Thiopurine Methyltransferase In Patients Research Articles

TPMT mRNA Expression: A Novel Prognostic Biomarker for Patients with Colon Cancer by Bioinformatics Analysis

BackgroundTo explore the clinicopathological significance and prognostic value of thiopurine methyltransferase (TPMT) in patients with colon cancer by bioinformatics analysis.Materials and MethodsThe clinicopathological information and TPMT expression data were downloaded from The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO). Wilcoxon signed-rank test was used to evaluate the relationship between TPMT mRNA expression levels and clinicopathological characteristics in patients with colon cancer. Then, the prognostic value of TPMT mRNA expression for disease-free survival (DFS) and overall survival (OS) in patients with colon cancer was assessed by Kaplan–Meier and Cox regression analyses. Additionally, gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses were performed to explore potential functions of TPMT in patients with colon cancer.ResultsTPMT mRNA was significantly downregulated in colon cancer compared with normal tissues (P < 0.05). Wilcoxon analysis revealed that lower TPMT mRNA expression was remarkably associated with lymph node metastasis (P = 0.008), distant metastasis (P = 0.012) and advanced pathological stage (P = 0.010). Besides, the high TPMT mRNA level was also correlated with a favorable DFS and OS in colon cancer patients (both P < 0.05). Moreover, GO enrichment analysis indicated that the co-expressed genes of TPMT function as extracellular matrix (ECM) structural constituent, insulin-like growth factor binding, cell adhesion molecule binding and growth factor binding. KEGG enrichment analysis suggested that the co-expressed genes of TPMT were particularly enriched in amino sugar and nucleotide sugar metabolism, ECM-receptor interaction and focal adhesion.ConclusionTPMT mRNA level might be a novel prognostic biomarker for patients with colon cancer.

Azathioprine Therapy in Multiple Sclerosis: Phosphoribosylated Metabolites and Thiopurine Methyltransferase Activity

Objective: In this prospective study, we examined the association between azathioprine dose, levels of its phosphoribosylated metabolites, and the activity of thiopurine methyltransferase in patients with multiple sclerosis (MS). Materials/Methods: Clinical data and blood samples were collected from 27 MS patients who were undergoing azathio- prine treatment. In red blood cells, thiopurine methyltransferase (TPMT) activity was determined, and after hydrolysis and cleavage of the phosphoribosyl residue, amounts of 6-thioguanine (6-TG), 6-methyl-thioguanine (6-MTG), 6- methylmercaptopurine (6-MMP) were measured. For clinical evaluation, the expanded disability status score (EDSS) and the multiple sclerosis functional composite (MSFC) were performed. Laboratory and clinical examinations were con- ducted twice with a 6-month-intervall. Results: Over a broad range of daily azathioprine dose, nearly constant levels of the immunosuppressive-active 6-TG (nucleotides) were found. There was, however, a marked relationship between daily azathioprine dose and 6-MMP nucleotide levels. Especially patients receiving an azathioprine dose of more than 1.5 mg/kg per day in particular presented an exponential increase in 6-MMP levels when TPMT activity was higher than 45 U/g Hb. All the biochemical measurements gave similar results when performed 6 months later. Conclusions: Patients with the combination of a high TPMT-activity and an azathioprine dose of more than 1.5 mg/kg/d exhibit significantly in- creased 6-MMP nucleotide levels. These patients are thus at risk for hepatotoxic side effects. Determination of TPMT ac- tivity before azathioprine therapy and monitoring of its metabolites might provide guidance for dose individualization.

High prevalence of polymorphism and low activity of thiopurine methyltransferase in patients with inflammatory bowel disease

BackgroundGene polymorphism of thiopurine methyltransferase (TPMT) correlates with decreased enzyme activity which determines a significant risk of adverse effect reactions (ADR) in patients treated with thiopurines. The aim of this study was to investigate TPMT genotype and phenotype status in patients with inflammatory bowel diseases (IBD). MethodsFifty-one consecutive out-patients with IBD were genotyped for the following allelic variants: rs1800462 (referred as TPMT*2 allele), rs1800460 (referred as TPMT *3B allele), and 1142345 (referred as TPMT *3C allele). Red blood cell TPMT activity was measured using a competitive micro-well immunoassay for the semi-quantitative determination of TPMT activity in red blood cells (RBC) by means of a 6-MP substrate. ResultsPolymorphism of TPMT was found in 5 out of 51 patients (10%; 95% CI 2%–18%), three heterozygous and two homozygous carriers. Six patients (11.8%; 95% CI 2.4%–19.5%) displayed very low, 12 (23.5%; 95% CI 11.4%–34.5%) intermediate, and 33 (64.7%; 95% CI 52%–78%) normal/high TPMT activity. There were no differences between TPMT genotype and phenotype groups according to age, type of disease, smoking, and chronic medications. A 71% (95% CI 61%–81%; κ=0.45) concordance rate was found between genotype and phenotype status. Six out of 27 (22%) current or past users of azathioprine developed ADR, with three (50%) displaying TPMT genotype and/or phenotype alterations. ConclusionCompared to the general population, IBD patients may have significantly higher prevalence of TPMT polymorphism and, even more, low activity. Phenotypic more than genotypic TPMT analysis could be useful to better manage IBD therapy with thiopurines.

Impact of Thiopurine Methyltransferase Activity and 6‐Thioguanine Nucleotide Concentrations in Patients with Chronic Inflammatory Diseases

As azathioprine is one of the standard immunosuppressive drugs used for treatment of patients with different chronic inflammatory diseases, the effect of the azathioprine metabolizing enzyme thiopurine methyltransferase (TPMT) activity on incidence of adverse events (AE) was examined. In addition, potential correlations between the concentration of the azathioprine metabolite 6-thioguanine nucleotide (6-TGN) in erythrocytes (RBC) and inflammatory disease activity as well as hematological AE were investigated. TPMT activities were investigated prospectively in 139 patients (35 male, 104 female) with chronic inflammatory diseases [systemic lupus erythematosus (SLE, 38), progressive systemic sclerosis (PSS, 13), Wegener's granulomatosis (4), rheumatoid arthritis (RA, 5), and other chronic inflammatory diseases (79)]. In addition, 6-TGN concentrations were investigated in a second cohort of 58 patients (17 patients with SLE, 5 with PSS, 5 with vasculitides, 4 with undifferentiated connective tissue diseases, 1 with dermatomyositis, 1 with Sjögren's syndrome, 1 with RA, 20 with Crohn's disease, and 4 with ulcerative colitis) prior to and during therapy with azathioprine. The distribution of activities of TPMT in 139 patients showed a normal Gaussian distribution in the Caucasian population. Within the group of 96 patients taking azathioprine, known azathioprine-related AE could be observed: minor AE (sickness, rash, and increase in cholestasis parameters) in 11 patients (11.4%), and severe AE (bone marrow toxicity) in 7 patients (7.3%). Below a "cutoff" value of 11.9 nmol/mL RBC x h of TPMT activity, AE were significantly more frequent. In the second cohort of patients, no significant correlations could be observed between 6-TGN concentrations and parameters of disease activity. Reduced activity of TPMT in patients with chronic inflammatory diseases requiring immunosuppressive therapy with azathioprine, especially below a distinct cutoff, appears to inherit a substantial risk for development of AE.

Cost-effectiveness of pharmacotherapy for autoimmune hepatitis

In > 80% of patients with autoimmune hepatitis, steroid therapy alone or in combination with azathioprine results in disease remission. Treatment response results in reversal of fibrosis and excellent long-term survival in many patients, whereas untreated patients may expect a 10-year survival of < 30%. The use of azathioprine monotherapy (2 mg/kg/day) has gained widespread acceptance in maintaining remission in clinical practice. Although all patients with autoimmune hepatitis may not need treatment, particularly those with mild disease, alternative strategies are required in patients who have failed to achieve remission on standard therapy of steroids with or without azathioprine, or patients with azathioprine-induced drug toxicity. In such circumstances, the use of salvage therapy in the form of ciclosporin, tacrolimus or mycophenolate mofetil may be warranted. Liver transplantation is the treatment of choice for patients who present with subacute liver failure or decompensated cirrhosis. Salvage therapy results in an exponential rise in cost with each increment in therapeutic escalation. As an alternative to standard therapy, it has also been suggested that novel therapies such as ciclosporin, tacrolimus or mycophenolate mofetil be initiated to achieve remission. However, a > 10-fold cost differential exists between the charges associated with more potent immunosuppression and standard therapy. Therefore, in evaluating novel immunosuppression in autoimmune hepatitis, it behoves clinicians not only to consider end points pertaining to efficacy, but also end points pertaining to cost-effectiveness. Moreover, the exact role of pharmacogenomics and genotyping of thiopurine methyltransferase in patients with autoimmune hepatitis needs to be fully defined.

Genotyping of thiopurine methyltransferase in patients with acute leukemia using LightCycler PCR

Patients with acute lymphoblastic leukemia (ALL) are treated with thiopurines. Thiopurine methyltransferase (TPMT) catalyses the S-methylation of thiopurines and is subject to genetic polymorphism. The TPMT genotype was determined in 55 patients with ALL. Three patients were heterozygous for allelic variants of TPMT. We describe an assay for the genotyping of the TPMT polymorphism using real-time fluorescence polymerase chain reaction (PCR) to facilitate rapid processing of samples. This strategy is superior to standard PCR-restriction fragment length polymorphism genotyping methods and provides informative data on TPMT polymorphisms in patients prior to treatment with thiopurines.