The association between UGT1A7 polymorphism and cancer risk: A meta-analysis

The Uridine diphosphate (UDP)-glycosyltransferases (UGTs) superfamily: the role in tumor cell metabolism

UDP-glycosyltransferases (UGTs), important enzymes in biotransformation, control the levels and distribution of numerous endogenous signaling molecules and the metabolism of a wide range of endogenous and exogenous chemicals. The UGT superfamily in mammals consists of the UGT1, UGT2, UGT3, and UGT8 families. UGTs are rate-limiting enzymes in the glucuronate pathway, and in tumors, they are either overexpressed or underexpressed. Alterations in their metabolism can affect gluconeogenesis and lipid metabolism pathways, leading to alterations in tumor cell metabolism, which affect cancer development and prognosis. Glucuronidation is the most common mammalian conjugation pathway. Most of its reactions are mainly catalyzed by UGT1A, UGT2A and UGT2B. The body excretes UGT-bound small lipophilic molecules through the bile, urine, or feces. UGTs conjugate a variety of tiny lipophilic molecules to sugars, such as galactose, xylose, acetylglucosamine, glucuronic acid, and glucose, thereby inactivating and making water-soluble substrates, such as carcinogens, medicines, steroids, lipids, fatty acids, and bile acids. This review summarizes the roles of members of the four UGT enzyme families in tumor function, metabolism, and multiple regulatory mechanisms, and its Inhibitors and inducers. The function of UGTs in lipid metabolism, drug metabolism, and hormone metabolism in tumor cells are among the most important topics covered.

Genome-wide DNA copy number profiling and bioinformatics analysis of ovarian cancer reveals key genes and pathways associated with distinct invasive/migratory capabilities

Ovarian cancer (OC) metastasis presents major hurdles that must be overcome to improve patient outcomes. Recent studies have demonstrated copy number variations (CNVs) frequently contribute to alterations in oncogenic drivers. The present study used a CytoScan HD Array to analyse CNVs and loss of heterozygosity (LOH) in the entire genomes of 6 OC patients and human OC cell lines to determine the genetic target events leading to the distinct invasive/migratory capacities of OC. The results showed that LOH at Xq11.1 and Xp21.1 and gains at 8q21.13 were novel, specific CNVs. Ovarian cancer-related CNVs were then screened by bioinformatics analysis. In addition, transcription factors-target gene interactions were predicted with information from PASTAA analysis. As a result, six genes (i.e., GAB2, AKT1, EGFR, COL6A3, UGT1A1 and UGT1A8) were identified as strong candidates by integrating the above data with gene expression and clinical outcome data. In the transcriptional regulatory network, 4 known cancer-related transcription factors (TFs) interacted with 6 CNV-driven genes. The protein/DNA arrays revealed 3 of these 4 TFs as potential candidate gene-related transcription factors in OC. We then demonstrated that these six genes can serve as potential biomarkers for OC. Further studies are required to elucidate the pathogenesis of OC.

Interethnic Variations of UGT1A1 and UGT1A7 Polymorphisms in the Jordanian Population

BACKGROUND

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSION

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

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.

Investigation of miR-136-5p key target genes and pathways in lung squamous cell cancer based on TCGA database and bioinformatics analysis

BACKGROUND

Lung squamous cell cancer (LUSC) is a common but challenging malignancy. It is important to illuminate the molecular mechanism of LUSC. Thus, we aim to explore the molecular mechanism of miR-136-5p in relation to LUSC.

METHODS

We used the Cancer Genome Atlas (TCGA) database to investigate the expression of miR-136-5p in relation to LUSC. Then, we identified the possible miR-136-5p target genes through intersection of the predicted miR-136-5p target genes and LUSC upregulated genes from TCGA. Bioinformatics analysis was performed to determine the key miR-136-5p targets and pathways associated with LUSC. Finally, the expression of hub genes, correlation between miR-136-5p and hub genes, and expected significance of hub genes were evaluated via the TCGA and Genotype-Tissue Expression (GTEx) project.

RESULTS

MiR-136-5p was significantly downregulated in LUSC patients. Glucuronidation, glucuronosyltransferase, and the retinoic acid metabolic process were the most enriched metabolic interactions in LUSC patients. Ascorbate and aldarate metabolism, pentose and glucuronate interconversions, and retinol metabolism were identified as crucial pathways. Seven hub genes (UGT1A1, UGT1A3, UGT1A6, UGT1A7, UGT1A10, SRD5A1, and ADH7) were found to be upregulated, and UGT1A1, UGT1A3, UGT1A6, UGT1A7, and ADH7 were negatively correlated with miR-136-5p. UGT1A7 and ADH7 were the most significantly involved miR-136-5p target genes, and high expression of these genes was correlated with better overall survival and disease-free survival of LUSC patients.

CONCLUSIONS

Downregulated miR-136-5p may target UGT1A7 and ADH7 and participate in ascorbate and aldarate metabolism, pentose and glucuronate interconversions, and retinol metabolism. High expression of UGT1A7 and ADH7 may indicate better prognosis of LUSC patients.

UGT1A polymorphisms as genetic biomarkers for hepatocellular carcinoma risk in Caucasian population

BACKGROUND & AIMS

The definition of new biomarkers of hepatocellular carcinoma (HCC) risk, especially in high-risk HBV/HCV-positive population, is urgently needed to improve HCC clinical management. This study focused on variants of UDP-glucuronosyltransferase 1A (UGT1A) enzymes that catalyse the reaction of glucuronidation, one of the most important chemical defence pathway of the body. The aim of this study was to elucidate the contribution of UGT1A polymorphisms in predicting HCC susceptibility in Caucasians.

METHODS

In this retrospective case-control analysis, 192 HCC liver transplanted patients represent the study group. Two age/sex-matched groups were used as control, one composed of 167 HBV- and/or HCV-infected individuals, and the other of 192 healthy subjects. All the cases were characterized for a panel of UGT1A1, UGT1A7 and UGT1A9 variants. The study end-point was the association between UGT1A markers and HCC onset.

RESULTS

UGT1A7*3 allele emerged as a protective marker for HCC development among both high-risk HBV/HCV-positive patients (OR=0.64, P=.0026), and healthy subjects (OR=0.47, P=.0051). UGT1A1*28 (OR=0.61, P=.0013) and UGT1A9*22 (OR=2.18, P=.0003) alleles were also associated to HCC occurrence, especially among healthy subjects. UGT1A haplotype, summarizing the UGT1A genetic alterations, confirmed the protective role against HCC development emerged for low-activity alleles. The observed associations could probably be linked to an increase of serum levels of health-beneficial molecules including free bilirubin.

CONCLUSION

A predictive effect of UGT1A polymorphisms on HCC risk was identified. If confirmed, these findings could contribute to improve the HCC surveillance, treatment tailoring and patients care.

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.

Gene-environment interactions in esophageal cancer

Esophageal cancer (EC) is one of the most common malignancies in low- and medium-income countries and represents a disease of public health importance because of its poor prognosis and high mortality rate in these regions. The striking variation in the prevalence of EC among different ethnic groups suggests a significant contribution of population-specific environmental and dietary factors to susceptibility to the disease. Although individuals within a demarcated geographical area are exposed to the same environment and share similar dietary habits, not all of them will develop the disease; thus genetic susceptibility to environmental risk factors may play a key role in the development of EC. A wide range of xenobiotic-metabolizing enzymes are responsible for the metabolism of carcinogens introduced via the diet or inhaled from the environment. Such dietary or environmental carcinogens can bind to DNA, resulting in mutations that may lead to carcinogenesis. Genes involved in the biosynthesis of these enzymes are all subject to genetic polymorphisms that can lead to altered expression or activity of the encoded proteins. Genetic polymorphisms may, therefore, act as molecular biomarkers that can provide important predictive information about carcinogenesis. The aim of this review is to discuss our current knowledge on the genetic risk factors associated with the development of EC in different populations; it addresses mainly the topics of genetic polymorphisms, gene-environment interactions, and carcinogenesis. We have reviewed the published data on genetic polymorphisms of enzymes involved in the metabolism of xenobiotics and discuss some of the potential gene-environment interactions underlying esophageal carcinogenesis. The main enzymes discussed in this review are the glutathione S-transferases (GSTs), N-acetyltransferases (NATs), cytochrome P450s (CYPs), sulfotransferases (SULTs), UDP-glucuronosyltransferases (UGTs), and epoxide hydrolases (EHs), all of which have key roles in the detoxification of environmental and dietary carcinogens. Finally, we discuss recent advances in the study of genetic polymorphisms associated with EC risk, specifically with regard to genome-wide association studies, and examine possible challenges of case-control studies that need to be addressed to better understand the interaction between genetic and environmental factors in esophageal carcinogenesis.

Transcriptional regulation of human UDP-glucuronosyltransferase genes

Glucuronidation is an important metabolic pathway for many small endogenous and exogenous lipophilic compounds, including bilirubin, steroid hormones, bile acids, carcinogens and therapeutic drugs. Glucuronidation is primarily catalyzed by the UDP-glucuronosyltransferase (UGT) 1A and two subfamilies, including nine functional UGT1A enzymes (1A1, 1A3-1A10) and 10 functional UGT2 enzymes (2A1, 2A2, 2A3, 2B4, 2B7, 2B10, 2B11, 2B15, 2B17 and 2B28). Most UGTs are expressed in the liver and this expression relates to the major role of hepatic glucuronidation in systemic clearance of toxic lipophilic compounds. Hepatic glucuronidation activity protects the body from chemical insults and governs the therapeutic efficacy of drugs that are inactivated by UGTs. UGT mRNAs have also been detected in over 20 extrahepatic tissues with a unique complement of UGT mRNAs seen in almost every tissue. This extrahepatic glucuronidation activity helps to maintain homeostasis and hence regulates biological activity of endogenous molecules that are primarily inactivated by UGTs. Deciphering the molecular mechanisms underlying tissue-specific UGT expression has been the subject of a large number of studies over the last two decades. These studies have shown that the constitutive and inducible expression of UGTs is primarily regulated by tissue-specific and ligand-activated transcription factors (TFs) via their binding to cis-regulatory elements (CREs) in UGT promoters and enhancers. This review first briefly summarizes published UGT gene transcriptional studies and the experimental models and tools utilized in these studies, and then describes in detail the TFs and their respective CREs that have been identified in the promoters and/or enhancers of individual UGT genes.

Quantitative assessment of the association between XPG Asp1104His polymorphism and bladder cancer risk

Published data regarding the association between XPG Asp1104His polymorphism and bladder cancer risk remained controversial. This meta-analysis of literatures was performed to draw a more precise estimation of the relationship. We systematically searched PubMed, Embase, and Web of Science with a time limit of June 22, 2013. Summary odds ratios (ORs) with 95 % CIs were used to assess the strength of the association between XPG Asp1104His polymorphism and bladder cancer risk using random effects model. A total of eight case-control studies including 2,613 cases and 2,934 controls were included for analysis. Overall, no significant association was found between XPG Asp1104His polymorphism and bladder cancer susceptibility for CC vs. GG (OR = 1.12, 95 % CI = 0.74-1.69), GC vs. GG (OR = 1.12, 95 % CI = 0.86-1.46), the dominant model CC + GC vs. GG (OR = 1.08, 95 % CI = 0.85-1.38), and the recessive model CC vs. GC + GG (OR = 0.92, 95 % CI = 0.66-1.29). In the subgroup analysis, no significant associations were found in either Asian or non-Asian population. This meta-analysis suggested that XPG Asp1104His polymorphism was not associated with bladder cancer risk.

Malignancies after kidney transplantation: Hong Kong renal registry

Manystudies have shown that kidney transplant recipients have a higher incidence of cancers when compared with general population. However, most data on the posttransplant malignancies (PTM) are derived from Western literature and large population-based studies are rare. There is also lack of information about the posttransplant cancer-specific mortality rate. We conducted a population-based study of 4895 kidney transplants between 1972 and 2011, with data from the Hong Kong Renal Registry. Patterns of cancer incidence and mortality in our kidney transplant recipients were compared with those of the general population using standardized incidence ratios (SIRs) and standardized mortality ratios (SMRs) respectively. With 40 246 person-years of follow-up, 299 PTM was diagnosed. The SIR of all cancers was 2.94 (female 3.58 and male 2.58). Non-Hodgkin lymphoma (NHL), kidney, and bladder cancers had the highest SIRs. The overall SMR was 2.3 (female 3.4 and male 1.7) and the highest SMR was NHL. The patterns of PTM differ among countries. Increases in cancer incidence can now translate into similar increases in cancer mortality. NHL is important in our kidney transplant recipients. Strategies in cancer screening in selected patient groups are needed to improve transplant outcomes.