyzed 286 Korean patients with IBD who had been treated with AZA/6-MP for at least 6 months between June 1996 and September 2006. Common TPMT mutations, including TPMT*1, *2, *3A, *3B, and *3C, and ITPA mutations, including 94C>A and IVS2+21A>C, were determined using a high-performance liquid chromatography method. TPMT activity was measured using liquid chromatography with coupled mass spectrometry/mass spectrometry. RESULTS Leukopenia occurred in 118 cases (41.3%). TPMT *1/*3C was detected in 7 cases (2.4%), and ITPA 94 C>A was detected in 66 cases (23.1%), including 63 heterozygotes (22.1%) and 3 homozygotes (1.0%). The median TPMT activity was 9.3 U/mL (interquartile range 10.4, range 2.1 to 76.2). Cox regression analysis revealed that patients with heterozygous *3C type TPMT had a higher probability of leukopenia than those with wild type TPMT (P=0.02). Patients with intermediate TPMT activity had a lower probability of leukopenia than those with low activity (P=0.01). However, the ITPA genotype did not affect the risk of leukopenia. CONCLUSIONS Our data showed that it could be helpful to examine TPMT genotypes and to measure TPMT activity in Korean patients taking AZA/6-MP to predict the development of leukopenia.
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Fotoohi AK, Coulthard SA, Albertioni F. Thiopurines: factors influencing toxicity and response. Biochem Pharmacol 2010; 79:1211-20. [PMID: 20096268 DOI: 10.1016/j.bcp.2010.01.006] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2009] [Revised: 12/22/2009] [Accepted: 01/12/2010] [Indexed: 11/17/2022]
Abstract
Thiopurines are the backbone of current anti-leukemia regimens and have also been effective immunosuppressive agents for the past half a century. Extensive research on their mechanism of action has been undertaken, yet many issues remain to be addressed to resolve unexplained cases of thiopurine toxicity or treatment failure. The aim of this review is to summarize current knowledge of the mechanism of thiopurine action in experimental models and put into context with clinical observations. Clear understanding of their metabolism will contribute to maximizing efficacy and minimizing toxicity by individually tailoring therapy according to the expression profile of relevant factors involved in thiopurine activation pathway.
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Affiliation(s)
- Alan Kambiz Fotoohi
- Department of Oncology and Pathology, Cancer Center Karolinska, Karolinska Institutet, SE-17176 Stockholm, Sweden
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Jung YS, Cheon JH, Park JJ, Moon CM, Kim ES, Lee JH, Kim SW, Kim JH, Hong SP, Kim TI, Kim WH. Correlation of genotypes for thiopurine methyltransferase and inosine triphosphate pyrophosphatase with long-term clinical outcomes in Korean patients with inflammatory bowel diseases during treatment with thiopurine drugs. J Hum Genet 2009; 55:121-3. [PMID: 19960028 DOI: 10.1038/jhg.2009.125] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
There is a lack of research describing the associations between thiopurine methyltransferase (TPMT)/inosine triphosphate pyrophosphatase (ITPA) genotypes and long-term clinical outcomes. We investigated whether TPMT/ITPA genotypes predicted long-term clinical response in Korean patients with inflammatory bowel diseases (IBDs) undergoing thiopurine treatment. A total of 204 patients with IBD in whom thiopurine treatment was indicated were enrolled and categorized by TPMT and ITPA genotypes. Long-term follow-up clinical data for these patients were analyzed with specific focus on disease relapse. Of the 204 patients, 162 (79.4%) patients using thiopurines achieved remission and were included in an analysis of long-term clinical outcomes. There were no significant differences in disease relapse-free survival between wild and mutant types of TPMT (P=0.903) or ITPA (P=0.392), according to the results of the log-rank analysis. Our study suggests that TPMT and ITPA genotypes may not affect the rates of disease relapse in IBD patients treated with thiopurines. Further studies are indicated to confirm the utility of TPMT/ITPA genotyping to guide clinicians formulating individualized treatments for IBD patients requiring thiopurine therapy.
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Affiliation(s)
- Yoon Suk Jung
- Department of Internal Medicine and Institute of Gastroenterology, Yonsei University College of Medicine, Seoul, Korea
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Thiopurine S-methyltransferase (TPMT) gene polymorphism in Brazilian children with acute lymphoblastic leukemia: association with clinical and laboratory data. Ther Drug Monit 2009; 30:700-4. [PMID: 19057372 DOI: 10.1097/ftd.0b013e31818b0f31] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
The frequency of allele variants of gene TPMT*2, *3A, *3B, and *3C was estimated in a population of 116 Brazilian children with acute lymphoblastic leukemia. The association between genotype and clinical and laboratory data obtained during chemotherapy maintenance phase and the correlation of intraerythrocyte concentration of 6-mercaptopurine metabolites (6-tioguanine nucleotide nucleotides and methylmercaptopurine) were analyzed. A multiplex amplification refractory mutation system-polymerase chain reaction (ARMS-PCR) was used in DNA amplification. Twelve patients presented TPMT gene mutation, all in heterozygous form. The most frequent allele variation was TPMT*3A (3.9%), followed by *3C (0.9%), *2 (0.4%), and *3B (0%). There was no significant association between clinical and laboratory data and the presence of mutation in TPMT gene. Of the 36 patients who were monitored for 6-mercaptopurine metabolite levels, only 1 had the mutation. In this patient, high 6-tioguanine nucleotide and low methylmercaptopurine concentrations were found. Event-free survival (EFS) for the whole group was 73.4%. There was no significant difference in event-free survival in the comparison between the groups with and without mutation (P = 0.06).
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Kudo M, Saito Y, Sasaki T, Akasaki H, Yamaguchi Y, Uehara M, Fujikawa K, Ishikawa M, Hirasawa N, Hiratsuka M. Genetic variations in the HGPRT, ITPA, IMPDH1, IMPDH2, and GMPS genes in Japanese individuals. Drug Metab Pharmacokinet 2009; 24:557-64. [PMID: 20045992 DOI: 10.2133/dmpk.24.557] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Thiopurines (such as azathioprine and 6-mercaptopurine) are widely used for the treatment of patients suffering from malignancies, rheumatic disease, inflammatory bowel disease and solid organ transplant rejection. These drugs are activated and eliminated by a number of enzymes in the human body. This analyzes all the exons and exon-intron junctions of 5 enzyme genes (hypoxanthine-guanine phosphoribosyltransferase, HGPRT; inosine triphosphate pyrophosphatase, ITPA; inosine monophosphate dehydrogenases 1 and 2, IMPDH1 and IMPDH2 and guanosine monophosphate synthetase, GMPS) involved in the metabolism of thiopurine drugs. Twelve novel single nucleotide polymorphisms (SNPs) (HGPRT: IVS6-12C>A (frequency:0.003); ITPA: 569T>C (Phe189Phe, 0.003); IMPDH1: IVS8-15C>A (0.003), IVS9+227A>G (0.003), IVS17+115C>T (0.003), and 930C>T (Thr310Thr, 0.005); IMPDH2: IVS1+50G>T (0.003), IVS2+15G>A (0.010), IVS3-20G>A (0.003), 609C>T (Arg203Arg, 0.003), and 1534C>T (Arg512Trp, 0.003); and GMPS: 1563T>C (Gly521Gly, 0.003)) and 7 known SNPs (ITPA: 94C>A (Pro32Thr, 0.005), 138G>A (Gln46Gln, 0.586), and 563G>A (Glu187Glu, 0.433); IMPDH1: 987G>C (Leu329Leu, 0.113) and 1575A>G (Ala525Ala, 0.620) and GMPS: IVS5-7T>C (0.153), 993A>G (Thr331Thr, 0.153)) were identified in 200 Japanese subjects. These data should provide useful information for thiopurine therapy in the Japanese and as well as other Asian populations.
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Affiliation(s)
- Mutsumi Kudo
- Department of Clinical Pharmaceutics, Tohoku Pharmaceutical University, Sendai, Miyagi 980-8578, Japan
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Functional characterization of 23 allelic variants of thiopurine S-methyltransferase gene (TPMT*2 - *24). Pharmacogenet Genomics 2008; 18:887-93. [PMID: 18708949 DOI: 10.1097/fpc.0b013e3283097328] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
OBJECTIVE Thiopurine S-methyltransferase (TPMT) is an enzyme responsible for the detoxification of the widely used thiopurine drugs. TPMT is genetically polymorphic and is associated with large interindividual variations in thiopurine drug toxicity and therapeutic efficacy. In this study, we performed an in-vitro analysis of TPMT variant alleles, namely, TPMT*2, *3A, *3B, *3C, *5, *6, *7, *8, *9, *10, *11, *12, *13, *14, *16, *17, *18, *19, *20, *21, *22, *23, and *24. METHODS The wild-type TPMT proteins, TPMT.1 and 23 variants were heterologously expressed in COS-7 cells, and the kinetic parameters Km, Vmax, and intrinsic clearance (Vmax/Km) of 6-thioguanine S-methylation were determined. RESULTS The expression levels of TPMT.2, TPMT.3A, TPMT.5, TPMT.12, TPMT.14, and TPMT.22 were considerably lower than that of TPMT.1 (P<0.005), and that of TPMT.18 was slightly reduced (P<0.05). The kinetic parameters of TPMT.3A, TPMT.3B, TPMT.5, TPMT.14, TPMT.18, TPMT.21, and TPMT.22 could not be accurately established because of no activity in 6-thioguanine S-methylation. The Vmax/Km values of TPMT.2, TPMT.7, TPMT.17, and TPMT.24 were displayed less than 10% of the wild-type. CONCLUSION This functional analysis with respect to TPMT variants could provide useful information for individualization of thiopurine drugs therapy.
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Andoh A, Tsujikawa T, Ban H, Hashimoto T, Bamba S, Ogawa A, Sasaki M, Saito Y, Fujiyama Y. Monitoring 6-thioguanine nucleotide concentrations in Japanese patients with inflammatory bowel disease. J Gastroenterol Hepatol 2008; 23:1373-7. [PMID: 18662197 DOI: 10.1111/j.1440-1746.2008.05419.x] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
BACKGROUND AND AIM There have been no reports on 6-thioguanine nucleotide (6-TGN) concentrations in Japanese patients with inflammatory bowel disease (IBD) undergoing azathioprine (AZA) or 6-mercaptopurine (6-MP) therapy. The aim of this study was to assess 6-TGN concentrations in Japanese IBD patients. METHODS Eighty-three patients with Crohn's disease (n = 42) and ulcerative colitis (n = 41) were enrolled. In 69 patients, AZA was prescribed at 50 mg/day, and seven patients were given 75 (n = 5) or 100 mg/day (n = 2). 6-MP was administered at 30 mg/day (n = 7). The 6-TGN concentrations were then assayed by high-performance liquid chromatography. RESULTS The mean 6-TGN concentrations of the entire study population (n = 83) were 277.9 +/- 179.8 pmol/8 x 10(8) red blood cells (RBC). The mean 6-TGN concentrations in those patients with active disease (n = 38) and those in remission (n = 45) were 232.9 +/- 159.7(mean +/- SD) and 342.8 +/- 184.6 pmol/8 x 10(8) RBC, respectively (P < 0.05). The odds ratio of being in remission and having a 6-TGN value >235 pmol/8 x 10(8) RBC was 2.6 (95% CI 1.05-6.2). A significant inverse correlation was found between the white blood cell (WBC) counts and 6-TGN concentrations (r = -0.301, P < 0.05, n = 83); the mean WBC counts of the active patients (6780 +/- 2412) were significantly higher than the patients in clinical remission (5468 +/- 1920, P < 0.05). Three patients with severe leukopenia and 10 patients with high 6-TGN concentrations had no thiopurine S-methyl transferase mutations. CONCLUSION The 6-TGN concentrations in Japanese patients with IBD on low-dose AZA and 6-MP therapy were comparable to those reported from Western countries. The monitoring of 6-TGN concentrations may be helpful for developing a therapeutic strategy for Japanese IBD patients.
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Affiliation(s)
- Akira Andoh
- Department of Medicine, Shiga University of Medical Science, Seta Tukinowa, Japan.
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Rutherford K, Daggett V. Four human thiopurine s-methyltransferase alleles severely affect protein structure and dynamics. J Mol Biol 2008; 379:803-14. [PMID: 18482735 PMCID: PMC2518407 DOI: 10.1016/j.jmb.2008.04.032] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2008] [Revised: 03/29/2008] [Accepted: 04/11/2008] [Indexed: 10/22/2022]
Abstract
Thiopurine S-methyltransferase (TPMT) metabolizes cytotoxic thiopurine drugs used in the treatment of leukemia and inflammatory bowel disease. TPMT is a major pharmacogenomic target with 23 alleles identified to date. Several of these alleles cause rapid protein degradation and/or aggregation, making it extremely difficult to study the structural impact of the TPMT polymorphisms experimentally. We, therefore, have performed multiple molecular dynamics simulations of the four most common alleles [TPMT*2 (A80P), *3A (A154T/Y240C), *3B (A154T) and *3C (Y240C)] to investigate the molecular mechanism of TPMT inactivation at an atomic level. The A80P polymorphism in TPMT*2 disrupts helix alpha3 bordering the active site, which breaks several salt-bridge interactions and opens up a large cleft in the protein. The A154T polymorphism is located within the co-substrate binding site. The larger threonine alters the packing of substrate-binding residues (P68, L69, Y166), increasing the solvent exposure of the polymorphic site. This packing rearrangement may account for the complete lack of activity in the A154T mutant. The Y240C polymorphism is located in beta-strand 9, distant from the active site. Side-chain contacts between residue 240 and helix alpha8 are lost in TPMT*3C. Residues 154 and 240 in TPMT*3A are connected through a hydrogen-bonding network. The dual polymorphisms result in a flattened, slightly distorted protein structure and an increase in the thiopurine-binding site solvent accessibility. The two variants that undergo the most rapid degradation in vivo, TPMT*2 and *3A, are also the most deformed in the simulations.
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Affiliation(s)
- Karen Rutherford
- Department of Biochemistry, University of Washington, Seattle WA 98195-5013
| | - Valerie Daggett
- Department of Biochemistry, University of Washington, Seattle WA 98195-5013
- Department of Bioengineering, University of Washington, Seattle WA 98195-5013
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Garat A, Cauffiez C, Renault N, Lo-Guidice JM, Allorge D, Chevalier D, Houdret N, Chavatte P, Loriot MA, Gala JL, Broly F. Characterisation of novel defective thiopurine S-methyltransferase allelic variants. Biochem Pharmacol 2008; 76:404-15. [PMID: 18602085 DOI: 10.1016/j.bcp.2008.05.009] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2008] [Revised: 04/29/2008] [Accepted: 05/01/2008] [Indexed: 10/22/2022]
Abstract
Human thiopurine S-methyltransferase (TPMT, EC 2.1.1.67) is a key enzyme in the detoxification of thiopurine drugs widely used in the treatment of various diseases, such as inflammatory bowel diseases, acute lymphoblastic leukaemia and rheumatic diseases. The TPMT gene is genetically polymorphic and the inverse relationship between TPMT activity and the risk of developing severe hematopoietic toxicity is well known. In this study, the entire coding sequence of TPMT, together with its 5'-flanking promoter region, was analysed in patients with an intermediate phenotype for thiopurine drug methylation. Four polymorphisms were identified, two previously described, c.356A>C (p.Lys(119)Thr, TPMT*9) and c.205C>G (p.Leu(69)Val, TPMT*21), and two novel missense mutations, c.537G>T (p.Gln(179)His, TPMT*24) and c.634T>C (p.Cys(212)Arg, TPMT*25). Structural investigations, using molecular modeling, were undertaken in an attempt to explain the potential impact of the amino acid substitutions on the structure and activity of the variant proteins. Additionally, in order to determine kinetic parameters (K(m) and V(max)) of 6-thioguanine (6-TG) methylation, the four variants were expressed in a recombinant yeast expression system. Assays were performed by HPLC and the results were compared with those of wild-type TPMT. The p.Leu(69)Val and the p.Cys(212)Arg substitutions encode recombinant enzymes with a significantly decreased intrinsic clearance compared to that of the wild-type protein, and, consequently, characterise non-functional alleles of TPMT. The p.Lys(119)Thr and the p.Gln(179)His substitutions do not affect significantly the catalytic activity of the corresponding variant proteins, which prevents to unambiguously describe these latter alleles as defective TPMT variants.
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Affiliation(s)
- A Garat
- Equipe d'accueil 2679, Faculté de Médecine de Lille, Pôle Recherche, Lille, France
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Hanzawa Y, Sasaki T, Mizugaki M, Ishikawa M, Hiratsuka M. Genetic Polymorphisms and Haplotype Structures of the Human CYP2W1 Gene in a Japanese Population. Drug Metab Dispos 2007; 36:349-52. [DOI: 10.1124/dmd.107.019141] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
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Winter JW, Gaffney D, Shapiro D, Spooner RJ, Marinaki AM, Sanderson JD, Mills PR. Assessment of thiopurine methyltransferase enzyme activity is superior to genotype in predicting myelosuppression following azathioprine therapy in patients with inflammatory bowel disease. Aliment Pharmacol Ther 2007; 25:1069-77. [PMID: 17439508 DOI: 10.1111/j.1365-2036.2007.03301.x] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
BACKGROUND Myelosuppression occurs in 2-7% of inflammatory bowel disease (IBD) patients treated with azathioprine, and can be associated with reduced activity of thiopurine methyltransferase (TPMT) in some patients. It has been proposed that pretreatment assessment of TPMT status reduces the incidence of toxicity and is cost-effective. AIMS To determine if screening for TPMT status predicts side-effects to azathioprine in patients with IBD and to ascertain whether screening by TPMT enzyme activity or genotype is superior. METHODS Sequential IBD patients were identified and azathioprine tolerance recorded. Blood was collected for measurement of TPMT activity and TPMT*3C, TPMT*3A and TPMT*2 genotypes. RESULTS Of 130 patients, 25% stopped azathioprine because of toxicity. Four patients experienced severe myelosuppression (WCC < 2). Eleven of 17 patients with reduced TPMT activity were heterozygotes, including one patient with marked TPMT deficiency who experienced severe myelosuppression. There was no association between intermediate TPMT deficiency and any side-effect. CONCLUSIONS Moderate reduction of TPMT activity in heterozygotes was not associated with toxicity, but very low TPMT activity caused severe myelosuppression in one patient. This would have been predicted by measuring TPMT activity but not by genotyping. Measurement of TPMT activity may therefore be superior to genotype in predicting severe myelosuppression.
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Affiliation(s)
- J W Winter
- Gastroenterology Unit, Gartnavel General Hospital, Glasgow, UK.
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Hanzawa Y, Sasaki T, Hiratsuka M, Ishikawa M, Mizugaki M. Three Novel Single Nucleotide Polymorphisme (SNPs) of CYP2S1 Gene in Japanese Individuals. Drug Metab Pharmacokinet 2007; 22:136-40. [PMID: 17495422 DOI: 10.2133/dmpk.22.136] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We analyzed all nine exons and exon-intron junctions of the CYP2S1 gene in 200 Japanese individuals and identified the following three novel single nucleotide polymorphisms (SNPs): 4612G>A (Glu147Glu) in exon 3, 5478C>T (Leu230Leu) and 5479T>G (Leu230Arg, CYP2S1*5A) in exon 5. The allele frequencies were 0.013 for 4612G>A, 0.058 for 5478C>T, and 0.003 for 5479T>G. In addition, a known SNP 1324C>G (Pro74Pro) was detected at a frequency of 0.300.
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Affiliation(s)
- Yoshiyuki Hanzawa
- Department of Clinical Pharmaceutics, Tohoku Pharmaceutical University, Sendai, Japan
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