Genetic polymorphisms in UDP-glucuronosyltransferases and glutathione S-transferases and colorectal cancer risk

Nutritional Sources and Anticancer Potential of Phenethyl Isothiocyanate: Molecular Mechanisms and Therapeutic Insights

Phenethyl isothiocyanate (PEITC), a compound derived from cruciferous vegetables, has garnered attention for its anticancer properties. This review synthesizes existing research on PEITC, focusing on its mechanisms of action in combatting cancer. PEITC has been found to be effective against various cancer types, such as breast, prostate, lung, colon, and pancreatic cancers. Its anticancer activities are mediated through several mechanisms, including the induction of apoptosis (programmed cell death), inhibition of cell proliferation, suppression of angiogenesis (formation of new blood vessels that feed tumors), and reduction of metastasis (spread of cancer cells to new areas). PEITC targets crucial cellular signaling pathways involved in cancer progression, notably the Nuclear Factor kappa-light-chain-enhancer of activated B cells (NF-κB), Protein Kinase B (Akt), and Mitogen-Activated Protein Kinase (MAPK) pathways. These findings suggest PEITC's potential as a therapeutic agent against cancer. However, further research is necessary to determine the optimal dosage, understand its bioavailability, and assess potential side effects. This will be crucial for developing PEITC-based treatments that are both effective and safe for clinical use in cancer therapy.

Interactions between folate intake and genetic predictors of gene expression levels associated with colorectal cancer risk

Observational studies have shown higher folate consumption to be associated with lower risk of colorectal cancer (CRC). Understanding whether and how genetic risk factors interact with folate could further elucidate the underlying mechanism. Aggregating functionally relevant genetic variants in set-based variant testing has higher power to detect gene-environment (G × E) interactions and may provide information on the underlying biological pathway. We investigated interactions between folate consumption and predicted gene expression on colorectal cancer risk across the genome. We used variant weights from the PrediXcan models of colon tissue-specific gene expression as a priori variant information for a set-based G × E approach. We harmonized total folate intake (mcg/day) based on dietary intake and supplemental use across cohort and case-control studies and calculated sex and study specific quantiles. Analyses were performed using a mixed effects score tests for interactions between folate and genetically predicted expression of 4839 genes with available genetically predicted expression. We pooled results across 23 studies for a total of 13,498 cases with colorectal tumors and 13,918 controls of European ancestry. We used a false discovery rate of 0.2 to identify genes with suggestive evidence of an interaction. We found suggestive evidence of interaction with folate intake on CRC risk for genes including glutathione S-Transferase Alpha 1 (GSTA1; p = 4.3E-4), Tonsuko Like, DNA Repair Protein (TONSL; p = 4.3E-4), and Aspartylglucosaminidase (AGA: p = 4.5E-4). We identified three genes involved in preventing or repairing DNA damage that may interact with folate consumption to alter CRC risk. Glutathione is an antioxidant, preventing cellular damage and is a downstream metabolite of homocysteine and metabolized by GSTA1. TONSL is part of a complex that functions in the recovery of double strand breaks and AGA plays a role in lysosomal breakdown of glycoprotein.

Circulating bilirubin levels and risk of colorectal cancer: serological and Mendelian randomization analyses

BACKGROUND

Bilirubin, a byproduct of hemoglobin breakdown and purported anti-oxidant, is thought to be cancer preventive. We conducted complementary serological and Mendelian randomization (MR) analyses to investigate whether alterations in circulating levels of bilirubin are associated with risk of colorectal cancer (CRC). We decided a priori to perform analyses separately in men and women based on suggestive evidence that associations may differ by sex.

METHODS

In a case-control study nested in the European Prospective Investigation into Cancer and Nutrition (EPIC), pre-diagnostic unconjugated bilirubin (UCB, the main component of total bilirubin) concentrations were measured by high-performance liquid chromatography in plasma samples of 1386 CRC cases and their individually matched controls. Additionally, 115 single-nucleotide polymorphisms (SNPs) robustly associated (P < 5 × 10-8) with circulating total bilirubin were instrumented in a 2-sample MR to test for a potential causal effect of bilirubin on CRC risk in 52,775 CRC cases and 45,940 matched controls in the Genetics and Epidemiology of Colorectal Cancer Consortium (GECCO), the Colon Cancer Family Registry (CCFR), and the Colorectal Transdisciplinary (CORECT) study.

RESULTS

The associations between circulating UCB levels and CRC risk differed by sex (Pheterogeneity = 0.008). Among men, higher levels of UCB were positively associated with CRC risk (odds ratio [OR] = 1.19, 95% confidence interval [CI] = 1.04-1.36; per 1-SD increment of log-UCB). In women, an inverse association was observed (OR = 0.86 (0.76-0.97)). In the MR analysis of the main UGT1A1 SNP (rs6431625), genetically predicted higher levels of total bilirubin were associated with a 7% increase in CRC risk in men (OR = 1.07 (1.02-1.12); P = 0.006; per 1-SD increment of total bilirubin), while there was no association in women (OR = 1.01 (0.96-1.06); P = 0.73). Raised bilirubin levels, predicted by instrumental variables excluding rs6431625, were suggestive of an inverse association with CRC in men, but not in women. These differences by sex did not reach formal statistical significance (Pheterogeneity ≥ 0.2).

CONCLUSIONS

Additional insight into the relationship between circulating bilirubin and CRC is needed in order to conclude on a potential causal role of bilirubin in CRC development.

Individual and combined effects of GSTM1 and GSTT1 polymorphisms on colorectal cancer risk: an updated meta-analysis

BACKGROUND

The presence or absence of glutathione S-transferase M1 gene (GSTM1) and glutathione S-transferase T1 gene (GSTT1) polymorphisms, and their combined effects have been suggested as a risk factor for colorectal cancer (CRC). However, the results are inconsistent.

OBJECTIVES

An updated meta-analysis was performed to solve the controversy.

METHODS

Meta-analyses of Observational Studies in Epidemiology (MOOSE) guidelines were used.

RESULTS

Overall, the GSTM1 null genotype was associated with an increased CRC risk in Caucasians (odds ratio (OR) = 1.14, 95% confidence interval (CI): 1.05-1.23), Asians (OR = 1.19, 95% CI: 1.08-1.32), high-quality studies (OR = 1.12, 95% CI: 1.06-1.18). Moreover, the GSTM1 null genotype was also associated with an increased colon cancer risk (OR = 1.32, 95% CI: 1.16-1.51). The GSTT1 null genotype was also associated with an increased CRC risk in Asians (OR = 1.08, 95% CI: 1.02-1.15) and Caucasians (OR = 1.24, 95% CI: 1.09-1.41). Moreover, The GSTT1 null genotype was associated with an increased rectal cancer risk (OR = 1.13, 95% CI: 1.01-1.27, I2 = 8.3%) in subgroup analysis by tumor location. Last, the GSTM1 null/GSTT1 null genotype was associated with an increased CRC risk in Asians.

CONCLUSION

This meta-analysis indicates that the GSTM1 and GSTT1 null genotypes are associated with increased CRC risk in Asians and Caucasians, and the GSTM1 null/GSTT1 null genotype was associated with increased CRC risk in Asians.

Increased number of subclones in lung squamous cell carcinoma elicits overexpression of immune related genes

Background

Intratumoral heterogeneity is a cause of drug resistance that leads to treatment failure. We investigated the clinical implication of intratumoral heterogeneity inferred from the number of subclones that constituted a tumor and reasoned the etiology of subclonal expansion using RNA sequencing data.

Methods

Simple nucleotide variation, clinical data, copy number variation, and RNA-sequencing data from 481 The Cancer Genome Atlas-Lung Squamous Cell Carcinoma (TCGA-LUSC) cases were obtained from the Genomic Data Commons data portal. Clonal status was estimated from the allele frequency of the mutated genes using the SciClone package.

Results

The number of subclones that comprised a tumor had a positive correlation with the total mutations in a tumor (σ=0.477, P-value <0.001) and tumor stage (σ=0.111, P-value <0.015). Male LUSC tumors had a higher probability of having more subclones than female tumors (2.28 vs. 1.89, P-value =0.002, Welch Two Sample t-test). On comparing the gene expression in the tumors that were comprised of five subclones with those of a single clone, 291 genes were found to be upregulated and 102 genes were found to be downregulated in the five subclone tumors. The upregulated genes included UGT1A10, SRY, FDCSP, MRLM, and EREG, in order of magnitude of upregulation, and the biologic function of the upregulated genes was strongly enriched for the positive regulation of immune processes and inflammatory responses.

Conclusions

Male LUSC tumors were composed of a greater number of subclones than female tumors. The tumors with large numbers of subclones had overexpressed genes that positively regulated the immune processes and inflammatory responses more than tumors that consisted of a single clone.

Sulforaphane suppresses carcinogenesis of colorectal cancer through the ERK/Nrf2‑UDP glucuronosyltransferase 1A metabolic axis activation

The long pre-cancerous state of colorectal cancer (CRC) provides an opportunity to prevent the occurrence and development of CRC. The detoxification of CRC food-borne carcinogenic heterocyclic amines is highly dependent on UDP glucuronosyltransferase 1A (UGT1A)-mediated glucuronidation. Sulforaphane (SFN), a phytochemical, possesses antioxidant, anti-inflammatory and anticarcinogenic effects on the prevention of CRC. Previous studies revealed that SFN upregulates the expression of UGT1A. The aim of the present study was to investigate the regulatory mechanism of SFN-induced UGT1A upregulation and provide novel understanding on the basic research and chemoprevention of CRC. In the present study, the viability and proliferation of CRC cells (HT-29 and SW480) treated with SFN were assessed by MTT, colony formation and EdU assays. Flow cytometry was used to detect the cell cycle arrest and apoptosis of cells treated with different concentrations of SFN. The motility of cells was determined by wound healing and Transwell assays. Nuclear factor, erythroid 2 like 2 (Nrf2) short hairpin RNA (shRNA) and negative control shRNA lentiviruses were used for cell transfection. Reverse transcription-quantitative polymerase chain reaction and western blotting were employed to verify the role of Nrf2 in SFN-induced UGT1A. HT-29 and SW480 cells were divided into a control, an SFN and a PD98059 [an extracellular signal-regulated kinase (ERK) inhibitor] + SFN group. Western blotting detected the protein levels of Nrf2 and UGT1A. Intracellular levels of reactive oxygen species (ROS) were detected using a reactive oxygen assay kit. The results revealed that SFN inhibits cell proliferation and colony formation, promotes apoptosis, and reduces the migratory ability of CRC cells. The phosphorylation of ERK induced by SFN promoted Nrf2 accumulation. Furthermore, a significant increase in the levels of UGT1A was observed, which coincided with SFN-induced upregulation of Nrf2 levels in nuclear fractions. Pretreatment with PD58059 reversed the SFN-induced subcellular translocation of Nrf2 and the expression of UGT1A. In addition, SFN-induced high levels of ROS in CRC cells may be associated with the ERK signaling pathway. Collectively, these results indicated that SFN inhibited the proliferation of CRC cells and upregulated the expression of UGT1A in CRC cells via the ERK/Nrf2 signaling pathway.

The UDP-Glycosyltransferase (UGT) Superfamily: New Members, New Functions, and Novel Paradigms

UDP-glycosyltransferases (UGTs) catalyze the covalent addition of sugars to a broad range of lipophilic molecules. This biotransformation plays a critical role in elimination of a broad range of exogenous chemicals and by-products of endogenous metabolism, and also controls the levels and distribution of many endogenous signaling molecules. In mammals, the superfamily comprises four families: UGT1, UGT2, UGT3, and UGT8. UGT1 and UGT2 enzymes have important roles in pharmacology and toxicology including contributing to interindividual differences in drug disposition as well as to cancer risk. These UGTs are highly expressed in organs of detoxification (e.g., liver, kidney, intestine) and can be induced by pathways that sense demand for detoxification and for modulation of endobiotic signaling molecules. The functions of the UGT3 and UGT8 family enzymes have only been characterized relatively recently; these enzymes show different UDP-sugar preferences to that of UGT1 and UGT2 enzymes, and to date, their contributions to drug metabolism appear to be relatively minor. This review summarizes and provides critical analysis of the current state of research into all four families of UGT enzymes. Key areas discussed include the roles of UGTs in drug metabolism, cancer risk, and regulation of signaling, as well as the transcriptional and posttranscriptional control of UGT expression and function. The latter part of this review provides an in-depth analysis of the known and predicted functions of UGT3 and UGT8 enzymes, focused on their likely roles in modulation of levels of endogenous signaling pathways.

A study of the association between UGT1A1*28 variant allele of UGT1A1 gene and colonic phenotype of sporadic colorectal cancer

INTRODUCTION

The transcriptional activity of the UGT1A1 gene is modulated by a variable number of repetitions of the dinucleotide (TA) within its promoter region. By comparison to the most common allele (TA)₆ (UGT1A1*1), decreased activity is observed with increasing TA repetitions. The aim of this study was to determine whether the presence of the variant allele UGT1A1*28, harbouring seven TA repetitions, (TA)₇, in the homozygous state, is associated with precancerous colonic lesions and/or with specific colorectal cancer characteristics.

MATERIAL AND METHODS

All patients treated for colorectal cancer in a tertiary care centre, between January 2009 and December 2013, who had routine UGT1A1 genotyping for irinotecan dose-adjustment were included. Data were retrospectively collected.

RESULTS

292 patients were enrolled, including 23 UGT1A1*28/*28 homozygous (7.9%), 137 wild type homozygous (46.9%) and 132 heterozygous (45.2%). There were no significant differences in phenotypic colonic characteristics between homozygous and heterozygous patients carrying the UGT1A1*28 allele as compared to *1/*1 homozygous. Patients treated with aspirin were significantly more common in the UGT1A1*28/*28 homozygous group than in the other groups (7/23 (30.4%) compared to 22/269 (8.2%), p = 0.001).

CONCLUSION

Dinucleotide polymorphism in the promoter region of the UGT1A1 gene is not associated with a specific colonic phenotype in patients with sporadic colorectal cancer.

Deletion and Single Nucleotide Polymorphisms in Common Glutathione-S Transferases Contribute to Colorectal Cancer Development

Glutathione-S transferases (GSTs) are xenobiotic-conjugation enzymes involved in the detoxification process of heterocyclic aromatic amines and polycyclic aromatic hydrocarbons, widely recognized risk factors of colorectal cancer (CRC) development. Polymorphism in GSTs often leads to alteration or complete lack of enzyme activity, which might have an effect on CRC carcinogenesis. Aim of this study was to investigate GST gene variants as risk factors in patients with CRC. A total of 523 CRC patients administered for surgical resection and 400 matched controls were included. Deletion polymorphism of GSTs M1 and T1 was investigated by polymerase chain reaction. Single nucleotide polymorphism of GST A1 and P1 was investigated by restriction fragment length polymorphism method. The association between GST genotype and risk of CRC development was found in carriers of GSTT1-null and GSTP1-variant genotypes individually (p = 0.050 and p = 0.016, respectively). Furthermore, statistically significant association was found when combination of GSTP1-variant genotype with any of other three common GST genotypes was analyzed with respect to CRC susceptibility. Additionally, patients with combined GSTM1-null/GSTT1-null/GSTA1 low-activity/GSTP1-variant genotype showed 2.71-fold increased risk of developing CRC (p = 0.037). This study supports hypothesis that GST polymorphisms might have an important role in the process of the CRC development. Additionally, GSTM1-null/ GSTT1-null/ GSTA1 low-activity/ GSTP1-variant genotype could be combination of GST genotypes whose carriers are more prone to CRC development.

Gene Regulatory Network Analysis Identifies Sex-Linked Differences in Colon Cancer Drug Metabolism

Understanding sex differences in colon cancer is essential to advance disease prevention, diagnosis, and treatment. Males have a higher risk of developing colon cancer and a lower survival rate than women. However, the molecular features that drive these sex differences are poorly understood. In this study, we use both transcript-based and gene regulatory network methods to analyze RNA-seq data from The Cancer Genome Atlas for 445 patients with colon cancer. We compared gene expression between tumors in men and women and observed significant sex differences in sex chromosome genes only. We then inferred patient-specific gene regulatory networks and found significant regulatory differences between males and females, with drug and xenobiotics metabolism via cytochrome P450 pathways more strongly targeted in females. This finding was validated in a dataset of 1,193 patients from five independent studies. While targeting, the drug metabolism pathway did not change overall survival for males treated with adjuvant chemotherapy, females with greater targeting showed an increase in 10-year overall survival probability, 89% [95% confidence interval (CI), 78-100] survival compared with 61% (95% CI, 45-82) for women with lower targeting, respectively (P = 0.034). Our network analysis uncovers patterns of transcriptional regulation that differentiate male and female colon cancer and identifies differences in regulatory processes involving the drug metabolism pathway associated with survival in women who receive adjuvant chemotherapy. This approach can be used to investigate the molecular features that drive sex differences in other cancers and complex diseases.Significance: A network-based approach reveals that sex-specific patterns of gene targeting by transcriptional regulators are associated with survival outcome in colon cancer. This approach can be used to understand how sex influences progression and response to therapies in other cancers. Cancer Res; 78(19); 5538-47. ©2018 AACR.

Protective effects of coffee against oxidative stress induced by the tobacco carcinogen benzo[α]pyrene

AIMS

Coffee consumption has been epidemiologically associated with a lower risk for liver cirrhosis and cancer. UDP-glucuronosyltransferases (UGT1A) catalyze the detoxification of reactive metabolites thereby acting as indirect antioxidants. Aim of the study was to examine UGT1A regulation in response to Benzo[α]pyrene (BaP) to elucidate the potentially protective effects of coffee on BaP-induced oxidative stress and toxicity.

RESULTS

In cell culture (HepG2, KYSE70 cells) and in htgUGT1A-WT mice, UGT1A transcription was activated by BaP, while it was reduced or absent htgUGT1A-SNP (containing 10 commonly occurring UGT1A-SNPs) mice. siRNA-mediated knockdown identified aryl hydrocarbon receptor (AhR) and nuclear factor erythroid2-related factor-2 (Nrf2) as mediators of BaP-induced UGT1A upregulation. Exposure to coffee led to a reduction of BaP-induced production of reactive oxygen species in vitro and in htgUGT1A-WT and -SNP mice. After UGT1A silencing by UGT1A-specific siRNA in cell culture, the coffee-mediated reduction of ROS production was significantly impaired compared to UGT1A expressing cells.

CONCLUSION

A common UGT1A haplotype, prevalent in 9% (homozygous) of the White population, significantly impairs the expression of UGT1A enzymes in response to the putative tobacco carcinogen BaP and is likely to represent a significant risk factor for reduced detoxification and increased genotoxicity. Coffee was demonstrated to inhibit BaP-induced production of oxidative stress by UGT1A activation, and is therefore an attractive candidate for chemoprotection in risk groups for HCC or other tumors.

Genetic polymorphisms in human UDP-glucuronosyltransferases 1A7 and the risk of gastrointestinal carcinomas: A systematic review and network meta-analysis

Objective

To identify the association between gastrointestinal carcinomas (GIC) risk and UDP-glucuronosyltransferases (UGTs) 1A7 polymorphisms through a systematic review and network meta-analysis.

Results

Seventeen studies were eligible, which included 7738 patients and 18 analyses. First, it was found that compared with non-cancer participants, UGT1A7*1 were significantly decreased in cancer patient groups, especially in hepatocellular carcinoma, colorectal carcinoma, and Asian population groups; UGT1A7*2 was significantly increased in hepatocellular carcinoma and Asian population groups; and UGT1A7*3 was significantly increased in hepatocellular carcinoma, colorectal carcinoma, Caucasian, and Asian population groups. Second, the UGT1A7 polymorphism alleles contrast model and the categorized UGT 1A7 genotypes were compared, and the outcomes revealed that the ratio of UGT1A7*3 vs *2 increased, which may indicate an increased risk for cancer, especially for the pancreatic carcinoma and Caucasian groups. The ratio of Intermediate vs Low increased as well, which may also indicate an increased risk for GIC.

Materials and Methods

PubMed, Embase, and the Cochrane library were searched for publications up until May 2017. First, the UGT 1A7 gene polymorphisms genotype in GIC patients were compared with a non-cancer control group, and second, the UGT1A7 polymorphism alleles contrast model and UGT 1A7 genotypes categorized according to enzymatic activity were examined.

Conclusions

There is a cancer risk associated with increased UGT1A7 *2 for the hepatocellular carcinoma and Asian groups and with increased UGT1A7 *3 for the hepatocellular carcinoma, colorectal carcinoma, Caucasian, and Asian groups. Moreover, in Caucasian patients with GIC, the ratio of UGT1A7 *3 vs *2 was increased.

UDP-glucuronosyltransferases (UGTs) and their related metabolic cross-talk with internal homeostasis: A systematic review of UGT isoforms for precision medicine

UDP-glucuronosyltransferases (UGTs) are the primary phase II enzymes catalyzing the conjugation of glucuronic acid to the xenobiotics with polar groups for facilitating their clearance. The UGTs belong to a superfamily that consists of diverse isoforms possessing distinct but overlapping metabolic activity. The abnormality or deficiency of UGTs in vivo is highly associated with some diseases, efficacy and toxicity of drugs, and precisely therapeutic personality. Despite the great effects and fruitful results achieved, to date, the expression and functions of individual UGTs have not been well clarified, the inconsistency of UGTs is often observed in human and experimental animals, and the complex regulation factors affecting UGTs have not been systematically summarized. This article gives an overview of updated reports on UGTs involving the various regulatory factors in terms of the genetic, environmental, pathological, and physiological effects on the functioning of individual UGTs, in turn, the dysfunction of UGTs induced disease risk and endo- or xenobiotic metabolism-related toxicity. The complex cross-talk effect of UGTs with internal homeostasis is systematically summarized and discussed in detail, which would be of great importance for personalized precision medicine.

Association of glutathione S-transferase (GSTM1 and GSTT1) genes with chronic myeloid leukemia

Chronic myeloid leukemia (CML), as most of cancers results from a complex interaction between genetic or non genetic factors. Exposures to xenobiotics endogenous or exogenous associated with a reduced individual ability in detoxifying activity, constitutes a risk of developing cancer. It is known that polymorphism of glutathione S-transferases (GSTs) genes affects the detoxification of xenobiotics. Thus, we conducted a case-control study in which 92 patients (Mean age ± SD, 40.62 ± 12.7 years) with CML and 93 healthy unrelated controls (Mean age ± SD, 41.38 ± 13.4 years) have participated. GSTM1 and GSTT1 genotypes were determined by multiplex polymerase chain reaction. Logistic regression was used to assess the possible link between GSTM1 and GSTT1 null genotypes and CML as well as between combined genotypes and CML. GSTM1 null genotype frequency was slightly higher in patients than control (48.9% vs. 40.9%) but, it was not associated with CML (OR 95% CI, 1.4, 0.78-2.48; p = 0.271). Moreover, GSTT1 null genotype frequency showed a similar trend between patients and control (17.4% vs. 9.7%; OR 95% CI, 1.97, 0.82-4.71; p = 0.13). Surprisingly, GSTT1 null genotype was significantly associated with the risk of CML in males (OR 95% CI, 5, 1.25-20.1; p = 0.023). The combined GSTM1 present/GSTT1 null genotype was found to have a limited effect against the risk of CML (OR 95% CI, 0.3, 0.08-0.99; p = 0.049). Our findings have shown that GSTT1 null genotype might be a risk factor of CML in males. While, GSTT1 present genotype might be considered as protective against CML. However, further studies with a large sample size are needed to confirm our findings.

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.

The effect of UGT1A and UGT2B polymorphisms on colorectal cancer risk: haplotype associations and gene–environment interactions

UDP-glucuronosyltransferases (UGTs) play an important role in the phase II metabolism of exogenous and endogenous compounds. As colorectal cancer (CRC) etiology is thought to involve the biotransformation of dietary factors, UGT polymorphisms may affect CRC risk by altering levels of exposure. Genotyping of over 1800 Caucasian subjects was completed to identify the role of genetic variation in nine UGT1A and five UGT2B genes on CRC risk. Unconditional logistic regression and haplotype analyses were conducted to identify associations with CRC risk and potential gene-environment interactions. UGT1A haplotype analysis found that the T-G haplotype in UGT1A10 exon 1 (block 2: rs17864678, rs10929251) decreased cancer risk for the colon [proximal (OR = 0.28, 95% CI = 0.11–0.69) and for the distal colon (OR = 0.32, 95% CI = 0.12–0.91)], and that the C-T-G haplotype in the 3′ region flanking the UGT1A shared exons (block 11: rs7578153, rs10203853, rs6728940) increased CRC risk in males (OR = 2.56, 95% CI = 1.10–5.95). A haplotype in UGT2B15 containing a functional variant (rs4148269, K523T) and an intronic SNP (rs6837575) was found to affect rectal cancer risk overall (OR = 2.57, 95% CI = 1.21–5.04) and in females (OR = 3.08, 95% CI = 1.08–8.74). An interaction was found between high NSAID use and the A-G-T haplotype (block 10: rs6717546, rs1500482, rs7586006) in the UGT1A shared exons that decreased CRC risk. This suggests that UGT genetic variation alters CRC risk differently by anatomical sub-site and gender and that polymorphisms in the UGT1A shared exons may have a regulatory effect on gene expression that allows for the protective effect of NSAIDs on CRC risk.

Potential antioxidant response to coffee - A matter of genotype?

In a human intervention study, coffee combining natural green coffee bean constituents and dark roast products was identified as a genotype-dependent inducer of the Nrf2/ARE pathway, significantly affecting Nrf2 gene expression and downstream GST1A1 and UGT1A1 gene transcription. The observed transcriptional changes correlated with the presence of specific Nrf2 genotypes suggesting their influence on both Nrf2 and subsequent ARE-dependent GST1A1 and UGT1A1 transcription. While the presence of the − 653 SNP seems to be advantageous, resulting in higher Nrf2, GST1A1 and UGT1A1 gene transcription following coffee consumption, in contrast, the presence of the − 651 SNP significantly down-regulated the response to the study coffee. Furthermore, the presence of the B/B genotype in GST1A1 along with the frequency of the [TA]_6/6 and [TA]_7/7 polymorphisms in UGT1A1 appeared to significantly increase sensitivity toward coffee-induced gene transcription. This data suggests that when examining the role of the Nrf2/ARE pathway in the regulation of antioxidative and chemopreventive phase II efficacy, individual genotypes should be included when considering the potency of bioactive food/food constituents and their therapeutic potential.

A systemic review of glutathione S-transferase P1 Ile105Val polymorphism and colorectal cancer risk

OBJECTIVES

To investigate the correlation between glutathione S-transferase P1 (GSTP1) Ile105Val polymorphism and colorectal cancer (CRC) risk.

METHODS

Studies were identified to investigate the association between GSTP1 Ile105Val polymorphism and CRC risk. Systematic computerized searches of the PubMed, Chinese National Knowledge Infrastructure, WANFANG and SinoMed were performed. Summary odds ratios (OR) and 95% confidence intervals (95% CI) were used to measure GSTP1 Ile105Val polymorphisms and CRC risk.

RESULTS

A total of 23 retrospective studies were included in the meta-analysis. During all studies including 6,981 cases and 8,977 controls, sample sizes ranged from 146 to 2,144. Overall, the pooled results revealed that Ile105Val polymorphism was not associated with CRC risk and confused results were found in subgroup analyses. Further meta-analyses were conducted after excluding low-quality studies. GSTP1 Ile105Val is associated with increased risk of CRC limited in studies with matched control. There was no significant heterogeneity in all genetic comparisons, but heterogeneity existed in subgroup analyses of heterozygous and dominant comparisons. The meta-regression analyses indicated that matched controls were the significant factor influencing between-study heterogeneity in all possible influential factors including published year, ethnicity, source of control, sample size, Hardy-Weinberg equilibrium (HWE) in control and matched controls. Sensitivity analysis revealed the pooled ORs were not changed before and after removal of each single study in all genetic comparisons, indicating the robustness of the results.

CONCLUSIONS

GSTP1 Ile105Val might be associated with increased risk of CRC. However, more high-quality case-control studies should be performed to confirm the authenticity of our conclusion.

GSTA1, GSTM1, GSTP1, and GSTT1 polymorphisms and susceptibility to smoking-related bladder cancer: a case-control study

OBJECTIVES

Glutathione S-transferases (GSTs) are a family of enzymes involved in detoxification. Genes encoding for GSTA1, GSTM1, GSTP1, and GSTT1 proteins are polymorphic, which can result in complete or partial loss of enzyme activity. Previous studies have associated polymorphisms of GSTA1, GSTM1, and GSTP1 genes with a higher risk of bladder cancer, but this is still controversial. Potential role of GSTA1 polymorphism in susceptibility to bladder cancer in Whites is lacking. We examined association between GSTA1, GSTM1, GSTP1, and GSTT1 gene variants and bladder cancer risk and evaluated whether they were modified by smoking.

MATERIALS AND METHODS

A hospital-based case-control study recruited 201 incidence cases and 122 age-matched controls. Deletion polymorphism of GSTM1 and GSTT1 was identified by polymerase chain reaction method. Single nucleotide polymorphism of GSTA1 and GSTP1 was identified by restriction fragment length polymorphism method. Uniconditional multivariate logistic regression was applied to model association between genetic polymorphisms and bladder cancer risk, as well as effect modification by smoking.

RESULTS

No significant difference was observed in the distributions of GSTM1, GSTT1, GSTA1, and GSTP1 gene variants between patients and controls. None of the examined polymorphisms was significantly associated with bladder cancer risk independently. The results of gene-smoking interaction analyses indicated a significant combined effect of smoking and all common GST polymorphisms tested (P for trend = 0.001). However, the most significant effect on bladder cancer risk was observed in smokers carrying lower activity GSTA1-AB/BB and GSTM-null genotype (OR = 3.5, P < 0.05) compared with GSTA1-AA and GSTM1-active non-smokers. Overall, the risk observed did not significantly differ with respect to quantity of cigarettes smoked. However, heavy smokers with GSTM1-null genotype had 2 times higher risk of bladder cancer than GSTM1-null light smokers (OR = 4.8 vs. OR = 2.0) when GSTM1-active non-smokers served as reference group. Smokers carrying both GSTM1-null and GSTA1-AB + BB genotypes exhibited the highest risk of bladder cancer (OR = 2.00, P = 0.123).

CONCLUSIONS

Null or low-activity genotypes of the GSTA1, GSTM1, GSTT1, and GSTP1 did not contribute independently towards the risk of bladder cancer in our patients. However, in association with smoking, both low activity GSTA1 and GSTM1-null genotype increase individual susceptibility to bladder cancer.

Influence of CYP1A1, GST polymorphisms and susceptibility risk of chronic myeloid leukemia in Syrian population

In the present study, we investigated the associations of polymorphisms in cytochrome P450 gene (CYP1A1), glutathione S-transferase genes (GSTM1 and GSTT1) with chronic myelogenous leukemia (CML). A total of 126 patients with CML and 172 healthy volunteers were genotyped, and the DNA was isolated from their blood samples. The polymorphisms were assessed by polymerase chain reaction (PCR) restriction fragment length polymorphism-based methods and multiplex PCR. Logistic regression analyses showed significant risk of CML associated with CYP1A1 Val allele [odds ratio (OR) 3.3, 95% confidence intervals (CI) 1.96-5.53], (p < 0.0001) while CYP1A1 Val/Val homozygotes were observed only in the CML patients. There was statistically significant difference in the frequency of GSTM1 and GSTT1 null genotypes. The GSTT1-null genotype was slightly higher in 27% of CML cases and 16.7% of controls (OR 1.98, 95% CI 1.12-3.5) (p < 0.020). The GSTM1 null was higher in 42.8% of CML cases and 22.7% of controls (OR 2.55, 95% CI 1.54-4.22) (p < 0.00024). The individuals carrying CYP1A1 Ile/Val (AG) and GSTM1 null genotype have 9.9 times higher risk to be CML than those carrying CYP1A1 Ile/Ile (AA) and GSTM1 present genotype (OR 9.9, 95% CI 2.7-36.3) (p < 0.0001). This suggests that the association of the GSTM1 null genotype, either alone or in combination with GSTT1 null, with CYP1AI heterozygous leads to the CML risk.

Glutathione S-transferase T1 gene polymorphism and colorectal cancer risk: an updated analysis

BACKGROUND AND OBJECTIVE

The association between glutathione S-transferase T1 (GSTT1) gene polymorphisms and colorectal cancer (CRC) susceptibility is still controversial. In order to clarify the effect of GSTT1 genotype on the CRC risk, we carried out an updated meta-analysis of published case-control studies to provide more precise evidence.

METHODS

Two investigators independently searched the databases of Pubmed, EMBASE and China National Knowledge Infrastructure (CNKI) up to October 15, 2012. Crude odds ratios (OR) and 95% confidence intervals (CI) were calculated to investigate the strength of the association in a fixed- or random-effects model depending on statistical heterogeneity.

RESULTS

Forty-six case-control studies with 15,373 colorectal cancer cases and 21,238 controls were included. Overall, the pooled results indicated that GSTT1 null genotype was significantly associated with increased CRC risk (OR=1.21, 95% CI=1.10-1.33). When stratifying for ethnicity and control sources, we also observed positive association between GSTT1 null genotype and increased risk of CRC. When stratifying by the location, we found there was a statistically significant association in the rectal cancer (OR=1.28, 95% CI=1.01-1.64), but not in colon cancer (OR=1.27, 95% CI=0.94-1.73). Subgroup analyses for Dukes stage, histological differentiation of CRC and smoking habit did not reveal any significant differences in genotype distribution. In addition, we observed a strong correlation between increased CRC risk and the combined GSTM1 and GSTT1 null genotype.

CONCLUSIONS

This meta-analysis suggests that the GSTT1 null genotype may contribute to increased risk of colorectal cancer. More well-designed studies based on larger population are needed to confirm our results.

Polymorphisms of glutathione-S-transferases M1, T1, P1 and susceptibility to colorectal cancer in a sample of the Tunisian population

In this study, we investigated the associations of polymorphisms in glutathione-S-transferases (GSTs) genes that are GSTM1, GSTT1, and GSTP1, with sporadic colorectal cancer (CRC). Hundred and fifty patients with CRC and 128 healthy controls were genotyped. DNA was isolated from blood samples. Polymorphisms were assessed by polymerase chain reaction-restriction fragment length polymorphism-based methods and polymerase chain reaction multiplex. Logistic regression analyses showed significant risk for CRC associated with GSTP1 homozygotes for Val-105 (OR 4.82; 95 % CI 1.97-11.80) or for individuals who possessed at least one Val-105 allele (OR 2.54; 95 % CI 1.751-3.703). There were no statistically significant differences in the frequency of GSTM1- and GSTT1-null genotypes (p > 0.05). The GSTM1-null was found in 70.47 % of all cases and 70.07 % of controls (OR 0.61; 95 % CI 0.33-1.12). The GSTT1-null genotype was found in 38.77 % of cases and 49.22 % of controls (OR 1.53; 95 % CI 0.94-2.47). No effect of any genotype for GSTM1 and GSTT1 on CRC was detected. But then an association between the polymorphism of the GSTP1 and the CRC susceptibility was detected.

Association between polymorphisms in UDP-glucuronosyltransferase 1A6 and 1A7 and colorectal cancer risk

Genetic polymorphisms of uridine diphosphate-glucuronosyltransferases 1A6 (UGT1A6) and 1A7 (UGT1A7) may lead to genetic instability and colorectal cancer carcinogenesis. Our objective was to measure the interaction between polymorphisms of these repair genes and tobacco smoking in colorectal cancer (CRC). A total of 68 individuals with CRC and 112 non-cancer controls were divided into non-smoker and smoker groups according to pack-years of smoking. Genetic polymorphisms of UGT1A6 and UGT1A7 were examined using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). We found a weak association of UGT1A6 polymorphisms with CRC risk (crude odds ratio [OR], 1.65; 95% confidence interval [95%CI], 0.9-3.1, P=0.107; adjusted OR 1.95, 95%CI 1.0-3.8, P=0.051). The ORs for the UGT1A7 polymorphisms were statistically significant (crude OR: 26.40, 95%CI: 3.5-198.4, P=0.001; adjusted OR: 21.52, 95%CI: 2.8-164.1, P=0.003). The joint effect of tobacco exposure and UGT1A6 polymorphisms was significantly associated with colorectal cancer risk in non-smokers (crude OR, 2.11; 95%CI, 0.9-5.0, P=0.092; adjusted OR 2.63, 95%CI 1.0-6.7, P=0.042). In conclusion, our findings suggest that UGT1A6 and UGT1A7 gene polymorphisms are associated with CRC risk in the Japanese population. In particular, UGT1A6 polymorphisms may strongly increase CRC risk through the formation of carcinogens not associated with smoking.

Common polymorphisms in GSTM1, GSTT1, GSTP1, GSTA1 and susceptibility to colorectal cancer in the Central European population

Background

Central Europe presents with the highest incidence of sporadic colorectal cancer (CRC) worldwide. As sporadic CRC represents a typical multifactorial disease, it is characterized by intense interaction of the genetic background with the environment. Glutathione S-transferases could act as attractive susceptibility genes for CRC, as they are directly involved in conjugation between glutathione and chemotherapeutics, environmental pollutants and a wide spectrum of xenobiotics.

Methods

In this study, we investigated associations of polymorphisms in glutathione S-transferases (GSTs) genes, that is GSTA1, GSTT1, GSTM1 and GSTP1, with CRC in a total of 197 cases and 218 controls originating from the Czech Central European population. Polymorphisms were assessed by polymerase chain reaction/restriction fragment length polymorphism-based methods, allele-specific multiplex and allelic discrimination by real-time polymerase chain reaction.

Results

None of investigated polymorphisms showed any associations with CRC, with the exception of GSTP1; where the heterozygote genotype Ile105Val was associated with decreased risk of CRC (P = 0.043).

Conclusions

The frequencies observed in our study are in accordance with those from other European Caucasian populations. Based on our studies, examined variability in GST genes is not a major determinant of CRC susceptibility in the Central European population.

Genetic variation and haplotype structures of the glutathione S-transferase genes GSTA1 and GSTA2 in Japanese colorectal cancer patients

Glutathione S-transferases (GSTs) play a vital role in the phase II biotransformation of many chemicals, including anticancer drugs. In this study, to elucidate the haplotype structures of the two closely related alpha-class genes GSTA1 and GSTA2, we screened for genetic variation in 214 Japanese colorectal cancer patients who received oxaliplatin-based chemotherapy. By direct resequencing of the 5'-flanking region, all the exons, and their flanking introns for 107 patients, 29 and 27 variants were identified in GSTA1 and GSTA2, respectively. The known functional single nucleotide polymorphisms (SNPs) -567T>G, -69C>T, and -52G>A in GSTA1*B were found at allele frequencies of 0.140. Of the four major GSTA2 allelic variants reported previously (GSTA2*A, *B, *C, and *E), only GSTA2*B (frequency = 0.154), *C (0.706), and *E (0.140) were detected. Following linkage disequilibrium analysis, haplotypes of both genes were separately estimated. Then, rapid genotyping methods for 7 and 6 SNPs tagging common haplotypes of GSTA1 and GSTA2, respectively, were developed using the single-base extension assay, and an additional 107 patients were genotyped. Finally, haplotype combinations of both genes were classified into 3 major types: GSTA1*A-GSTA2*C, GSTA1*A-GSTA2*B, and GSTA1*B-GSTA2*E. These findings will be useful in pharmacogenomic studies on xenobiotics including anticancer drugs.

Metabolism and biomarkers of heterocyclic aromatic amines in molecular epidemiology studies: lessons learned from aromatic amines

Aromatic amines and heterocyclic aromatic amines (HAAs) are structurally related classes of carcinogens that are formed during the combustion of tobacco or during the high-temperature cooking of meats. Both classes of procarcinogens undergo metabolic activation by N-hydroxylation of the exocyclic amine group to produce a common proposed intermediate, the arylnitrenium ion, which is the critical metabolite implicated in toxicity and DNA damage. However, the biochemistry and chemical properties of these compounds are distinct, and different biomarkers of aromatic amines and HAAs have been developed for human biomonitoring studies. Hemoglobin adducts have been extensively used as biomarkers to monitor occupational and environmental exposures to a number of aromatic amines; however, HAAs do not form hemoglobin adducts at appreciable levels, and other biomarkers have been sought. A number of epidemiologic studies that have investigated dietary consumption of well-done meat in relation to various tumor sites reported a positive association between cancer risk and well-done meat consumption, although some studies have shown no associations between well-done meat and cancer risk. A major limiting factor in most epidemiological studies is the uncertainty in quantitative estimates of chronic exposure to HAAs, and thus, the association of HAAs formed in cooked meat and cancer risk has been difficult to establish. There is a critical need to establish long-term biomarkers of HAAs that can be implemented in molecular epidemioIogy studies. In this review, we highlight and contrast the biochemistry of several prototypical carcinogenic aromatic amines and HAAs to which humans are chronically exposed. The biochemical properties and the impact of polymorphisms of the major xenobiotic-metabolizing enzymes on the biological effects of these chemicals are examined. Lastly, the analytical approaches that have been successfully employed to biomonitor aromatic amines and HAAs, and emerging biomarkers of HAAs that may be implemented in molecular epidemiology studies are discussed.

Interactions among genetic variants in tobacco metabolizing genes and smoking are associated with head and neck cancer susceptibility in North Indians

It is becoming clearly evident that single gene or single environmental factor cannot explain susceptibility to diseases with complex etiology such as head and neck cancer. In this study, we applied the multifactor dimensionality reduction method to explore potential gene-environment and gene-gene interactions that may contribute to predisposition to head and neck cancer in the North Indian population. We genotyped 203 patients with head and neck cancer and 201 healthy controls for 13 functional polymorphisms in genes coding for tobacco metabolizing enzymes; CYP1A1, CYP2A13, GSTM1, and UGT1A7 using polymerase chain reaction-restriction fragment length polymorphism method, real-time polymerase chain reaction quantitative assay, and denaturing high-performance liquid chromatography followed by direct sequencing. We found that GSTM1 copy number variations were the most influential factor for head and neck cancer. We also observed significant gene-gene interactions among GSTM1 copy number variants, CYP1A1 T3801C and UGT1A7 T622C variants among smokers. Multifactor dimensionality reduction approach showed that the three-factor model, including smoking status, CYP1A1 T3801C, and GSTM1 copy number variants, conferred more than fourfold increased risk of head and neck cancer (odds ratio 4.89; 95% confidence interval: 3.15-7.32, p < 0.01). These results support the hypothesis that genetic variants in tobacco metabolizing genes may contribute to head and neck cancer risk through gene-gene and gene-environmental interactions.

GSTP1 I105V polymorphism and susceptibility to colorectal cancer in Kashmiri population

The glutathione S-transferase (GST) enzyme encoded by the GSTP1 gene is one of the critical enzymes involved in detoxification of carcinogens. The substitution of isoleucine to valine residue at position 105 of the GSTP1 protein results in decreased enzyme activity and hence less capability of effective detoxification. Hence, we investigated the role of GSTP1 I105V polymorphism in modulating the risk of colorectal cancer (CRC) associated in a Kashmiri population. We designed a case-control study in which 86 CRC cases were studied for GSTP1 I105V polymorphism against 160 controls taken from the general population employing the polymerase chain reaction-restriction length fragment polymorphism technique. There was no significant association between GSTP1 I105V genotypes and the disease, but the Val/Val genotype was associated with an increased risk with some clinicopathological parameters (odds ratio=1.5; 95% confidence interval=0.55-4.57). This study suggests that the GSTP1 I105V polymorphism may modulate CRC risk in the Kashmiri population.

Influence of drug transporters and UGT polymorphisms on pharmacokinetics of phenolic glucuronide metabolite of mycophenolic acid in Japanese renal transplant recipients

Mycophenolic acid (MPA) is mainly glucuronized by uridine diphosphate-glucuronosyltransferases (UGTs) into the phenolic MPA glucuronide (MPAG). MPAG is excreted by transporters such as organic anion-transporting polypeptide (gene SLCO), multidrug resistance protein 2 (gene ABCC2), breast cancer resistance protein (BCRP, gene ABCG2) or P-glycoprotein (gene ABCB1). This study investigated the association of UGTs, SLCOs, ABCB1, ABCC2, and ABCG2 polymorphisms with MPAG pharmacokinetics in 80 Japanese renal transplant recipients. Eighty recipients were given repeated doses of combination immunosuppressive therapy consisting of mycophenolate mofetil and tacrolimus every 12 hours at a designated time (0900 and 2100). On day 28, after renal transplantation, plasma concentrations of MPA and MPAG were measured by high-performance liquid chromatography. There were no significant differences in the area under the plasma concentration-time curve (AUC) ratio of MPAG/MPA between UGT1A1, UGT1A6, UGT1A7, UGT1A8, and UGT1A9 I399C/T genotypes. On the other hand, the median dose-adjusted AUC0-12 of MPAG in SLCO1B1 1a/1a+1a/1b+1b+1b (n = 53) and 1a/*15 + 1b/*15+*15/*15 (n = 27) were 1549 and 1134 mg.h L g, respectively (P = 0.03004 in multivariate analysis). The median dose-adjusted AUC0-12 of MPAG in SLCO1B3 334T/T+T/G (699G/G+G/A, n = 46) and 334G/G (699A/A, n = 34) was 1191 and 1580 mg.h L g, respectively (P = 0.02792 in multivariate analysis). There were no significant differences in the dose-adjusted AUC0-12 of MPAG between the ABCB1 C3435T and ABCC2 C-24T genotypes. However, the dose-adjusted AUC0-12 of MPAG was significantly lower in recipients with ABCG2 421C/A+A/A (n = 44) than in those with C/C (n = 36) (P = 0.0295). In conclusion, our findings showed that MPAG pharmacokinetics were significantly influenced by SLCO1B1 and SLCO1B3 polymorphisms and not by UGT polymorphisms. BCRP rather than multidrug resistance protein 2 seems to be the transporter associated with biliary excretion of MPAG.

Polymorphisms in CYP2A13 and UGT1A7 genes and head and neck cancer susceptibility in North Indians

OBJECTIVES

To examine role of genetic variants of CYP2A13 and UGT1A7 genes, involved in activation and detoxification of tobacco carcinogens, with risk of head and neck cancer as well as to assess the potential modifying role of gene-gene and gene-environment interactions.

METHODS

203 head and neck cancer patients and 201 healthy controls were genotyped for functional polymorphisms of CYP2A13 and UGT1A7 genes using polymerase chain reaction-restriction fragment length polymorphism, denaturing high-performance liquid chromatography and sequencing.

RESULTS

We identified two novel polymorphisms T478C and T494C in CYP2A13 gene which were associated with significantly reduced risk of cancer (OR 0.37; 95% CI 0.19-0.71; P < 0.05). A CYP2A13 haplotype carrying variant alleles of T478C/T494C was found to be associated with reduced risk of head and neck cancer (OR 0.42; 95% CI 0.22-0.78; P = 0. 005). Mutant 'T' allele of CYP2A13 C578T polymorphism was found to be present in cancer patients only. A sevenfold increased risk of cancer was observed in smokers with UGT1A7 low activity genotypes (OR 7.01; 95% CI 1.02-48.37; P < 0.05). UGT1A7 haplotype carrying C allele (T622C) showed 10-fold increased risk of cancer (OR 10.12; 95% CI 1.29-79.4; P < 0.05).

CONCLUSION

  Interplay between genetic variants of CYP2A13 and UGT1A7 genes and smoking may modulate susceptibility to head and neck cancer.

Coffee induces expression of glucuronosyltransferases by the aryl hydrocarbon receptor and Nrf2 in liver and stomach

BACKGROUND & AIMS

Coffee is one of the most widely consumed beverages worldwide. Epidemiologic data indicate that coffee consumption protects against the progression of chronic liver disease and development of hepatocellular carcinoma and diabetes, but the mechanisms are not clear. UDP glucuronosyltransferases (UGT1A) are proteins with indirect antioxidant, cytoprotective, and genoprotective capabilities; we examined UGT1A regulation in response to coffee in cultured cells and mice.

METHODS

HepG2 and CaCo2 cells were incubated with regular, metal- or paper-filtered, decaffeinated, or instant coffee; green or black tea; cocoa; or metabolic products of caffeine. The effects of UGT1A regulation were investigated with reporter gene assays, immunoblot, TaqMan polymerase chain reaction, mutagenesis, and short interfering (si)RNA analyses. We also studied the effects of coffee in humanized transgenic mice that express human UGT1A.

RESULTS

Incubation of cells with coffee induced transcription of UGT1A1 (5.4-fold), UGT1A3 (5.2-fold), UGT1A4 (4.8-fold), UGT1A7 (6.2-fold), UGT1A8 (5.2-fold), UGT1A9 (3.5-fold), and UGT1A10 (6.1-fold). Induction was independent of caffeine, methylxanthines, or the diterpenes cafestol and kahweol. Mutagenesis and short interfering RNA knockdown studies showed that UGT1A is regulated by the aryl hydrocarbon receptor (AhR) and the nuclear factor erythroid-related factor 2 (Nrf2) by cis-acting antioxidant and xenobiotic response elements (ARE/XRE). In transgenic UGT1A mice, administration of coffee resulted in a 10- and 14-fold induction of UGT1A transcription in liver and stomach, respectively.

CONCLUSIONS

UGT1A genes are induced in vitro and in vivo by coffee, independent of caffeine content, cafestol, or kahweol. Coffee up-regulates glucuronidation by AhR signaling and Nrf2 binding to the ARE/XRE. Glucuronidation could mediate the protective and antioxidant effects of coffee.

Bilirubin, cardiovascular diseases and cancer: epidemiological perspectives

Owing to a potent antioxidant property of bilirubin, a growing interest has been drawn to the potential protective effects of bilirubin against oxidative stress-related diseases. This article evaluates associations of bilirubin with atherosclerotic diseases and cancer. Serum bilirubin has consistently been shown to be inversely associated with diverse atherosclerotic diseases, mostly among men in different populations. A limited number of prospective studies have shown a U-shaped or reversed J-shaped relationship between bilirubin and coronary heart disease in men and no evident association in women. Few studies have provided evidence supportive of a protective association between bilirubin and cancer risk. The findings on bilirubin-related genetic polymorphisms are inconsistent in relation to coronary heart disease and cancer.

Glutathione S-transferase M1 polymorphism and sporadic colorectal cancer risk: An updating meta-analysis and HuGE review of 36 case-control studies

PURPOSE

Sporadic colorectal cancer (CRC) is considered to be a multifactorial disease, in which multiple exposures to endogenous factors interact with individual genetic background in a complex manner, resulting in modulation of the risk. The glutathione S-transferase M1 gene (GSTM1) is a particularly attractive candidate for CRC susceptibility because it codes an enzyme involved in the metabolism of environmental carcinogens. However, the epidemiological findings have been inconsistent.

METHODS

To evaluate this association, we performed an extensive meta-analysis of 36 case-control studies (including 10,009 cases and 15,070 controls).

RESULTS

Overall, the combined data showed that GSTM1 deficiency is associated with a marginal effect on CRC risk (odds ratio [OR] = 1.13; 95% confidence interval [CI]: 1.03-1.23; P for heterogeneity <0.001). When stratified by race and tumor site, significant results were only observed in Caucasians (OR = 1.14, 95% CI: 1.01-1.27; P for heterogeneity <0.001), whereas no increased risk was detected in other subgroups.

CONCLUSIONS

The findings of our study support the suggestion that GSTM1 polymorphism is associated with an increased risk of CRC, especially in the Caucasian population. Further investigation into the association between GSTM1 polymorphism and the risk of CRC is warranted and should include larger sample sizes and other genetic polymorphisms in metabolism of environmental carcinogens.

GSTM1, GSTT1, GSTP1, GSTA1 and colorectal cancer risk: a comprehensive meta-analysis

Glutathione S-transferases (GSTs) catalyse reactions between glutathione and lipophilic compounds with electrophilic centres, leading to neutralisation of toxic compounds, xenobiotics and products of oxidative stress. Controversy exists about whether GST polymorphisms (GSTM1 null/present genotype, GSTT1 null/present genotype, GSTP1 Ile105Val and GSTA1 *A/*B) represent risk factors for colorectal cancer. This meta-analysis aims to examine the associations between the above-mentioned polymorphisms and colorectal cancer risk. Forty-four studies were eligible for GSTM1 (11,998 colorectal cancer cases, 17,552 controls), 34 studies for GSTT1 (8596 cases, 13,589 controls), 19 studies for GSTP1 (5421 cases, 7671 controls) and four studies for GSTA1 polymorphism (1648 cases, 2039 controls). Pooled odds ratios (ORs) were appropriately derived from fixed-effects or random-effects models. Separate analyses were conducted on Caucasian and Chinese populations. Where appropriate, sensitivity analysis concerning the deviation of genotype frequencies in controls from the Hardy-Weinberg equilibrium was performed. GSTM1 null allele carriers exhibited increased colorectal cancer risk in Caucasian populations (pooled OR=1.150, 95% confidence interval (CI): 1.060-1.248, random effects); no significant association was detected for Chinese subjects (pooled OR=1.025, 95% CI: 0.903-1.163, fixed effects). Similarly, GSTT1 null allele carriers exhibited increased colorectal cancer risk in Caucasian populations (pooled OR=1.312, 95% CI: 1.119-1.538, random effects); the association in Chinese subjects was not significant (pooled OR=1.068, 95% CI: 0.788-1.449, random effects). Concerning GSTP1 Ile105Val no significant associations were demonstrated in either race. GSTA1 *A/*B polymorphism was not associated with colorectal cancer risk. GSTM1 and GSTT1 null genotypes confer additional risk for colorectal cancer in Caucasian populations.

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.

An updating meta-analysis of the glutathione S-transferase T1 polymorphisms and colorectal cancer risk: a HuGE review

INTRODUCTION

GSTT1 status has been extensively studied as a colorectal cancer risk factor. However, the results are inconsistent. To examine this controversy, we performed a meta-analysis to evaluate the relationship between GSTT1 polymorphism and colorectal cancer.

MATERIALS AND METHODS

We performed a literature search using PUBMED, EMBASE, Cochrane Library, and HuGNet database to February 2009, with no restrictions. All articles were independent and contained the minimum information necessary to estimate the colorectal cancer risk associated with GSTT1 null. Summary odds ratio (ORs) and 95% confidence intervals (CIs) were calculated using random-effect or fixed-effect models based on the heterogeneity of included studies.

RESULTS

A total of 23 case-control studies, including a total of 11,057 subjects (5,058 cases and 5,999 controls), that related to GSTT1 polymorphism and risk of colorectal cancer were identified and included for analysis. The random-effect meta-analyses of all the 23 studies suggested that there was a small increased risk of colorectal cancer for individuals with GSTT1 null (OR was 1.23; 95% CI 1.02-1.49; I (2) = 76.9%, P for heterogeneity <0.001). The fixed-effect meta-analyses reached a similar results in Caucasians populations of ten studies (OR = 1.39; 95% CI 1.21-1.59; I (2) = 29.8%, P for heterogeneity = 0.171) and Asians populations of five studies (OR = 1.23; 95% CI 1.04-1.45; I (2) = 0.0%, P for heterogeneity = 0.428), with as inversely association in the other ethnic populations from four studies (OR = 0.69; 95% CI 0.54-0.877; I (2) = 0.0%, P for heterogeneity = 0.58).

CONCLUSION

There was a small increased risk of colorectal cancer for individuals with GSTT1 null, especially for Caucasians populations and Asian populations.