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author:("Yu, Ming-when")
1.  Global hypomethylation in hepatocellular carcinoma and its relationship to aflatoxin B1 exposure 
World Journal of Hepatology  2012;4(5):169-175.
AIM: To determine global DNA methylation in paired hepatocellular carcinoma (HCC) samples using several different assays and explore the correlations between hypomethylation and clinical parameters and biomarkers, including that of aflatoxin B1 exposure.
METHODS: Using the radio labeled methyl acceptance assay as a measure of global hypomethylation, as well as two repetitive elements, including satellite 2 (Sat2) by MethyLight and long interspersed nucleotide elements (LINE1), by pyrosequencing.
RESULTS: By all three assays, mean methylation levels in tumor tissues were significantly lower than that in adjacent tissues. Methyl acceptance assay log (mean ± SD) disintegrations/min/ng DNA are 70.0 ± 54.8 and 32.4 ± 15.6, respectively, P = 0.040; percent methylation of Sat2 42.2 ± 55.1 and 117.9 ± 88.8, respectively, P < 0.0001 and percent methylation LINE1 48.6 ± 14.8 and 71.7 ± 1.4, respectively, P < 0.0001. Aflatoxin B1-albumin (AFB1-Alb) adducts, a measure of exposure to this dietary carcinogen, were inversely correlated with LINE1 methylation (r = -0.36, P = 0.034).
CONCLUSION: Consistent hypomethylation in tumor compared to adjacent tissue was found by the three different methods. AFB1 exposure is associated with DNA global hypomethylation, suggesting that chemical carcinogens may influence epigenetic changes in humans.
PMCID: PMC3365436  PMID: 22666524
Hepatocellular carcinoma; Epigenetics; Hypomethylation; [3H]-methyl acceptance assay; Satellite 2; Long interspersed nucleotide element-1; Aflatoxin B1
2.  Genome-wide aberrant DNA methylation of microRNA host genes in hepatocellular carcinoma 
Epigenetics  2012;7(11):1230-1237.
Mature microRNAs (miRNAs) are a class of small non-coding RNAs involved in posttranslational gene silencing. Previous studies found that downregulation of miRNAs is a common feature observed in solid tumors, including hepatocellular carcinoma (HCC). We employed a genome-wide approach to test the hypothesis that DNA methylation alterations in miRNA host genes may cause deregulated miRNA expression in HCC. We analyzed tumor and adjacent non-tumor tissues from 62 Taiwanese HCC cases using Infinium HumanMethylation27 DNA Analysis BeadChips that include 254 CpG sites covering 110 miRNAs from 64 host genes. Expression levels of three identified miRNAs (miR-10a, miR-10b and miR-196b) were measured in a subset of 37 HCC tumor and non-tumor tissues. After Bonferroni adjustment, a total of 54 CpG sites from 27 host genes significantly differed in DNA methylation levels between tumor and adjacent non-tumor tissues with 53 sites significantly hypermethylated in tumor tissues. Among the 54 significant CpG sites, 15 sites had more than 2-fold tumor/non-tumor changes, 17 sites had differences > 10%, and 10 sites had both features [including 8 significantly hypermethylated CpG sites in the host genes of miR-10a, miR-10b and miR-196b (HOXB4, HOXD4 and HOXA9, respectively)]. Significant downregulation of miR-10a was observed in tumor compared with non-tumor tissues (0.50 vs. 1.73, p = 0.031). The concordance for HOXB4 methylation alteration and dysregulation of miR-10a was 73.5%. No significant change was observed for miR-10b expression. Unexpectedly, miR-196b was significantly upregulated in tumor compared with non-tumor tissues (p = 0.0001). These data suggest that aberrant DNA methylation may lead to dysregulation of miR-10a in HCC tumor tissues.
PMCID: PMC3499324  PMID: 22976466
HCC; genome-wide; host gene; microRNA; DNA methylation
3.  Impact of Genetic Heterogeneity in Polymerase of Hepatitis B Virus on Dynamics of Viral Load and Hepatitis B Progression 
PLoS ONE  2013;8(7):e70169.
The hepatitis B virus (HBV)-polymerase region overlaps pre-S/S genes with high epitope density and plays an essential role in viral replication. We investigated whether genetic variation in the polymerase region determined long-term dynamics of viral load and the risk of hepatitis B progression in a population-based cohort study.
We sequenced the HBV-polymerase region using baseline plasma from treatment-naïve individuals with HBV-DNA levels≥1000 copies/mL in a longitudinal viral-load study of participants with chronic HBV infection followed-up for 17 years, and obtained sequences from 575 participants (80% with HBV genotype Ba and 17% with Ce).
Patterns of viral sequence diversity across phases (i.e., immune-tolerant, immune-clearance, non/low replicative, and hepatitis B e antigen (HBeAg)-negative hepatitis phases) of HBV-infection, which were associated with viral and clinical features at baseline and during follow-up, were similar between HBV genotypes, despite greater diversity for genotype Ce vs. Ba. Irrespective of genotypes, however, HBeAg-negative participants had 1.5-to-2-fold higher levels of sequence diversity than HBeAg-positive participants (P<0.0001). Furthermore, levels of viral genetic divergence from the population consensus sequence, estimated by numbers of nucleotide substitutions, were inversely associated with long-term viral load even in HBeAg-negative participants. A mixed model developed through analysis of the entire HBV-polymerase region identified 153 viral load-associated single nucleotide polymorphisms in overall and 136 in HBeAg-negative participants, with distinct profiles between HBV genotypes. These polymorphisms were most evident at sites within or flanking T-cell epitopes. Seven polymorphisms revealed associations with both enhanced viral load and a more than 4-fold increased risk of hepatocellular carcinoma and/or liver cirrhosis.
The data highlight a role of viral genetic divergence in the natural course of HBV-infection. Interindividual differences in the long-term dynamics of viral load is not only associated with accumulation of mutations in HBV-polymerase region, but differences in specific viral polymorphisms which differ between genotypes.
PMCID: PMC3728348  PMID: 23936156
4.  Genome-wide DNA Methylation Profiles in Hepatocellular Carcinoma 
Hepatology (Baltimore, Md.)  2012;55(6):1799-1808.
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 prior to 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 non-tumor tissues from 62 Taiwanese HCC cases using Illumina methylation arrays 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 non-tumor tissues. Array data were validated with pyrosequencing in a subset of 5 of these genes; correlation coefficients ranged from 0.92 to 0.97. Analysis of plasma DNA from 38 cases demonstrated that 37% to 63% of cases had detectable hypermethylated DNA (≥5% methylation) for these 5 genes individually. At least one of these genes was hypermethylated in 87% of cases, suggesting that measurement of DNA methylation in plasma samples is feasible. The panel of methylated genes indentified in the current study will be further tested in large cohort of prospectively collected samples to determine their utility as early biomarkers of hepatocellular carcinoma.
PMCID: PMC3330167  PMID: 22234943
Genome-wide; DNA mehtylation; Hepatocellular Carcinoma
5.  Silencing of Hint1, a novel tumor suppressor gene, by promoter hypermethylation in hepatocellular carcinoma 
Cancer letters  2008;275(2):277-284.
The Hint1 protein, a member of the histidine triad (HIT) family, is highly conserved in diverse species and ubiquitously expressed in mammalian tissues. Previous studies in mice provided evidence that Hint1 may be haplosufficient with respect to its function as a tumor suppressor. In the present study, we investigated the aberrant methylation of Hint1 and explored possible relationships between aberrant methylation and clinicopathological features in hepatocellular carcinoma (HCC). Hypermethylation of Hint1 was evaluated by the methylation specific PCR (MSP) method in 40 patients with HCC (tumor and paired adjacent non-tumor tissues) from Taiwan, 22 cases of normal liver tissue (14 from Taiwan and 8 from the U.S.). HINT1 expression in tissues was detected by immunohistochemistry. The frequencies of hypermethylation of Hint1 in tumor, paired adjacent non-tumor and normal liver tissue were 55.0%, 37.5% and 9.1%, respectively. A statistically significant inverse association was found between Hint1 methylation status and expression of the HINT1 protein in tumor tissues (p<0.003). The relationship between Hint1 methylation status and clinical features and other, previously measured biomarkers was also analyzed. p16 hypermethylation was statistically significantly associated with Hint1 methylation status (p=0.035). There were no correlations between Hint1 methylation and HBV or HCV infection status or AFB1- and PAH-DNA adduct levels. These results suggest that promoter hypermethylation of Hint1 may play a role in hepatocarcinogenesis.
PMCID: PMC3522093  PMID: 19081673
Hint1; HCC; epigenetic changes; promoter hypermethylation; p16; environmental carcinogens
6.  Insulin, glucose and hepatocellular carcinoma risk in male hepatitis B carriers: results from 17-year follow-up of a population-based cohort 
Carcinogenesis  2011;32(6):876-881.
This study aimed to investigate the association of fasting insulin and glucose levels with hepatocellular carcinoma (HCC) risk in a case–cohort study within a cohort (1989–2006) of 2903 male government employees chronically infected with hepatitis B virus (HBV) in Taiwan. Insulin, glucose and HBV-related factors were assayed in baseline plasma among 124 HCC cases and a random subcohort of 1084 of the total cohort. After adjustment for demographics and HBV-related factors, including viral load and genotype, the HCC risk was higher for the highest [>6.10 μU/ml, hazard ratio (HR) = 2.36, 95% confidence interval (CI): 1.43–3.90] and lowest (<2.75 μU/ml, HR = 1.57, 95% CI: 0.96–2.58) categories of insulin, compared with insulin of 2.75–4.10 μU/ml. The dose–response relationship between insulin and HCC varied by follow-up time, with stronger association for the HCC cases that occurred ≥8 years after baseline (P for trend <0.0001). The effect of higher insulin on HCC risk remained after adjustment for other metabolic factors, and was fairly consistent across strata of age, body mass index, and HBV genotypic variants. However, it was more profound among those with viral load <4.39 log10 copies/ml at recruitment (>6.10 μU/ml, HR = 6.15, 95% CI: 2.48–15.22). Higher insulin was also associated with an increased risk for cirrhosis diagnosed by ultrasonography and elevated alanine aminotransferase. No association with either cirrhosis or HCC was noted for glucose or diabetes after adjusting for insulin. In conclusion, elevated insulin levels are an independent risk factor for HCC among HBV carriers, especially for those with lower viral load.
PMCID: PMC3146359  PMID: 21464041
7.  Evidence for association with hepatocellular carcinoma at the PAPSS1 locus on chromosome 4q25 in a family-based study 
European Journal of Human Genetics  2009;17(10):1250-1259.
A region on chromosome 4q25 has recently been highlighted as linked to hepatocellular carcinoma (HCC). In this study, we performed a family-based association analysis with 67 single-nucleotide polymorphisms (SNPs) to map this linkage region in 240 families with HCC, 212 (88.3%) of which were ascertained through hepatitis B virus surface antigen (HBsAg)-positive index cases. Individual SNP analysis with correction for multiple testing identified 10 SNPs in two correlated haplotype blocks, located in or around the 3′-phosphoadenosine 5′-phosphosulfate synthetase-1 (PAPSS1) gene (all P-values: <0.0075). Our linkage data and GIST (Genotype identity-by-descent sharing test) indicate that 6 of these 10 SNPs contributed to the linkage signal. The haplotype block of the strongest association with HCC extended from the intron 5 to the 3′-flanking region of PAPSS1; multiple consecutive three-SNP haplotypes in this region were significant. The most significant haplotype showed odd ratios of 3.41 (95% confidence interval (CI)=1.36–8.53) for homozygous individuals in a case-unaffected sibling analysis. This haplotype also revealed an association with elevated serum α-fetoprotein and with poor survival in familial cases and an independent series of HBsAg-positive cases with small tumor present at the time of hospital admission. These results implicate PAPSS1 as a candidate HCC-susceptibility gene in hepatitis B carriers.
PMCID: PMC2986632  PMID: 19337310
chromosome 4q; hepatocellular carcinoma; haplotype; single-nucleotide polymorphisms; hepatitis B; PAPSS1 gene

Results 1-7 (7)