Association between heterozygosity for HFE gene mutations and hepatitis viruses in hepatocellular carcinoma

Hepatocellular carcinoma in nonalcoholic fatty liver: Role of environmental and genetic factors

Hepatocellular carcinoma (HCC) is the fourth cause of cancer related mortality, and its incidence is rapidly increasing. Viral hepatitis, alcohol abuse, and exposure to hepatotoxins are major risk factors, but nonalcoholic fatty liver disease (NAFLD) associated with obesity, insulin resistance, and type 2 diabetes, is an increasingly recognized trigger, especially in developed countries. Older age, severity of insulin resistance and diabetes, and iron overload have been reported to predispose to HCC in this context. Remarkably, HCCs have been reported in non-cirrhotic livers in a higher proportion of cases in NAFLD patients than in other etiologies. Inherited factors have also been implicated to explain the different individual susceptibility to develop HCC, and their role seems magnified in fatty liver, where only a minority of affected subjects progresses to cancer. In particular, the common I148M variant of the PNPLA3 gene influencing hepatic lipid metabolism influences HCC risk independently of its effect on the progression of liver fibrosis. Recently, rare loss-of-function mutations in Apolipoprotein B resulting in very low density lipoproteins hepatic retention and in Telomerase reverse transcriptase influencing cellular senescence have also been linked to HCC in NAFLD. Indeed, hepatic stellate cells senescence has been suggested to bridge tissue aging with alterations of the intestinal microbiota in the pathogenesis of obesity-related HCC. A deeper understanding of the mechanisms mediating hepatic carcinogenesis during insulin resistance, and the identification of its genetic determinants will hopefully provide new diagnostic and therapeutic tools.

PNPLA3 I148M variant and hepatocellular carcinoma: a common genetic variant for a rare disease

Hepatocellular carcinoma (HCC) is highly associated with chronic liver disease. The rs738409 genetic variant in the patatin-like phospholipase domain-containing 3 (PNPLA3, adiponutrin) gene has been implicated as a genetic determinant of the entire spectrum of liver diseases, ranging from steatosis, chronic hepatitis, cirrhosis and ultimately to HCC. In this review, first we will examine the current genetic theories of disease susceptibility. Next, we will analyze the evidences for the association between PNPLA3 I148M variant and HCC. Moreover, we will exploit this association to propose a new paradigm in human genetics: a common genetic variant contributing to a rare disease. Finally, we will examine the molecular genetics of PNPLA3 and, specifically, the theories that have been proposed to explain the function of PNPLA3 in health and disease.

Patatin-like phospholipase domain containing-3 gene I148M polymorphism, steatosis, and liver damage in hereditary hemochromatosis

AIM: To investigate whether the patatin-like phospholipase domain containing-3 gene (PNPLA3) I148M polymorphism is associated with steatosis, fibrosis stage, and cirrhosis in hereditary hemochromatosis (HH).

METHODS: We studied 174 consecutive unrelated homozygous for the C282Y HFE mutation of HH (C282Y+/+ HH) patients from Northern Italy, for whom the presence of cirrhosis could be determined based on histological or clinical criteria, without excessive alcohol intake (< 30/20 g/d in males or females) or hepatitis B virus and hepatitis C virus viral hepatitis. Steatosis was evaluated in 123 patients by histology (n = 100) or ultrasound (n = 23). The PNPLA3 rs738409 single nucleotide polymorphism, encoding for the p.148M protein variant, was genotyped by a Taqman assay (assay on demand, Applied Biosystems). The association of the PNPLA3 I148M protein variant (p.I148M) with steatosis, fibrosis stage, and cirrhosis was evaluated by logistic regression analysis.

RESULTS: PNPLA3 genotype was not associated with metabolic parameters, including body mass index (BMI), the presence of diabetes, and lipid levels, but the presence of the p.148M variant at risk was independently associated with steatosis [odds ratio (OR) 1.84 per p.148M allele, 95% confidence interval (CI): 1.05-3.31; P = 0.037], independently of BMI and alanine aminotransaminase (ALT) levels. The p.148M variant was also associated with higher aspartate aminotransferase (P = 0.0014) and ALT levels (P = 0.017) at diagnosis, independently of BMI and the severity of iron overload. In patients with liver biopsy, the 148M variant was independently associated with the severity (stage) of fibrosis (estimated coefficient 0.56 ± 0.27, P = 0.041). In the overall series of patients, the p.148M variant was associated with cirrhosis in lean (P = 0.049), but not in overweight patients (P = not significant). At logistic regression analysis, cirrhosis was associated with BMI ≥ 25 (OR 1.82, 95% CI: 1.02-3.55), ferritin > 1000 ng/mL at diagnosis (OR 19.3, 95% CI: 5.3-125), and with the G allele in patients with BMI < 25 (OR 3.26, 95% CI: 1.3-10.3).

CONCLUSION: The PNPLA3 I148M polymorphism may represent a permissive factor for fibrosis progression in patients with C282Y+/+ HH.

Polymorphisms of hemochromatosis, and alpha-1 antitrypsin genes in Egyptian HCV patients with and without hepatocellular carcinoma

Hereditary hemochromatosis and alpha-1antitrypsin deficiency are genetic diseases characterized by endoplasmic reticulum (ER) stress with subsequent development of liver disease. Our aim was to estimate the frequency of hemochromatosis gene (HFE) mutant alleles (C282Y and H63D) and alpha-1 antitrypsin S/Z variants among Egyptian HCV cirrhotic patients and in hepatocellular carcinoma patients and to evaluate their effects on disease progression. HFE and alpha-1 antitrypsin polymorphisms were characterized in 200 Egyptian patients with HCV infection (100 patients complicated with cirrhosis, 100 patients with HCC) and 100 healthy subjects who had no history of any malignancy. The frequencies of HD genotype of H63D mutation were significantly increased in HCC patients compared to control group and to cirrhosis group. Also, the frequencies of DD genotype were significantly increased In HCC group compared to control group and to cirrhosis group. Our results suggested that Carriers of the D allele of H63D mutation were significantly more likely to develop HCC.

Beyond hereditary hemochromatosis: new insights into the relationship between iron overload and chronic liver diseases

Following the model of hereditary hemochromatosis, the possible role of iron overload as a cofactor for disease progression in acquired liver diseases has been investigated with controversial results. In recent years, progress has been made in understanding the regulation of iron metabolism, thereby allowing the evaluation of the mechanisms linking liver diseases to excessive iron accumulation. Indeed, deregulation of the transcription of hepcidin, emerging as the master regulator of systemic iron metabolism, has been implicated in the pathogenesis of hepatic iron overload in chronic liver diseases. Whatever the cause, hepatocellular iron deposition promotes liver fibrogenesis, while an emerging possible aggravating factor is represented by the strong link between iron stores and insulin resistance, a recently recognized risk factor for the progression of liver diseases. Overall, these pathogenic mechanisms, together with the known proliferative and mutagenic effect of excess iron, converge in determining an increased susceptibility to hepatocellular carcinoma. Finally, an association between serum ferritin levels and mortality in patients with end-stage liver disease has recently been reported. Prospective, randomized studies are required to evaluate whether iron depletion may reduce fibrosis progression, hepatocellular carcinoma development, and eventually mortality in patients with chronic liver diseases.

Relationship between host genetic polymorphisms and the outcome of hepatitis C virus infection

Acute hepatitis C virus (HCV) infection can induce host innate and adaptive immune responses. Approximately 15%-25% of HCV-infected patients successfully eliminated the virus whereas the majority of these patients developed chronic liver disease, cirrhosis and hepatocellular carcinoma. Numerous studies have demonstrated that host genetic polymorphisms may lead to differences in host immune function and therefore influence the clinical outcome of HCV infection. This review briefly summarizes the relationship between host genetic polymorphisms and the outcome of HCV infection.

Iron-dependent regulation of MDM2 influences p53 activity and hepatic carcinogenesis

Iron overload is a risk factor for hepatocarcinoma, but the pathways involved are poorly characterized. Gene expression analysis in immortalized mouse hepatocytes exposed to iron or the iron chelator deferoxamine revealed that iron downregulated, whereas deferoxamine upregulated, mRNA levels of mouse double minute gene 2 (MDM2), the ubiquitin ligase involved in the degradation of the oncosuppressor p53. Regulation of MDM2 by iron status was observed at protein levels in mouse hepatocytes and rat liver, and was associated with specular changes in p53 expression. Iron dependent regulation of MDM2/p53 was confirmed ex-vivo in human monocytes, by manipulation of iron pool and in a genetic model of iron deficiency, leading to modulation of p53 target genes involved in the antioxidant response and apoptosis. Iron status influenced p53 ubiquitination and degradation rate, and the MDM2 inhibitor nutlin increased p53 levels in iron-depleted cells. Furthermore, nutlin enhanced the antiproliferative activity of deferoxamine in HepG2 hepatoblastoma cells. The MDM2 -309T > G promoter polymorphism, determining increased MDM2 and lower p53 activity, was associated with higher risk of hepatocarcinoma in cirrhotic patients with hemochromatosis, and with HFE mutations in patients with hepatocarcinoma without hemochromatosis, suggesting an interaction between MDM2 and iron in the pathogenesis of hepatocarcinoma. In conclusion, iron status influences p53 activity and antioxidant response by modulating MDM2 expression. MDM2 inhibitors may enhance the antiproliferative activity of iron chelators.

Iron-dependent regulation of MDM2 influences p53 activity and hepatic carcinogenesis

Iron overload is a risk factor for hepatocarcinoma, but the pathways involved are poorly characterized. Gene expression analysis in immortalized mouse hepatocytes exposed to iron or the iron chelator deferoxamine revealed that iron downregulated, whereas deferoxamine upregulated, mRNA levels of mouse double minute gene 2 (MDM2), the ubiquitin ligase involved in the degradation of the oncosuppressor p53. Regulation of MDM2 by iron status was observed at protein levels in mouse hepatocytes and rat liver, and was associated with specular changes in p53 expression. Iron dependent regulation of MDM2/p53 was confirmed ex-vivo in human monocytes, by manipulation of iron pool and in a genetic model of iron deficiency, leading to modulation of p53 target genes involved in the antioxidant response and apoptosis. Iron status influenced p53 ubiquitination and degradation rate, and the MDM2 inhibitor nutlin increased p53 levels in iron-depleted cells. Furthermore, nutlin enhanced the antiproliferative activity of deferoxamine in HepG2 hepatoblastoma cells. The MDM2 -309T > G promoter polymorphism, determining increased MDM2 and lower p53 activity, was associated with higher risk of hepatocarcinoma in cirrhotic patients with hemochromatosis, and with HFE mutations in patients with hepatocarcinoma without hemochromatosis, suggesting an interaction between MDM2 and iron in the pathogenesis of hepatocarcinoma. In conclusion, iron status influences p53 activity and antioxidant response by modulating MDM2 expression. MDM2 inhibitors may enhance the antiproliferative activity of iron chelators.

Iron-dependent regulation of MDM2 influences p53 activity and hepatic carcinogenesis

Iron overload is a risk factor for hepatocarcinoma, but the pathways involved are poorly characterized. Gene expression analysis in immortalized mouse hepatocytes exposed to iron or the iron chelator deferoxamine revealed that iron downregulated, whereas deferoxamine upregulated, mRNA levels of mouse double minute gene 2 (MDM2), the ubiquitin ligase involved in the degradation of the oncosuppressor p53. Regulation of MDM2 by iron status was observed at protein levels in mouse hepatocytes and rat liver, and was associated with specular changes in p53 expression. Iron dependent regulation of MDM2/p53 was confirmed ex-vivo in human monocytes, by manipulation of iron pool and in a genetic model of iron deficiency, leading to modulation of p53 target genes involved in the antioxidant response and apoptosis. Iron status influenced p53 ubiquitination and degradation rate, and the MDM2 inhibitor nutlin increased p53 levels in iron-depleted cells. Furthermore, nutlin enhanced the antiproliferative activity of deferoxamine in HepG2 hepatoblastoma cells. The MDM2 -309T > G promoter polymorphism, determining increased MDM2 and lower p53 activity, was associated with higher risk of hepatocarcinoma in cirrhotic patients with hemochromatosis, and with HFE mutations in patients with hepatocarcinoma without hemochromatosis, suggesting an interaction between MDM2 and iron in the pathogenesis of hepatocarcinoma. In conclusion, iron status influences p53 activity and antioxidant response by modulating MDM2 expression. MDM2 inhibitors may enhance the antiproliferative activity of iron chelators.

The effects of air pollution on mortality in socially deprived urban areas in Hong Kong, China

BACKGROUND

Poverty is a major determinant of population health, but little is known about its role in modifying air pollution effects.

OBJECTIVES

We set out to examine whether people residing in socially deprived communities are at higher mortality risk from ambient air pollution.

METHODS

This study included 209 tertiary planning units (TPUs), the smallest units for town planning in the Special Administrative Region of Hong Kong, China. The socioeconomic status of each TPU was measured by a social deprivation index (SDI) derived from the proportions of the population with a) unemployment, b) monthly household income < US$250, c) no schooling at all, d) one-person household, e) never-married status, and f ) subtenancy, from the 2001 Population Census. TPUs were classified into three levels of SDI: low, middle, and high. We performed time-series analysis with Poisson regression to examine the association between changes in daily concentrations of ambient air pollution and daily number of deaths in each SDI group for the period from January 1996 to December 2002. We evaluated the differences in pollution effects between different SDI groups using a case-only approach with logistic regression.

RESULTS

We found significant associations of nitrogen dioxide, sulfur dioxide, particulate matter with aerodynamic diameter < 10 mum, and ozone with all nonaccidental and cardiovascular mortality in areas of middle or high SDI (p < 0.05). Health outcomes, measured as all nonaccidental, cardiovascular, and respiratory mortality, in people residing in high SDI areas were more strongly associated with SO(2) and NO(2) compared with those in middle or low SDI areas.

CONCLUSIONS

Neighborhood socioeconomic deprivation increases mortality risks associated with air pollution.

Prevalence of common HFE and SERPINA1 mutations in patients with hepatocellular carcinoma in a Moroccan population

BACKGROUND

Hereditary hemochromatosis and SERPINA1 mutation were reported to affect liver functions. Our objective was to estimate the prevalence of HFE and SERPINA1 (formerly known as alpha1-antitrypsin, AAT) mutations and assess their influence on hepatocellular carcinoma development.

METHODS

This study included 222 controls and 96 cases with hepatocellular carcinoma. PCR-RFLP was used to characterize S and Z alleles in SERPINA1, as well as C282Y/H63D alleles of HFE.

RESULTS

In healthy subjects and hepatocellular carcinoma patients as well, no homozygotes for the C282Y mutation were found. In controls, heterozygosity and homozygosity for the H63D mutation were 27 and 0.9%, respectively. Among patients, homozygosity for the H63D mutation was 3.1%, whereas heterozygosity for C282Y and H63D was 2.1 and 35.4%, respectively. Interestingly, albeit it does not reach significance (p=0.062), H63D was more prevalent in hepatocellular carcinoma patients than in controls (38.5 vs. 27.9%, respectively). The association was stronger when considering only male patients with hepatocellular carcinoma (47.1 vs. 23.6, p=0.001). Allele frequencies of S and Z in controls were 0.45% (95% CI=0.2-1.07) and 0.22% (95% CI=0.2-0.6), respectively, and 1 for S and 0% for Z in HCC. No significant difference was found between cases and controls.

CONCLUSIONS

We provide a novel appraisal of HFE and SERPINA1 mutations prevalence in the Moroccan population. Results are consistent with the worldwide spread of the H63D and S mutation and the north European restriction of the C282Y and Z. Our results show that H63D carriage is increased among hepatocellular carcinoma patients, suggesting that it may confer an increased susceptibility to hepatocellular carcinoma even in a heterozygous state. On the contrary, HFE C282Y and SERPINA1 mutations do not contribute to hepatocellular carcinoma development.

Hepatocellular carcinoma: epidemiology and molecular carcinogenesis

Primary liver cancer, which consists predominantly of hepatocellular carcinoma (HCC), is the fifth most common cancer worldwide and the third most common cause of cancer mortality. HCC has several interesting epidemiologic features including dynamic temporal trends; marked variations among geographic regions, racial and ethnic groups, and between men and women; and the presence of several well-documented environmental potentially preventable risk factors. Moreover, there is a growing understanding on the molecular mechanisms inducing hepatocarcinogenesis, which almost never occurs in healthy liver, but the cancer risk increases sharply in response to chronic liver injury at the cirrhosis stage. A detailed understanding of epidemiologic factors and molecular mechanisms associated with HCC ultimately could improve our current concepts for screening and treatment of this disease.