硫鸟嘌呤 (TG)、硫唑嘌呤 (AZA) 和巯嘌呤 (MP) 是硫嘌呤前药，常用于治疗白血病和炎症性肠病 (IBD) 等疾病。 6-硫鸟嘌呤核苷酸 (6-TGN) 通常用于监测治疗。红细胞 (RBC) 中高水平的 6-TGN 与白细胞减少症有关，但预测这种副作用的临界水平仍不确定。硫嘌呤被代谢并掺入白细胞 DNA 中。测量 DNA 掺入硫鸟嘌呤 (DNA-TG) 的水平可能是预测临床反应和毒性（如白细胞减少症）更合适的方法。不幸的是，大多数检测 6-TGN 的方法无法识别 NUDT15 变体的影响，这些变体主要影响种族群体（例如华人、印度人、马来人、日本人和西班牙人）。 DNA-TG 通过直接测量 DNA 中的硫鸟嘌呤来解决这个问题，而硫鸟嘌呤可能受到 TPMT 和 NUDT15 变体的影响。虽然 RBC 6-TGN 浓度传统上因其测量简便且经济实惠而被用于优化硫嘌呤治疗，但液相色谱-串联质谱 (LC-MS/MS) 技术的最新发展使得淋巴细胞中 DNA-TG 浓度的测量变得准确、可重复且价格实惠。本系统评价的目的是评估 DNA-TG 水平作为硫嘌呤治疗标志物的当前证据，特别是关于 NUDT15 变体。对 DNA-TG 作为标志物的当前证据进行了系统评价和荟萃分析用于监测硫嘌呤治疗，包括测量方法以及 DNA-TG 和各种基因变异（例如 TPMT、NUDT15、ITPA、NT5C2 和 MRP4）之间的说明性关系。使用关键字“DNA-TG”以及 MeSH 术语和同义词，对 PubMed 和 Embase 进行了截至 2024 年 4 月已发表研究的系统检索。通过对文章中引用的参考文献、最近的评论、社论和荟萃分析进行手动检查，增强了电子检索策略。使用 R studio 4.1.3 进行荟萃分析。研究 DNA-TG 和 6-TGN 水平的系数（Fisher z 变换相关系数）之间的差异。使用 RevMan 5.4 版进行荟萃分析，利用随机效应大小模型研究患有或不患有白细胞减少症的患者之间 DNA-TG 水平的差异。使用纽卡斯尔-渥太华质量评估量表评估偏倚风险。在这项系统评价中，纳入了 21 项研究，这些研究测量了 ALL (n = 16) 或 IBD (n = 5) 患者白细胞中的 DNA-TG 水平）。在我们的荟萃分析中，白细胞减少症 (ALL IBD) 患者与无白细胞减少症患者之间的总体平均差异为 134.15 fmol TG/μg DNA [95% 置信区间 (CI) (83.78-184.35)，P < 0.00001；异质性卡方为5.62，I2为47%]。伴有和不伴有白细胞减少症的 IBD 患者的 DNA-TG 水平存在显着差异 [161.76 fmol TG/μg DNA； 95% CI (126.23-197.29)，P < 0.00001；异质性卡方为0.20，I2为0%]。患有或不患有白细胞减少症的 ALL 患者之间的 DNA-TG 水平没有发现显着差异（57.71 fmol TG/μg DNA [95% CI（- 22.93 至 138.35），P < 0.80]）。 DNA-TG 监测被发现是预测 ALL 患者复发率的一种有前景的方法，并且 DNA-TG 水平可能比 RBC 6-TGN 水平更能预测 IBD 患者白细胞减少症。多项研究表明，DNA-TG 水平与各种基因变异（TPMT、NUDT15、ITPA 和 MRP4）相关，表明其作为指导不同遗传背景的硫嘌呤治疗的信息更丰富的标记物的潜力。该系统评价强烈支持DNA-TG 作为监测硫嘌呤治疗标记物的进一步研究。它与治疗结果的相关性，例如 ALL 的无复发生存率和 IBD 的白细胞减少风险，强调了它在增强个性化治疗方法方面的作用。 DNA-TG 可有效识别 NUDT15 变异并预测 IBD 患者的晚期白细胞减少症，无论其 NUDT15 变异状态如何。建议使用 DNA-TG 预测 IBD 患者晚期白细胞减少症的推荐阈值在 320 至 340 fmol/μg DNA 之间。为了改善患者护理并提高硫嘌呤治疗的包容性，必须进行更多关于 DNA-TG 实施的临床研究。© 2024。作者。

Thioguanine (TG), azathioprine (AZA), and mercaptopurine (MP) are thiopurine prodrugs commonly used to treat diseases, such as leukemia and inflammatory bowel disease (IBD). 6-thioguanine nucleotides (6-TGNs) have been commonly used for monitoring treatment. High levels of 6-TGNs in red blood cells (RBCs) have been associated with leukopenia, the cutoff levels that predict this side effect remain uncertain. Thiopurines are metabolized and incorporated into leukocyte DNA. Measuring levels of DNA-incorporated thioguanine (DNA-TG) may be a more suitable method for predicting clinical response and toxicities such as leukopenia. Unfortunately, most methodologies to assay 6-TGNs are unable to identify the impact of NUDT15 variants, effecting mostly ethnic populations (e.g., Chinese, Indian, Malay, Japanese, and Hispanics). DNA-TG tackles this problem by directly measuring thioguanine in the DNA, which can be influenced by both TPMT and NUDT15 variants. While RBC 6-TGN concentrations have traditionally been used to optimize thiopurine therapy due to their ease and affordability of measurement, recent developments in liquid chromatography-tandem mass spectrometry (LC-MS/MS) techniques have made measuring DNA-TG concentrations in lymphocytes accurate, reproducible, and affordable. The objective of this systematic review was to assess the current evidence of DNA-TG levels as marker for thiopurine therapy, especially with regards to NUDT15 variants.A systematic review and meta-analysis were performed on the current evidence for DNA-TG as a marker for monitoring thiopurine therapy, including methods for measurement and the illustrative relationship between DNA-TG and various gene variants (such as TPMT, NUDT15, ITPA, NT5C2, and MRP4). PubMed and Embase were systematically searched up to April 2024 for published studies, using the keyword "DNA-TG" with MeSH terms and synonyms. The electronic search strategy was augmented by a manual examination of references cited in articles, recent reviews, editorials, and meta-analyses. A meta-analysis was performed using R studio 4.1.3. to investigate the difference between the coefficients (Fisher's z-transformed correlation coefficient) of DNA-TG and 6-TGNs levels. A meta-analysis was performed using RevMan version 5.4 to investigate the difference in DNA-TG levels between patients with or without leukopenia using randomized effect size model. The risk of bias was assessed using the Newcastle-Ottowa quality assessment scale.In this systematic review, 21 studies were included that measured DNA-TG levels in white blood cells for either patients with ALL (n = 16) or IBD (n = 5). In our meta-analysis, the overall mean difference between patients with leukopenia (ALL + IBD) versus no leukopenia was 134.15 fmol TG/µg DNA [95% confidence interval (CI) (83.78-184.35), P < 0.00001; heterogeneity chi squared of 5.62, I2 of 47%]. There was a significant difference in DNA-TG levels for patients with IBD with and without leukopenia [161.76 fmol TG/µg DNA; 95% CI (126.23-197.29), P < 0.00001; heterogeneity chi squared of 0.20, I2 of 0%]. No significant difference was found in DNA-TG level between patients with ALL with or without leukopenia (57.71 fmol TG/µg DNA [95% CI (- 22.93 to 138.35), P < 0.80]). DNA-TG monitoring was found to be a promising method for predicting relapse rates in patients with ALL, and DNA-TG levels are likely a better predictor for leukopenia in patients with IBD than RBC 6-TGNs levels. DNA-TG levels have been shown to correlate with various gene variants (TPMT, NUDT15, ITPA, and MRP4) in various studies, points to its potential as a more informative marker for guiding thiopurine therapy across diverse genetic backgrounds.This systematic review strongly supports the further investigation of DNA-TG as a marker for monitoring thiopurine therapy. Its correlation with treatment outcomes, such as relapse-free survival in ALL and the risk of leukopenia in IBD, underscores its role in enhancing personalized treatment approaches. DNA-TG effectively identifies NUDT15 variants and predicts late leukopenia in patients with IBD, regardless of their NUDT15 variant status. The recommended threshold for late leukopenia prediction in patients with IBD with DNA-TG is suggested to be between 320 and 340 fmol/µg DNA. More clinical research on DNA-TG implementation is mandatory to improve patient care and to improve inclusivity in thiopurine treatment.© 2024. The Author(s).