Differences in frequencies of UGT1A9, 1A7, and 1A1 genetic polymorphisms in Chinese Tibetan versus Han Chinese populations

Bilirubin metabolism and UDP-glucuronosyltransferase 1A1 variants in Asians: Pathogenic implications and therapeutic response

In the Asian general population, at least six single-nucleotide variants (SNVs) in the UDP-glucuronosyltransferase (UGT) 1A1 gene have been identified: -3279T>G, -53A(TA)₆ TAA>A(TA)₇ TAA, 211G>A, 686C>A, 1091C>T, and 1456T>G. Each of these six SNVs was observed in at least four ethnic groups of the 12 Asian populations studied. In East Asian populations, the descending frequency of these six SNVs was as follows: -3279G>[-53A(TA)₇ TAA, 211A]>(686A, 1091T)>1456G. Because of the presence of linkage disequilibrium and the expulsion phenomenon, when the SNVs -3279G, -53A(TA)₇ TAA, 211A, and 686A were simultaneously involved, 15 instead of the estimated 81 genotypes were observed. Those carrying 686AA or 1456GG developed Gilbert's syndrome or Crigler-Najjar syndrome type 2. Both -53A(TA)₇ TAA/A(TA)₇ TAA and 211AA are the main causes of Gilbert's syndrome in East Asian populations. In East Asian populations, the 211AA genotype is the main cause of neonatal hyperbilirubinemia, whereas -53A(TA)₇ TAA/A(TA)₇ TAA exerts a protective effect on hyperbilirubinemia development in neonates fed with breast milk. Both 211A and -53A(TA)₇ TAA are significantly associated with adverse drug reactions induced by irinotecan (one of the most widely used anticancer agents) in Asians. However, at least three common SNVs (-3279G, -53A(TA)₇ TAA, and 211A) should be comprehensively analyzed. This study investigated the clinical significance of these six SNVs and demonstrated that examining UGT1A1 variants in Asian populations is considerably challenging.

Comparison of UGT1A1 polymorphism as guidance of irinotecan dose escalation in RAS wild type metastatic colorectal cancer patients treated with cetuximab or bevacizumab plus FOLFIRI as the first-line therapy

Uridine diphosphate glucuronosyltransferase 1A1 (UGT1A1) polymorphism plays a crucial role in the increased susceptibility and toxicity of patients to irinotecan. This retrospective, observational study compared the clinical outcomes and adverse events (AEs) in RAS wild-type metastatic colorectal cancer (mCRC) patients treated with cetuximab or bevacizumab plus FOLFIRI with UGT1A1 genotyping and irinotecan dose escalation as the first-line therapy. In total, 173 patients with mCRC with RAS wild-type were enrolled. Among them, 98 patients were treated with cetuximab, whereas 75 patients were treated with bevacizumab. All patients received irinotecan dose escalation based on UGT1A1 genotyping. We compared the progression-free survival (PFS), overall survival (OS), objective response rates (ORRs), disease control rates (DCRs), metastatectomy, and severe adverse events (SAEs) between the two groups. The clinical effects of primary tumor sidedness and target therapy crossover were further analyzed. Over a median follow-up of 23.0 months [interquartile range (IQR), 15.0–32.5 months], no significant differences were observed between the cetuximab and bevacizumab groups in PFS [18.0 months vs. 14.0 months; 95% confidence interval (CI), 0.517–1.027; hazard ratio (HR), 0.729; p = 0.071], OS (40.0 months vs. 30.0 months; 95% CI, 0.410–1.008; HR, 0.643; p = 0.054), ORR (65.3% vs. 62.7%; p = 0.720), DCR (92.8% vs. 86.7%; p = 0.175), metastatectomy (36.7% vs. 29.3%; p = 0.307), and SAEs (p = 0.685). Regardless of primary tumor sidedness and target therapy crossover, no significant differences were noted in efficacy and safety between the two groups (all p > 0.05). Our results revealed that patients with wild-type RAS mCRC, regardless of biologics, with UGT1A1 genotyping can tolerate escalated doses of irinotecan and potentially achieve a more favorable clinical outcome without significantly increased toxicity.

Correlation between UGT1A1 gene polymorphism and irinotecan chemotherapy in metastatic colorectal cancer: a study from Guangxi Zhuang

Background

There are obviously ethnic differences between the UGT1A1 gene polymorphisms. Due to the difference of genetic background and environment, the treatment with colorectal cancer patients of Guangxi Zhuang should not completely follow the Euramerican or Chinese han patients. The study aimed to explore the correlation of UGT1A1 gene polymorphism of Guangxi Zhuang metastatic colorectal cancer (mCRC) with irinotecan -based chemotherapy, in order to develop an individualized irinotecan regimen for mCRC patients of Guangxi Zhuang.

Methods

From June 2013 and June 2015, a total of 406 patients of Guangxi who were histologically diagnosed as metastatic colorectal cancer with 102 patients of this cohort with three generations of Zhuang, and 86 patients that conformed to inclusion and exclusion criteria were competitively enrolled. The distribution of UGT1A1 gene polymorphism was analyzed-retrospectively in all patients. Pyrosequencing method was used to detect the UGT1A1*28 and*6 gene polymorphism in the 86 Guangxi Zhuang mCRC patients. After first-line chemotherapy with FOLFIRI regimen, the relationship between gene polymorphism of UGT1A1 and adverse reactions, and efficacy of Irinotecan were analyzed with χ2 test and Kaplan-Meier method.

Results

UGT1A1*28 wild-type (TA6/6), heterozygous mutant (TA6/7) and homozygous mutant (TA7/7) accounted for 69.8, 30.2 and 0%, respectively. UGT1A1*6 wild type (G/G), heterozygous mutation type (G/A) and homozygous mutant (A/A) accounted for 76.7%, 20.9 and 2.3%, respectively. UGT1A1*28 TA6/7 type could increase the risk of grade 3~4 diarrhea (p = 0.027), which did not increase the risk of grade 3~4 neutropenia (p = 0.092). UGT1A1*6G/A and A/A type could increase the risk of grade 3~4 diarrhea and neutropenia (p = 0.001; p = 0.017). After chemotherapy with FOLFIRI, there was no significant difference in response rate (RR) (p = 0.729; p = 0.745) or in median progression-free survival (mPFS) between the wild-type, mutant treatment of UGT1A1*28 and UGT1A1*6 (7.0 m vs 7.4 m, p = 0.427; 6.9 m vs 7.0 m p = 0.408).

Conclusions

The distribution of UGT1A1*28 and UGT1A1*6 gene polymorphism in Guangxi Zhuang patients were differed from the existing reported of European people and Chinese Han population. The UGT1A1 gene polymorphism with irinotecan chemotherapy-associated diarrhea and neutropenia were closely related. There was no significant association between UGT1A1 gene polymorphism and therapeutic efficacy of irinotecan.

Interethnic Variations of UGT1A1 and UGT1A7 Polymorphisms in the Jordanian Population

BACKGROUND

Glucuronidation is one of the most important phase II metabolic pathways. It is catalyzed by a family of UDP-glucuronosyltransferase enzymes (UGTs). UGT1A1 and UGT1A7 catalyze the glucuronidation of a diverse range of medications, environmental chemicals and endogenous compounds. Polymorphisms in the UGT1A gene could potentially be significant for the pharmacological, toxicological and physiological effects of the enzymes.

OBJECTIVE

The UGT1A gene is polymorphic among ethnic groups and the aim of this study was to investigate the different UGT1A1 and UGT1A7 polymorphisms in Circassians, Chechens and Jordanian-Arabs.

METHODS

A total of 168 healthy Jordanian-Arabs, 56 Circassians and 54 Chechens were included in this study. Genotyping of 20 different Single-nucleotide polymorphism (SNPs) was done by using polymerase chain reaction- DNA sequencing.

RESULTS

We found that Circassians and Chechens have significantly higher allele frequencies of UGT1A7*2, UGT1A7*3 and UGT1A7*4 than the Jordanian-Arab population, but all three populations have similar frequencies of UGT1A1*28. Therefore, Circassians and Chechens are expected to have significantly lower levels of the UGT1A7 enzyme with almost 90% of these populations having genes that encode low or intermediate enzyme activity.

CONCLUSION

This inter-ethnic variation in the UGT1A alleles frequencies may affect drug response and susceptibility to cancers among different subethnic groups in Jordan. Our results can also provide useful information for the Jordanian population and for future genotyping of Circassian and Chechen populations in general.

Impact of clinical factors and UGT1A9 and CYP2B6 genotype on inter-individual differences in propofol pharmacokinetics

PURPOSE

Propofol is one of the most widely used fast-acting intravenously administered anesthetics. However, although large inter-individual differences in dose requirements and recovery time have been observed, there are few previous studies in which the association between several potential covariates, including genetic factors such as the UGT1A9 and CYP2B6 genotypes, and propofol pharmacokinetics was simultaneously examined. This study aimed to identify factors determining propofol pharmacokinetics.

METHODS

Eighty-three patients were enrolled, and their blood samples were collected 1, 5, 10, and 15 min after administering a single intravenous bolus of propofol at a dose of 2.0 ml/kg to measure propofol plasma concentration. Area under the time-plasma concentration curve from zero up to the last measurable time point (AUC_15min) was determined from the concentration data. The inter-individual variability of the propofol pharmacokinetics was evaluated by investigating relationships between AUC_15min and genotype of UGT1A9 and CYP2B6; clinical factors, such as age, sex, body mass index (BMI), and preoperative hematological examination; and hemodynamic variables measured by a pulse dye densitogram analyzer. The Spearman rank correlation coefficient and the Mann-Whitney U test were used for the statistical analysis of continuous and categorical values, respectively. Subsequently, clinical factors that had p values of < 0.05 in the univariate analysis were examined in a multivariate analysis using multiple linear regression analysis.

RESULTS

Age, BMI, indocyanine green disappearance ratio (K-ICG), hepatic blood flow (HBF), preoperative hemoglobin level, and sex were correlated with AUC_15min (p < 0.05) in univariate analysis. Multivariate analysis performed to adjust for age, BMI, K-ICG, HBF, preoperative hemoglobin level, and sex revealed only BMI as an independent factor associated with AUC_15min.

CONCLUSIONS

This study demonstrated that BMI influences propofol pharmacokinetics after its administration as a single intravenous injection, while UGT1A9 and CYP2B6 SNPs, other clinical factors, and hemodynamic variables do not. These results suggest that BMI is an independent factor associated with propofol pharmacokinetics in several potential covariates.

CLINICAL TRIALS REGISTRATION NUMBER

University Hospital Medical Information Network (UMIN000022948).