Thiopurine methyltransferase activity in children with acute myeloid leukemia

Abstract

Activity of the enzyme thiopurine methyltransferase (TPMT) determines the anti-leukemic effect of thiopurines used in the chemotherapy of acute lymphoblastic leukemia (ALL) and acute myeloblastic leukemia (AML). TPMT status and its effects on treatment outcome have been studied extensively in ALL and autoimmune disorders, but few data is available on TPMT in AML. The present study assessed the genetic polymorphisms and activity of TPMT in children with AML at different treatment stages, and compared the results with those obtained for children with ALL. The study included 33 children with AML (0.7-19.7 years) treated with 6-thioguanine (6-TG) according to the AML-BFM 2004 Protocol. Blood samples were collected at diagnosis, during and following maintenance chemotherapy from 8, 10 and 17 patients with AML (the assay was performed at two time points in 2 patients), respectively. Blood samples from 105 children with ALL were obtained at diagnosis, during the maintenance chemotherapy and following the cessation of the chemotherapy from 16, 55 and 34 children, respectively. The activity of TPMT in red blood cells lysates was measured using an enzymatic reaction based on the conversion of 6-mercaptopurine into 6-methylmercaptopurine, involving S-adenozyl-L-methionine as the methyl group donor. TPMT mutations were determined using a polymerase chain reaction/restriction fragment length polymorphism method. Median TPMT activity at diagnosis, during maintenance chemotherapy and following chemotherapy was 43.1, 47,3 and 41.7 nmol 6-mMP g Hb h, respectively. All patients with AML exhibited the homozygous TPMT*1/*1 genotype, with the exception of 1, who was a heterozygote with the TPMT*1/*3C genotype and demonstrated a TPMT activity level at diagnosis of 42.5 nmol 6-mMP g Hb h. At each chemotherapy stage, the median TPMT activities in children with AML were significantly increased compared with the median TPMT activities in children with ALL. The preliminary results suggest that the TPMT activity in AML may be increased compared with that in ALL. Comprehensive studies on the association between thiopurine metabolism and treatment outcome in AML are required, with regard to the cytogenetic and molecular factors currently used for AML risk stratification.

Effect of changes in metabolic enzymes and transporters on drug metabolism in the context of liver disease: Impact on pharmacokinetics and drug–drug interactions

“…It catalyses methylation of thiopurine drugs used in oncology, such as mercaptopurine and thioguanine, used in acute lymphoblastic leukaemia. 64 Azathioprine, an T A B L E 2 Enzymes involved in endoplasmic reticulum stress. 29 immunosuppressive drug used in patients with various autoimmune disorders including autoimmune hepatitis, is also a substrate of TPMT.…”

“…Thiopurine methyltransferase (TPMT) is a cytoplasmic transmethylase present in the liver. It catalyses methylation of thiopurine drugs used in oncology, such as mercaptopurine and thioguanine, used in acute lymphoblastic leukaemia 64 . Azathioprine, an immunosuppressive drug used in patients with various autoimmune disorders including autoimmune hepatitis, is also a substrate of TPMT.…”

Genome wide association studies for treatment‐related adverse effects of pediatric acute lymphoblastic leukemia

“…Thiopurine mojeties are substrates of the enzyme thiopurine methyl transferase (TPMT). Methylated derivates are not incorporated into DNA and can impair purine de novo biosynthesis, potentially contributing to mercaptopurine cytotoxic effects (de Boer et al, 2018; Sobiak et al, 2018). TPMT is a highly polymorphic gene, and the most frequent SNPs in Caucasians are rs1142345 (T > C, Tyr240Cys) and rs1800460 (C > T, Ala154Thr), that constitute the haplotype TPMT *3A, and the rs1142345 (T > C, Tyr240Cys), that constitute the allele TPMT *3C.…”

“…Intermediate enzymatic activity is detected in approximately 5–11% of Caucasians, who are heterozygous for a variant TPMT allele; no or lowTPMT activity is detected approximately in 1 to 300 European individuals who are poor metabolizers. (Sobiak et al, 2018) International TPMT genotype based guidelines for thiopurine dose adjustment in both pediatric and adult patients have been already published (Relling et al, 2011; Relling et al, 2013; Relling et al, 2019; Whirl‐Carrillo et al, 2012). To examine the question whether genes other than TPMT influence TPMT activity, GWAS analyses have been performed.…”

Scorpion primer PCR analysis for genotyping of allele variants of thiopurine s‑methyltransferase*3

“…Thiopurines have been widely applied in clinical practice; among these, 6-thioguanine (6-TG), 6-thiopurine (6-MP) and its pro-drug azathioprine (AZA) are the most commonly used ( 1 , 2 ). 6-TG and 6-MP have been demonstrated to induce and maintain the stable stage of inflammatory bowel disease ( 3 , 4 ) and are also the most widely used drugs in the treatment of children with acute lymphoblastic leukemia ( 5 , 6 ). AZA plays an important role in the treatment of autoimmune diseases and acute rejection after organ transplantation ( 7 ).…”