Alcohol dehydrogenase 3, glutathione S-transferase M1 and T1 polymorphisms, alcohol consumption and hepatocellular carcinoma (Italy)

Alcohol-Induced Oxidative Stress and the Role of Antioxidants in Alcohol Use Disorder: A Systematic Review

Alcohol use disorder (AUD) is a highly prevalent, comorbid, and disabling disorder. The underlying mechanism of ethanol neurotoxicity and the involvement of oxidative stress is still not fully elucidated. However, ethanol metabolism has been associated with increased oxidative stress through alcohol dehydrogenase, the microsomal ethanol oxidation system, and catalase metabolic pathways. We searched the PubMed and genome-wide association studies (GWAS) catalog databases to review the literature systematically and summarized the findings focusing on AUD and alcohol abstinence in relation to oxidative stress. In addition, we reviewed the ClinicalTrials.gov resource of the US National Library of Medicine to identify all ongoing and completed clinical trials that include therapeutic interventions based on antioxidants. The retrieved clinical and preclinical studies show that oxidative stress impacts AUD through genetics, alcohol metabolism, inflammation, and neurodegeneration.

Critical review on the use and abuse of alcohol. When the dose makes the difference

Nowadays harmful alcohol consumption represents one of the most important risk factors for the development of several type of chronic and acute diseases in the western countries, contributing to a great number of deaths. Focusing the attention on cancer development and progression, the scientific community has a large consensus in declaring the existence of a harmful association between alcohol consumption and liver, breast, upper aerodigestive tract (mouth, oropharynx, hypopharynx, and esophagus), pancreas and colon cancer appearance. However the precise biological links by which the alcohol could be responsible for cancer initiation and progression are not fully understood yet, even if the International Agency for Research on Cancer (IARC) indicated both ethanol and acetaldehyde as carcinogen for humans. The possible explanation of the effect exerted by ethanol and acetaldehyde could be related to direct genotoxicity, hormonal disturbance, triggering of oxidative stress and inflammation. In this review, we examine the relationship between alcohol dosage and associated diseases, with focus on alcohol-related cancers. Furthermore, to understand the potential molecular mechanisms of these diseases, the results of in vivo experiments on animal models were discussed.

Alcohol and Cancer: Mechanisms and Therapies

Several scientific and clinical studies have shown an association between chronic alcohol consumption and the occurrence of cancer in humans. The mechanism for alcohol-induced carcinogenesis has not been fully understood, although plausible events include genotoxic effects of acetaldehyde, cytochrome P450 2E1 (CYP2E1)-mediated generation of reactive oxygen species, aberrant metabolism of folate and retinoids, increased estrogen, and genetic polymorphisms. Here, we summarize the impact of alcohol drinking on the risk of cancer development and potential underlying molecular mechanisms. The interactions between alcohol abuse, anti-tumor immune response, tumor growth, and metastasis are complex. However, multiple studies have linked the immunosuppressive effects of alcohol with tumor progression and metastasis. The influence of alcohol on the host immune system and the development of possible effective immunotherapy for cancer in alcoholics are also discussed here. The conclusive biological effects of alcohol on tumor progression and malignancy have not been investigated extensively using an animal model that mimics the human disease. This review provides insights into cancer pathogenesis in alcoholics, alcohol and immune interactions in different cancers, and scope and future of targeted immunotherapeutic modalities in patients with alcohol abuse.

Alcohol consumption and liver cancer risk: a meta-analysis

PURPOSE

Alcohol is a confirmed risk factor of liver cancer. Yet, its dose-response function and synergistic effects with other risk factors remain unclear.

METHODS

We performed a meta-analysis on publications up to May 2014. A total of 112 publications were identified. The meta-relative risk (mRR) and the dose-response trend were calculated. Tests for heterogeneity, publication bias, and sensitivity analyses were performed. The synergy index (SI) was recorded or calculated, whenever possible.

RESULTS

Compared to individuals who never drank or drank at very low frequencies, the mRR for ever drinkers was 1.29 (95% confidence interval, CI 1.16-1.42) and 1.46 (95% CI 1.27-1.65) for case-control studies, and 1.07 (95% CI 0.87-1.27) for cohort studies. Being a current drinker was associated with an increased liver cancer risk in case-control studies (mRR = 1.55, 95% CI 0.38-2.73), but not in cohort studies (mRR = 0.86, 95% CI 0.74-0.97). The dose-response relation between alcohol and liver cancer was apparent with RR = 1.08 (95% CI 1.04-1.11) for 12 g/day (~1 drink), 1.54 (95% CI 1.36-1.74) for 50 g/day, 2.14 (95% CI 1.74-2.62) for 75 g/day, 3.21 (95% CI 2.34-4.40) for 100 g/day, and 5.20 (95% CI 3.25-8.29) for 125 g/day of alcohol consumption. There were synergistic effects of alcohol consumption with hepatitis (S = 2.14, 95% CI 1.31-2.98) and with diabetes (S = 3.57, 95% CI 2.29-4.84) on the risk of liver cancer, although this may be subject to publication bias.

CONCLUSION

Overall, one alcoholic drink per day (~12 g/day) may be associated with a 1.1 times higher liver cancer risk. Further studies on the synergistic effects of alcohol consumption and other major risk factors are warranted.

The effect of CYP, GST, and SULT polymorphisms and their interaction with smoking on the risk of hepatocellular carcinoma

Aim. The aim of our study was to assess whether selected single nucleotide polymorphisms of CYP1A1 and 2E1, GSTM1, GSTT1, and SULT1A1 influence susceptibility towards HCC, considering their interaction with cigarette smoking. Methods. We recruited HCC cases and controls among patients admitted to the hospital "Agostino Gemelli," from January 2005 until July 2010. Odds ratios (OR) of HCC were derived from unconditional multiple logistic regression. Gene-gene and gene-smoking interaction were quantified by computing the attributable proportion (AP) due to biological interaction. Results. The presence of any CYP2E1 (*) 5B variant allele (OR: 0.23; 95% CI: 0.06-0.71) and CYP2E1 (*) 6 variant allele (OR: 0.08; 95% CI: 0.01-0.33) was inversely related to HCC. There was a borderline increased risk among carriers of combined CYP1A1 (*) 2A and SULT1A1 variant alleles (OR: 1.67; 95% CI: 0.97-3.24). A significant biological interaction was observed between GSTT1 and smoking (AP = 0.48; 95% CI: 0.001-0.815), with an OR of 3.13 (95% CI: 1.69-5.82), and borderline significant interaction was observed for SULT1A1 and smoking (AP = 0.36; 95% CI: -0.021-0.747), with an OR of 3.05 (95% CI: 1.73-5.40). Conclusion. CYP2E1 (*) 5B and CYP2E1 (*) 6 polymorphisms have a favourable effect on the development of HCC, while polymorphisms of GSTT1 and SULT1A1 might play role in increasing the susceptibility among smokers.

Glutathione and redox signaling in substance abuse

Throughout the last couple decades, the cause and consequences of substance abuse has expanded to identify the underlying neurobiological signaling mechanisms associated with addictive behavior. Chronic use of drugs, such as cocaine, methamphetamine and alcohol leads to the formation of oxidative or nitrosative stress (ROS/RNS) and changes in glutathione and redox homeostasis. Of importance, redox-sensitive post-translational modifications on cysteine residues, such as S-glutathionylation and S-nitrosylation could impact on the structure and function of addiction related signaling proteins. In this commentary, we evaluate the role of glutathione and redox signaling in cocaine-, methamphetamine- and alcohol addiction and conclude by discussing the possibility of targeting redox pathways for the therapeutic intervention of these substance abuse disorders.

Quantitative assessment of the effect of glutathione S-transferase genes GSTM1 and GSTT1 on hepatocellular carcinoma risk

Hepatocellular carcinoma (HCC) is one of the most serious health problems worldwide. As in many other diseases, environment and genetic factors are believed to be involved in the pathogenesis of HCC. Numerous epidemiologic investigations including case-control and cohort studies have suggested the association of glutathione S-transferase (GST) genetic polymorphisms and HCC risk. However, some studies have produced conflicting results. Therefore, we performed an updated meta-analysis to clarify this inconsistency and to establish a comprehensive picture of the association of the polymorphisms of GSTM1 and GSTT1 with HCC susceptibility. We searched PubMed, Embase, ISI Web of Science, and CNKI databases to identify eligible studies meeting the inclusion criteria up to August 30, 2013. Odds ratios (ORs) and 95% confidence intervals (CIs) were used to assess the strength of association. Finally, there were a total of 33 studies with 4,232 cases and 6,601 controls included in this meta-analysis. In the pooled analysis, significantly increased HCC risks were found for null genotype of GSTM1 (OR = 1.31, 95% CI = 1.07-1.61, P = 0.010, P heterogeneity < 10(-5)) and GSTT1 (OR = 1.47, 95% CI = 1.25-1.74, P < 10(-5), P heterogeneity < 10(-5)). Potential sources of heterogeneity were explored by subgroup analysis based on ethnicity, sample size, and source of control. Significant results were found among East Asians and Indians when stratified by ethnicity, while no evidence of significant associations was observed among Caucasian and African populations. In the gene-gene interaction analysis, a statistically significant increased risk for HCC was detected for individuals with combined deletion mutations in both genes compared to those with wild genotypes (OR = 1.88, 95% CI = 1.41-2.50, P < 10(-4), P heterogeneity = 0.004). The present meta-analysis demonstrated that the GSTM1 and GSTT1 null genotype may be associated with an increased risk of HCC and that individuals having the combination of both defective GST genotypes may be more susceptible to developing HCC.

Non-viral factors contributing to hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a major cause of cancer death worldwide, accounting for over half a million deaths per year. The geographic pattern of HCC incidence is parallel to exposure to viral etiologic factors. Its incidence is increasing, ranging between 3% and 9% annually depending on the geographical location, and variability in the incidence rates correspond closely to the prevalence and pattern of the primary etiologic factors. Chronic infections with hepatitis B viruses or hepatitis C viruses have both been recognized as human liver carcinogens with a combined attributable fraction of at least 75% of all HCC cases. Multiple non-viral factors have been implicated in the development of HCC. Increased body mass index and diabetes with subsequent development of non-alcoholic steatohepatitis represent significant risk factors for HCC. Other non-viral causes of HCC include iron overload syndromes, alcohol use, tobacco, oral contraceptive, aflatoxin, pesticides exposure and betel quid chewing, a prevalent habit in the developing world. Wilson disease, α-₁ antitrypsin deficiency, Porphyrias, autoimmune hepatitis, Schistosoma japonicum associated with positive hepatitis B surface antigen, and thorotrast-ray are also contributing hepatocellualar carcinoma. In addition, primary biliary cirrhosis, congestive liver disease and family history of liver cancer increase the risk of HCC incident. In conclusion, clarification of relevant non-viral causes of HCC will help to focus clinicians on those risk factors that are modifiable. The multilevel preventative approach will hopefully lead to a reduction in incidence of non-viral HCC, and a decrease in the patient morbidity and mortality as well as the societal economic burden associated with HCC.

Non-viral factors contributing to hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a major cause of cancer death worldwide, accounting for over half a million deaths per year. The geographic pattern of HCC incidence is parallel to exposure to viral etiologic factors. Its incidence is increasing, ranging between 3% and 9% annually depending on the geographical location, and variability in the incidence rates correspond closely to the prevalence and pattern of the primary etiologic factors. Chronic infections with hepatitis B viruses or hepatitis C viruses have both been recognized as human liver carcinogens with a combined attributable fraction of at least 75% of all HCC cases. Multiple non-viral factors have been implicated in the development of HCC. Increased body mass index and diabetes with subsequent development of non-alcoholic steatohepatitis represent significant risk factors for HCC. Other non-viral causes of HCC include iron overload syndromes, alcohol use, tobacco, oral contraceptive, aflatoxin, pesticides exposure and betel quid chewing, a prevalent habit in the developing world. Wilson disease, α-1 antitrypsin deficiency, Porphyrias, autoimmune hepatitis, Schistosoma japonicum associated with positive hepatitis B surface antigen, and thorotrast-ray are also contributing hepatocellualar carcinoma. In addition, primary biliary cirrhosis, congestive liver disease and family history of liver cancer increase the risk of HCC incident. In conclusion, clarification of relevant non-viral causes of HCC will help to focus clinicians on those risk factors that are modifiable. The multilevel preventative approach will hopefully lead to a reduction in incidence of non-viral HCC, and a decrease in the patient morbidity and mortality as well as the societal economic burden associated with HCC.

Etiological and molecular profile of hepatocellular cancer from India

Hepatocellular carcinoma (HCC) cases are underreported in India. Our study was designed to investigate the etiological profile of HCC cases in India and compare with global incidence. The study included 348 HCC and 375 chronic liver disease cases without HCC as controls. Samples were screened for hepatitis B virus (HBV)/hepatitis C virus (HCV) infections using enzyme-linked immunosorbent assay and polymerase chain reaction (PCR). HBV-DNA and HCV-RNA genotyping was performed by PCR-restriction fragment length polymorphism. All cases were also assessed for other possible risk factors of HCC. Among HCC cases, 62.6% were positive for HBV, 26.7% for HCV and 3.2% had coinfection. Around 17% of HCC cases had aflatoxin-B1 exposure. HBV genotype D (odds ratio, OR = 1.76) and mixed genotypes (OR = 6.86) had higher risk of HCC development. The risk of HCC was twofold (OR = 2.26) in patients with high HBV-DNA levels. Moreover, our findings were unable to establish a clear differential effect of HCV genotype (OR = 1.48) and high viral load (OR = 1.21) on HCC development. In India, HBV is the major risk factors, whereas alcohol, smoking and diabetes are nonsignificantly associated. Asian countries such as Hong Kong and Taiwan also had high incidence of HBV-related HCC. Contrarily, countries from Europe and USA reported HCV as predominant cause of HCC. Further, aflatoxin could be a possible risk of HCC in the population. However, in comparison to the countries such as China and Taiwan (high Aflatoxin exposure), the aflatoxin level is relatively low in our patients. High HBV-DNA levels and HBV/D increased the risk of HCC. However, neither genotype nor virus loads of HCV affected prognosis of HCC patients in our study.

Genetic polymorphisms of glutathione S-transferase genes GSTM1, GSTT1 and risk of hepatocellular carcinoma

BACKGROUND

A number of case-control studies were conducted to investigate the association of glutathione S-transferase (GST) genetic polymorphisms and hepatocellular carcinoma (HCC) risk. However, these studies have yielded contradictory results. We therefore performed a meta-analysis to derive a more precise estimation of the association between polymorphisms on GSTM1, GSTT1 and HCC.

METHODOLOGY/PRINICPAL FINDINGS

PubMed, EMBASE, ISI web of science and the CNKI databases were systematically searched to identify relevant studies. Data were abstracted independently by two reviewers. Odds ratios (ORs) and 95% confidence intervals (95% CIs) were used to assess the strength of association. Potential sources of heterogeneity were also assessed by subgroup analysis and meta-regression. Funnel plots and Egger's linear regression were used to test publication bias among the articles. A total of 34 studies including 4,463 cases and 6,857 controls were included in this meta-analysis. In a combined analysis, significantly increased HCC risks were found for null genotype of GSTM1 (OR = 1.29, 95% CI: 1.06-1.58; P = 0.01) and GSTT1 (OR = 1.43, 95% CI: 1.22-1.68; P<10(-5)). Potential sources of heterogeneity were explored by subgroup analysis and meta-regression. Significant results were found in East Asians and Indians when stratified by ethnicity; whereas no significant associations were found among Caucasians and African populations. By pooling data from 12 studies that considered combinations of GSTT1 and GSTM1 null genotypes, a statistically significant increased risk for HCC (OR = 1.88, 95% CI: 1.41-2.50; P<10(-4)) was detected for individuals with combined deletion mutations in both genes compared with positive genotypes.

CONCLUSIONS/SIGNIFICANCE

This meta-analysis suggests that the GSTM1 and GSTT1 null genotype may slightly increase the risk of HCC and that interaction between unfavourable GSTs genotypes may exist.

Proteomics for the discovery of nuclear bile acid receptor FXR targets

Nuclear receptors (NRs) are important pharmacological targets for a number of diseases, including cancer and metabolic disorders. To unmask the direct role of NR function it is fundamental to find the NR targets. During the last few years several NRs have been shown to affect microRNA expression, thereby modulating protein levels. The farnesoid X receptor (FXR), the main regulator of bile acid (BA) homeostasis, also regulates cholesterol, lipid and glucose metabolism. Here we used, for the first time, a proteomics approach on mice treated with a FXR ligand to find novel hepatic FXR targets. Nineteen spots with a more than two-fold difference in protein amounts were found by 2D-DIGE and 20 proteins were identified by MALDI-TOF MS as putative novel FXR targets. The most striking feature of the protein list was the great number of mitochondrial proteins, indicating a substantial impact of FXR activation on mitochondrial function in the liver. To examine if the differences found in the proteomics assay reflected differences at the mRNA level, a microarray assay was generated on hepatic samples from wild type and FXR^−/− mice treated with a FXR ligand and compared to vehicle treatment. At least six proteins were shown to be regulated only at a post-transcriptional level. In conclusion, our study provides the impetus to include proteomic analysis for the identification of novel targets of transcription factors, such as NRs. This article is part of a Special Issue entitled: Translating nuclear receptors from health to disease.

Null genotypes of GSTM1 and GSTT1 contribute to hepatocellular carcinoma risk: evidence from an updated meta-analysis

BACKGROUND & AIMS

Studies investigating the associations between glutathione S-transferase (GST) genetic polymorphisms and hepatocellular carcinoma (HCC) risk have reported controversial results. Thus, a meta-analysis was performed to clarify the effects of GSTM1 and GSTT1 polymorphisms on HCC risk.

METHODS

We identified 132 relevant records through a literature search up to November 22, 2009, and 24 individual case-control studies from 23 publications were finally included, involving a total of 3349 HCC cases and 5609 controls. Subgroup analyses were performed by ethnicity, or by area according to the incidence rate and hepatitis virus status.

RESULTS

Analyses of total relevant studies showed an increased HCC risk was significantly associated with null genotypes of GSTM1 (OR=1.26, 95% CI 1.03-1.54, p(OR)=0.027) and GSTT1 (OR=1.28, 95% CI 1.09-1.51, p(OR)=0.002). In addition, the GSTM1-GSTT1 interaction analysis showed that the dual null genotype of GSTM1/GSTT1 was significantly associated with increased HCC risk (OR=1.89, 95% CI 1.38-2.60, p(OR)<0.001). Subgroup analyses showed that the associations above were still statistically significant in Asians (p(GSTM1)=0.017, p(GSTT1)=0.001, p(Dual null genotype)<0.001), high-rate areas (p(GSTM1)=0.012, p(GSTT1)=0.006, p(Dual null genotype)<0.001), and HBV-dominant areas (p(GSTM1)=0.003, p(GSTT 1)=0.003, p(Dual null genotype)<0.001).

CONCLUSIONS

This meta-analysis suggests null genotypes of GSTM1 and GSTT1 are both associated with increased HCC risk in Asians, and individuals with the dual null genotype of GSTM1/GSTT1 are particularly susceptible to developing HCC.

Non-viral causes of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the most common primary liver malignancy and represents an international public health concern as one of the most deadly cancers worldwide. The main etiology of HCC is chronic infection with hepatitis B and hepatitis C viruses. However, there are other important factors that contribute to the international burden of HCC. Among these are obesity, diabetes, non-alcoholic steatohepatitis and dietary exposures. Emerging evidence suggests that the etiology of many cases of HCC is in fact multifactorial, encompassing infectious etiologies, comorbid conditions and environmental exposures. Clarification of relevant non-viral causes of HCC will aid in preventative efforts to curb the rising incidence of this disease.

Alcohol and genetic polymorphisms: effect on risk of alcohol-related cancer

Public health guidelines aim to limit the consumption of alcoholic beverages worldwide and the subsequent health burden. In particular, alcohol consumption is an avoidable risk factor for cancer. In human beings, ethanol in alcoholic drinks is mainly oxidised in the liver by alcohol dehydrogenases to acetaldehyde, and is further detoxified to acetate by aldehyde dehydrogenases. Functional variants in genes involved in alcohol metabolism result in differences between individuals in exposure to carcinogenic acetaldehyde, suggesting a possible interaction of genetic susceptibility and alcohol exposure in cancer. We reviewed available studies of the combined effects of alcohol drinking and genetic polymorphisms on alcohol-related cancer risk. Most available data were for polymorphisms in alcohol and folate metabolism. We give an overview of published studies on the combined effects of alcohol drinking and polymorphisms in genes for alcohol dehydrogenase (ADH), aldehyde dehydrogenase (ALDH), cytochrome P450 2E1, and methylene-tetrahydrofolate reductase on the risk of alcohol-related cancer. Current data lend support to a role of polymorphisms ADH1B and ALDH2 combined with alcohol consumption in cancer. Other available data are insufficient or inconclusive, highlighting the need for additional studies.

Recent progress in genomic [corrected] research of liver cancer

Along the course of occurrence and development of liver cancer, the corresponding somatic cells accumulate some important genetic variations. These variations may be divided into two categories. For the genetic changes closely related to etiology of liver cancer, the well-known cases include insertion and integration of the hepatitis B virus (HBV) DNA after infection, and mutations at site 249 of the tumor suppressor gene p53 induced by exposure to aflatoxin B1. The secondary genetic changes include amplification and deletion of certain chromosome regions, mutations in p53 at the sites other than 249, as well as the mutational activation of the Wnt/beta-catenin signal pathway. The tumor cells with these genetic variations may gradually become the dominant clones under evolutionary selection. Besides, identification of genetic susceptible against risk of liver malignancy is also an important aspect of research in this field.

Glutathione-S-transferase expression in the brain: possible role in ethanol preference and longevity

Identification of genes that are differentially expressed in rats bidirectionally selected for alcohol preference might reveal biological mechanisms underlying alcoholism or related phenotypes. Microarray analysis from medial prefrontal cortex (mPFC), a key brain region for drug reward, indicated increased expression of glutathione-S-transferases of the alpha (Gsta4) and mu (Gstm1-5) classes in ethanol-preferring AA rats compared with nonpreferring ANA rats. Real-time RT polymerase chain reaction (RT-PCR) analysis demonstrated approximately 2-fold higher Gsta4 transcript levels in several brain regions of ethanol-naive AA compared with ANA rats. Differences in mRNA levels were accompanied by differential levels of GSTA4 protein. We identified a novel haplotype variant in the rat Gsta4 gene, defined here as var3. Allele frequencies of var3 were markedly different between AA and ANA rats, 52% and 100%, respectively. Gsta4 expression was strongly correlated with the gene dose of var3, with approximately 60% of the variance in expression accounted for by genotype at this locus. The contribution of glutathione S-transferase expression to the ethanol-preferring phenotype is presently unclear. It could, however, underlie observed differences in life span between AA and ANA lines, prompting a utility of this animal model in aging research.

Southern Europe as an example of interaction between various environmental factors: a systematic review of the epidemiologic evidence

Hepatitis B virus (HBV), hepatitis C virus (HCV) and alcohol consumption are major causes of hepatocellular carcinoma (HCC) worldwide. We performed a systematic review of epidemiologic studies carried out on HCC aetiology in Southern Europe, an area with an intermediate-high prevalence of these agents as well as of putative risk factors such as tobacco smoking, diabetes and obesity. To retrieve the articles, we performed a Medline search for titles and abstracts of articles. After the Medline search, we reviewed the papers and reference lists to identify additional articles. A synergism between HCV infection and HBV infection, overt (hepatitis B virus antigen (HbsAg) positivity) or occult (HBsAg negativity with presence of HBV DNA in liver or serum), is suggested by the results of some studies. The pattern of the risk for HCC due to alcohol intake shows a continuous dose-effect curve without a definite threshold, although most studies found that HCC risk increased only for alcohol consumption above 40-60 g of ethanol per day. Some evidence supports a positive interaction of alcohol intake probably with HCV infection and possibly with HBV infection. A few studies found that coffee has a protective effect on HCC risk due to various risk factors. Some data also support a role of tobacco smoking, diabetes and obesity as single agents or preferably co-factors in causing HCC. In countries with a relatively high alcohol consumption and intermediate levels of HCV and HBV infections (1-3% of population infected by each virus), such as Mediterranean countries, the three main risk factors together account for about 85% of the total HCC cases, leaving little space to other known risk factors, such as haemochromatosis, and to new, still unrecognised, factors as independent causes of HCC.