Felix Stickel

Molecular mechanisms of alcohol-mediated carcinogenesis.

Approximately 3.6% of cancers worldwide derive from chronic alcohol drinking, including those of the upper aerodigestive tract, the liver, the colorectum and the breast. Although the mechanisms for alcohol-associated carcinogenesis are not completely understood, most recent research has focused on acetaldehyde, the first and most toxic ethanol metabolite, as a cancer-causing agent. Ethanol may also stimulate carcinogenesis by inhibiting DNA methylation and by interacting with retinoid metabolism. Alcohol-related carcinogenesis may interact with other factors such as smoking, diet and comorbidities, and depends on genetic susceptibility.

Genetic variation in the PNPLA3 gene is associated with alcoholic liver injury in caucasians.

A recent genome‐wide study revealed an association between variation in the PNPLA3 gene and liver fat content. In addition, the PNPLA3 single‐nucleotide polymorphism rs738409 (M148I) was reported to be associated with advanced alcoholic liver disease in alcohol‐dependent individuals of Mestizo descent. We therefore evaluated the impact of rs738409 on the manifestation of alcoholic liver disease in two independent German cohorts. Genotype and allele frequencies of rs738409 (M148I) were determined in 1,043 alcoholic patients with or without alcoholic liver injury and in 376 at‐risk drinkers from a population‐based cohort. Relative to alcoholic patients without liver damage (n = 439), rs738409 genotype GG was strongly overrepresented in patients with alcoholic liver cirrhosis (n = 210; OR 2.79; Pgenotype = 1.2 × 10−5; Pallelic = 1.6 × 10−6) and in alcoholic patients without cirrhosis but with elevated alanine aminotransferase levels (n = 219; OR 2.33; Pgenotype = 0.0085; Pallelic = 0.0042). The latter, biochemically defined association was confirmed in an independent population‐based cohort of at‐risk drinkers with a median alcohol intake of 300 g/week (OR 4.75; Pgenotype = 0.040; Pallelic = 0.022), and for aspartate aminotransferase (AST) levels. Frequencies of allele PNPLA3 rs738409(G) in individuals with steatosis and normal alanine aminotransferase (ALT) and AST levels were lower than in alcoholics without steatosis and normal ALT/AST (Pcombined = 0.03). The population attributable risk of cirrhosis in alcoholic carriers of allele PNPLA3 rs738409(G) was estimated at 26.6%. Conclusion: Genotype PNPLA3 rs738409(GG) is associated with alcoholic liver cirrhosis and elevated aminotransferase levels in alcoholic Caucasians. (HEPATOLOGY 2011)

Risk factors and mechanisms of hepatocarcinogenesis with special emphasis on alcohol and oxidative stress.

Abstract Hepatocellular cancer is the fifth most frequent cancer in men and the eighth in women worldwide. Established risk factors are chronic hepatitis B and C infection, chronic heavy alcohol consumption, obesity and type 2 diabetes, tobacco use, use of oral contraceptives, and aflatoxin-contaminated food. Almost 90% of all hepatocellular carcinomas develop in cirrhotic livers. In Western countries, attributable risks are highest for cirrhosis due to chronic alcohol abuse and viral hepatitis B and C infection. Among those with alcoholic cirrhosis, the annual incidence of hepatocellular cancer is 1–2%. An important mechanism implicated in alcohol-related hepatocarcinogenesis is oxidative stress from alcohol metabolism, inflammation, and increased iron storage. Ethanol-induced cytochrome P-450 2E1 produces various reactive oxygen species, leading to the formation of lipid peroxides such as 4-hydroxy-nonenal. Furthermore, alcohol impairs the antioxidant defense system, resulting in mitochondrial damage and apoptosis. Chronic alcohol exposure elicits hepatocyte hyperregeneration due to the activation of survival factors and interference with retinoid metabolism. Direct DNA damage results from acetaldehyde, which can bind to DNA, inhibit DNA repair systems, and lead to the formation of carcinogenic exocyclic DNA etheno adducts. Finally, chronic alcohol abuse interferes with methyl group transfer and may thereby alter gene expression.

Acetaldehyde as an underestimated risk factor for cancer development: role of genetics in ethanol metabolism

Chronic ethanol consumption is a strong risk factor for the development of certain types of cancer including those of the upper aerodigestive tract, the liver, the large intestine and the female breast. Multiple mechanisms are involved in alcohol-mediated carcinogenesis. Among those the action of acetaldehyde (AA), the first metabolite of ethanol oxidation is of particular interest. AA is toxic, mutagenic and carcinogenic in animal experiments. AA binds to DNA and forms carcinogenic adducts. Direct evidence of the role of AA in alcohol-associated carcinogenesis derived from genetic linkage studies in alcoholics. Polymorphisms or mutations of genes coding for AA generation or detoxifying enzymes resulting in elevated AA concentrations are associated with increased cancer risk. Approximately 40% of Japanese, Koreans or Chinese carry the AA dehydrogenase 2*2 (ALDH2*2) allele in its heterozygous form. This allele codes for an ALDH2 enzyme with little activity leading to high AA concentrations after the consumption of even small amounts of alcohol. When individuals with this allele consume ethanol chronically, a significant increased risk for upper alimentary tract and colorectal cancer is noted. In Caucasians, alcohol dehydrogenase 1C*1 (ADH1C*1) allele encodes for an ADH isoenzyme which produces 2.5 times more AA than the corresponding allele ADH1C*2. In studies with moderate to high alcohol intake, ADH1C*1 allele frequency and rate of homozygosity was found to be significantly associated with an increased risk for cancer of the upper aerodigestive tract, the liver, the colon and the female breast. These studies underline the important role of acetaldehyde in ethanol-mediated carcinogenesis.

DNA Methylation Analysis in Nonalcoholic Fatty Liver Disease Suggests Distinct Disease-Specific and Remodeling Signatures after Bariatric Surgery

Nonalcoholic fatty liver disease (NAFLD) is the most common chronic liver disorder in industrialized countries. Liver samples from morbidly obese patients (n = 45) with all stages of NAFLD and controls (n = 18) were analyzed by array-based DNA methylation and mRNA expression profiling. NAFLD-specific expression and methylation differences were seen for nine genes coding for key enzymes in intermediate metabolism (including PC, ACLY, and PLCG1) and insulin/insulin-like signaling (including IGF1, IGFBP2, and PRKCE) and replicated by bisulfite pyrosequening (independent n = 39). Transcription factor binding sites at NAFLD-specific CpG sites were >1,000-fold enriched for ZNF274, PGC1A, and SREBP2. Intraindividual comparison of liver biopsies before and after bariatric surgery showed NAFLD-associated methylation changes to be partially reversible. Postbariatric and NAFLD-specific methylation signatures were clearly distinct both in gene ontology and transcription factor binding site analyses, with >400-fold enrichment of NRF1, HSF1, and ESRRA sites. Our findings provide an example of treatment-induced epigenetic organ remodeling in humans.

Hepatitis induced by Kava (Piper methysticum rhizoma).

BACKGROUND/AIMS Botanical drugs are widely used and often contain highly active compounds. Kava root (Piper methysticum rhizoma), used frequently in Europe as a remedy against anxiety, contains kavapyrones with sedative effects. Seven case reports suggested the development of hepatitis after the intake of Kava. METHODS We analyzed 29 novel cases of hepatitis along with Kava ingestion which occurred between 1990 and 2002 in addition to the seven already published case reports using a clinical diagnostic scale established for adverse hepatic drug reactions. RESULTS Hepatic necrosis or cholestatic hepatitis were noticed with both alcoholic and acetonic Kava extracts. The majority of the 29 patients and the additional seven published reports were women (27 females, nine males). Both the cumulative dose and the latency to when the hepatotoxic reaction emerged were highly variable. Nine patients developed fulminant liver failure, of which eight patients underwent liver transplantation. Three patients died, two following unsuccessful liver transplantation and one without. In all other patients, a complete recovery was noticed after the withdrawal of Kava. Pathophysiologically, both immunoallergic and idiosyncratic factors may be responsible. CONCLUSIONS The present report emphasizes the potentially severe hepatotoxicity of Kava which has recently led to the retraction of Kava-containing drugs by the pharmacovigilance authorities in Germany.

Cocarcinogenic effects of alcohol in hepatocarcinogenesis

Alcohol is a major aetiological factor in hepatocarcinogenesis but our understanding of its importance as a modulating factor is just beginning to emerge. In the present review, a number of possible cofactors and mechanisms are discussed by which alcohol may enhance the development of hepatoma. These include dietary or environmental carcinogens ingested along with alcoholic beverages, alcoholic cirrhosis as a precancerous condition, and the effects of alcohol metabolism.

Genome-Wide Association Study Identifies Variants Associated With Autoimmune Hepatitis Type 1

BACKGROUND & AIMS Autoimmune hepatitis (AIH) is an uncommon autoimmune liver disease of unknown etiology. We used a genome-wide approach to identify genetic variants that predispose individuals to AIH. METHODS We performed a genome-wide association study of 649 adults in The Netherlands with AIH type 1 and 13,436 controls. Initial associations were further analyzed in an independent replication panel comprising 451 patients with AIH type 1 in Germany and 4103 controls. We also performed an association analysis in the discovery cohort using imputed genotypes of the major histocompatibility complex region. RESULTS We associated AIH with a variant in the major histocompatibility complex region at rs2187668 (P = 1.5 × 10(-78)). Analysis of this variant in the discovery cohort identified HLA-DRB1*0301 (P = 5.3 × 10(-49)) as a primary susceptibility genotype and HLA-DRB1*0401 (P = 2.8 × 10(-18)) as a secondary susceptibility genotype. We also associated AIH with variants of SH2B3 (rs3184504, 12q24; P = 7.7 × 10(-8)) and CARD10 (rs6000782, 22q13.1; P = 3.0 × 10(-6)). In addition, strong inflation of association signal was found with single-nucleotide polymorphisms associated with other immune-mediated diseases, including primary sclerosing cholangitis and primary biliary cirrhosis, but not with single-nucleotide polymorphisms associated with other genetic traits. CONCLUSIONS In a genome-wide association study, we associated AIH type 1 with variants in the major histocompatibility complex region, and identified variants of SH2B3and CARD10 as likely risk factors. These findings support a complex genetic basis for AIH pathogenesis and indicate that part of the genetic susceptibility overlaps with that for other immune-mediated liver diseases.

Pharmacological Inhibition of Integrin αvβ3 Aggravates Experimental Liver Fibrosis and Suppresses Hepatic Angiogenesis

The vitronectin receptor integrin αvβ3 promotes angiogenesis by mediating migration and proliferation of endothelial cells, but also drives fibrogenic activation of hepatic stellate cells (HSCs) in vitro. Expecting antifibrotic synergism, we studied the effect of αvβ3 inhibition in two in vivo models of liver fibrogenesis. Liver fibrosis was induced in rats by way of bile duct ligation (BDL) for 6 weeks or thioacetamide (TAA) injections for 12 weeks. A specific αvβ3 (αvβ5) inhibitor (Cilengitide) was given intraperitoneally twice daily at 15 mg/kg during BDL or after TAA administration. Liver collagen was determined as hydroxyproline, and gene expression was quantified by way of quantitative polymerase chain reaction. Liver angiogenesis, macrophage infiltration, and hypoxia were assessed by way of CD31, CD68 and hypoxia‐inducible factor‐1α immunostaining. Cilengitide decreased overall vessel formation. This was significant in portal areas of BDL and septal areas of TAA fibrotic rats and was associated with a significant increase of liver collagen by 31% (BDL) and 27% (TAA), and up‐regulation of profibrogenic genes and matrix metalloproteinase‐13. Treatment increased gamma glutamyl transpeptidase in both models, while other serum markers remained unchanged. αvβ3 inhibition resulted in mild liver hypoxia, as evidenced by up‐regulation of hypoxia‐inducible genes. Liver infiltration by macrophages/Kupffer cells was not affected, although increases in tumor necrosis factor α, interleukin‐18, and cyclooxygenase‐2 messenger RNA indicated modest macrophage activation. Conclusion: Specific inhibition of integrin αvβ3 (αvβ5) in vivo decreased angiogenesis but worsened biliary (BDL) and septal (TAA) fibrosis, despite its antifibrogenic effect on HSCs in vitro. Angiogenesis inhibitors should be used with caution in patients with hepatic fibrosis. (HEPATOLOGY 2009.)

Non-alcoholic fatty liver disease as a risk factor for hepatocellular carcinoma: mechanisms and implications

The pathophysiological significance of hepatic lipid accumulation in the absence of significant alcohol consumption is increasingly recognised. Thus, non-alcoholic fatty liver disease (NAFLD) is now considered the most common cause of liver enzyme elevation in Western countries.1 It is regarded as the hepatic manifestation of the metabolic syndrome (MS), characterised by central obesity and insulin resistance (IR), and resulting diabetes type 2, dyslipidaemia and hypertension.2 NAFLD encompasses mild hepatic steatosis to steatohepatitis (non-alcoholic steatohepatitis (NASH)) with significant necroinflammation and progressive fibrosis. NAFLD is believed to account for a large fraction, if not entirely for what was previously termed ‘cryptogenic cirrhosis’.3 Since cirrhosis is the main risk factor for hepatocellular carcinoma (HCC), liver cancer could be simply a complication of end-stage NAFLD, similar to the situation encountered in other chronic fibrosing liver diseases. However, accumulating evidence suggests that hepatocarcinogenesis may also be related to earlier stages of NAFLD. Case series of patients with HCC and NAFLD as the only identified risk factor strongly suggest that hepatocarcinogenesis is part of the natural history of NAFLD. Based on the known association of NAFLD with IR and MS, approximately two-thirds of the patients were obese and/or diabetic,4 and a remarkable 25% of these patients had no cirrhosis. Considering the rapidly increasing prevalence of both conditions in affluent societies, and their significance in the pathophysiology of NAFLD, a rising incidence of NAFLD and its complications—including HCC—can be expected in the mid-term future. Therefore, it is particularly worrying that the most persuasive evidence for an association between NAFLD and HCC derives from studies on the risk of HCC in patients with MS. In a large prospective cohort study HCC mortality was significantly higher in obese subjects than in those with normal body mass index.5 The most comprehensive data underlining the significance …