Ming-Whei Yu

Epidemiological characteristics and risk factors of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the major cancers in the world. There is a striking variation in HCC incidence rates between various countries, with a highest‐to‐lowest ratio of 112.5 for males and 54.7 for females. The high‐risk populations are clustered in sub‐Saharan Africa and eastern Asia. The male‐to‐female ratio for HCC ranges from < 1 to 6.4 and mostly from 2 to 4. There exist significant variations in the incidence of HCC among different ethnic groups living in the same area and among migrants of the same ethnic groups living in different areas. The age curves of HCC are significantly different in various countries, suggesting variability in exposure to risk factors. Chronic carriers of hepatitis B and C viruses (HBV and HCV, respectively) have an increased risk of HCC. The relative and attributable HCC risk of HBV and HCV carrier status varies in different countries. There exists a synergistic interaction on HCC between the two viruses. Aflatoxin exposure, cigarette smoking, heavy alcohol consumption, low vegetable intake, inorganic arsenic ingestion, radioactive thorium dioxide exposure, iron overload and the use of oral contraceptives and anabolic steroids have been documented as HCC risk factors. Recent molecular epidemiological studies have shown that low serum retinol levels as well as elevated serum levels of testosterone, neu oncoprotein and aflatoxin B1‐albumin adduct are associated with an increased HCC risk. There is a synergistic interaction on HCC between chronic HBV infection and aflatoxin exposure. Familial aggregation of HCC exists and a major susceptibility gene of HCC has been hypothesized. Patients of some genetic diseases are at an increased risk of HCC. The genetic polymorphisms of cytochrome P450 2E1 and 2D6 and arylamine N‐acetyltransferase 2 are associated with the development of HCC. A doseresponse relationship between aflatoxin exposure and HCC has been observed among chronic HBV carriers who have null genotypes of glutathione S‐transferase M1 or T1, but not among those who have non‐null genotypes. Human hepatocarcinogenesis is a multistage process with the involvement of a multifactorial aetiology. Gene‐environment interactions are involved in the development of HCC in humans.

Cytochrome P450 2E1 and glutathione S-transferase M1 polymorphisms and susceptibility to hepatocellular carcinoma.

BACKGROUND & AIMS Genetic polymorphisms in enzymes involved in carcinogen metabolism have been found to influence susceptibility to cancer. The aim of this study was to examine whether cytochrome P450 2E1 (CYP2E1) and/or glutathione S-transferase M1 (GSTM1) genetic polymorphisms were related to susceptibility to hepatocellular carcinoma (HCC). METHODS Genotyping of CYP2E1 and GSTM1 was performed using the polymerase chain reaction on peripheral white blood cell DNA from 30 patients with HCC and 150 controls nested in a cohort study. RESULTS The c1/c1 genotype of CYP2E1, detected by PstI or RsaI digestion, was found in 83.3% of patients with HCC and in 63.3% of controls (P = 0.034). Homozygosity for the c1/c1 genotype significantly increased the risk of developing HCC in cigarette smokers (P = 0.001) but posed no increased risk in those who never smoked. The HCC risk associated with cumulative exposure to cigarette smoke was also more striking in individuals who carried the c1/c1 genotype. Habitual alcohol drinking modified the HCC risk of cigarette smoking among those with the c1/c1 genotype. No association with the risk of HCC was observed for the DraI polymorphism of CYP2E1 or for the GSTM1-null genotype. CONCLUSIONS Polymorphisms of CYP2E1 may play an important role in cigarette smoking-related hepatocarcinogenesis.

Hepatitis B and C viruses in the development of hepatocellular carcinoma

2. Descriptive epidemiology of HCC ........................................................ 72 2.1. Demographic CharanWiStics ....................................................... 72 2.2. Gaographical variation ............................................................ 73 2.3. Migrant studies .................................................................. 73 2.4. Tii trends ..................................................................... 73

Genome-wide DNA methylation profiles in hepatocellular carcinoma†‡

Alterations in DNA methylation frequently occur in hepatocellular cancer (HCC). We have previously demonstrated that hypermethylation in candidate genes can be detected in plasma DNA before HCC diagnosis. To identify, with a genome‐wide approach, additional genes hypermethylated in HCC that could be used for more accurate analysis of plasma DNA for early diagnosis, we analyzed tumor and adjacent nontumor tissues from 62 Taiwanese HCC cases using Illumina methylation arrays (Illumina, Inc., San Diego, CA) that screen 26,486 autosomal CpG sites. After Bonferroni adjustment, a total of 2,324 CpG sites significantly differed in methylation level, with 684 CpG sites significantly hypermethylated and 1,640 hypomethylated in tumor, compared to nontumor tissues. Array data were validated with pyrosequencing in a subset of five of these genes; correlation coefficients ranged from 0.92 to 0.97. Analysis of plasma DNA from 38 cases demonstrated that 37%‐63% of cases had detectable hypermethylated DNA (≥5% methylation) for these five genes individually. At least one of these genes was hypermethylated in 87% of the cases, suggesting that measurement of DNA methylation in plasma samples is feasible. Conclusion: The panel of methylated genes indentified in the current study will be further tested in a large cohort of prospectively collected samples to determine their utility as early biomarkers of HCC. (HEPATOLOGY 2012;55:1799–1810)

Temporal relationship between hepatitis B virus enhancer II/basal core promoter sequence variation and risk of hepatocellular carcinoma

Background and aims: To investigate the temporal relationship between sequence variation in the enhancer II (EnhII), basal core promoter (BCP), and precore regions of hepatitis B virus (HBV) and the risk of hepatocellular carcinoma (HCC), we conducted a nested case–control study within a cohort of 4841 male HBV carriers who were recruited during the period 1988–1992. Methods: The HBV DNA sequence was determined in baseline blood samples taken from 132 incident cases and 204 controls. Base exchanges during follow-up in 71 cases were compared with 81 controls with samples taken during a similar length of follow-up. Results: Nine single nucleotide polymorphisms in the EnhII/BCP regions (six of which were genotype C HBV related) were associated with subsequent risk of HCC. The strength of these associations decreased as the lag time between baseline measurement and diagnosis increased over 3 years. However, an increased disease risk in subjects with BCP double variants (mostly T1762/A1764) or genotype C HBV-related variants was evident 9 years or more before diagnosis. The BCP double variants (odds ratio, 1.92 (95% confidence interval, 1.14 to 3.25)) were statistically significantly associated with HCC risk even after adjusting for alanine aminotransferase levels, antibodies against HBV e antigen, HBV genotype, HBV viral load, and other sequence variants. Longitudinal analysis indicated that the increased HCC risks for at-risk sequence variants were attributable to the persistence of these variants. Conclusions: HCC risk is associated with sequence variation in the EnhII/BCP regions of HBV, and persistence of at-risk sequence variants is critical for HCC development.

Effect of aflatoxin metabolism and DNA adduct formation on hepatocellular carcinoma among chronic hepatitis B carriers in Taiwan

BACKGROUND/AIMS Aflatoxins (AFs) are established hepatic carcinogens in several animal species. This study was performed to establish whether aflatoxin exposure may affect the risk of developing hepatocellular carcinoma in chronic hepatitis B virus carriers. METHODS Urinary AF metabolites were measured for 43 HCC cases and 86 matched controls nested in a cohort of 7342 men in Taiwan. Thirty hepatocellular carcinoma cases and 63 controls were also tested for AFB1-albumin adducts. RESULTS There was a dose-response relationship between urinary AFM1 levels and risk of hepatocellular carcinoma in chronic hepatitis B virus carriers. Comparing the highest with the lowest tertile of urinary AFM1 levels, the multivariate-adjusted odds ratio (OR) was 6.0 (95% confidence interval (CI) = 1.2-29.0). The hepatocellular carcinoma risk associated with AFB1 exposure was more striking among the hepatitis B virus carriers with detectable AFB1-N7-guanine adducts in urine. Compared with chronic hepatitis B virus carriers who were negative for AFB1-albumin adducts and urinary AFB1-N7-guanine, no elevated risk was observed for those who were positive for either marker. But an extremely high risk of hepatocellular carcinoma among those having both markers was found (OR = 10.0, 95% CI = 1.6-60.9). The proportion of AFB1 converted to AFM1 decreased with the progress of liver disease, whereas the formation of AFP1 increased. The difference in patterns of AFB1 metabolite formation was an independent risk factor for hepatocellular carcinoma after adjustment for total AFB1 excretion. There was a synergistic interaction between glutathione S-transferase M1 genotype and AFB1 exposure in hepatocellular carcinoma risk. CONCLUSIONS AFB1 intake and expression of enzymes involved in AFB1 activation/detoxification may play an important role in hepatitis B virus-related hepatocarcinogenesis.

Hepatitis B viral factors in HBeAg-Negative carriers with persistently normal serum alanine aminotransferase levels†

Chronic hepatitis B patients with high‐normal serum ALT (levels of 0.5‐1× upper limit of normal) are still at risk of liver disease progression. We thus investigated the correlation between serum ALT level and hepatitis B viral factors in HBeAg‐negative carriers with persistently normal serum ALT level (PNALT). Baseline clinical and virological features of 414 HBeAg‐negative carriers, including 176 (42.5%) with low‐normal ALT (levels of less than 0.5× upper limit of normal) and 238 (57.5%) with high‐normal ALT, were compared. Compared with HBV carriers with low‐normal ALT, those with high‐normal ALT were older (41 vs. 37 years, P < 0.001) and had a greater frequency of serum HBV DNA level >10 4 copies/ml (63.4% vs. 47.5%, P < 0.001) as well as a higher prevalence of basal core promoter T1762/A1764 mutant (36.5% vs. 24.2%, P = 0.01). Multivariate analysis showed that factors associated with a high‐normal serum ALT level included male sex [odds ratio (OR), 1.82; 95% confidence interval (CI), 1.10‐3.01, P = 0.019], increasing age (OR, <30 years: 1, reference; 30‐39 years: 2.43, 95% CI, 1.18‐5.03, P = 0.016; 40‐49 years: 4.22, 95% CI, 1.99‐8.93, P < 0.001; ≥50 years: 4.06, 95% CI, 1.69‐9.78, P = 0.002) and serum HBV DNA level >10 4 copies/ml (OR, 1.83; 95% CI, 1.07‐3.13, P = 0.027). Conclusion: HBeAg‐negative patients with persistently normal ALT are not a homogenous group, and those with high‐normal ALT share some of the characteristics that have been associated with adverse long‐term outcomes. (HEPATOLOGY 2007;45:1193–1198.)

Aflatoxin B1 and polycyclic aromatic hydrocarbon adducts, p53 mutations and p16 methylation in liver tissue and plasma of hepatocellular carcinoma patients

Elevated aflatoxin B1‐albumin adducts (AFB1‐Alb) have been associated with an increased risk for HCC development. However, there are no studies in humans, correlating albumin adducts in blood with liver DNA adducts. Forty frozen tumor tissues and 39 paired plasma samples from HCC patients were collected in Taiwan, to determine the relationship between albumin adducts in blood and DNA adducts in liver tissue as well as mutations in p53 and methylation of p16. AFB1‐ and polycyclic aromatic hydrocarbon (PAH)‐DNA adducts in tissue and albumin adducts in plasma were determined by immunohistochemistry and competitive ELISA, respectively. Plasma AFB1‐Alb adducts in subjects with low, medium and high levels of AFB1‐DNA adducts in tumor tissues were 51.0 ± 36.5, 70.5 ± 48.1 and 84.9 ± 48.2 fmol/mg, respectively (ptrend = 0.05). No significant correlation was found for PAH. Fourteen of 40 (36%) tissues were positive for mutant p53 protein by immunohistochemistry; 11 of 40 tissue DNA samples (28%) were positive for p53 mutations, but not their corresponding plasma DNAs. p16 was methylated in 24 of 40 (62%) tissues and 12 of 39 (32%) plasma DNAs. Significant correlations were observed between AFB1‐Alb adducts and p53 mutations and p16 methylation. These data suggest that genetic, epigenetic and environmental exposure biomarkers in plasma may help in estimating the risk for the development of HCC.

Body-Mass Index and Progression of Hepatitis B: A Population-Based Cohort Study in Men

PURPOSE To determine prospectively whether body-mass index (BMI) is associated with liver-related morbidity and mortality among male hepatitis B virus (HBV) carriers. PATIENTS AND METHODS We performed a prospective study of 2,903 male HBV surface antigen-positive government employees who were free of cancer at enrollment between 1989 and 1992. Main outcome measures included ultrasonography, biochemical tests, incident hepatocellular carcinoma (HCC), and liver-related death. RESULTS During mean follow-up of 14.7 years, 134 developed HCC and 92 died as a result of liver-related causes. In Cox proportional hazards models adjusting for age, number of visits, diabetes, and use of alcohol and tobacco, the hazard ratios for incident HCC were 1.48 (95% CI, 1.04 to 2.12) in overweight men (BMI between 25.0 and 29.9 kg/m(2)) and 1.96 (95% CI, 0.72 to 5.38) in obese men (BMI >or= 30.0 kg/m(2)), compared with normal-weight men (BMI between 18.5 and 24.9 kg/m(2)). Liver-related mortality had adjusted hazard ratios of 1.74 (95% CI, 1.15 to 2.65) in overweight men and 1.50 (95% CI, 0.36 to 6.19) in obese men. Excess BMI was also associated with the occurrence of fatty liver and cirrhosis detected by ultrasonography, as well as elevated ALT and gamma-glutamyltransferase (GGT) activity during follow-up. The association of BMI with GGT was stronger than with ALT, and elevated GGT activity and cirrhosis were the strongest predictors for incident HCC and liver-related death. CONCLUSION This longitudinal cohort study indicates that excess body weight is involved in the transition from healthy HBV carrier state to HCC and liver-related death among men.

Cytochrome P450 1A1 genetic polymorphisms and risk of hepatocellular carcinoma among chronic hepatitis B carriers.

SummaryCigarette smoking has been associated with increased risk of hepatocellular carcinoma (HCC) in some epidemiological studies. Cytochrome P450 1A1 (CYP1A1) is involved in the biotransformation of tobacco-derived polycyclic aromatic hydrocarbons (PAHs) into carcinogenic metabolites. The aim of this study was to determine whether CYP1A1 polymorphisms were related to HCC risk among chronic hepatitis B virus (HBV) carriers. Genotypic variants of CYP1A1 were determined using polymerase chain reaction in 81 incident cases of HCC and 409 controls nested in a cohort study of 4841 male chronic HBV carriers. No overall association between CYP1A1 genotypes and HCC was observed. The presence of the MspI (odds ratio (OR) 3.15, P= 0.0196) or Ile-Val (OR 1.99, P= 0.0855) variant allele of CYP1A1 increased HCC risk among smokers, but posed no increased risk among non-smokers. The smoking-related HCC risk was most pronounced among those who had a susceptible allele of the CYP1A1 and a deficient genotype of glutathione S-transferase M1, which detoxifies PAH electrophilic metabolites produced by CYP1A1. In the absence of the Ile-Val variant allele, the MspI polymorphism was still associated with smoking-related HCC. This study suggests that tobacco-derived PAHs play a role in HCC risk among chronic HBV carriers, and CYP1A1 polymorphism is an important modulator of the hepatocarcinogenic effect of PAHs. The MspI and Ile-Val polymorphisms of CYP1A1 may have different mechanisms for increasing susceptibility to smoking-related HCC.