NUDT15 Rs116855232 Research Articles

The frequency of NUDT15 rs116855232 and its impact on mercaptopurine-induced toxicity in Syrian children with acute lymphoblastic leukemia.

Polymorphisms in NUDT15 may result in differences in mercaptopurine-induced toxicity. This study aimed to identify the frequency of the NUDT15 (c.415C>T; rs116855232) polymorphism and investigate the effect of this polymorphism on mercaptopurine-induced toxicity in a population of Syrian patients with childhood acute lymphoblastic leukemia (ALL). This is a retrospective study that included children with ALL reaching at least 6 months of maintenance therapy. The NUDT15 genotyping was determined using standard targeted sequencing of polymerase chain reaction products. The odds ratio (OR) for the association between toxicity and genotype was evaluated. A total of 92 patients were enrolled. The majority of the patients in the study population were low-risk (63.04%), followed by intermediate-risk (25%), and high-risk (11.96%). There were 5 patients (5.4%) with NUDT15 (c.415C>T; rs116855232) CT genotype, and 1 patient (1.08%) with NUDT15 TT genotype, with allele frequencies of C=0.962 and T=0.038. The mercaptopurine median dose intensity was 100%, 54.69%, and 5% for the genotypes CC, CT, and TT, respectively (P=0.009). Early onset leukopenia was significantly associated with the NUDT15 polymorphism (OR: 6.16, 95% CI: 1.11-34.18, P=0.037). There was no association between the NUDT15 genotype and hepatotoxicity. Approximately 6.5% of the study population exhibited reduced NUDT15 activity. The mercaptopurine dose intensity was considerably low in NUDT15 rs116855232 TT genotype compared with CT and CC. The dosage of mercaptopurine should be adjusted according to the NUDT15 genotype in pediatric patients with ALL.

NUDT15 and TPMT polymorphisms in three distinct native populations of the Brazilian Amazon.

This is the first report of the distribution of TPMT and NUDT15 single nucleotide polymorphisms and metabolic phenotypes associated with cytotoxicity of thiopurine drugs, in indigenous groups of Brazilian Amazon: Munduruku, Paiter-Suruí and Yanomami. The minor allele frequency (MAF) of NUDT15 rs116855232 did not differ significantly across the groups; TPMT rs1800462 was absent, while rs1800460 and rs1142345 were in strong linkage disequilibrium, and 10- and 30-fold more common in Paiter-Suruí. Indeed, the MAFs in Paiter-Surui (0.193 and 0.188) are the largest report globally. The distribution of combined NUDT15/TPMT metabolic phenotypes differed significantly (p < 0.0001) and largely (Cramér´s V = 0.37) across cohorts. This has important pharmacogenetic implications: the Clinical Pharmacogenetics Implementation Consortium recommendations to reduce or consider reduction of thiopurine dose applies to 4.4% Yanomami, 5.6% Munduruku, versus 41% Paiter-Suruí. The proportion of Paiter-Suruí at risk of thiopurine intolerance is 3- to 4-fold higher than any other population worldwide.

Azathioprine dose tailoring based on pharmacogenetic information: Insights of clinical implementation

Azathioprine is commonly used as an immunosuppressive antimetabolite in the treatment of acute lymphoblastic leukemia, autoimmune disorders (such as Crohn's disease and rheumatoid arthritis), and in patients receiving organ transplants. Thiopurine-S-methyltransferase (TPMT) is a cytoplasmic trans-methylase catalyzing the S-methylation of thiopurines. The active metabolites obtained from thiopurines are hydrolyzed into inactive forms by the Nudix hydrolase 15 (NUDT15). The TPMT*2 (defined by rs1800462), *3A (defined by rs1800460 and rs1142345), *3B (defined by rs1800460), *3C (defined by rs1142345), *6 (defined by rs75543815), and NUDT15 rs116855232 genetic variant have been associated, with the highest level of evidence, with the response to azathioprine, and, the approved drug label for azathioprine and main pharmacogenetic dosing guidelines recommend starting with reduced initial doses in TPMT intermediate metabolizer (IM) patients and considering an alternative treatment in TPMT poor metabolizer (PM) patients. This study aims to assess the clinical impact of azathioprine dose tailoring based on TPMT genotyping studying the azathioprine toxicity and efficacy, treatment starts, and dose adjustments during follow-up, comparing TPMT IM/PM and normal metabolizer (NM) patients. It also studied the association of NUDT15 rs116855232 with response to azathioprine in patients receiving a tailored treatment based on TPMT and characterized the TMPT and NUDT15 studied variants in our population. Results show that azathioprine dose reduction in TPMT IM patients (TPMT*1/*2, *1/*3A, or *1/*3C genotypes) is related to lower toxicity events compared to TPMT NM (TPMT *1/*1 genotype), and lower azathioprine dose adjustments during follow-up without showing differences in the efficacy. The results support the hypothesis of existing other genetic variants affecting azathioprine toxicity.

Mercaptopurine induced myelosuppression in a child with a NUDT15 rs116855232 homozygous variant.

Mercaptopurine (6-MP) is the backbone of the consolidation and maintenance therapy for paediatric acute lymphoblastic leukaemia (ALL). Nevertheless, it can cause critical myelosuppression. Predicting adverse reactions to 6-MP often involves the investigation of pharmacogenetic variants; in particular thiopurine S-methyltransferase (TPMT) and nudix hydrolase 15 (NUDT15). Lately, NUDT15 variants have been shown to play a significant pharmacogenetic role in predicting 6-MP intolerance in children of Asian descent. We present a six-year-old male child of Indian origin with persistent cytopenia after treatment. This prompted targeted sequencing of the genes TPMT and NUD15. The results revealed two copies of the variant of NUD15 rs116855232, that is, NUDT15*2 genotype. Since the NUDT15*2 allele classified the patient as a poor metabolizer, he was restarted on a low dose of 6-MP, which he tolerated. Individuals with the NUDT15*2allele (*2/*2 genotype) are poor metabolizers of thiopurines which results in an adverse reaction to 6-MP. About 3.5% of Indians show variations in the TPMT gene as compared to 19.4% variations observed in NUDT15, which makes the latter a more reliable disease marker.

XDH genotypes through gene-gene interactions with NUDT15 affect azathioprine-induced leukopenia in Chinese patients.

Aim: To investigate whether genotypes of XDH, GMPS and MOCOS were associated with azathioprine-induced adverse drug reaction (ADR) and had the gene-gene interactions with NUDT15 rs116855232 to induce leukopenia. Methods: Patients who had taken azathioprine were recruited. Genotyping of those gene was performed. Risk factor to ADR was analyzed by logistic regression. The generalized multifactor dimensionality reduction (GMDR) was assessed based on gene-gene interactions with ADR. Results: A total of 111 patients were included in this study, all of whom were Han Chinese. XDH rs2295475 was a risk factor of myelotoxicity (p=0.022). NUDT15 rs116855232 was a risk factor of myelotoxicity, grade ≥2 leukopenia and drug treatment termination (p-values were <0.05). Rs2295475and rs116855232 had agene-gene interaction. The model was associated with grade ≥2 leukopenia (OR: 17.99; 95% CI: 4.11-78.81). Conclusion: Combined testing genotype for rs2295475 and rs116855232 could improve the prediction of azathioprine-induced leukopenia.

Effect of genetic polymorphism of TPMT and NUDT15 on the tolerance of 6-mercaptopurine therapy in adult acute lymphoblastic leukemia

目的探讨TPMT*2 rs1800462、TPMT*3B rs1800460、TPMT*3C rs1142345和NUDT15 rs116855232基因多态性对成人急性淋巴细胞白血病（ALL）患者6-巯基嘌呤（6-MP）耐受性的影响。方法选取2015年9月至2019年12月于中国医学科学院血液病医院确诊并接受环磷酰胺、阿糖胞苷和6-MP（CAM方案）治疗的216例成人ALL患者，利用Taqman SNP基因分型方法检测患者的TPMT、NUDT15基因型。结合临床资料，分析基因多态性对ALL治疗中含6-MP方案耐受性的影响。结果216例患者中B-ALL 185例（85.65％）、T-ALL 31例（14.35％）。TPMT*2 rs1800462 CC型216例（100.00％）；TPMT*3B rs1800460 CC型216例（100.00％）；TPMT*3C rs1142345 TT型209例（96.76％）、TC型7例（3.24％），等位基因突变频率为1.62％。NUDT15 rs116855232 CC型166例（76.85％）、CT型48例（22.22％）、TT型2例（0.93％），等位基因突变频率为12.04％。TPMT*3C rs1142345突变型组（TC+CC型）悬浮红细胞的输注量少于野生型组（CC型）（P＝0.036）；TPMT*3C rs1142345突变型组出现肝损害（天冬氨酸转氨酶升高）的风险高于野生型组（OR＝9.559, 95％CI 1.135～80.475, P＝0.038）。NUDT15 rs116855232突变型组（CT+TT型）WBC<1×109/L和中性粒细胞绝对计数<0.5×109/L的持续时间均长于野生型组（CC型）（P＝0.005，P＝0.007）；突变型组单采血小板的输注量多于野生型组（P＝0.014）。结论TMPT、NUDT15基因多态性可以影响成人ALL患者对6-MP的耐受性。治疗前检测患者基因型，进而优化6-MP使用剂量，有助于缩短骨髓抑制时间和减少血制品输注量。临床试验注册：中国临床试验注册中心（ChiCTR-TNC-09000397）

Association of APEX1 and NUDT15 Polymorphisms with Mercaptopurine-Related Neutropenia in Pediatric Acute Lymphoblastic Leukemia

Introduction: Mercaptopurine (MP) is one of the main chemotherapeutics for acute lymphoblastic leukemia (ALL), and constant MP dose titration is essential to maintain steady drug exposure, while minimizing myelosuppression. Throughout previous studies, thiopurine methyltransferase (TPMT) is proved to be one of the most responsible genes in the pharmacogenetics of MP. However, most of East Asian patients still show sensitivity to MP after adjusting for TPMT variants, suggesting the existence of other yet unknown factors that are related to MP sensitivity. In this study, the genetic factors affecting the toxicity of MP were investigated in Korean children with ALL.Methods: Two-stage pharmacogenetic analyses were performed to identify genetic determinants of MP-related neutropenia in Korean pediatric ALL patients who received maintenance chemotherapy including daily MP. A total of 287 patients with ALL who were diagnosed and treated at the Seoul National University Children's Hospital and Asan medical center were included. First, targeted sequencing was carried out using a novel gene panel of 147 pharmacogenetics related genes and 8 SNPs in 44 patients who received less than 25% of initial dose during maintenance therapy due to MP intolerance. Next, significant genes identified in the first analysis were re-sequenced in a total of 287 patients. The relationship between mutation of each gene identified through sequencing and toxicity or dose of MP were analyzed.Results: As a result of the first stage analysis, 4 functionally interesting variants other than NUDT15 were selected (ABCC4, APEX1 , CYP1A1 ,and CYP4F2). Including these 4 variants, total 23 variants in 12 genes potentially linked to MP adverse reactions were selected as final candidates for subsequent analysis in 287 patients. The distribution of variant alleles were NUDT15 rs116855232 (20.7%), APEX1 rs2307486 (13.0%), ABCC4 rs2274407 (36.2%), ABCC4 rs3765534 (15.4%), ABCC4 rs11568658 (26.2%), CYP4F2 rs2108622 (54.5%), CYP1A1 rs4646422 (30.6%), SLCO1B1 rs11045879 (52.1%), SLCOB1 rs4149056 (27.0%), ITPA rs1127354 (25.6%), ITPA rs7270101 (0%), MTHFR rs1801131 (28.2%), MTHFR rs1801133 (68.3%), MTHFR rs1901133 (54.1%), GRIA1 rs4958351 (2.4%), MOCOS rs594445 (50.3%), PACSIN2 rs2413739 (9.4%), BAG3 rs78439745 (8.4%) and TPMT (* 1 / * 3C and *6, 3.1%). Grade 4 neutropenia (neutrophil<500/㎕) was observed in 177 patients (61.7%) during the administration of MP. When frequency of neutropenia during MP administration was crosstabulated with variant frequencies, the risk of neutropenia was 4.64 times higher in patients with T allele in ABCC4 rs3765534 (95% CI; 1.4 to 20.7, P=0.013). The cumulative incidence of neutropenia was significantly higher in patients with variant forms of APEX1 rs2307486 (AA:AG:GG=59.2%:66.7%:100%, P=0.005) (Figure 1). The cumulative incidence of neutropenia was also significantly increased in patients with NUDT15 rs116855232 mutations (CC:CT:TT=56.2%:73.6%:100%, P <0.001). According to the Cox regression analysis regarding neutropenia, GG genotype in APEX1 rs2307486 conferred a multivariate hazard ratio of 12.03 (95% CI; 1.4 to 101.2, P=0.022), and TT genotype in NUDT15 rs116855232 showed a hazard ratio of 11.42 (95% CI; 3.35 to 38.97, P <0.001). Comparing the average doses of MP used in the study, the T allele type of NUDT15 rs116855232 was significantly associated with a lower tolerated dose of MP as 61.7, 44.6, 20.1% of initially planned doses for CC, CT, and TT genotypes (P <0.001). However, MP doses by TPMT mutations were not significantly different in this study.Conclusion: This study revealed that genetic variations APEX1 increases the cumulative incidence of neutropenia associated with MP, and the variant allele in NUDT15 was related to MP intolerance. APEX1 and NUDT15 both contribute to cell protection from DNA damage or misincorporation, so alleles that impair the function of either gene may affect MP sensitivities, thereby inducing MP-related neutropenia. In Korean ALL patients, toxicity and tolerance of MP were more affected by APEX1 and NUDT15 than by TPMT, which has a lower variant allele frequency in Asian.Figure 1. Estimated cumulative incidence of mercaptopurine-related neutropenia according to the (A) APEX1 rs2307486 and (B) NUDT15 rs116855232 genotypes. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

Population impact of pharmacogenetic tests in admixed populations across the Americas

The current population of the Americas (~1 billion people) is highly heterogeneous as a result of five centuries of admixture between three major parental populations, namely Native Amerindians, Europeans, and subSaharan Africans. This heterogeneity has important pharmacogenetic (PGx) implications. The present study explores this issue with respect to the population impact of PGx tests listed in the CPIC and DWPG guidelines for the cancer chemotherapeutic agents fluoropyrimidines, irinotecan, and thiopurines. Population impact was assessed by the number of individuals needed to genotype (NNG) and to treat [NNT] in order to prevent one additional adverse effect. The 1000 Genomes Project database was accessed to obtain genotypes for the relevant PGx markers and to estimate individual proportions of Native, European, and African ancestry for six recently admixed populations across the Americas. The ancestry proportions were then employed to devise three sub-cohorts, denoted NAT, EUR, and AFR, in which one of the three major ancestral roots predominates largely (8 to 30-fold) over the other two. Minor allele frequency (MAF) of NUDT15 rs116855232, TPMT rs1800460, and UGT1A1 rs887829 differed significantly across the three sub-cohorts, whereas no difference was observed for TPMT rs1142345 and 1800462, and the four DPYD variants interrogated. The frequency of combined TPMT/NUDT and UGT1A1, but not DPD, metabolic phenotypes differed significantly among the sub-cohorts. The NNGs for the drug/sub-cohorts pairs, ranged from 12 (irinotecan/UGT1A1 in EUR) to 360 (fluoropyrimidines/DPYD in NAT). Differences in MAF of the interrogated variants and consequently in the distribution of metabolic phenotypes, plus the variable individual proportions of biogeographical ancestry concur to the 30-fold range of NNGs for the PGx tests, across the sub-cohorts. This large variation is likely to influence the perceived benefits and the clinical adoption of PGx screening for the chemotherapeutic agents investigated. This is of especial concern for fluoropyrimidines, in view of the large NNGs observed in the study sub-cohorts (NNG = 176-360) and confirmed in cancer patients from Brazil (NNG = 312).

Pharmacogenomics of thiopurines: distribution of TPMT and NUDT15 polymorphisms in the Brazilian Amazon.

Reduced function alleles in the TPMT and NUDT15 genes are risk factors for thiopurine toxicity. This study evaluated the influence of Native ancestry on the distribution of TPMT (rs1142345, rs1800460 and rs1800462) and NUDT15 (rs116855232) polymorphisms and compound metabolic phenotypes in 128 healthy males from the Brazilian Amazon. The average proportion of Native and European ancestry differed greatly and significantly between self-declared Amerindians and non-Amerindians, although extensive admixture in both groups was evident. Native ancestry was not significantly associated with the frequency distribution of the TPMT or NUDT15 polymorphisms investigated. The apparent discrepancy with our previous results for NUDT15 rs116855232 in the Ad Mixed American superpopulation of the 1000 Genomes Project is ascribed to the diversity of the Native populations of the Americas. Based on the inferred TPMT/NUDT15 compound metabolic phenotypes, the Clinical Pharmacogenetics Implementation Consortium recommendations for starting thiopurine therapy with reduced doses or to consider dose reduction applied respectively to 3-5% and to 12-20% of the study cohorts.

An intronic FTO variant rs16952570 confers protection against thiopurine-induced myelotoxicities in multiethnic Asian IBD patients

Thiopurines are used in the treatment of inflammatory bowel disease (IBD) but remain clinically challenging to manage due to wide interpatient variability in clinical outcomes and adverse events. Apart from genetic variants in thiopurine S-methyltransferase (TPMT) and nudix hydrolase 15 (NUDT15) genes, polymorphisms in FTO alpha-ketoglutarate dependent dioxygenase (FTO) were found predictive of thiopurine-induced leukopenia, albeit with conflicting results. To clarify the role of FTO variants in a multiethnic Asian IBD cohort, we recruited 149 patients on thiopurine-based therapy and genotyped two FTO variants p.Ala134Thr (rs79206939) and rs16952570 T > C using Sanger sequencing. FTO p.Ala134Thr (rs79206939) was non-polymorphic and absent whereas intronic rs16952570 T > C was equally prevalent in Chinese (22%) and Indians (18%) and higher in Malays (28%). Higher nadir white blood cell (WBC) and absolute neutrophil count (ANC) levels were observed in patients harboring FTO rs16952570 CC genotypes compared with TT carriers at 4, 8, and 12 weeks after start of thiopurine therapy (P < 0.05). A similar trend was observed in patients carrying the previously well-characterized NUDT15 rs116855232 wild-type CC genotypes. Further in silico analysis suggests that FTO variants linked to rs16952570, particularly rs74018601, may play a regulatory role in altering the FTO expression. The findings from this study indicate a novel protective association with the FTO variant rs16952570 CC genotype and hematological parameters.

NUDT15 Genetic Variation Is the Strongest Predictive Marker of Tolerance to 6-Mercaptopurine in Japanese Childhood ALL Patients: A Genome-Wide Association Study

Introduction In Asians, NUDT15 genetic variants have been reported to be associated with low tolerance to 6-mercaptopurine (6-MP). However, variation in 6-MP tolerance is still observed among patients without the NUDT15 variants. Some patients required high doses of 6-MP to obtain treatment effect. We performed a genome-wide association study (GWAS) in Japanese to confirm reported associations as well as to identify additional genetic loci associated with variation of 6-MP tolerance in childhood acute lymphoblastic leukemia (ALL) patients. Methods We included ALL patients enrolled into a Tokyo Children's Cancer Study Group (TCCSG) trial who started maintenance therapy by normal protocol dose (30-50 mg/m2/day). Whole genome single nucleotide polymorphism (SNP) microarray genotyping was performed followed by whole genome SNP imputation (Japanese reference genome). Data for over six million SNPs were available for analysis. Association analysis was performed adjusting for age at diagnosis and considering average 6-MP dose during 168 days from maintenance therapy initiation as the outcome. Results A total of 224 patients were included in the analysis. The median age at diagnosis was 4.7 (range = 0.9-15.7) years old and boys comprised 56.3%. The average 6-MP dose during the 168 days of maintenance therapy was 41.1 (range = 13.3-78.5) mg/m2/day. Variants representing 10 genomic regions showed potential association (P &amp;lt; 5 x 10-6) with average 6-MP dose, in which one locus was genome-wide significant (13q14.2, rs116855232). Variant rs116855232 is located in the previously identified NUDT15 gene and represents the strongest association with average 6-MP dose within our Japanese study (β = -11.45, P = 8.5 x 10-10). In contrast, the TPMT locus, which is predictive of 6-MP intolerance in populations of European ancestry, was not associated with 6-MP dose in Japanese. Among the suggestive loci requiring further follow-up is a locus residing in AFF3 (2q11.2, P = 2.1 x 10-6), a gene previously implicated in childhood leukemia. Conclusion We have validated that NUDT15 rs116855232 is a locus with strong association with 6-MP tolerable dose, and it currently represents the most meaningful clinically predictive marker in Japanese. These findings indicated that NUDT15 genotyping should be considered prior to initiation of 6-MP treatment. Prospects for the identification of additional loci of 6-MP tolerance are high after further validation of suggestive loci observed in this Japanese study. Figure Disclosures No relevant conflicts of interest to declare.

Optimal predictor for 6-mercaptopurine intolerance in Chinese children with acute lymphoblastic leukemia: NUDT15, TPMT, or ITPA genetic variants?

Background6-mercaptopurine (6-MP) contributes substantially to remarkable improvement in the survival of childhood acute lymphoblastic leukemia (ALL) patients. However, 6-MP also has dose-limiting toxicities, particularly life-threatening myelosuppression, due to genetic polymorphisms in enzymes that metabolize 6-MP. Promising biomarkers for predicting 6-MP-induced leukopenia is still unclear in Chinese population. Here, we evaluated the associations of NUDT15, TPMT and ITPA genotypes with 6-MP intolerance in our cohort of childhood ALL patients.MethodsA total of 105 Chinese pediatric patients with a confirmed diagnosis of ALL were enrolled. We identified the NUDT15 coding variant rs116855232 (c.415C > T), a newly discovered 6-MP toxicity-related locus in Asians, and polymorphisms in TPMT rs1142345 and ITPA rs11273540. Associations between genotypes and 6-MP dose sensitivity, leukopenia, hepatotoxicity, and therapy interruption were evaluated.ResultsThe minor allele frequencies (MAFs) of NUDT15 rs116855232, TPMT rs1142345 and ITPA rs11273540 were 15.7, 2.9, and 18.1%, respectively. NUDT15 and TPMT genetic variants were strongly associated with 6-MP dose intensity. Patients with NUDT15 homogenous genotype (TT) were highly sensitive to 6-MP (dose intensity of 60.27%) compared to these with heterozygous genotype (TC) or wild type (CC), who tolerated an average dose intensity of 83.83 and 94.24%, respectively. The NUDT15 variant was a predictor for leukopenia (OR: 3.62, 95% CI 1.377–9.501, P = 0.009) and early-onset leukopenia (OR: 9.63, 95% CI 2.764–33.514, P = 3.75 × 10− 4). No differences were found between 6-MP dose intensity and ITPA polymorphisms.ConclusionNUDT15 variant is an optimal predictor for 6-MP intolerance in Chinese pediatric ALL patients and may have greatly clinical implications for individualized therapy.

Antituberculosis Drug-Induced Adverse Events in the Liver, Kidneys, and Blood: Clinical Profiles and Pharmacogenetic Predictors.

Antituberculosis drug‐induced adverse drug reactions (ATD‐ADRs) are increasing globally, and it is key to identify candidate ATD‐ADRs loci for clinical management. We prospectively enrolled 1,235 highly suspicious tuberculosis (TB) inpatients to investigate the profiles and genetic risk factors of ATD‐ADRs in the liver, kidneys, and blood. Overall, 644 subjects were eligible and genotyped for seven polymorphisms in drug‐metabolizing enzymes and transporter genes. Clinical follow‐up and blood analysis were performed regularly. We found that a notable rate of ATD‐ADRs (incidence: 16.5%, drug intervention rate: 10.4%), mainly involving hepatotoxicity (10.6%) and leukopenia (3.3%) in western China. CYP2D6 rs1135840 and NUDT15 rs116855232 increased the risks of hepatotoxicity and leukopenia with an odds ratio of 2.52 and 4.97, respectively. Both variants showed excellent negative predictive values (93.7% and 98.1%, respectively) but moderate sensitivities (72.7% and 52.4%, respectively). These data provide new insight into ATD‐ADRs in the Chinese population and may offer future leads for diagnosis and treatment.

APEX1 Polymorphism and Mercaptopurine-Related Early Onset Neutropenia in Pediatric Acute Lymphoblastic Leukemia.

PurposeMercaptopurine (MP) is one of the main chemotherapeutics for acute lymphoblastic leukemia (ALL). To improve treatment outcomes, constant MP dose titration is essential to maintain steady drug exposure, while minimizing myelosuppression. We performed two-stage analyses to identify genetic determinants of MP-related neutropenia in Korean pediatric ALL patients.Materials and MethodsTargeted sequencing of 40 patients who exhibited definite MP intolerance was conducted using a novel panel of 211 pharmacogenetic-related genes, and subsequent analysis was performed with 185 patients.ResultsUsing bioinformatics tools and genetic data, four functionally interesting variants were selected (ABCC4, APEX1, CYP1A1, and CYP4F2). Including four variants, 23 variants in 12 genes potentially linked to MP adverse reactions were selected as final candidates for subsequent analysis in 185 patients. Ultimately, a variant allele in APEX1 rs2307486was found to be strongly associated with MP-induced neutropenia that occurred within 28 days of initiating MP (odds ratio, 3.44; p=0.02). Moreover, the cumulative incidence of MP-related neutropenia was significantly higher in patients with APEX1 rs2307486 variants, as GG genotypes were associated with the highest cumulative incidence (p < 0.01). NUDT15 rs116855232 variants were strongly associated with a higher cumulative incidence of neutropenia (p < 0.01), and a lower median dose of tolerated MP throughout maintenance treatment (p < 0.01).ConclusionWe have identified that APEX1 rs2307486 variants conferred an increased risk of MP-related early onset neutropenia. APEX1 and NUDT15 both contribute to cell protection from DNA damage or misincorporation, so alleles that impair the function of either gene may affect MP sensitivities, thereby inducing MP-related neutropenia.

Interaction between NUDT15 and ABCC4 variants enhances intolerability of 6-mercaptopurine in Japanese patients with childhood acute lymphoblastic leukemia.

6-Mercaptopurine (6-MP) is a main component of childhood acute lymphoblastic leukemia (ALL) treatment. Some candidate gene variants are associated with its toxicities, but the major variants and effects of combined variants remain unclear. We used Cox regression analysis to evaluate the time-dependent association between candidate variants and the cumulative incidence of 6-MP intolerability in 95 Japanese patients. The major risk factors for severe leukopenia were ABCC4 rs3765534, NUDT15 rs116855232 and rs186364861 in multi-covariate analysis (P<0.05). NUDT15 intermediate activity variant, that is, heterozygous rs116855232 or rs186364861 variant, and the ABCC4 rs3765534 variant showed leukopenia more frequently than either variant alone. All patients with both the intermediate activity NUDT15 variant and the ABCC4 rs3765534 variant suffered from leukopenia, and 57.1% patients required 50% protocol dose by day 168. These data indicate that NUDT15 and ABCC4 are major factors for 6-MP intolerability and that the interaction between these variants enhances intolerability to 6-MP.

Susceptibility to 6-mercaptopurine toxicity related with NUDT15 and ABCC4 variants in Japanese childhood acute lymphoblastic leukemia.

6-Mercaptopurine (6-MP) is one of the main components for the treatment of childhood acute lymphoblastic leukemia (ALL). However, many patients require a dose reduction of 6-MP due to its severe toxicities. NUDT15 variants are one of the factors that cause 6-MP intolerability in Asians. In each patient with heterozygous variants of NUDT15, 6-MP intolerability differs. Therefore, we hypothesized that the combination of NUDT15 genotype with ABCC4 genotype, which is associated with 6-MP efflux, might enable to accurately predict 6-MP intolerability. We analyzed the association between 6-MP-related events and the genotypes of NUDT15 and ABCC4. All patients with both NUDT15 rs116855232 heterozygous variants and ABCC4 rs3765534 variants suffered from severe leukopenia and required 6-MP dose reduction to less than 35 mg/m2/day. In conclusion, genotyping NUDT15 and ABCC4 facilitates the prediction of 6-MP intolerability. The results of this study will improve personalized medicines in Japanese patients with childhood ALL.