Genetic Polymorphisms of Drug-Metabolizing Enzymes Involved in 6-Mercaptopurine-Induced Myelosuppression in Thai Pediatric Acute Lymphoblastic Leukemia Patients

Detailed resume of S-methyltransferases: Categories, structures, biological functions and research advancements in related pathophysiology and pharmacotherapy

Methylation is a vital chemical reaction in the metabolism of many drugs, neurotransmitters, hormones, and exogenous compounds. Among them, S-methylation plays a significant role in the biotransformation of sulfur-containing compounds, particularly chemicals with sulfhydryl groups. Currently, only three S-methyltransferases have been reported: thiopurine methyltransferase (TPMT), thiol methyltransferase (TMT), and thioether methyltransferase (TEMT). These enzymes are involved in various biological processes such as gene regulation, signal transduction, protein repair, tumor progression, and biosynthesis and degradation reactions in animals, plants, and microorganisms. Furthermore, they play pivotal roles in the metabolic pathways of essential drugs and contribute to the advancement of diseases such as tumors. This paper reviews the research progress on relevant structural features, metabolic mechanisms, inhibitor development, and influencing factors (gene polymorphism, S-adenosylmethionine level, race, sex, age, and disease) of S-methyltransferases. We hope that a better comprehension of S-methyltransferases will help to provide a reference for the development of novel strategies for related disorders and improve long-term efficacy.

Meta-Analysis of NUDT15 Genetic Polymorphism on Thiopurine-Induced Myelosuppression in Asian Populations

Backgound: The high incidence of thiopurine-induced myelosuppression in Asians is known to be attributable to genetic variation in thiopurine metabolism. A quantitative synthesis to summarize the genetic association with thiopurine-induced myelosuppression in Asians was therefore conducted.

Methods: A Literature search was performed from January 2016 to May 2021 in the following databases: PubMed, Web of Science, and Embase and addition search included the studies from Zhang et al. Two reviewers independently extracted the following data: the author’s name, year of publication, ethnicity, drugs, diseases, genetic polymorphisms, onset, type of myelosuppression and results of Hardy-Weinberg equilibrium. The Newcastle-Ottawa Scale was used to assess the quality of the studies. The pooled odds ratios (OR) and 95% confidence intervals (CI) were calculated to evaluate the associations of NUDT15 and the risk of thiopurine-induced myelosuppression stratified by onset and type of myelosuppressive. Subgroup analysis by NUDT15 genetic polymorphisms was performed.

Results: A total of 30 studies was included in this meta-analysis. The overall OR for the relationship between NUDT15 genetic polymorphisms and thiopurine-induced early onset of leukopenia and neutropenia in Asian populations were 11.43 (95% CI 7.11–18.35) and 16.35 (95% CI 10.20–26.22). Among NUDT15 polymorphisms, NUDT15*3 showed a significantly increased risk of early leukopenia (OR 15.31; 95% CI 9.65–24.27) and early neutropenia (OR 15.85; 95% CI 8.80–28.53). A significantly higher thiopurine-induced early neutropenic risk was also found for NUDT15*2 (OR 37.51; 95% CI 1.99–708.69). Whereas, NUDT15*5 and NUDT15*6 variants showed a lower risk of leukopenia.

Conclusion: This study suggests that NUDT15*3 and NUDT15*2 are important genetic markers of thiopurine-induced early onset of myelotoxicity in Asians, therefore, early detection of these variants before initiating thiopurine therapy is necessary.