UGT1A1*28 and Other UGT1A Polymorphisms as Determinants of Irinotecan Toxicity

Abstract

Irinotecan is a drug commonly used for the treatment of cancer patients, both as a single agent or in combination therapy. Neutropenia and diarrhea are the dose-limiting toxicities. Genetic variations of proteins involved in irinotecan metabolism and transport have been considered in the development of irinotecan toxicity. In particular, polymorphisms affecting UDP-glucuronosyltransferase isoform 1A1 (UGT1A1) expression or activity are being investigated. Among these, UGT1A1*28 has been considered as the major predictive pharmacogenetic marker for severe hematological toxicity (neutropenia). However, translation to clinical practice of UGT1A1*28 testing as a predictive marker of adverse effects needs to be further investigated and the available data are not conclusive in defining a precise genotype-based dosage.

Further prospective studies are required to reach a personalization of chemotherapy with irinotecan.     

UGT1A1*28 genotype and irinotecan-induced neutropenia: dose matters

The Food and Drug Administration and Pfizer changed the package insert for irinotecan to include a patient's UGT1A1*28 genotype as a risk factor for severe neutropenia on the basis of the findings of four pharmacogenetic studies, which found that irinotecan-treated patients who were homozygous for the UGT1A1*28 allele had a greater risk of hematologic toxic effects than patients who had one or two copies of the wild-type allele (UGT1A1*1). Findings of subsequent irinotecan pharmacogenetic studies have been inconsistent. In a meta-analysis, we reviewed data presented in nine studies that included a total of 10 sets of patients (for a total of 821 patients) and assessed the association of irinotecan dose with the risk of irinotecan-related hematologic toxicities (grade III-IV) for patients with a UGT1A1*28/*28 genotype. The risk of toxicity was higher among patients with a UGT1A1*28/*28 genotype than among those with a UGT1A1*1/*1 or UGT1A1*1/*28 genotype at both medium (odds ratio [OR] = 3.22, 95% confidence interval [CI] = 1.52 to 6.81; P = .008) and high (OR = 27.8, 95% CI = 4.0 to 195; P = .005) doses of irinotecan. However, risk was similar at lower doses (OR = 1.80, 95% CI = 0.37 to 8.84; P = .41). Low doses of irinotecan (100-125 mg/m2) are in the commonly used therapeutic range. The risk of experiencing irinotecan-induced hematologic toxicity for patients with a UGT1A1*28/*28 genotype thus appears to be a function of the dose of irinotecan administered.     

Associations between UGT1A1*6 or UGT1A1*6/*28 polymorphisms and irinotecan-induced neutropenia in Asian cancer patients

Purpose

Neutropenia is a life-threatening side effect of irinotecan, and uridine diphosphate glucuronosyltransferases (UGTs) gene polymorphisms are considered to be one of the predictive markers of irinotecan-related toxicities. Many studies have demonstrated that patients bearing UGT1A1*28 have a higher risk of severe neutropenia on toxicity of irinotecan. However, UGT1A1 (TA7/TA7) was very rare in Asian populations. Some researches reported that UGT1A1*28 and/or UGT1A1*6 could predict irinotecan-induced toxicities in Asian populations, but controversial conclusions still remained. This study aims to investigate the association between UGT1A1 gene polymorphisms *6, *6/*28 and irinotecan-related neutropenia in Asian cancer patients receiving irinotecan regimen chemotherapy.

Experimental design

Meta-analyses were done to assess the relationship between UGT1A1*6 or UGT1A1*6/*28 and irinotecan-induced neutropenia.

Results

The risk of neutropenia was significantly higher among patients with a UGT1A1*6 genotype than among those carrying the UGT1A1*1 allele(s) [odds ratio (OR) 3.276; 95 % confidence interval (CI) 1.887–5.688; P = 0.000 (*6/*6 vs. *1/*6 or *1/*1)], [OR 1.542; 95 % CI 1.180–2.041; P = 0.001 (*6/*6 or *1/*6 vs. *1/*1)]. Also, the risk was significantly higher among patients with a UGT1A1*6/*28 than among those carrying the UGT1A1*1 allele(s) [OR 3.275; 95 % CI 2.152–4.983; P = 0.000 (*6/*6 or *28/*28 or *6/*28 vs. *1/*6 or *1/*28 or *1/*1)].

Conclusions

In conclusion, the UGT1A1*6 and UGT1A1*6/*28 genotypes were associated with an increased risk of irinotecan-induced neutropenia in Asian cancer patients.     

Genotype-directed, dose-finding study of irinotecan in cancer patients with UGT1A1*28 and/or UGT1A1*6 polymorphisms

Irinotecan-induced severe neutropenia is associated with homozygosity for the UGT1A1*28 or UGT1A1*6 alleles. In this study, we determined the maximum-tolerated dose (MTD) of irinotecan in patients with UGT1A1 polymorphisms. Patients who had received chemotherapy other than irinotecan for metastatic gastrointestinal cancer were enrolled. Patients were divided into three groups according to UGT1A1 genotypes: wild-type (*1/*1); heterozygous (*28/*1, *6/*1); or homozygous (*28/*28, *6/*6, *28/*6). Irinotecan was given every 2 weeks for two cycles. The wild-type group received a fixed dose of irinotecan (150 mg/m(2)) to serve as a reference. The MTD was guided from 75 to 150 mg/m(2) by the continual reassessment method in the heterozygous and homozygous groups. Dose-limiting toxicity (DLT) and pharmacokinetics were evaluated during cycle 1. Of 82 patients enrolled, DLT was assessable in 79 patients (wild-type, 40; heterozygous, 20; and homozygous, 19). Dose-limiting toxicity occurred in one patient in the wild-type group, none in the heterozygous group, and six patients (grade 4 neutropenia) in the homozygous group. In the homozygous group, the MTD was 150 mg/m(2) and the probability of DLT was 37.4%. The second cycle was delayed because of neutropenia in 56.3% of the patients given the MTD. The AUC(0-24 h) of SN-38 was significantly greater (P < 0.001) and more widely distributed in the homozygous group. Patients homozygous for the UGT1A1*28 or UGT1A1*6 allele can receive irinotecan in a starting dose of 150 mg/m(2), but many required dose reductions or delayed treatment in subsequent cycles. UMIN Clinical Trial Registration number: UMIN000000618.     

Role of UGT1A1*28 and UGT1A1*6 for irinotecan-induced adverse drug reaction

Irinotecan is widely used in the treatment of colorectal, gastric, and lung cancers. However, adverse drug reactions such as severe diarrhea and neutropenia limit the dose of this drug. Irinotecan is metabolized by carboxylesterase to form an active metabolite, 7-ethyl-10-hydroxycamptothecin(SN-38), which in turn is subsequently conjugated by UGT-glucuronosyltransferase 1A1(UGT1A1)to yield an inactive form, SN-38 glucuronide(SN-38 G). The UGT1A1 gene polymorphisms contribute to the individual variation in adverse events among patients administered irinotecan. However, the distribution of polymorphisms shows large interethnic differences. The distribution of UGT1A1*28 greatly differs between Caucasians and Japanese; the frequency of UGT1A1*28 is high in Caucasians, whereas it is low in Asians including Japanese. Recently, it has been demonstrated that genetic variants of UGT1A1*6 in addition to UGT1A1*28 are associated with the occurrence of adverse events in irinotecan chemotherapy in Asians. This review summarizes recent studies to outline the role of UGT1A1*28 and UGT1A1*6 for irinotecan-induced adverse drug reaction in Japanese cancer patients.     

Pharmacogenetic impact of polymorphisms in the coding region of the UGT1A1 gene on SN-38 glucuronidation in Japanese patients with cancer

Pharmacogenetic testing for UDP-glucuronosyltransferase (UGT) 1A1*28, a promoter variant of the UGT1A1 gene, is now carried out clinically to estimate the risk of irinotecan-associated toxicity. We studied the clinical significance of UGT1A1*6 and UGT1A1*27, two variants in exon 1 of the UGT1A1 gene that are found mainly in Asians. The study group comprised 46 Japanese patients who received various regimens of chemotherapy including irinotecan at doses from 50 to 180 mg/m(2). Pharmacogenetic relationships were explored between the UGT1A1 genotype and the ratio of the area under the plasma concentration-time curve (AUC) of the active metabolite of irinotecan (SN-38) to that of SN-38 glucuronide (SN-38G), used as a surrogate for UGT1A1 activity (AUC(SN-38)/AUC(SN-38G)). No patient was homozygous for UGT1A1*28, and none had UGT1A1*27. Two were heterozygous for UGT1A1*28. Two were homozygous and 15 heterozygous for UGT1A1*6, all of whom were wild type with respect to UGT1A1*28. Two patients were simultaneously heterozygous for UGT1A1*28 and UGT1A1*6, present on different chromosomes. The other 25 patients had none of the variants studied. The two patients simultaneously heterozygous for UGT1A1*28 and UGT1A1*6 and the two patients homozygous for UGT1A1*6 had significantly higher AUC(SN-38)/AUC(SN-38G) ratios than the others (P = 0.0039). Concurrence of UGT1A1*28 and UGT1A1*6, even when heterozygous, altered the disposition of irinotecan remarkably, potentially increasing susceptibility to toxicity. Patients homozygous for UGT1A1*6 should also be carefully monitored. UGT1A1 polymorphisms in the coding region of the UGT1A1 gene should be genotyped in addition to testing for UGT1A1*28 to more accurately predict irinotecan-related toxicity, at least in Asian patients.     

川东北地区人群结直肠癌患者UGT1A1*28基因多态性与伊立替康所致毒副反应的相关性

目的:观察结直肠癌患者UGT1A1*28基因多态性的分布频率,了解UGT1A1*28基因多态性与结直肠癌患者应用伊立替康联合5-氟尿嘧啶化疗毒副反应的相关性。方法:从384例接受伊立替康联合氟尿嘧啶一线化疗的晚期结直肠癌病例中采外周血提取DNA。采用PCR 法扩增目的基因片段,直接测序法分析UGT1A1*28基因多态性。临床观察并评价患者化疗毒副反应分级,统计分析UGT1A1*28基因表型与化疗毒副反应相关性。结果:全部 384例患者 UGT1A1*28基因多态性分布情况:TA6/6野生基因型287例(74.7％),TA6/7杂合基因型73例（19.0％）,TA7/7纯合基因型24例（6.3％）。化疗毒副反应和UGT1A1*28基因多态性进行临床单因素分析显示UGT1A1*28基因纯合型TA7/7、杂合型TA6/7与3-4度白细胞减少、中性粒细胞减少、腹泻、胆红素升高具有明显相关性（P<0.01）,UGT1A1*28基因纯合型TA7/7及杂合型TA6/7患者发生中性粒细胞减少的风险较UGT1A1*28基因野生型TA6/6患者高5.625倍（OR=5.625）。UGT1A1*28基因纯合型TA7/7和UGT1A1*28基因杂合型TA6/7患者发生腹泻的风险较UGT1A1*28基因野生型TA6/6患者高6.778倍（OR=6.778）。结论:UGT1A1*28基因纯合型TA7/7及杂合型TA6/7患者应用伊立替康化疗后发生重度中性粒细胞减少、重度腹泻的风险高于UGT1A1*28基因野生型TA6/6,为临床伊立替康用药选择、剂量调整、毒副反应的提前干预提供理论依据。     

Prevalence of topoisomerase I genetic mutations and UGT1A1 polymorphisms associated with irinotecan in individuals of Asian descent

Topoisomerase I (TOP-I) mutations have been shown to be correlated to irinotecan resistance in vitro. However, the prevalence of TOP-I germline mutations has yet to be systematically elucidated. On the other hand, polymorphisms of UGT1A1 have been shown to be associated with CPT-11 toxicity in clinical situations. The primary aim of this study was to investigate the prevalence of mutations in the TOP-I exons associated with CPT-11 resistance, including untreated cancer tissue. A secondary aim was to confirm the less frequent UGT1A1*28 and more frequent UGT1A1*6 in individuals of Asian descent compared to Caucasians and individuals of African descent. The prevalence of 5 reported TOP-I mutations in exons was investigated in volunteers (n=236) using DNA sequencing of the PCR products. The prevalence of TOP-I mutations in untreated lung cancer tissues (n=16) was also investigated. Additionally, 3 UGT1A1 polymorphisms, UGT1A1*6, *27 and *28, were investigated in volunteers (n=126). There were no mutations of TOP-I in any of the 236?subjects or in the untreated lung tissues. Among 128?subjects, the distribution of homozygous polymorphisms of UGT1A1 was: UGT1A1*28 in 3 (2.4%) and UGT1A1*6 in 4 (3.2%) subjects, and co-occurrence of heterozygous polymorphisms for both UGT1A1*6 and UGT1A1*28 in 4 (3.2%) subjects, and for UGT1A1*27 and UGT1A1*28 in 1 subject (0.8%). The Hardy-Weinberg deviation test showed there was no significant deviation from the equilibrium, and the association analysis indicated no significant linkage between UGT1A1*6 and UGT1A1*28. In conclusion, TOP-I genetic mutations correlated to CPT-11 resistance were not detected in any of the subjects and untreated lung cancer tissues. Less frequent UGT1A1*28 and more frequent UGT1A1*6 were confirmed in East Asian individuals compared to Caucasians and individuals of African descent. Linkage disequilibrium was not detected between UGT1A1*6 and UGT1A1*28.     

UGT1A1基因多态性与伊立替康临床用药安全性及疗效的关系

目的：研究 UGT1A1基因多态性与伊立替康治疗结直肠癌患者的不良反应及疗效之间的关系。方法：自外周血中抽提基因组 DNA,进行 PCR 扩增,应用直接测序法分析2012年3月至2013年3月,于我院行基因检测的65例结直肠癌患者 UGT1A1*28和 UGT1A1*6基因多态性的分布情况。并对这65例应用含伊立替康方案化疗的患者出现的不良反应及化疗疗效,进行观察记录,比较不同基因型间的差异。结果：65例患者中,UGT1A1*28野生型 TA6／6有49例（75．4％）,杂合突变型 TA6／7有14例（21．5％）,纯合突变型TA7／7有2例（3．1％）。UGT1A1*6野生型 G／G 有47例（72．3％）,杂合突变型 G／A 有15例（23．1％）,纯合突变型 A ／A 有3例（4．6％）。在以上65例结直肠癌患者中,UGT1A1基因启动子区28位点,TA6／6、TA6／7和TA7／7型,发生3级以上腹泻者分别为8．2％、37．5％;发生3级以上中性粒细胞减少者分别为28．6％、62．5％。UGT1A1基因启动子区6位点,G／G、G／A 和 A ／A 型,发生3级以上腹泻者分别为12．8％、44．4％;发生3级以上中性粒细胞减少者分别为14．9％、22．2％。各组之间疗效无统计学差异。结论：患者 UGT1A1*28和UGT1A1*6多态性分布基本一致,UGT1A1*28突变型可以使应用含伊立替康化疗患者发生3级以上腹泻和中性粒细胞减少的风险增加。UGT1A1*6突变型可增加3级以上腹泻的发生风险。因此,UGT1A1基因型的检测对伊立替康相关的不良反应有一定的预测作用,可提高用药安全性,在临床用药中起到了指导作用。     

UGT1A1*28 polymorphism in ovarian cancer patients

(Uridino-diphosphate)glucuronosyl-transferase enzyme 1A1 isoform (UGT1A1) is involved in glucuronidation of antineoplastic drugs such as SN38, the active metabolite of irinotecan, as well as estrogens and their metabolites. UGT1A1*28 polymorphism decreases UGT1A1 expression and could alter estrogens disposition influencing tumour growth in hormone sensitive tissues. The UGT1A1*28 distribution among an ovarian cancer patient (OCP) population of 217 mono-institutional individuals was investigated to clarify its possible involvement in the pathogenesis and chemotherapy of ovarian cancer. Data were compared with those of 205 female healthy blood donors. In 160 patients also the tumour tissue was genotyped to describe the occurrence of loss of heterozygosity (LOH). A PCR based assay followed by automated fragment analysis was used. Odds ratios (OR), and 95% confidence intervals (95% CI), were computed by a multiple logistic regression model using as dependent variable in a case-control or in a case-case approach the histological classification. No significant prevalence of the polymorphism was observed in the cases versus controls. In a case-case approach, a higher frequency of the polymorphism was observed in patients with mucinous tumours (6/11, 54.6%) compared to non-mucinous (30/206, 14.6%) (p=0.009, OR=7.20; 95% CI 2.06-25.19). LOH was observed in 12 cases out of 160 (7.5%) and was associated with non-mucinous tumours, 10 (83.3%) cases determined a retention of the wild-type allele. In conclusion, the prevalence of UGT1A1*28 found in mucinous OCP could suggest a role in the development of specific histologic sub-groups and could become a marker to be considered when planning ovarian cancer chemotherapy.     

Linkage disequilibrium of UGT1A1 *6 and UGT1A1 *28 in relation to UGT1A6 and UGT1A7 polymorphisms

UDP-glucuronosyltransferase (UGT) enzymes are responsible for the glucuronidation and detoxification of many endogenous or exogenous xenobiotics. Gilbert's syndrome (GS) and Crigler Najjar syndrome type 2 (CNS-II) are characterized by unconjugated hyperbilirubinemia due to reduced enzymatic activity of UGT1A1. Recent studies have demonstrated the frequent co-existence of UGT1A1 *28 (-53 [TA]6>7) with other polymorphisms of UGT1A6 and UGT1A7. This finding suggests the occurrence of linkage disequilibrium (LD) among UGT1A1, UGT1A6 and UGT1A7 polymorphisms. UGT1A1 *6 (211G>A, G71R) and UGT1A1 *28 are common in Asian populations. In the present study, we investigated the LD of UGT1A1 *6 and UGT1A1 *28 in relation to UGT1A6 and UGT1A7 polymorphisms. Exon 1 of UGT1A1, UGT1A6 and UGT1A7 was sequenced using genomic DNA isolated from peripheral leukocytes of 390 Japanese subjects. LD and haplotypes were analyzed using SNPAlyze ver. 5.0 software. UGT1A1 *6 had a strong LD in relation to UGT1A6 variants including 541A>G and 552A>C (D'=0.846-0.848, r(2)=0.413-0.438) and UGT1A7 variants including 387T>G, 391C>A, 392G>A and 622T>C (D'=0.667-0.858, r(2)=0.207-0.413). UGT1A1 *28 had a lower degree of LD than UGT1A1 *6 in relation to these variants (D'=0.245-0.401, r(2)=0.025-0.063). All the haplotypes with G71R lacked -53[TA]6>7. The present study showed for the first time that the LD of UGT1A1 *6 in relation to UGT1A6 and 1A7 polymorphisms is far stronger than UGT1A1 *28. The UGT1A1 *6 allele appears to be independent of the UGT1A1 *28 allele. Although patients with GS and CNS-II are believed to have good prognosis, a subgroup of GS or CNS-II patients with the UGT1A1 *6 polymorphism might be at risk of abnormal drug metabolism and of developing malignant disease.     

UGT1A7 and UGT1A9 polymorphisms predict response and toxicity in colorectal cancer patients treated with capecitabine/irinotecan.

PURPOSE: Capecitabine and irinotecan are commonly used in the treatment of metastatic colorectal cancer (CRC). We hypothesized that germline polymorphisms within genes related to drug target (thymidylate synthase) or metabolizing enzymes (UDP-glucuronosyltransferase, UGT) would impact response and toxicity to the combination of capecitabine plus irinotecan (CPT-11). EXPERIMENTAL DESIGN: Sixty-seven patients with measurable CRC were treated with irinotecan i.v. (100 or 125 mg/m(2)) on days 1 and 8 and capecitabine orally (900 or 1,000 mg/m(2), twice daily) on days 2 through 15 of each 3-week cycle. Genomic DNA was extracted from peripheral blood and genotyped using Pyrosequencing, GeneScan, and direct sequencing (Big Dye terminator) technologies. RESULTS: The overall objective response rate was 45% with 21 patients (31%) exhibiting grade 3 or 4 diarrhea and 3 patients (4.5%) demonstrating grade 3 or 4 neutropenia in the first two cycles. Low enzyme activity UGT1A7 genotypes, UGT1A7*2/*2 (six patients) and UGT1A7*3/*3 (seven patients), were significantly associated with antitumor response (p = 0.013) and lack of severe gastrointestinal toxicity (p = 0.003). In addition, the UGT1A9 -118 (dT)(9/9) genotype was significantly associated with reduced toxicity (p = 0.002) and increased response (p = 0.047). There were no statistically significant associations between UGT1A1, UGT1A6, or thymidylate synthase genotypes and toxicity or tumor response. CONCLUSIONS: These data strongly suggest that UGT1A7 and/or UGT1A9 genotypes may be predictors of response and toxicity in CRC patients treated with capecitabine plus irinotecan. Specifically, patients with genotypes conferring low UGT1A7 activity and/or the UGT1A9 (dT)(9/9) genotype may be particularly likely to exhibit greater antitumor response with little toxicity.     

伊立替康联合顺铂或5-FU治疗UGT1A1*28野生型TA6/6患者不良反应的比较

目的：比较尿苷二磷酸葡萄糖醛酸转移酶1A1（UGT1A1）*28启动子为野生型的TA6/6患者在使用伊立替康（irinotecan,CPT-11）联合顺铂与CPT-11联合5-FU/亚叶酸钙治疗时不良反应方面的差异。方法根据采取的治疗方案将98例UGT1A1*28野生型TA6/6患者分为CPT-11联合顺铂组（IP组,n＝47）和CPT-11联合5-FU/亚叶酸钙组（FOLFIRI组,n＝51）,对患者进行UGT1A1*28启动子多态性检测,比较不良反应差异。结果在总体3～4级不良反应方面,IP组的发生率（61.7%）明显高于FOLFIRI组（39.2%）,且组间差异具有统计学意义（P=0.026）。在血液学不良反应方面,IP组3～4级白细胞减少、中性粒细胞减少、血小板减少和血红蛋白减少发生率分别为34.0%、51.1%、14.9%和8.5%,FOLFIRI组的发生率分别为11.8%、29.4%、2.0%、0,组间差异均有统计学意义（均P＜0.05）;在非血液学方面,FOLFIRI组3～4级迟发性腹泻发生率为9.8%,IP组未发生3～4级腹泻,两组间发生率的差异有统计学意义（P=0.028）。结论 UGT1A1*28野生型TA6/6患者在接受CPT-11联合顺铂和CPT-11联合5-FU/亚叶酸钙两种化疗方案治疗的不良反应谱存在差异;应用CPT-11时,不但要考虑到UGT1A1*28启动子多态性对不良反应的影响,而且还要考虑CPT-11联合不同药物出现不良反应情况。     

UGT1A1 gene variations and irinotecan treatment in patients with metastatic colorectal cancer

SN-38 is the active metabolite of irinotecan and it is metabolised through conjugation by uridine diphosphate glucuronosyl transferase (UGT1A1). The major toxicity of irinotecan therapy is diarrhoea, which has been related to the enzymatic activity of UGT1A1. We examined the influence of the UGT1A1 gene promoter polymorphism in the toxicity profile, in the response rate and in the overall survival (OS) in 95 patients with metastatic colorectal cancer treated with an irinotecan-containing chemotherapy. Genotypes were determined by analysing the sequence of TATA box of UGT1A1 of genomic DNA from the patients. Clinical parameters and genotypes were compared by univariate and multivariate statistical methods. The more frequent adverse effects were asthenia (34 patients), diarrhoea (29 patients) and neutropenia (20 patients). Severe diarrhoea was observed in 7/10 homozygous (70%) and 15/45 heterozygous (33%) in comparison to 7/40 (17%) wild-type patients (P=0.005). These results maintained the statistical significance in logistic regression analysis (P=0.01) after adjustment for other clinical relevant variables. The presence of severe haematological toxicity increased from wild-type patients to UGT1A1(*)28 homozygotes, but without achieving statistical significance. No relationship was found between the UGT1A1(*)28 genotypes and infection, nausea or mucositis. In univariate studies, patients with the UGT1A1(*)28 polymorphism showed a trend to a poorer OS (P=0.09). In the multivariate analysis, the genotype was not related to clinical response or to OS. The role of the UGT1A1 genotype as a predictor of toxicity in cancer patients receiving irinotecan demands the performance of a randomized trial to ascertain whether genotype-adjusted dosages of the drug can help to establish safe and effective doses not only for patients with the UGT1A1(*)28 homozygous genotype but also for those with the most common UGT1A1 6/6 or 6/7 genotype.     

中国人尿苷二磷酸葡糖苷酸转移酶1A基因多态性与伊立替康毒性的相关性

目的评价伊立替康(CVT-11)联合5-氟尿嘧啶(5-Fu)和亚叶酸钙(LV)治疗晚期大肠癌的毒性与尿苷二磷酸葡糖苷酸转移酶1A(UGT1A)基因多态性的相关性。方法收集70例晚期大肠癌患者及健康志愿者的外周血,提取基因组DNA,PCR法扩增目的基因片段,直接测序法分析UGT1A基因多态性,并与毒性进行相关性分析。结果70例晚期大肠癌患者的3～4度中性粒细胞减少发生率为20.O%(14/70);2～4度迟发性腹泻发生率为22.9%(16/70),其中3-4度迟发性腹泻率仅为5.7%(4/70)。UGT1A1*28的野生基因型TA6/6患者的2-4度迟发性腹泻发生率为15.7%,低于TA6/7和TA7/7基因型的患者(P=0.027)。健康人群和大肠癌患者UGT1A基因家族中各个基因多态性的分布无差别。结论UGT1A1*28的野生基因型TA6/6在中国人中分布频率较高,这也是CPT-11为主方案治疗晚期大肠癌发生严重迟发性腹泻较少的原因。     

Clinical and pharmacogenetic factors associated with irinotecan toxicity

Irinotecan is a topo-isomerase-I inhibitor with broad antitumor activity in solid tumors. Its use may lead to severe toxicities, predominantly neutropenia and diarrhea which can be life-threatening. This review discusses clinical determinants and pharmacogenetic factors associated with irinotecan toxicity. Age, performance status, co-medication and elevated transaminases have been associated with increased risk of diarrhea or neutropenia. Also, elevated bilirubin levels, due to liver impairment, conjugation disorders or UGT1A1 *28 genotype, have been associated with increased incidence of grades 3 intestinal toxicity and neutropenia. UGT1A1 *28 homozygosity is strongly associated with irinotecan-induced neutropenia and polymorphisms in the transporting peptides ABCB1 and OATP1B1 have also been associated with gastrointestinal toxicity and irinotecan pharmacokinetics, respectively. In the irinotecan product label, it is advised to reduce the irinotecan starting dose for UGT1A1 *28 homozygotes. However, due to the lack of prospective data, it is yet unknown whether dose reduction leads to reduced toxicity or altered antitumor effect. Combined toxicity analysis reveals that most patients experiencing grade 3-4 diarrhea and/or neutropenia are not homozygous for UGT1A1 *28. Future studies should combine pharmacogenetics with clinical determinants such as performance status and co-medication as to predict irinotecan toxicity and to develop predefined dosing algorithms.     

UGT1A1*28 polymorphism predicts irinotecan-induced severe toxicities without affecting treatment outcome and survival in patients with metastatic colorectal carcinoma

BACKGROUND: It is known that the uridine-diphosphoglucuronosyl transferase 1A1 (UGT1A1)*28 polymorphism reduces UGT1A1 enzyme activity, which may lead to severe toxicities in patients who receive irinotecan. This study was conducted to assess the influence of this polymorphism on the efficacy and toxicity of irinotecan treatment in Chinese patients with metastatic colorectal carcinoma (CRC). METHODS: In total, 128 patients with metastatic CRC who had received previous treatment with irinotecan plus 5-fluorouracil/leucovorin were analyzed retrospectively. Genomic DNA samples were obtained from patients' leukocytes, and genotypes were determined by analyzing the sequence of TATA boxes in the UGT1A1 gene. The influence of the UGT1A1*28 polymorphism on toxicity and treatment outcome was analyzed. RESULTS: Approximately 20% of patients were identified with the UGT1A1*28 polymorphism, including 15.6% (n = 20 patients) with the thymine-adenine (TA)6/TA7 genotype and 4.7% (n = 6 patients) with the TA7/TA7 genotype. The remaining 79.7% of patients (n = 102) had wild type TA6/TA6. Marked increases in grade 3 or 4 neutropenia (53.8% vs 4.9%; P < .01), neutropenic fever (38.5% vs 3.9%; P < .01), diarrhea (26.9% vs 5.9%; P < .01), and pretreatment bilirubin level (23.1% vs 8.8%; P = .04) were observed in patients who had the TA6/TA7 or TA7/TA7 genotypes. Patients' pretreatment bilirubin levels correlated well with irinotecan-induced neutropenia (P < .01). It was noted that, although the requirement for irinotecan dose reduction was significantly greater in patients who had this genetic variant (42.3% vs 12.7%; P < .01), it did not affect the response rate to irinotecan-based chemotherapy (42.3% vs 45.1%; P = .80), and it did not significantly affect progression-free survival (10 months vs 11 months; P = .94) or overall survival (19 months vs 18 months; P = .84). CONCLUSIONS: The current data suggested that the UGT1A1*28 polymorphism may be a key determinant for predicting irinotecan-induced severe toxicities without affecting treatment outcome for patients with metastatic CRC. Further prospective studies are warranted for using this polymorphism to optimize irinotecan-based chemotherapy.     

Impact of UGT1A1 genetic polymorphism on toxicity in unresectable pancreatic cancer patients undergoing FOLFIRINOX

Studies have indicated an association between UDP‐glucuronosyltransferase‐1A1 (UGT1A1) genetic polymorphisms and irinotecan‐induced toxicity. We undertook this study to investigate the association between UGT1A1 genetic polymorphisms and toxicity in patients treated with the FOLFIRINOX (comprising oxaliplatin, irinotecan, fluorouracil, and leucovorin) chemotherapy regimen in the JASPAC 06 study. Patients screened for UGT1A1*6 and UGT1A1*28, and treated with either the original FOLFIRINOX (oxaliplatin 85 mg/m², irinotecan 180 mg/m², leucovorin 200 mg/m², bolus 5‐fluorouracil [5‐FU] 400 mg/m², and continuous 5‐FU 2400 mg/m²) or a modified FOLFIRINOX (oxaliplatin 85 mg/m², irinotecan 150 mg/m², leucovorin 200 mg/m², and continuous 5‐FU 2400 mg/m²) as first‐line chemotherapy were included. Of 199 patients eligible for this analysis, 79 patients were treated with the original FOLFIRINOX regimen and 120 patients were treated with the modified FOLFIRINOX regimen. In the original FOLFIRINOX group, 54 were UGT1A1 WT, and 25 were UGT1A1 heterozygous type (?/*6, 12 patients; ?/*28, 13 patients). In the modified FOLFIRINOX group, 64 were UGT1A1 WT and 56 were UGT1A1 heterozygous type (?/*6, 33 patients; ?/*28, 23 patients). In the original FOLFIRINOX group, the incidence of diarrhea was significantly higher among patients with UGT1A1 heterozygous type than among those with UGT1A1 WT and the incidence of leukopenia and diarrhea was significantly higher among patients with UGT1A1 ?/*6 than among those with UGT1A1 ?/*28. Patients with UGT1A1 heterozygous type, especially those with UGT1A1 ?/*6, tended to show a higher incidence rate of severe adverse events, but this was not statistically significant. However, for patients who received the modified FOLFIRINOX, there was no difference in the frequency of adverse events due to UGT1A1 status. In conclusion, patients with heterozygous UGT1A1 polymorphisms treated with the original FOLFIRINOX regimen experienced severe toxicity more frequently than patients with WT UGT1A1.     

UGT1A1*6, 1A7*3, and 1A9*22 genotypes predict severe neutropenia in FOLFIRI‐treated metastatic colorectal cancer in two prospective studies in Japan

Retrospective studies have suggested that UDP‐glucuronosyltransferase (UGT)1A1, UGT1A7, and UGT1A9 predict severe toxicity and efficacy of irinotecan‐containing regimens. We prospectively evaluated the impact of UGT1A genotypes and haplotypes on severe toxicity and efficacy in patients treated with fluorouracil, leucovorin, and irinotecan combination chemotherapy (FOLFIRI) for metastatic colorectal cancer (mCRC) from the two prospective multicenter phase II studies in Japan. The FLIGHT1 study was a first‐line FOLFIRI trial, and FLIGHT2 was a FOLFOX‐refractory, second‐line FOLFIRI trial. A total of 73 patients agreed to additional analysis, and were genotyped for UGT1A polymorphisms, UGT1A1*28 (TA6>TA7), UGT1A1*6 (211G>A), UGT1A1*27 (686C>A), UGT1A1*60 (?3279T>G), UGT1A1*93 (?3156G>A), UGT1A7 (?57T>G), UGT1A7*3 (387T>G, 622T>C), and UGT1A9*22 (T9>T10). Of 73 patients, 34 developed G3/4 severe hematological toxicities. The toxicities were significantly more frequent in patients with UGT1A1*6 (211A), UGT1A7 (387G), and UGT1A9*22 reference alleles (T9). Haplotype I, which consists of all favorable alleles, was associated with a significant reduction in hematologic toxicity (P = 0.031). In contrast, haplotype II, which contains four high‐risk alleles, showed significantly higher hematologic toxicity than the other haplotypes (P = 0.010). Six out of seven patients who were homozygous for UGT1A1*28 or *6 experienced severe hematological toxicity despite the fact that their response rate was not impaired (42.9%). We concluded that UGT1A polymorphisms, especially UGT1A1*6, are important for the prediction of severe toxicity of FOLFIRI in northeast Asian populations. In this regard, haplotype analyses should substantially impact the prediction of severe hematological toxicities of FOLFIRI. (Clinical Trial Registration: UMIN000002388 and UMIN000002476).