Human UGT1A6 pharmacogenetics

Development of a Dose-Adjusted Polygenic Risk Model for Anthracycline-Induced Cardiotoxicity

BACKGROUND

Anthracyclines, which are effective chemotherapeutic agents, cause cardiac dysfunction in up to 57% of patients. The cumulative anthracycline dose is a crucial predictor of cardiotoxicity; however, the cumulative dose alone cannot explain all cardiotoxic events. Strongly associated genetic variants in SLC28A3, UGT1A6, and RARG contribute to anthracycline-induced cardiotoxicity in pediatric patients and may help identify those most susceptible. This study aimed to examine how these pharmacogenetic effects are modulated by cumulative anthracycline doses in the development of cardiotoxicity.

METHODS

A total of 595 anthracycline-treated children were genotyped and cardiotoxicity cases were identified. A dose-stratified analysis was performed to compare the contributions of SLC28A3 rs7853758, UGT1A6 rs17863783, and RARG rs2229774 variants to the development of cardiotoxicity in low-dose (<150 mg/m2 cumulative dose) and high-dose (>250 mg/m2 cumulative dose) patient groups. Logistic regression was used to model the relationships between the cumulative anthracycline dose, genetic variants, and cardiotoxicity in the full cohort.

RESULTS

At < 150 mg/m2 cumulative anthracycline dose, the SLC28A3 protective variant did not reach statistical significance [odds ratio (OR) 0.46 (95% confidence interval (CI) 0.10-1.45), P = 0.23], but it was statistically significant at doses >250 mg/m2 [OR 0.43 (95% CI 0.22-0.78), P = 0.0093]. Conversely, the UGT1A6 and RARG risk variants were either statistically significant or approaching significance at doses <150 mg/m2 [OR 7.18 (95% CI 1.78-28.4), P = 0.0045 for UGT1A6 and OR 2.76 (95% CI 0.89-7.63), P = 0.057 for RARG], but not at doses >250 mg/m2 [OR 2.91 (95% CI 0.80-11.0), P = 0.10; OR 1.56 (95% CI 0.89-2.75), P = 0.12].

CONCLUSIONS

These findings suggest that the SLC28A3 variant imparts more significant protection for patients receiving higher anthracycline doses, whereas the UGT1A6 and RARG risk variants significantly increased the risk of cardiotoxicity at low anthracycline doses.

Effects of genetic polymorphism of drug-metabolizing enzymes on the plasma concentrations of antiepileptic drugs in Chinese population

As a chronic brain disease, epilepsy affects ~50 million people worldwide. The traditional antiepileptic drugs (AEDs) are widely applied but showing various problems. Although the new AEDs have partially solved the problems of traditional AEDs, the current clinical application of traditional AEDs are not completely replaced by new drugs, particularly due to the large individual differences in drug plasma concentrations and narrow therapeutic windows among patients. Therefore, it is still clinically important to continue to treat patients using traditional AEDs with individualized therapeutic plans. To date, our understanding of the molecular and genetic mechanisms regulating plasma concentrations of AEDs has advanced rapidly, expanding the knowledge on the effects of genetic polymorphisms of genes encoding drug-metabolizing enzymes on the plasma concentrations of AEDs. It is increasingly imperative to summarize and conceptualize the clinical significance of recent studies on individualized therapeutic regimens. In this review, we extensively summarize the critical effects of genetic polymorphisms of genes encoding drug-metabolizing enzymes on the plasma concentrations of several commonly used AEDs as well as the clinical significance of testing genotypes related to drug metabolism on individualized drug dosage. Our review provides solid experimental evidence and clinical guidance for the therapeutic applications of these AEDs.

Pharmacogenetic testing to guide therapeutic decision-making and improve outcomes for children undergoing anthracycline-based chemotherapy

Anthracyclines are widely used as part of chemotherapeutic regimens in paediatric oncology patients. The most serious adverse drug reaction caused by anthracycline use is cardiotoxicity, a serious condition that can lead to cardiac dysfunction and subsequent heart failure. Both clinical and genetic factors contribute to a patient's risk of experiencing anthracycline-induced cardiotoxicity. In particular, genetic variants in RARG, UGT1A6 and SLC28A3 have been consistently shown to influence an individual's risk of experiencing this reaction. By combining clinical and genetic risks, decision-making can be improved to optimize treatment and prevent potentially serious adverse drug reactions. As part of a precision medicine initiative, we used pharmacogenetic testing, focused on RARG, UGT1A6 and SLC28A3 variants, to help predict an individual's risk of experiencing anthracycline-induced cardiotoxicity. Pharmacogenetic results are currently being used in clinical decision-making to inform treatment regimen choice, anthracycline dosing and decisions to initiate cardioprotective agents. In this case series, we demonstrate examples of the impact of genetic testing and discuss its potential to allow patients to be increasingly involved in their own treatment decisions.

Salicylic Acid and Risk of Colorectal Cancer: A Two-Sample Mendelian Randomization Study

Salicylic acid (SA) has observationally been shown to decrease colorectal cancer (CRC) risk. Aspirin (acetylsalicylic acid, that rapidly deacetylates to SA) is an effective primary and secondary chemopreventive agent. Through a Mendelian randomization (MR) approach, we aimed to address whether levels of SA affected CRC risk, stratifying by aspirin use. A two-sample MR analysis was performed using GWAS summary statistics of SA (INTERVAL and EPIC-Norfolk, N = 14,149) and CRC (CCFR, CORECT, GECCO and UK Biobank, 55,168 cases and 65,160 controls). The DACHS study (4410 cases and 3441 controls) was used for replication and stratification of aspirin-use. SNPs proxying SA were selected via three methods: (1) functional SNPs that influence the activity of aspirin-metabolising enzymes; (2) pathway SNPs present in enzymes' coding regions; and (3) genome-wide significant SNPs. We found no association between functional SNPs and SA levels. The pathway and genome-wide SNPs showed no association between SA and CRC risk (OR: 1.03, 95% CI: 0.84-1.27 and OR: 1.08, 95% CI: 0.86-1.34, respectively). Results remained unchanged upon aspirin use stratification. We found little evidence to suggest that an SD increase in genetically predicted SA protects against CRC risk in the general population and upon stratification by aspirin use.

Promising genes and variants to reduce chemotherapy adverse effects in acute lymphoblastic leukemia

Almost two decades ago, the sequencing of the human genome and high throughput technologies came to revolutionize the clinical and therapeutic approaches of patients with complex human diseases. In acute lymphoblastic leukemia (ALL), the most frequent childhood malignancy, these technologies have enabled to characterize the genomic landscape of the disease and have significantly improved the survival rates of ALL patients. Despite this, adverse reactions from treatment such as toxicity, drug resistance and secondary tumors formation are still serious consequences of chemotherapy, and the main obstacles to reduce ALL-related mortality. It is well known that germline variants and somatic mutations in genes involved in drug metabolism impact the efficacy of drugs used in oncohematological diseases therapy. So far, a broader spectrum of clinically actionable alterations that seems to be crucial for the progression and treatment response have been identified. Although these results are promising, it is necessary to put this knowledge into the clinics to help physician make medical decisions and generate an impact in patients' health. This review summarizes the gene variants and clinically actionable mutations that modify the efficacy of antileukemic drugs. Therefore, knowing their genetic status before treatment is critical to reduce severe adverse effects, toxicities and life-threatening consequences in ALL patients.

Unraveling heterogeneity of the clinical pharmacogenomic guidelines in oncology practice among major regulatory bodies

Pharmacogenomics (PGx) implementation in clinical practice is steadily increasing. PGx uses genetic information to personalize medication use, which increases medication efficacy and decreases side effects. The availability of clinical PGx guidelines is essential for its implementation in clinical settings. Currently, there are few organizations/associations responsible for releasing those guidelines, including the Clinical Pharmacogenetics Implementation Consortium, Dutch Pharmacogenetics Working Group, the Canadian Pharmacogenomics Network for Drug Safety and the French National Network of Pharmacogenetics. According to the US FDA, oncology medications are highly correlated to PGx biomarkers. Therefore, summarizing the PGx guidelines for oncology drugs will positively impact the clinical decisions for cancer patients. This review aims to scrutinize side-by-side available clinical PGx guidelines in oncology.

Human variability in isoform-specific UDP-glucuronosyltransferases: markers of acute and chronic exposure, polymorphisms and uncertainty factors

UDP-glucuronosyltransferases (UGTs) are involved in phase II conjugation reactions of xenobiotics and differences in their isoform activities result in interindividual kinetic differences of UGT probe substrates. Here, extensive literature searches were performed to identify probe substrates (14) for various UGT isoforms (UGT1A1, UGT1A3, UGT1A4, UGT1A6, UGT1A9, UGT2B7 and UGT2B15) and frequencies of human polymorphisms. Chemical-specific pharmacokinetic data were collected in a database to quantify interindividual differences in markers of acute (Cmax) and chronic (area under the curve, clearance) exposure. Using this database, UGT-related uncertainty factors were derived and compared to the default factor (i.e. 3.16) allowing for interindividual differences in kinetics. Overall, results show that pharmacokinetic data are predominantly available for Caucasian populations and scarce for other populations of different geographical ancestry. Furthermore, the relationships between UGT polymorphisms and pharmacokinetic parameters are rarely addressed in the included studies. The data show that UGT-related uncertainty factors were mostly below the default toxicokinetic uncertainty factor of 3.16, with the exception of five probe substrates (1-OH-midazolam, ezetimibe, raltegravir, SN38 and trifluoperazine), with three of these substrates being metabolised by the polymorphic isoform 1A1. Data gaps and future work to integrate UGT-related variability distributions with in vitro data to develop quantitative in vitro-in vivo extrapolations in chemical risk assessment are discussed.

Paediatric cardio-oncology: epidemiology, screening, prevention, and treatment

With 5-year survival of children with cancer exceeding 80% in developed countries, premature cardiovascular disease is now a major cause of early morbidity and mortality. In addition to the acute and chronic cardiotoxic effects of anthracyclines, related chemotherapeutics, and radiation, a growing number of new molecular targeted agents may also have detrimental effects on the cardiovascular system. Survivors of childhood cancer also may have earlier development of conventional cardiovascular risk factors such as hypertension, dyslipidaemia, and diabetes, which further increase their risk of serious cardiovascular disease. This review will examine the epidemiology of acute and chronic cardiotoxicity relevant to paediatric cancer patients, including genetic risk factors. We will also provide an overview of current screening recommendations, including the evidence regarding both imaging (e.g. echocardiography and magnetic resonance imaging) and blood-based biomarkers. Various primary and secondary prevention strategies will also be discussed, primarily in relation to anthracycline-related cardiomyopathy. Finally, we review the available evidence related to the management of systolic and diastolic dysfunction in paediatric cancer patients and childhood cancer survivors.

Morphine biotransformation genes and neonatal clinical factors predicted behaviour problems in very preterm children at 18 months

Background

Behaviour problems are prevalent among children born very preterm (≤ 32 weeks gestation), and have been associated with morphine exposure. Morphine accumulation in the brain is determined by genetic variations related to morphine biotransformation. The objective of the study was to investigate whether morphine-biotransformation genotypes contribute to individual differences in long-term effects of morphine on behaviour at 18 months corrected age (CA).

Methods

198 children born very preterm (24–32 weeks gestation) were followed from birth and seen at 18 months CA. Relationships between child behavior (Internalizing, Externalizing on the Child Behavior Checklist), morphine exposure, neonatal clinical variables, and morphine biotransformation gene variants in ABCB1, UGT1A9, UGT 2B7*2, ABCC2, ABCC3, SLCO1B1, CYP3A4, COMT were examined.

Findings

Neonatal clinical predictors and genotypes accounted for 39% of the overall variance in behaviour. In children with the minor allele of UGT1A9 rs17863783 (marker of UGT1A6*4, UDP-glucuronosyltransferase), greater morphine exposure (p = ·0011) was associated with more Internalizing behaviour. More Externalizing behaviour was predicted by greater morphine exposure in children with the COMT rs4680 Met/Met genotype (p = ·0006).

Interpretation

Genetic variations that affect relative accumulation of morphine in the brain, together with neonatal clinical factors, are differentially related to anxiety and depressive symptoms (internalizing) and to acting out (externalizing) behaviours at 18 months CA in children born very preterm.

Fund

NIH/NICHD HD039783 (REG); CIHR MOP86489 (REG), MOP68898 (SPM), MOP79262 (SPM, REG).

Regioselectivity significantly impacts microsomal glucuronidation efficiency of R/S-6, 7-, and 8-hydroxywarfarin

Coumadin (R/S-warfarin) metabolism plays a critical role in patient response to anticoagulant therapy. Several cytochrome P450s oxidize warfarin into R/S-6-, 7-, 8-, 10, and 4'-hydroxywarfarin that can undergo subsequent glucuronidation by UDP-glucuronosyltransferases (UGTs); however, current studies on recombinant UGTs cannot be adequately extrapolated to microsomal glucuronidation capacities for the liver. Herein, we estimated the capacity of the average human liver to glucuronidate hydroxywarfarin and identified UGTs responsible for those metabolic reactions through inhibitor phenotyping. There was no observable activity toward R/S-warfarin, R/S-10-hydroxywarfarin or R/S-4'-hydroxywarfarin. The observed metabolic efficiencies (V_max/K_m) toward R/S-6-, 7-, and especially 8-hydroxywarfarin indicated a high glucuronidation capacity to metabolize these compounds. UGTs demonstrated strong regioselectivity toward the hydroxywarfarins. UGT1A6 and UGT1A1 played a major role in R/S-6- and 7-hydroxywarfarin glucuronidation, respectively, whereas UGT1A9 accounted for almost all of the generation of the R/S-8-hydroxywarfarin glucuronide. In summary, these studies expanded insights to glucuronidation of hydroxywarfarins by pooled human liver microsomes, novel roles for UGT1A6 and 1A9, and the overall degree of regioselectivity for the UGT reactions.

Interaction between polymorphisms in aspirin metabolic pathways, regular aspirin use and colorectal cancer risk: A case-control study in unselected white European populations

Regular aspirin use is associated with reduced risk of colorectal cancer (CRC). Variation in aspirin's chemoprevention efficacy has been attributed to the presence of single nucleotide polymorphisms (SNPs). We conducted a meta-analysis using two large population-based case-control datasets, the UK-Leeds Colorectal Cancer Study Group and the NIH-Colon Cancer Family Registry, having a combined total of 3325 cases and 2262 controls. The aim was to assess 42 candidate SNPs in 15 genes whose association with colorectal cancer risk was putatively modified by aspirin use, in the literature. Log odds ratios (ORs) and standard errors were estimated for each dataset separately using logistic regression adjusting for age, sex and study site, and dataset-specific results were combined using random effects meta-analysis. Meta-analysis showed association between SNPs rs6983267, rs11694911 and rs2302615 with CRC risk reduction (All P<0.05). Association for SNP rs6983267 in the CCAT2 gene only was noteworthy after multiple test correction (P = 0.001). Site-specific analysis showed association between SNPs rs1799853 and rs2302615 with reduced colon cancer risk only (P = 0.01 and P = 0.004, respectively), however neither reached significance threshold following multiple test correction. Meta-analysis of SNPs rs2070959 and rs1105879 in UGT1A6 gene showed interaction between aspirin use and CRC risk (Pinteraction = 0.01 and 0.02, respectively); stratification by aspirin use showed an association for decreased CRC risk for aspirin users having a wild-type genotype (rs2070959 OR = 0.77, 95% CI = 0.68-0.86; rs1105879 OR = 0.77 95% CI = 0.69-0.86) compared to variant allele cariers. The direction of the interaction however is in contrast to that published in studies on colorectal adenomas. Both SNPs showed potential site-specific interaction with aspirin use and colon cancer risk only (Pinteraction = 0.006 and 0.008, respectively), with the direction of association similar to that observed for CRC. Additionally, they showed interaction between any non-steroidal anti-inflammatory drugs (including aspirin) use and CRC risk (Pinteraction = 0.01 for both). All gene x environment (GxE) interactions however were not significant after multiple test correction. Candidate gene investigation indicated no evidence of GxE interaction between genetic variants in genes involved in aspirin pathways, regular aspirin use and colorectal cancer risk.

Chemotherapy-Related Cardiac Dysfunction: A Systematic Review of Genetic Variants Modulating Individual Risk

Chemotherapy-related cardiac dysfunction is a significant side effect of anticancer treatment. Risk stratification is based on clinical- and treatment-related risk factors that do not adequately explain individual susceptibility. The addition of genetic variants may improve risk assessment. We conducted a systematic literature search in PubMed and Embase, to identify studies investigating genetic risk factors for chemotherapy-related cardiac dysfunction. Included were articles describing genetic variants in humans altering susceptibility to chemotherapy-related cardiac dysfunction. The validity of identified studies was assessed by 10 criteria, including assessment of population stratification, statistical methodology, and replication of findings. We identified 40 studies: 34 exploring genetic risk factors for anthracycline-induced cardiotoxicity (n=9678) and 6 studies related to trastuzumab-associated cardiotoxicity (n=642). The majority (35/40) of studies had a candidate gene approach, whereas 5 genome-wide association studies have been performed. We identified 25 genetic variants in 20 genes and 2 intergenic variants reported significant at least once. The overall validity of studies was limited, with small cohorts, failure to assess population ancestry and lack of replication. SNPs with the most robust evidence up to this point are CELF4 rs1786814 (sarcomere structure and function), RARG rs2229774 (topoisomerase-2β expression), SLC28A3 rs7853758 (drug transport), UGT1A6 rs17863783 (drug metabolism), and 1 intergenic variant (rs28714259). Existing evidence supports the hypothesis that genetic variation contributes to chemotherapy-related cardiac dysfunction. Although many variants identified by this systematic review show potential to improve risk stratification, future studies are necessary for validation and assessment of their value in a diagnostic and prognostic setting.

Correlations between polymorphisms in the uridine diphosphate-glucuronosyltransferase 1A and C-C motif chemokine receptor 5 genes and infection with the hepatitis B virus in three ethnic groups in China

Objective

To determine whether genetic polymorphisms in the uridine diphosphate-glucuronosyltransferase 1A (UGT1A) and the C-C motif chemokine receptor 5 (CCR5) genes are associated with hepatitis B virus (HBV) infection in Yi, Yao and Han ethnic groups in the Guizhou Province of China.

Methods

The study enrolled subjects with and without HBV infection. Whole blood was used for DNA genotyping using standard techniques. The study determined the frequencies of several polymorphic alleles (UGT1A6 [rs2070959], UGT1A1 [rs8175347], CCR5-59029 [rs1799987] and CCR5Δ32 [rs333]) and then characterized their relationship with HBV infection.

Results

A total of 404 subjects were enrolled in the study: 138 from the Yao group, 101 from the Yi group and 165 from the Han group. There was a significant difference in the frequency of UGT1A1 rs8175347 polymorphisms among the three groups. The rates of 7TA carriers of UGT1A1 rs8175347 in all three groups were significantly higher than the other genotypes. Individuals with genotype AA of UGT1A6 rs2070959 in the Yi group had a higher risk for HBV infection than in the Yao and Han groups. The frequency of genotype GG in CCR5-59029 in the Yao group was significantly higher than in the Yi group. The genotypes of CCR5Δ32 were not associated with HBV infection.

Conclusion

These findings provide genetic and epidemiological evidence for an association of UGT1A and CCR5-59029 polymorphisms with HBV infection in Chinese Yi and Yao populations.

Early post-traumatic seizures are associated with valproic acid plasma concentrations and UGT1A6/CYP2C9 genetic polymorphisms in patients with severe traumatic brain injury

BACKGROUND

Seizure is a common complication for severe traumatic brain injury (TBI). Valproic acid (VPA) is a first-line antiepileptic drug, though its metabolism is affected by genetic polymorphisms and varies between individuals. The aim of this study was to investigate such association and to explore its influence on the occurrence of early post-traumatic seizure.

METHODS

A prospective case control study was conducted from 2012 to 2016 recruiting adult patients with severe TBI. Electroencephalograph (EEG) monitoring was performed approximately 4 h for each patient from day 1 to day 7 after injury. If seizures were detected, EEG monitoring was extended until 12 h after seizures being controlled. Genetic polymorphisms in UGT1A6, UGT2B7, CYP2C9, and CYP2C19 were analyzed in association with daily VPA plasma concentrations, adjusted dosages, and occurrence of seizures.

RESULTS

Among the 395 recruited patients, eighty-three (21%) had early post-traumatic seizure, of which 30 (36.14%) were non-convulsive. Most seizures were first detected on day 1 (34.94%) and day 2 (46.99%) after injury. Patients with seizure had longer ICU length of stay and relatively lower VPA plasma concentrations. Patients with UGT1A6_19T > G/541A > G/552A > C double heterozygosities or CYP2C9 extensive metabolizers (EMs) initially had lower adjusted VPA plasma concentrations (power >0.99) and accordingly require higher VPA dosages during later time of treatment (power >0.99). The odds ratio indicated a higher risk of early post-traumatic seizure occurrence in male patients (OR 1.96, 95% CI 1.01-3.81, p = 0.043), age over 65 (OR 2.13, 95% CI 1.01-4.48), and with UGT1A6_19T > G/541A > G/552A > C double heterozygosities (OR 2.38, 95% CI 1.11-5.10, p = 0.02), though the power of the difference was between 0.54 to 0.61.

DISCUSSION

Due to limited facility, the actual frequency of non-convulsive seizures is suspected to be higher than identified. There has been discrepancy regarding to genetic polymorphisms and VPA metab olism between this study and some previous reports. This could be related to confounders such as sample size, race, and patient age. Another limitation is that the case numbers of certain genotypes are limited in this study.

CONCLUSIONS

Continuous EEG monitoring is necessary to detect both convulsive and non-convulsive early post-traumatic seizures in severe TBI patients. UGT1A6/CYP2C9 polymorphisms have influence on VPA metabolism. UGT1A6_19T > G/541A > G/552A > C double heterozygositie is associated with occurrence of early post-traumatic seizures in addition to patients' age and gender. Further investigations with larger sample size are required to confirm the difference.

TRIAL REGISTRATION

Retrospectively registered with Chinese Clinical Trail Registry on 1st Jan 2016 ( ChiCTR-OPC-16007687 ).

Effects of UGT1A9 genetic polymorphisms on monohydroxylated derivative of oxcarbazepine concentrations and oxcarbazepine monotherapeutic efficacy in Chinese patients with epilepsy

AIM

The human UDP-glucuronosyltransferase which is genetically polymorphic catalyzes glucuronidations of various drugs. The interactions among UGT1A4, UGT1A6, UGT1A9, and UGT2B15 genetic polymorphisms, monohydroxylated derivative (MHD) of oxcarbazepine (OXC) plasma concentrations, and OXC monotherapeutic efficacy were explored in 124 Chinese patients with epilepsy receiving OXC monotherapy.

METHOD

MHD is the major active metabolite of OXC, and its plasma concentration was measured using high-performance liquid chromatography when patients reached their maintenance dose of OXC. Genomic DNA was extracted from whole blood and SNP genotyping performed using PCR followed by dideoxy chain termination sequencing. We followed the patients for at least 1 year to evaluate the OXC monotherapy efficacy. Patients were divided into two groups according to their therapeutic outcome: group 1, seizure free; group 2, not seizure free. The data were analyzed using T test, one-way analysis of variance (ANOVA), Kruskal-Wallis test, chi-square test, Fisher's exact test, correlation analysis, and multivariate regression analysis.

RESULT

T test analysis showed that MHD plasma concentrations were significantly different between the two groups (p = 0.002). One-way ANOVA followed by Bonferroni post hoc testing of four candidate SNPs revealed that carriers of the UGT1A9 variant allele I399 C > T (TT 13.28 ± 7.44 mg/L, TC 16.41 ± 6.53 mg/L) had significantly lower MHD plasma concentrations and poorer seizure control than noncarriers (CC 22.24 ± 8.49 mg/L, p < 0.05).

CONCLUSION

In our study, we have demonstrated the effects of UGT1A9 genetic polymorphisms on MHD plasma concentrations and OXC therapeutic efficacy. Through MHD monitoring, we can predict OXC therapeutic efficacy, which may be useful for the personalization of OXC therapy in epileptic patients.

Recommendations for genetic testing to reduce the incidence of anthracycline-induced cardiotoxicity

AIMS

Anthracycline-induced cardiotoxicity (ACT) occurs in 57% of treated patients and remains an important limitation of anthracycline-based chemotherapy. In various genetic association studies, potential genetic risk markers for ACT have been identified. Therefore, we developed evidence-based clinical practice recommendations for pharmacogenomic testing to further individualize therapy based on ACT risk.

METHODS

We followed a standard guideline development process, including a systematic literature search, evidence synthesis and critical appraisal, and the development of clinical practice recommendations with an international expert group.

RESULTS

RARG rs2229774, SLC28A3 rs7853758 and UGT1A6 rs17863783 variants currently have the strongest and the most consistent evidence for association with ACT. Genetic variants in ABCC1, ABCC2, ABCC5, ABCB1, ABCB4, CBR3, RAC2, NCF4, CYBA, GSTP1, CAT, SULT2B1, POR, HAS3, SLC22A7, SCL22A17, HFE and NOS3 have also been associated with ACT, but require additional validation. We recommend pharmacogenomic testing for the RARG rs2229774 (S427L), SLC28A3 rs7853758 (L461L) and UGT1A6*4 rs17863783 (V209V) variants in childhood cancer patients with an indication for doxorubicin or daunorubicin therapy (Level B - moderate). Based on an overall risk stratification, taking into account genetic and clinical risk factors, we recommend a number of management options including increased frequency of echocardiogram monitoring, follow-up, as well as therapeutic options within the current standard of clinical practice.

CONCLUSIONS

Existing evidence demonstrates that genetic factors have the potential to improve the discrimination between individuals at higher and lower risk of ACT. Genetic testing may therefore support both patient care decisions and evidence development for an improved prevention of ACT.

Clinical and Genetic Determinants of Cardiomyopathy Risk among Hematopoietic Cell Transplantation Survivors

Cardiomyopathy has been recognized as a complication after hematopoietic cell transplantation (HCT). Using a nested case-cohort design, we examined the relationships between demographic, therapeutic, and selected cardiovascular disease risk factors among ≥1-year HCT survivors who developed cardiomyopathy before (n = 43) or after (n = 89) 1 year from HCT as compared to a randomly selected subcohort of survivors without cardiomyopathy (n = 444). Genomic data were available for 79 cases and 267 noncases. Clinical and genetic covariates were examined for association with the risk of early or late cardiomyopathy. Clinical risk factors associated with both early- and late-onset cardiomyopathy included anthracycline exposure ≥250 mg/m(2) and pre-existing hypertension. Among late-onset cardiomyopathy cases, the development of diabetes and ischemic heart disease further increased risk. We replicated several previously reported genetic associations among early-onset cardiomyopathy cases, including rs1786814 in CELF4, rs2232228 in HAS3, and rs17863783 in UGT1A6. None of these markers were associated with risk of late-onset cardiomyopathy. A combination of demographic, treatment, and clinical covariates predicted early-onset cardiomyopathy with reasonable accuracy (area under the curve [AUC], .76; 95% confidence interval [CI], .68 to .83), but prediction of late cardiomyopathy was poor (AUC, .59; 95% CI .53 to .67). The addition of genetic polymorphisms with marginal associations (odds ratios ≥1.3) did not enhance prediction for either early- or late-onset cardiomyopathy. Conventional cardiovascular risk factors influence the risk of both early- and late-onset cardiomyopathy in HCT survivors. Although certain genetic markers may influence the risk of early-onset disease, further work is required to validate previously reported findings and to determine how genetic information should be incorporated into clinically useful risk prediction models.

Tissue-specific patterns of gene expression in the epithelium and stroma of normal colon in healthy individuals in an aspirin intervention trial

Regular aspirin use reduces colon adenoma and carcinoma incidence. UDP-glucuronosyltransferases (UGT) are involved in aspirin metabolism and clearance, and variant alleles in UGT1A6 have been shown to alter salicylic acid metabolism and risk of colon neoplasia. In a randomized, cross-over, placebo-controlled trial of 44 healthy men and women, homozygous for UGT1A6*1 or UGT1A6*2, we explored differences between global epithelial and stromal expression, using Affymetrix U133 + 2.0 microarrays and tested effects of 60-day aspirin supplementation (325 mg/d) on epithelial and stromal gene expression and colon prostaglandin E2 (PGE2) levels. We conducted a comprehensive study of differential gene expression between normal human colonic epithelium and stroma from healthy individuals. Although no statistically significant differences in gene expression were observed in response to aspirin or UGT1A6 genotype, we have identified the genes uniquely and reproducibly expressed in each tissue type and have analyzed the biologic processes they represent. Here we describe in detail how the data, deposited in the Gene Expression Omnibus (GEO) - accession number GSE71571 - was generated including the basic analysis as contained in the manuscript published in BMC Medical Genetics with the PMID 25927723 (Thomas et al., 2015 [9]).

Tissue-specific patterns of gene expression in the epithelium and stroma of normal colon in healthy individuals in an aspirin intervention trial

Background

Regular aspirin use reduces colon adenoma and carcinoma incidence. UDP-glucuronosyltransferases (UGT) are involved in aspirin metabolism and clearance, and variant alleles in UGT1A6 have been shown to alter salicylic acid metabolism and risk of colon neoplasia.

Methods

In a randomized, cross-over, placebo-controlled trial of 44 healthy men and women, homozygous for UGT1A6*1 or UGT1A6*2, we explored differences between global epithelial and stromal expression, using Affymetrix U133 + 2.0 microarrays and tested effects of 60-day aspirin supplementation (325 mg/d) on epithelial and stromal gene expression and colon prostaglandin E2 (PGE2) levels.

Results

No statistically significant differences in gene expression were observed in response to aspirin or UGT1A6 genotype, but tissue PGE2 levels were lower with aspirin compared to placebo (p <0.001). Transcripts differentially expressed between epithelium and stroma (N = 4916, P <0.01, false discovery rate <0.001), included a high proportion of genes involved in cell signaling, cellular movement, and cancer. Genes preferentially expressed in epithelium were involved in drug and xenobiotic metabolism, fatty acid and lipid metabolism, apoptosis signaling, and ion transport. Genes preferentially expressed in stroma included those involved in inflammation, cellular adhesion, and extracellular matrix production. Wnt-Tcf4 pathway genes were expressed in both epithelium and stroma but differed by subcellular location.

Conclusions

These results suggest that, in healthy individuals, subtle effects of aspirin on gene expression in normal colon tissue are likely overwhelmed by inter-individual variability in microarray analyses. Differential expression of critical genes between colonic epithelium and stroma suggest that these tissue types need to be considered separately.

Electronic supplementary material

The online version of this article (doi:10.1186/s12881-015-0161-6) contains supplementary material, which is available to authorized users.

Biotransformation of xenobiotics in the human colon and rectum and its association with colorectal cancer

In humans, the liver is generally considered to be the major organ contributing to drug metabolism, but studies during the last years have suggested an important role of the extra-hepatic drug metabolism. The gastrointestinal tract (GI-tract) is the major path of entry for a wide variety of compounds including food, and orally administered drugs, but also compounds - with neither nutrient nor other functional value - such as carcinogens. These compounds are metabolized by a large number of enzymes, including the cytochrome P450 (CYP), the glutathione S-transferase (GST) family, the uridine 5'-diphospho- glucuronosyltransferase (UDP-glucuronosyltransferase - UGT) superfamily, alcohol-metabolizing enzymes, sulfotransferases, etc. These enzymes can either inactivate carcinogens or, in some cases, generate reactive species with higher reactivity compared to the original compound. Most data in this field of research originate from animal or in vitro studies, wherein human studies are limited. Here, we review the human studies, in particular the studies on the phenotypic expression of these enzymes in the colon and rectum to get an impression of the actual enzyme levels in this primary organ of exposure. The aim of this review is to give a summary of currently available data on the relation between the CYP, the GST and the UGT biotransformation system and colorectal cancer obtained from clinical and epidemiological studies in humans.

Intravenous paracetamol as an antipyretic and analgesic medication: the significance of drug metabolism

One prospective, open-label, non-randomized study was conducted in 100 patients to define the antipyretic and analgesic effect of a new intravenous formulation of 1 g of paracetamol; 71 received paracetamol for the management of fever and 29 received paracetamol for pain relief after abdominal surgery or for neoplastic pain. Serial follow-up measurements of core temperature and of pain intensity were done for 6 h. Additional rescue medications were recorded for 5 days. Blood was sampled for the measurement of free paracetamol (APAP) and of glucuronide-APAP and N-sulfate-APAP by an HPLC assay. Defervescence, defined as core temperature below or equal to 37.1°C, was achieved in 52 patients (73.2%) within a median time of 3 h. Patients failing to become afebrile with the first dose of paracetamol became afebrile when administered other agents as rescue medications. Analgesia was achieved in 25 patients (86.4%) within a median time of 2 h. Serum levels of glucuronide-APAP were greater among non-responders to paracetamol. The presented results suggest that the intravenous formulation of paracetamol is clinically effective depending on drug metabolism.

Validation of variants in SLC28A3 and UGT1A6 as genetic markers predictive of anthracycline-induced cardiotoxicity in children

BACKGROUND

The use of anthracyclines as effective antineoplastic drugs is limited by the occurrence of cardiotoxicity. Multiple genetic variants predictive of anthracycline-induced cardiotoxicity (ACT) in children were recently identified. The current study was aimed to assess replication of these findings in an independent cohort of children.

PROCEDURE

. Twenty-three variants were tested for association with ACT in an independent cohort of 218 patients. Predictive models including genetic and clinical risk factors were constructed in the original cohort and assessed in the current replication cohort.

RESULTS

. We confirmed the association of rs17863783 in UGT1A6 and ACT in the replication cohort (P = 0.0062, odds ratio (OR) 7.98). Additional evidence for association of rs7853758 (P = 0.058, OR 0.46) and rs885004 (P = 0.058, OR 0.42) in SLC28A3 was found (combined P = 1.6 × 10(-5) and P = 3.0 × 10(-5), respectively). A previously constructed prediction model did not significantly improve risk prediction in the replication cohort over clinical factors alone. However, an improved prediction model constructed using replicated genetic variants as well as clinical factors discriminated significantly better between cases and controls than clinical factors alone in both original (AUC 0.77 vs. 0.68, P = 0.0031) and replication cohort (AUC 0.77 vs. 0.69, P = 0.060).

CONCLUSIONS

. We validated genetic variants in two genes predictive of ACT in an independent cohort. A prediction model combining replicated genetic variants as well as clinical risk factors might be able to identify high- and low-risk patients who could benefit from alternative treatment options.

UGT1A6 polymorphisms modulated lung cancer risk in a Chinese population

Uridine diphosphoglucuronosyltransferases (UGTs) 1A6 is the only UGT1A isoform expressed in lung tissue. It is responsible for the detoxification of carcinogens such as benezo[a]pyrene from cigarette smoke. The purpose of this study was to evaluate the association of UGT1A6 polymorphisms and haplotypes with lung cancer risk and to evaluate the functional significance of UGT1A6 polymorphisms. Genomic DNA was isolated from leukocytes. Eight UGT1A6 polymorphisms were sequenced in a test set of 72 Chinese lung cancer patients and 62 healthy controls. Potential risk modifying alleles were validated in a separate set of 95 Chinese lung cancer patients and 100 healthy controls. UGT1A6 19T>G, 541A>G and 552A>C showed significant association with increased lung cancer risk, while UGT1A6 105C>T and IVS1+130G>T were significantly associated with reduced lung cancer risk. Multivariate logistic regression analysis demonstrated a significant association of lung cancer with UGT1A6 541A>G (OR: 3.582, 95% CI: 1.27–10.04, p = 0.015), 552A>C (OR: 5.364, 95% CI: 1.92–14.96, p = 0.001) and IVS1+130G>T (OR: 0.191, 95% CI: 0.09–0.36, p<0.001). Functional test demonstrated that UGT1A6 105C>T increased mRNA stability, providing a plausible explanation of its association with reduced lung cancer risk. Thus UGT1A6 polymorphisms may be used to identify people with increased risk of developing lung cancer.

Functional impact and prevalence of polymorphisms involved in the hepatic glucuronidation of valproic acid

Metabolism of valproic acid, a widely used drug, is only partially understood. It is mainly metabolized through glucuronidation and acts as a substrate for various UDP-glucuronosyltransferases (UGTs). UGTs metabolizing valproic acid in the liver are UGT1A3, UGT1A4, UGT1A6, UGT1A9 and UGT2B7, with UGT1A6 and UGT2B7 being the most prominent. Polymorphisms in genes expressing these enzymes may have clinical consequences, regarding dosing, blood levels of the drug and adverse reactions. Not all genes are well studied and studies, where they exist, report conflicting results. Prevalence of polymorphisms and various haplotypes is also of great importance, as it may suggest different therapeutic approaches in various populations. Presented here is a review of currently known polymorphisms, their functional impact, when known, and their prevalence in different populations, highlighting the current state of understanding and areas where there is a lack of data and suggesting new perspectives for further research.

Genetic variations and haplotype diversity of the UGT1 gene cluster in the Chinese population

Vertebrates require tremendous molecular diversity to defend against numerous small hydrophobic chemicals. UDP-glucuronosyltransferases (UGTs) are a large family of detoxification enzymes that glucuronidate xenobiotics and endobiotics, facilitating their excretion from the body. The UGT1 gene cluster contains a tandem array of variable first exons, each preceded by a specific promoter, and a common set of downstream constant exons, similar to the genomic organization of the protocadherin (Pcdh), immunoglobulin, and T-cell receptor gene clusters. To assist pharmacogenomics studies in Chinese, we sequenced nine first exons, promoter and intronic regions, and five common exons of the UGT1 gene cluster in a population sample of 253 unrelated Chinese individuals. We identified 101 polymorphisms and found 15 novel SNPs. We then computed allele frequencies for each polymorphism and reconstructed their linkage disequilibrium (LD) map. The UGT1 cluster can be divided into five linkage blocks: Block 9 (UGT1A9), Block 9/7/6 (UGT1A9, UGT1A7, and UGT1A6), Block 5 (UGT1A5), Block 4/3 (UGT1A4 and UGT1A3), and Block 3′ UTR. Furthermore, we inferred haplotypes and selected their tagSNPs. Finally, comparing our data with those of three other populations of the HapMap project revealed ethnic specificity of the UGT1 genetic diversity in Chinese. These findings have important implications for future molecular genetic studies of the UGT1 gene cluster as well as for personalized medical therapies in Chinese.

Non tumoral hyperserotoninaemia responsive to octreotide due to dual polymorphism in UGT1A1 and UGT1A6

Gilbert's syndrome is a common inherited metabolic disorder, caused by genetic aberration in the enzyme UDP-glucuronosyl-transferase 1A1 that leads to reduced glucuronidation of bilirubin. Recent advances in molecular genetics have frequently reported the concurrence of dual genetic polymorphisms in UDP glucuronosyl-transferases 1A6 and 1A1 in patients with Gilbert's syndrome, leading to defective glucuronidation of bilirubin, as well as several other endogenous and exogenous substrates, such as serotonin. We present a case of Gilbert's syndrome with severe persistent hyperserotoninaemia, mimicking carcinoid syndrome, due to dual polymorphisms in UDP-glucuronosyl-transferases 1A1 and 1A6. The patient was treated with a long-acting somatostatin analogue (octreotide) for 8 months, resulting in a significant reduction in serum serotonin levels and immediate relief of the symptomatology, followed by a long-term remission. The frequent occurrence of hyperserotoninaemia in Gilbert's syndrome may contribute, at least partly, to the nonspecific symptomatology commonly seen in these patients and should be promptly evaluated.

The effect of Plantago major Linnaeus on serum total sialic acid, lipid-bound sialic acid, some trace elements and minerals after administration of 7,12-dimethylbenz(a)anthracene in rats

The present study was designed to evaluate the effect of Plantago major Linnaeus (PM) extract on serum total sialic acid (TSA), lipid-bound sialic acid (LSA), some trace elements (copper (Cu), zinc (Zn) and iron) and mineral levels (magnesium, calcium and sodium) in Wistar albino rat administrated 7,12-dimethylbenz(a)anthracene (DMBA). Rats were divided into three equal groups (n = 6). Group I comprised the control group, group II was treated with DMBA (100 mg/kg, single dose) and group III was treated with DMBA (100 mg/kg single dose) and aqueous extract of PM 100 mg/kg/day for 60 days. After 60 days, statistical analyses showed that TSA and LSA levels in DMBA and DMBA + PM groups were significantly higher compared to the control group (TSA: p < 0.01, p < 0.05; LSA: p < 0.05, p < 0.05, respectively). Serum Zn levels were decreased in subjects treated with DMBA (p < 0.01) and DMBA + PM (p < 0.05) compared to the control group values. Serum Cu levels were increased in DMBA group and PM-treated group compared to the control group values. The results of this investigation showed that the levels of TSA and LSA changed significantly, which are sensitive markers for detecting the toxic effects of DMBA. On the other hand, observed decline in Zn levels in rats from DMBA + PM group might be due to decreased generation of free radicals and oxidative stress. Results from this study suggest that PM may be partially effective in preventing carcinogenesis initiated by environmental carcinogen DMBA.

UGT1A6 and UGT2B15 polymorphisms and acetaminophen conjugation in response to a randomized, controlled diet of select fruits and vegetables

Acetaminophen (APAP) glucuronidation is thought to occur mainly by UDP-glucuronosyltransferases (UGT) in the UGT1A family. Interindividual variation in APAP glucuronidation is attributed in part to polymorphisms in UGT1As. However, evidence suggests that UGT2B15 may also be important. We evaluated, in a controlled feeding trial, whether APAP conjugation differed by UGT1A6 and UGT2B15 genotypes and whether supplementation of known dietary inducers of UGT (crucifers, soy, and citrus) modulated APAP glucuronidation compared with a diet devoid of fruits and vegetables (F&V). Healthy adults (n = 66) received 1000 mg of APAP orally on days 7 and 14 of each 2-week feeding period and collected saliva and urine over 12 h. Urinary recovery of the percentage of the APAP dose as free APAP was higher (P = 0.02), and the percentage as APAP glucuronide (APAPG) was lower (P = 0.004) in women. The percentage of APAP was higher among UGT1A6*1/*1 genotypes, relative to *1/*2 and *2/*2 genotypes (P = 0.045). For UGT2B15, the percentage of APAPG decreased (P < 0.0001) and that of APAP sulfate increased (P = 0.002) in an allelic dose-dependent manner across genotypes from *1/*1 to *2/*2. There was a significant diet × UGT2B15 genotype interaction for the APAPG ratio (APAPG/total metabolites × 100) (P = 0.03), with *1/*1 genotypes having an approximately 2-fold higher F&V to basal diet difference in response compared with *1/*2 and *2/*2 genotypes. Salivary APAP maximum concentration (C(max)) was significantly higher in women (P = 0.0003), with F&V (P = 0.003), and among UGT1A6*2/*2 and UGT2B15*1/*2 genotypes (P = 0.02 and 0.002, respectively). APAP half-life was longer in UGT2B15*2/*2 genotypes with F&V (P = 0.009). APAP glucuronidation was significantly influenced by the UGT2B15*2 polymorphism, supporting a role in vivo for UGT2B15 in APAP glucuronidation, whereas the contribution of UGT1A6*2 was modest. Selected F&V known to affect UGT activity led to greater glucuronidation and less sulfation.

Determinants of aspirin metabolism in healthy men and women: effects of dietary inducers of UDP-glucuronosyltransferases

BACKGROUND/AIMS

Interindividual variation in aspirin (ASA) metabolism is attributed to concomitant use of drugs or alcohol, urine pH, ethnicity, sex, and genetic variants in UDP-glucuronosyltransferases (UGT). Little is known about the effects of diet.

METHODS

We evaluated cross-sectionally whether urinary excretion of ASA and its metabolites [salicylic acid (SA), salicyluric acid (SUA) phenolic glucuronide (SUAPG), salicylic acid acyl glucuronide (SAAG) and salicylic acid phenolic glucuronide (SAPG)] differed by UGT1A6 genotype and dietary factors shown to induce UGT. Following oral treatment with 650 mg ASA, urine was collected over 8 h in 264 men and 264 women (21-45 years old).

RESULTS

There were statistically significant differences in metabolites excreted between sexes and ethnicities. Men excreted more SUA; women more ASA (p = 0.03), SA, SAAG and SAPG (p ≤ 0.001 for all). Compared to Caucasians, Asians excreted more ASA, SA and SAAG, and less SUA and SUAPG (p ≤ 0.03 for all); African-Americans excreted more SAAG and SAPG and less SUA (p ≤ 0.04). There was no effect of UGT1A6 genotypes. Increased ASA and decreased SUAPG excretion was observed with increased servings of vegetables (p = 0.008), specifically crucifers (p = 0.05).

CONCLUSION

Diet may influence the pharmacokinetics of ASA, but effects may be through modulation of glycine conjugation rather than glucuronidation.

Genetic polymorphism in metabolism and host defense enzymes: implications for human health risk assessment

Genetic polymorphisms in xenobiotic metabolizing enzymes can have profound influence on enzyme function, with implications for chemical clearance and internal dose. The effects of polymorphisms have been evaluated for certain therapeutic drugs but there has been relatively little investigation with environmental toxicants. Polymorphisms can also affect the function of host defense mechanisms and thus modify the pharmacodynamic response. This review and analysis explores the feasibility of using polymorphism data in human health risk assessment for four enzymes, two involved in conjugation (uridine diphosphoglucuronosyltransferases [UGTs], sulfotransferases [SULTs]), and two involved in detoxification (microsomal epoxide hydrolase [EPHX1], NADPH quinone oxidoreductase I [NQO1]). This set of evaluations complements our previous analyses with oxidative and conjugating enzymes. Of the numerous UGT and SULT enzymes, the greatest likelihood for polymorphism effect on conjugation function are for SULT1A1 (*2 polymorphism), UGT1A1 (*6, *7, *28 polymorphisms), UGT1A7 (*3 polymorphism), UGT2B15 (*2 polymorphism), and UGT2B17 (null polymorphism). The null polymorphism in NQO1 has the potential to impair host defense. These highlighted polymorphisms are of sufficient frequency to be prioritized for consideration in chemical risk assessments. In contrast, SNPs in EPHX1 are not sufficiently influential or defined for inclusion in risk models. The current analysis is an important first step in bringing the highlighted polymorphisms into a physiologically based pharmacokinetic (PBPK) modeling framework.

Interindividual variability in hepatic drug glucuronidation: studies into the role of age, sex, enzyme inducers, and genetic polymorphism using the human liver bank as a model system

The human liver bank has provided an invaluable model system for the study of interindividual variability in expression and activity of the major hepatic UGTs, including UGT1A1, 1A4, 1A6, 1A9, 2B7, and 2B15. Based on studies using UGT-isoform-selective probes, the rank order of activity variability is UGT 1A1>1A6>2B15>1A4 = 1A9>2B7, with coefficient of variation values ranging from 92 to 45%. Liver donor age, sex, enzyme inducers, and genetic polymorphism are factors that have been implicated as sources of this variability in UGT activity. The expression of UGTs prior to, and immediately following, birth is quite limited, explaining the susceptibility of neonates to certain drug toxicities. Old age appears to have minimal effect on UGT function. Sex differences in UGT activity are relatively small and are confined to several UGTs, including UGT2B15, which shows higher activity in males, compared with females. Enzyme inducers, including coadministered drugs, smoking, and alcohol, may increase hepatic UGT levels. Human liver bank phenotype-genotype studies, using UGT-isoform-selective probes have identified common genetic polymorphisms that are predictive of glucuronidation activity in vitro and that were subsequently verified as predictors of probe-drug clearance by glucuronidation in vivo.

Modulation of UDP-glucuronosyltransferase activity by protein-protein association

Drug oxidation and conjugation mediated by cytochrome P450 (P450) and UDP-glucuronosyltransferase (UGT) have long been considered to take place separately. However, our recent studies have suggested that CYP3A4 specifically associates with UGT2B7 and alters the regioselectivity of morphine glucuronidation. This observation strongly supports the view that there is functional cooperation between P450 and UGT to facilitate multistep drug metabolism. In recent years, accumulating evidence has suggested an interaction between UGT isoforms or between P450 and UGTs and a change in UGT function by protein-protein association. In this review, we summarize these interactions and discuss their relevance to UGT function.

Uridine 5'-diphospho-glucuronosyltransferase genetic polymorphisms and response to cancer chemotherapy

Pharmacogenetics aims to elucidate how genetic variation affects the efficacy and side effects of drugs, with the ultimate goal of personalizing medicine. Clinical studies of the genetic variation in the uridine 5'-diphosphoglucuronosyltransferase gene have demonstrated how reduced-function allele variants can predict the risk of severe toxicity and help identify cancer patients who could benefit from reduced-dose schedules or alternative chemotherapy. Candidate polymorphisms have also been identified in vitro, although the functional consequences of these variants still need to be tested in the clinical setting. Future approaches in uridine 5'-diphosphoglucuronosyltransferase pharmacogenetics include genetic testing prior to drug treatment, genotype-directed dose-escalation studies, study of genetic variation at the haplotype level and genome-wide studies.

Green tea (Camellia sinensis) catechins and vascular function

The health benefits of green tea (Camellia sinensis) catechins are becoming increasingly recognised. Amongst the proposed benefits are the maintenance of endothelial function and vascular homeostasis and an associated reduction in atherogenesis and CVD risk. The mounting evidence for the influential effect of green tea catechins on vascular function from epidemiological, human intervention and animal studies is subject to review together with exploration of the potential mechanistic pathways involved. Epigallocatechin-3-gallate, one of the most abundant and widely studied catechin found in green tea, will be prominent in the present review. Since there is a substantial inconsistency in the published data with regards to the impact of green tea catechins on vascular function, evaluation and interpretation of the inter- and intra-study variability is included. In conclusion, a positive effect of green tea catechins on vascular function is becoming apparent. Further studies in animal and cell models using physiological concentrations of catechins and their metabolites are warranted in order to gain some insight into the physiology and molecular basis of the observed beneficial effects.

UGT1A1, UGT1A6 and UGT1A7 genetic analysis: repercussion for irinotecan pharmacogenetics in the São Miguel Island Population (Azores, Portugal)

BACKGROUND

Glucuronidation reactions, catalyzed by uridine-diphosphate glucuronosyltransferase (UGT) enzymes, constitute a detoxification process that adds glucuronic acid to endogenous and exogenous compounds, aiding their excretion. UGT1A proteins have been implicated as risk factors for both the development of cancer and adverse drug effects.

METHODS

Here, we assess the genome of 469 individuals from São Miguel Island (Azores, Portugal) in order to determine the frequencies of polymorphisms and haplotypes in UGT1A1, UGT1A6, and UGT1A7, the co-occurrence of reduced enzyme activity UGT1A variants related to irinotecan toxicity, and to calculate the extent of linkage disequilibrium (LD) in the genomic region encompassing these genes.

RESULTS

Allelic analysis disclosed the presence of rare alleles - UGT1A1*36 and UGT1A1*37--only found in individuals of African descent, and UGT1A7*4. These alleles confirm our previous results on the São Miguel Island genetic background. We identified five different genotypes in UGT1A1 and UGT1A6 and nine in UGT1A7. Haplotype analysis showed that three haplotypes constituted approximately 80% of the allelic variants. Interestingly, haplotype 3 (UGT1A1*28-UGT1A6*2-UGT1A7*3), with a frequency of 0.235, gathers the three alleles encoding the low-function UGT isoforms. Additionally, LD indicates a strong interaction between functional polymorphisms related to the alteration of the UGT enzyme activity.

CONCLUSIONS

In summary, the results demonstrate a high variability of alleles and haplotypes, which have important roles in modifying expression and activity of UGTs. The data presented here could improve the understanding of the predisposition to cancers and susceptibility to the adverse effects of irinotecan in the São Miguel Island population.

Systematic screening for polymorphisms within the UGT1A6 gene in three Chinese populations and function prediction through structural modeling

AIMS

To date, there have been relatively few studies on the UGT1A6 gene in the Chinese population. The present study was designed to determine the allele frequencies and haplotypes of this gene in the population and predict the candidate functional mutations.

MATERIALS & METHODS

We carried out the first systematic screening of polymorphisms of the gene in an SNP analysis involving 1074 Chinese subjects from three ethnic groups, namely Han, Dong and She, using direct sequencing. We identified the putative substrate binding pocket using a homology-modeled structure and produced a practical model for predicting the function of polymorphisms in UGT1A6.

RESULTS

A total of six SNPs and 10 mutations were detected including nine known and seven novel ones. The novel mutations were 73G>A (V25I), 89T>G (L30R), 222A>C, 657C>A, 773A>T (D258V), 1040A>G (N347S) and 1467C>T. In addition, we detected, for the first time in the Chinese population, SNPs 105C>T, 627G>T as well as mutations 308C>A (S103X), IVS2+15T>C and 1088C>T (P363L). Strong linkage disequilibrium was observed among 19T>G, 315A>G, 541A>G and 552A>C. There were seven haplotypes whose frequencies were more than 0.01 in one or more of the three ethnic groups. P363L in the C-terminal domain might weaken the binding of cofactor UDPGA to the domain and induce a poor metabolism genotype of UGT1A6.

CONCLUSION

Our study suggests that genetic polymorphisms in UGT1A6 may contribute to interindividual and intra-ethnic differences. The results should prove helpful in the development of pharmacogenomics in China.

Pharmacokinetic analysis of irinotecan plus bevacizumab in patients with advanced solid tumors

PURPOSE

The purpose of this study was to evaluate the effect of bevacizumab on the pharmacokinetics (PK) of irinotecan and its active metabolite. Exploratory analyses of the impact of variability in uridine diphosphate glucuronosyltransferase 1A (UGT1A) genes on irinotecan metabolism and toxicity were conducted.

METHODS

This was an open-labeled, fixed-sequence study of bevacizumab with FOLFIRI (irinotecan, leucovorin, and infusional 5-fluorouracil). Pharmacokinetic assessments were conducted in cycles 1 and 3.

RESULTS

Forty-five subjects were enrolled. No difference in dose-normalized AUC(0-last) for irinotecan and SN-38 between irinotecan administered alone or in combination with bevacizumab was identified. Leukopenia was associated with higher exposure to both irinotecan and SN-38. UGT1A1 polymorphisms were associated with variability in irinotecan PK. Gastrointestinal toxicity was associated with UGT1A6 genotype. No other associations between UGT1A genotypes and toxicity were detected.

CONCLUSION

Bevacizumab does not affect irinotecan PK when administered concurrently. A variety of pharmacogenetic relationships may influence the pharmacokinetics of irinotecan and its toxicity.

Antioxidative effects of novel synthetic organoselenium compound in rat lung and kidney

The effects of environmental chemicals, drugs, and physical agents on the developing lung and kidney are influenced by the state of development and maturation. Selenium is an essential element with physiological nonenzymatic antioxidant properties. Therefore, we undertook the present study to evaluate the antioxidant potential of the novel synthetic organoselenium compounds (Se I and Se II). In this study, adult female Wistar rats were treated with DMBA and the novel organoselenium compounds [1-isopropyl-3-methylbenzimidazole-2-selenone (Se I) and 1,3-di-p-methoxybenzylpyrimidine-2-selenone (Se II)] in the determined doses. The protective effects of novel synthetic organoselenium compounds (Se I and Se II) against DMBA-induced changes in levels of some [superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), and glutathione reductase (GR) activities and total glutathione (GSH), malonedialdehyde (MDA)] parameters in rat lung and kidney were investigated. As a result, it was found that both Se I and Se II had provided the antioxidant effects against DMBA-induced oxidative stress in rat lung and kidney and lipid peroxidation had also been decreased by these organoselenium compounds.

Variability and function of family 1 uridine-5'-diphosphate glucuronosyltransferases (UGT1A)

The substrate spectrum of human UDP-glucuronosyltransferase 1A (UGT1A) proteins includes the glucuronidation of non-steroidal anti-inflammatory drugs, anticonvulsants, chemotherapeutics, steroid hormones, bile acids, and bilirubin. The unique genetic organization of the human UGT1A gene locus, and an increasing number of functionally relevant genetic variants define tissue specificity as well as a broad range of interindividual variabilities of glucuronidation. Genetic UGT1A variability has been conserved throughout the protein's evolution and shows ethnic diversity. It is the biochemical and genetic basis for clinical phenotypes such as Gilbert's syndrome and Crigler-Najjar's disease as well as for the potential for severe, unwanted drug side effects such as in irinotecan treatment. UGT1A variants influence the metabolic effects of xenobiotic exposure and therefore have been linked to cancer risk. Detailed knowledge of the organization, function, and pharmacogenetics of the human UGT1A gene locus is likely to significantly contribute to the improvement of drug safety and efficacy as well as to the provision of steps toward the goal of individualized drug therapy and disease risk prediction.