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

Genic-intergenic polymorphisms of CYP1A genes and their clinical impact

The humancytochrome P450 1A (CYP1A) subfamily genes, CYP1A1 and CYP1A2, encoding monooxygenases are critically involved in biotransformation of key endogenous substrates (estradiol, arachidonic acid, cholesterol) and exogenous compounds (smoke constituents, carcinogens, caffeine, therapeutic drugs). This suggests their significant involvement in multiple biological pathways with a primary role of maintaining endogenous homeostasis and xenobiotic detoxification. Large interindividual variability exist in CYP1A gene expression and/or catalytic activity of the enzyme, which is primarily due to the existence of polymorphic alleles which encode them. These polymorphisms (mainly single nucleotide polymorphisms, SNPs) have been extensively studied as susceptibility factors in a spectrum of clinical phenotypes. An in-depth understanding of the effects of polymorphic CYP1A genes on the differential metabolic activity and the resulting biological pathways is needed to explain the clinical implications of CYP1A polymorphisms. The present review is intended to provide an integrated understanding of CYP1A metabolic activity with unique substrate specificity and their involvement in physiological and pathophysiological roles. The article further emphasizes on the impact of widely studied CYP1A1 and CYP1A2 SNPs and their complex interaction with non-genetic factors like smoking and caffeine intake on multiple clinical phenotypes. Finally, we attempted to discuss the alterations in metabolism/physiology concerning the polymorphic CYP1A genes, which may underlie the reported clinical associations. This knowledge may provide insights into the disease pathogenesis, risk stratification, response to therapy and potential drug targets for individuals with certain CYP1A genotypes.

A novel m6A-related prognostic signature for predicting the overall survival of hepatocellular carcinoma patients

Liver hepatocellular carcinoma (LIHC) comprises most cases of liver cancer with a poor prognosis. N⁶‐methyladenosine (m6A) plays important biological functions in cancers. Thus, the present research was aimed to determine biomarkers of m6A regulators that could effectively predict the prognosis of LIHC patients. Based on the data collected from the Cancer Genome Atlas (TCGA) database, the correlation between the mRNA expression levels and copy number variation (CNV) patterns were determined. Higher mRNA expression resulted from the increasing number of 9 genes. Using the univariate Cox regression analysis, 11 m6A regulators that had close correlations with the LIHC prognosis were identified. In addition, under the support of the multivariate Cox regression models and the least absolute shrinkage and selection operator, a 4‐gene (YTHDF2, IGF2BP3, KIAA1429, and ALKBH5) signature of m6A regulators was constructed. This signature was expected to present a prognostic value in LIHC (log‐rank test p value < 0.0001). The GSE76427 (n = 94) and ICGC‐LIRI‐JP (n = 212) datasets were used to validate the prognostic signature, suggesting strong power to predict patients' prognosis for LIHC. To sum up, genetic alterations in m6A regulatory genes were identified as reliable and effective biomarkers for predicting the prognosis of LIHC patients.

Nuclear localization dictates hepatocarcinogenesis suppression by glycine N-methyltransferase

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GNMT gene expression contributes to determine hepatocellular carcinoma (HCC) prognosis.

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GNMT expression is genetically determined.

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Nuclear GNMT binds to CYP1A1, PREX2, PARP1, and NFKB gene promoters and strongly inhibits their expression.

Background

GNMT (glycine N-methyltransferase) is a tumor suppressor gene, but the mechanisms mediating its suppressive activity are not entirely known.

Methods

We investigated the oncosuppressive mechanisms of GNMT in human hepatocellular carcinoma (HCC). GNMT mRNA and protein levels were evaluated by quantitative RT-PCR and immunoblotting. GNMT effect in HCC cell lines was modulated through GNMT cDNA induced overexpression or anti-GNMT siRNA transfection.

Results

GNMT was expressed at low level in human HCCs with a better prognosis (HCCB) while it was almost absent in fast-growing tumors (HCCP). In HCCB, the nuclear localization of the GNMT protein was much more pronounced than in HCCP. In Huh7 and HepG2 cell lines, GNMT forced expression inhibited the proliferation and promoted apoptosis. At the molecular level, GNMT overexpression inhibited the expression of CYP1A (Cytochrome p450, aromatic compound-inducible), PREX2 (Phosphatidylinositol-3,4,5-trisphosphate-dependent Rac exchange factor 2), PARP1 [Poly (ADP-ribose) polymerase 1], and NFKB (nuclear factor-kB) genes. By chromatin immunoprecipitation, we found GNMT binding to the promoters of CYP1A1, PREX2, PARP1, and NFKB genes resulting in their strong inhibition. These genes are implicated in hepatocarcinogenesis, and are involved in the GNMT oncosuppressive action.

Conclusion

Overall, the present data indicate that GNMT exerts a multifaceted suppressive action by interacting with various cancer-related genes and inhibiting their expression.

Downregulation of CYP2A6 and CYP2C8 in Tumor Tissues Is Linked to Worse Overall Survival and Recurrence-Free Survival from Hepatocellular Carcinoma

Objective

This study aimed to evaluate the links between CYP450 family genes in tumor tissues and hepatocellular carcinoma (HCC) outcomes.

Methods

Gene Expression Omnibus (GEO) databases GSE14520 and GSE36376 were used to identify differential expressed CYP450 genes between tumor and nontumor tissues and related to HCC clinicopathological features and survivals.

Results

Seven CYP450 genes including CYP1A2, CYP2A6, CYP2C8, CYP2C9, CYP2E1, CYP3A4, and CYP4A11 were downregulated in tumor tissues, which were validated in both GSE14520 and GSE36376. HCC patients with CYP2A6 and CYP2C8 low levels in tumor tissues suffered from poorer overall survival (OS) compared to those with high CYP2A6 and CYP2C8 in GSE14520 profile (log ranks P = 0.01 and P = 0.006, respectively). In addition, HCC patients with lower CYP2A6 and CYP2C8 in tumors had worse recurrence-free survival (RFS) than those with higher CYP2A6 and CYP2C8 (log ranks P = 0.02 and P = 0.012, respectively). In GSE36376 validation dataset, HCC patients with lower CYP2A6 and CYP2C8 had worse OS and RFS than those with higher CYP2A6 and CYP2C8 (all P < 0.05), in line with results in GSE14520 dataset. Additionally, lower CYP2A6 and CYP2C8 are associated with advanced clinicopathological features including tumor staging, vascular invasion, intrahepatic metastasis, and high alpha fetoprotein (all P < 0.05).

Conclusion

Downregulation of CYP2A6 and CYP2C8 in tumor tissues links to poorer OS and RFS in HCC patients.

The Identification of Core Gene Expression Signature in Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is one of the most common malignancies, which causes serious financial burden worldwide. This study aims to investigate the potential mechanisms contributing to HCC and identify core biomarkers. The HCC gene expression profile GSE41804 was picked out to analyze the differentially expressed genes (DEGs). Gene ontology (GO) and the Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses were carried out using DAVID. We constructed a protein-protein interaction (PPI) network to visualize interactions of the DEGs. The survival analysis of these hub genes was conducted to evaluate their potential effects on HCC. In this analysis, 503 DEGs were captured (360 downregulated genes and 143 upregulated genes). Meanwhile, 15 hub genes were identified. GO analysis showed that the DEGs were mainly enriched in oxidative stress, cell cycle, and extracellular structure. KEGG analysis suggested the DEGs were enriched in the absorption, metabolism, and cell cycle pathway. PPI network disclosed that the top3 modules were mainly enriched in cell cycle, oxidative stress, and liver detoxification. In conclusion, our analysis uncovered that the alterations of oxidative stress and cell cycle are two major signatures of HCC. TOP2A, CCNB1, and KIF4A might promote the development of HCC, especially in proliferation and differentiation, which could be novel biomarkers and targets for diagnosis and treatment of HCC.

The Interaction of Smoking with Gene Polymorphisms on Four Digestive Cancers: A Systematic Review and Meta-Analysis

The main purpose of this study was to perform a meta-analysis to assess the interaction between smoking and nine genes (GSTM1, GSTT1, GSTP1, CYP1A1, NAT2, SULT1A1, hOGG1, XRCC1 and p53) on colorectal cancer, gastric cancer, liver cancer and oesophageal cancer. Published articles from the PubMed, ISI and EMBASE databases were retrieved. A total of 67 case-control studies or nested case-control studies were identified for the analysis. The pooled jodds ratio (OR) with 95% confidence interval (CI) was calculated using the random effect model. The overall study showed that the GSTM1 polymorphism was associated with the risk of the four digestive cancers among Asian population (OR 1.284, 95% CI: 1.122-1.470, p: 0). Subgroup analyses by cancer site showed that GSTM1 null genotype increased the gastric cancer risk in total population (OR 1.335, 95% CI: 1.145-1.556, p: 0). However, the association of GSTM1 null genotype with the oesophageal cancer risk was found in smokers (OR 1.382, 95% CI: 1.009-1.894, p:0.044), but not in non-smokers (OR 1.250, 95% CI: 0.826-1.891, p:0.290). Moreover, smokers with the CYP1A1 IIe462Val polymorphism were at an increased cancer risk in Asian population (OR=1.585, 95% CI 1.029-2.442, p: 0.037). None of the other gene-smoking interactions was observed in the above cancers. This meta-analysis reveals two potential gene-smoking interactions, one is between smoking and GSTM1 on oesophageal cancer, and the other is between smoking and CYP1A1 IIe462Val on the four cancers in Asian population. Future studies need to be conducted to verify the conclusions.

Cytochrome P450 Genes (CYP2E1 and CYP1A1) Variants and Susceptibility to Chronic Hepatitis B Virus Infection

Hepatitis B virus (HBV) infection is a worldwide health concern which is associated with significant morbidity and mortality. Both viral and host factors have a significant effect on infection, replication and pathogenesis of HBV. The aim of this study was to investigate the effect of CYP2E1 and CYP1A1 genetic variants on susceptibility to HBV. 143 individuals including 54 chronic HBV patients and 89 healthy controls were enrolled in the genotyping procedure. rs2031920 and rs3813867 at CYP2E1 as well as rs4646421 and rs2198843 at CYP1A1 loci were studied in all subjects using PCR-RFLP (restriction fragment length polymorphism) analysis. Both variants at CYP2E1 locus were monomorphic in all studied subjects. Genotype frequency of rs4646421 was significantly different between chronic HBV patients and healthy blood donors (P = 0.04, OR 4.31; 95% CI 1.04-17.7). Furthermore, individuals carrying at least one C allele (CC or CT genotypes) for rs4646421 seemed to have a decrease risk of hepatitis in comparison with TT genotype (P = 0.039). Our results showed a relationship between rs4646421 TT genotype (rare genotype) and the risk for developing chronic HBV infection (four times higher). Further studies are needed to examine the role of CYP1A1 polymorphism in susceptibility to chronic HBV infection.

Meta-analysis of association studies of CYP1A1 genetic polymorphisms with digestive tract cancer susceptibility in Chinese

BACKGROUND

A great number of studies have shown that cytochrome P450 1A1 (CYP1A1) genetic polymorphisms, CYP1A1 Msp I and CYP1A1 Ile/Val, might be risk factors for digestive tract cancers, including esophageal cancer (EC), gastric cancer (GC), hepatic carcinoma (HC), as well as colorectal cancer (CC), but the results are controversial. In this study, a meta-analysis of this literature aimed to clarify associations of CYP1A1 genetic polymorphisms with digestive tract cancer susceptibility in Chinese populations.

MATERIALS AND METHODS

Eligible case-control studies published until December 2013 were retrieved by systematic literature searches from PubMed, Embase, CBM, CNKI and other Chinese databases by two investigators independently. The associated literature was acquired through deliberate search and selection based on established inclusion criteria. Fixed- effects or random-effects models were used to estimate odds ratios (ORs and 95%CIs). The meta-analysis was conducted using Review Manager 5.2 and Stata 12.0 softwares with stability evaluated by both stratified and sensitivity analyses. Moreover, sensitivity analysis and publication bias diagnostics confirmed the reliability and stability.

RESULTS

Eighteen case control studies with 1, 747 cases and 2, 923 controls were selected for CYP1A1 MspI polymorphisms, and twenty case-control studies with 3, 790 cases and 4, 907 controls for the CYP1A1 Ile/ Val polymorphisms. Correlation associations between CYP1A1 Ile/Val polymorphisms and digestive tract cancers susceptibility were observed in four genetic models in the meta-analysis (GG vs AA:OR= 2.03, 95%CI =1.52- 2.72; AG vs AA: OR=1.26, 95%CI =1.07-1.48; [ GG+AG vs AA] :OR =1.42, 95%CI=1.20-1.68, [GG vs AA+AG ]:OR=1.80, 95%CI =1.40-2.31). There was no association between CYP1A1 Msp I polymorphisms and digestive tract cancer risk. Subgroup analysis for tumor type showed a significant association of CYP1A1 Ile/Val genetic polymorphisms with EC in China. However, available data collected by the study failed to reveal remarkable associations of GC or HC with CYP1A1 Ile/Val genetic polymorphisms and EC, GC or CC with CYP1A1 MspI genetic polymorphisms.

CONCLUSIONS

Our results indicated that CYP1A1 Ile/Val genetic polymorphisms, but not CYP1A1 Msp I polymorphisms, are associated with an increased digestive tract cancer risk in Chinese population. Additional well-designed studies, with larger sample size, focusing on different ethnicities and cancer types are now warranted to validate this finding.

Cytochrome P450 in Cancer Susceptibility and Treatment

Cytochrome 450 (CYP450) designates a group of enzymes abundant in smooth endoplasmic reticulum of hepatocytes and epithelial cells of small intestines. The main function of CYP450 is oxidative catalysis of various endogenous and exogenous substances. CYP450 are implicated in phase I metabolism of 80% of drugs currently in use, including anticancer drugs. They are also involved in synthesis of various hormones and influence hormone-related cancers. CYP450 genes are highly polymorphic and their variants play an important role in cancer risk and treatment. Association studies and meta-analyses have been performed to decipher the role of CYP450 polymorphisms in cancer susceptibility. Cancer treatment involves multimodal therapies and evaluation of CYP450 polymorphisms is necessary for pharmacogenetic assessment of anticancer therapy outcomes. In addition, CYP450 inhibitors are being evaluated for improved pharmacokinetics and oral formulation of several anticancer drugs.

Serum hepatitis B surface antigen is correlated with intrahepatic total HBV DNA and cccDNA in treatment-naïve patients with chronic hepatitis B but not in patients with HBV related hepatocellular carcinoma

The aim of the study was to investigate correlations between intrahepatic hepatitis B virus total DNA, covalently closed circular DNA (cccDNA), and serum HBsAg in treatment-naïve chronic hepatitis B and HBV related hepatocellular carcinoma (HCC). Liver tissues were taken from 42 HBV related HCC and 36 patients with chronic hepatitis B. A fraction of DNA extracted from liver tissue was digested with a plasmid-safe ATP-dependent DNase and used for HBV cccDNA detection. The remaining DNA was used for the detection of HBV total DNA and β-globin, the latter of which is a housekeeping gene and quantified for normalization by real-time PCR. Quantitation of serum HBsAg was performed by a chemiluminescence assay. Serum HBsAg had positive correlations with serum HBV DNA (r = 0.636, P < 0.001), intrahepatic HBV total DNA (r = 0.519, P = 0.001) and cccDNA (r = 0.733, P < 0.001) in 36 treatment-naïve chronic hepatitis B, while HBsAg correlated poorly with DNA (r = 0.224, P = 0.210), intrahepatic total DNA and cccDNA in the tumor (r = 0.351, P = 0.031; r = 0.164, P = 0.324, respectively) and non-tumor (r = 0.237, P = 0.152; r = 0.072, P = 0.667, respectively) liver tissues of 42 HCC. HBV cccDNA and total DNA were significantly higher in liver tissue from chronic hepatitis B than in tumor and non-tumor of HCC (P < 0.001). Serum HBsAg and HBV DNA were also higher in chronic hepatitis B than in HCC (P < 0.001). It was concluded that levels of serum HBsAg and intrahepatic cccDNA and total DNA were significantly higher in chronic hepatitis B than in HCC, and significant correlations among them were observed in treatment-naïve chronic hepatitis B but not in HCC.

Identification of CYP2C9*2 allele in HepG2 cell line

BACKGROUND

Hepatoma is caused by many factors including alcohol, chemicals, viral infection, and chronic inflammation. Cytochrome P450 polymorphism plays an important role in its pathogenesis. CYP2D6, CYP2E1, and CYP1A1 have been identified to be related with hepatic carcinogenesis and tumor size and stage. However, no studies have been performed on CYP2C9, a major CYP in the liver and hepatoma.

AIM OF THE STUDY

To identify if there is polymorphism of CYP2C9 in a HepG2 cell line.

METHODS

A pair of primers was used to clone CYP2C9 exon 3 region and subsequently sequenced. The sequence was compared to normal CYP2C9 for identification of any mutation.

RESULTS

A point mutation was identified. It was located in the amino acid number 144 of CYP2C9 protein with the change of normal amino acid arginine into cysteine, which is the same as identified in poor metabolism patients as homozygous CYP2C9*2.

CONCLUSIONS

There is a mutation (CYP2C9*2/ CYP2C9*2) in a HepG2 cell line. Thus, polymorphism of CYP2C9 may also be involved in the carcinogenesis of hepatoma as CYPs2D6 and 2E1.

GST polymorphisms are associated with hepatocellular carcinoma risk in Chinese population

AIM: To investigate the association between GSTM1 and GSTT1 polymorphisms and the risk of hepatocellular carcinoma (HCC) in Chinese population.

METHODS: Literature databases including PubMed, ISI web of science and other databases were searched. Pooled odds ratio (OR) and 95% CI were calculated using random- or fixed- effects model. Subgroup analysis and sensitivity analysis were also performed.

RESULTS: Nineteen studies of GSTM1 (2660 cases and 4017 controls) and 16 studies of GSTT1 (2410 cases and 3669 controls) were included. The GSTM1/GSTT1 null genotypes were associated with increased risk of HCC in Chinese population (for GSTM1, OR = 1.487, 95% CI: 1.159 to 1.908, P = 0.002; for GSTT1, OR = 1.510, 95% CI: 1.236 to 1.845, P = 0.000). No publication bias was detected. In subgroup analysis, glutathione S-transferases polymorphisms were significantly associated with HCC risk among the subjects living in high-incidence areas, but not among the subjects living in low-incidence areas.

CONCLUSION: The present meta-analysis suggests that GSTM1/GSTT1 null genotypes are associated with increased risk of HCC in Chinese population.

Interactions of chemical carcinogens and genetic variation in hepatocellular carcinoma

In the etiology of hepatocellular carcinoma (HCC), in addition to hepatitis B virus and hepatitis C virus infections, chemical carcinogens also play important roles. For example, aflatoxin B(1) (AFB(1)) epoxide reacts with guanine in DNA and can lead to genetic changes. In HCC, the tumor suppressor gene p53 codon 249 mutation is associated with AFB(1) exposure and mutations in the K-ras oncogene are related to vinyl chloride exposure. Numerous genetic alterations accumulate during the process of hepatocarcinogenesis. Chemical carcinogen DNA-adduct formation is the basis for these genetic changes and also a molecular marker which reflects exposure level and biological effects. Metabolism of chemical carcinogens, including their activation and detoxification, also plays a key role in chemical hepatocarcinogenesis. Cytochrome p450 enzymes, N-acetyltransferases and glutathione S-transferases are involved in activating and detoxifying chemical carcinogens. These enzymes are polymorphic and genetic variation influences biological response to chemical carcinogens. This genetic variation has been postulated to influence the variability in risk for HCC observed both within and across populations. Ongoing studies seek to fully understand the mechanisms by which genetic variation in response to chemical carcinogens impacts on HCC risk.

Association of a variant in MIR 196A2 with susceptibility to hepatocellular carcinoma in male Chinese patients with chronic hepatitis B virus infection

MicroRNAs (miRNAs) are small noncoding RNAs with regulatory functions as tumor suppressors and oncogenes. Recent studies have implicated that the rs11614913 SNP in MIR196A2 was associated with susceptibility of lung cancer, congenital heart disease, breast cancer and shortened survival time of nonsmall cell lung cancer. To assess whether this polymorphism is associated with susceptibility to and clinicopathologic characteristics of hepatitis B virus (HBV)-related hepatocellular carcinoma (HCC), a total of 560 patients with chronic HBV infection and 391 healthy volunteers were enrolled, and MIR196A2 polymorphism was genotyped by polymerase chain reaction-ligation detection reaction (PCR-LDR). In our study group, there was no significant association between MIR196A2 polymorphism and the risk of HBV-related HCC in all subjects, however, the risk of HCC was significantly higher with MIR196A2 rs11614913 CC genotype or C allele compared with those with the TT genotype or T allele in male patients. Furthermore, in a subsequent analysis of the association between this polymorphism and clinicopathologic characteristics, there was still no significant difference in both the distribution of genotype or allelic frequency. However, we observed that the T allele was significantly more frequent in male HCC patients with lymphatic metastasis. Our results suggested that MIR196A2 polymorphism was associated with susceptibility to HBV-related HCC in a male Chinese population.

No association of EGF 5'UTR variant A61G and hepatocellular carcinoma in Chinese patients with chronic hepatitis B virus infection

OBJECTIVE

Epidermal growth factor (EGF) has many biological functions, including mitogenesis, tumorigenesis, and proliferation of epidermal tissues. Previous studies have reported that the EGF +61 (A/G) single nucleotide polymorphism in the 5'-untranslated region of the EGF gene is functional, and is associated with development of hepatocellular carcinoma (HCC) in liver cirrhosis and various malignancy. Our aim was to investigate whether EGF gene A61G polymorphism could be implicated in susceptibility to and/or clinicopathological characteristics of HCC in Chinese patients with chronic hepatitis B virus (HBV) infection.

METHODS

This polymorphism was studied in 387 patients with chronic HBV infection and in 208 healthy volunteers using restriction fragment-length polymorphism. The patients were divided into two groups: those without (n = 172) and those with HCC (n = 215). These 215 HCC patients with chronic HBV infection were designated as cases, and the remaining 172 patients without HCC served as controls.

RESULTS

There were no significant differences in EGF genotype or allelic frequencies between cases and controls nor was EGF genotype or allelic frequencies associated with tumour number, size, growth phase, stage, and invasiveness. We also found ethnic heterogeneity in the functional EGF polymorphism.

CONCLUSIONS

The present results show that although EGF gene A61G polymorphism is associated with development of HCC in liver cirrhosis, it is not sufficient for HCC in Chinese patients with chronic HBV infection.

Interaction between cytochrome P450 1A2 genetic polymorphism and cigarette smoking on the risk of hepatocellular carcinoma in a Japanese population

Limited epidemiological evidence suggests that genetic polymorphisms of drug-metabolizing enzymes such as cytochrome P450 (CYP), glutathione S-transferase (GST) and N-acetyltransferase (NAT) may be involved in tobacco-related hepatocarcinogenesis. We conducted a case-control study, including 209 incident cases with hepatocellular carcinoma (HCC) and two different control groups [275 hospital controls and 381 patients with chronic liver disease (CLD) without HCC], to investigate whether CYP1A1, CYP1A2, CYP2A6, CYP2E1, GSTM1 and NAT2 polymorphisms are related to the risk of HCC with any interaction with cigarette smoking. Overall, no significant associations with HCC were observed for any genotypes against either control group. However, we found a significant interaction (P = 0.0045) between CYP1A2 -3860G>A polymorphism and current smoking on HCC risk when we compared HCC cases with CLD patients; adjusted odds ratios [ORs; and 95% confidence intervals (CIs)] for G/A and A/A genotypes relative to G/G genotype were 0.28 (0.12-0.66) and 0.18 (0.04-0.94), respectively, among current smokers (P trend = 0.002), as compared with 1.28 (0.80-2.06) and 0.76 (0.34-1.71), respectively, among never/former smokers (P trend = 0.96). Similarly, in CYP1A2 G/G genotype, significant risk increase was observed for current smoking (OR = 4.08, 95% CI = 2.02-8.25) or more recent cigarette use (e.g. pack-years during last 5 years, P trend = 0.0003) but not in G/A and A/A genotypes combined (OR for current smoking = 1.39, 95% CI = 0.63-3.03; P trend for pack-years during last 5 years = 0.40). These results suggest that the CYP1A2 -3860G>A polymorphism modifies the smoking-related HCC risk among CLD patients.

[Genetic epidemiological study on single nucleotide polymorphisms associated with hepatocellular carcinoma in patients with chronic HBV infection]

Hepatocellular carcinoma (HCC) is associated with hepatitis B virus (HBV) as an etiologic agent in 80% of cases, and is the major cause of death among HBV carriers. Family history of HCC is a known risk factor for the development of HCC among chronically HBV infected patients; therefore, genetic factors are likely to modify the risk of HCC. However, the genetic factors that determine progression to HCC remain mostly to be recovered. It is estimated that there are millions of single nucleotide polymorphisms (SNPs) within human genome and they are likely to explain much of the genetic diversity of individuals. In this review, the natural history of HBV infection and host genetic factors related to HCC, study design and target gene selection for the detection of SNPs related to the occurrence of HCC were discussed. Also, several SNPs or haplotypes, which were reportedly associated with increased or reduced risk of HCC occurrence in patients with chronic HBV infection, were reviewed. Especially, recent studies in Korea, one of the HBV endemic areas, were discussed. Screening of these polymorphisms might be useful in clinical practice to stratify the lower or higher risk group for HCC and might modify the design of HCC surveillance programs in patients with chronic HBV infection, if further genetic susceptibilities are identified. The ongoing studies of the distributions and functions of the implicated allele polymorphisms will not only provide insight into the pathogenesis of HCC, but may also provide a novel rationale for new methods of diagnosis and therapeutic strategies.

Cytochrome p450 1A1 gene polymorphisms in patients with psoriatic arthritis

OBJECTIVE

To investigate the associations of cytochrome p450 1A1 (CYP1A1) gene polymorphisms with susceptibility to psoriatic arthritis in Taiwan.

METHODS

CYP1A1 gene polymorphisms were determined in 52 patients with psoriatic arthritis and in 90 healthy controls by polymerase chain reaction/restriction fragment length polymorphism.

RESULTS

The genotype frequency of CYP1A1 4889A/G was significantly increased in patients with psoriatic arthritis in comparison with healthy controls. The phenotype frequency of CYP1A1 4889G was also significantly increased in patients with psoriatic arthritis. The genotype frequency of CYP1A1 4887C/A was significantly higher in patients with psoriatic arthritis than in controls. The allele and phenotype frequencies of 4887A were also significantly increased in patients with psoriatic arthritis. We also found that the association of CYP1A1 4887A with psoriatic arthritis was independent of 4889G but a synergistic effect was present between CYP1A1 4887A and 4889G. The CYP1A1 4889A/G and 4887C/A polymorphisms were not associated with the manifestations and severity of psoriatic arthritis.

CONCLUSION

CYP1A1 4887A and 4889G may be precipitating factors for susceptibility to psoriatic arthritis in Taiwan. An additive effect was found between CYP1A1 4887A and 4889G.

Lack of association between the functional polymorphisms in the estrogen-metabolizing genes and risk for hepatocellular carcinoma

Estrogens have been proposed to act as tumor promoters and induce hepatocarcinogenesis. Recently, we observed a significant association between the risk for hepatocellular carcinoma and the polymorphisms of the estrogen receptor (ESR) alpha (ESR1) gene, supporting the hypothesis of involvement for the estrogen-ESR axis in the estrogen-induced hepatocarcinogenesis. In this study, based on another hypothesis in which estrogen metabolites can directly cause DNA damage and affect tumor initiation, we examined whether the polymorphisms of the estrogen-metabolizing enzymes (EME), which are involved in biogenesis (CYP17, CYP19), bioavailability (CYP1A1, CYP1B1), and degradation (catechol-O-methyltransferase) of the estrogens, have any bearing on the risk for hepatocellular carcinoma. Seven functional polymorphisms in five EMEs (CYP17 MspAI site, CYP19 Trp39Arg, Ile462Val and MspI site in CYP1A1, CYP1B1 Val432Leu, and Ala72Ser and Val158Met in catechol-O-methyltransferase) were genotyped in 434 patients with hepatocellular carcinoma and 480 controls by PCR-RFLP analysis. The associations between the polymorphisms and hepatocellular carcinoma risk were evaluated while controlling for confounding factors. No significant association with the risk for hepatocellular carcinoma was observed with the seven polymorphisms in hepatitis B virus carriers and non-hepatitis B virus carriers after correction for multiple comparisons. After stratification by common confounding factors of hepatocellular carcinoma, the EME polymorphism remained no significant association with the hepatocellular carcinoma risk. Furthermore, no signs of gene-gene interactions were observed for each combination of the seven polymorphisms. Our findings suggest that the polymorphisms of EMEs may not contribute significantly to the risk for hepatocellular carcinoma.

Common genetic variations of the cytochrome P450 1A1 gene and risk of hepatocellular carcinoma in a Chinese population

Cytochrome P450 1A1 is a major enzyme in the bioactivation of exogenous procarcinogens of hepatocellular carcinoma (HCC). However, the contribution of common genetic variants in CYP1A1 to the HCC risk in Chinese populations has not been thoroughly investigated. In this study, we examined the association between HCC and four selected tagging single nucleotide polymorphisms (SNPs) of CYP1A1, and the risk of CYP1A1 haplotypes/diplotypes in 1006 pathologically confirmed HCC patients and 1015 cancer-free controls, from a Han Chinese population. Haplotypes/diplotypes were constructed from observed genotypes using the Haplo.Stats program. Relative risk was estimated by using multivariable logistic regression method. To summarise, we detected an increased HCC risk in rs4646421 variant carriers (OR 1.30, 95% CI 1.05-1.61) and rs2198843 variant carriers (OR 1.33, 95% CI 1.05-1.69), and a reduced risk of HCC (OR 0.70. 95% CI 0.52-0.94) associated with homozygote carriers of rs4886605 variant. These association signals were also observed in non-smokers with rs4646421 (OR 1.56, 95% CI 1.16-2.08) and rs4886605 (OR 0.61, 95% CI 0.40-0.91). Compared to the most common CYP1A1 haplotype CCAG, the haplotype TTGC conferred an increased risk of HCC (OR 1.26, 95% CI 1.04-1.52). Similarly, the TTGC/TTGC diplotype conferred an increased risk of HCC compared with diplotype CCAG/CCAG (OR 2.06, 95% CI 1.23-3.45, P=0.006). Interestingly, the diplotype TTAC/CCAG also conferred an increased risk of HCC (OR 1.76, 95% CI 1.22-2.54, P=0.003). Our results suggested that common genetic variants in CYP1A1 may modulate the risk of developing HCC in the study population, particularly in non-smokers. However, our findings need to be validated in at least one independent study of Han Chinese population.

An Interethnic Comparison of Polymorphisms of the Genes Encoding Drug-Metabolizing Enzymes and Drug Transporters: Experience in Singapore

Much of the interindividual variability in drug response is attributable to the presence of single nucleotide polymorphisms (SNPs) in genes encoding drug-metabolizing enzymes and drug transporters. In recent years, we have investigated the polymorphisms in a number of genes encoding phase I and II drug-metabolizing enzymes including CYPIA1, CYP3A4, CYP3A5, GSTM1, NAT2, UGT1A1, and TPMT and drug transporter (MDR1) in three distinct Asian populations in Singapore, namely the Chinese, Malays, and Indians. Significant differences in the frequencies of common alleles encoding these proteins have been observed among these three ethnic groups. For example, the frequency of the variant A2455G polymorphism of CYP1A1 was 28% in Chinese and 31% in Malays, but only 18% in Indians. CYP3A4*4 was detected in two of 110 Chinese subjects, but absent in Indians and Malays. Many Chinese and Malays (61-63%) were homozygous for the GSTM1*0 null genotype compared with 33% of Indians. The frequency of the UGTIA1*28 allele was highest in the Indian population (35%) compared to similar frequencies that were found in the Chinese (16%) and Malay (19%) populations. More importantly, our experience over the years has shown that the pharmacogenetics of these drug-metabolizing enzymes and MDR1 in the Asian populations are different from these in the Caucasian and African populations. For example, the CYP3A4*1B allele, which contains an A-290G substitution in the promoter region of CYP3A4, is absent in all three Asian populations of Singapore studied, but occurs in more than 54% of Africans and 5% of Caucasians. There were no difference in genotype and allelic variant frequencies in exon 12 of MDR1 between the Chinese, Malay, and Indian populations. When compared with other ethnic groups, the distribution of the wild-type C allele in exon 12 in the Malays (34.2%) and Indians (32.8%) was relatively high and similar to the Japanese (38.55%) and Caucasians (41%) but different from African-Americans (15%). The frequency of wild-type TT genotype in Asians (43.5% to 52.1%) and Japanese (61.5%) was much higher than those found in Caucasians (13.3%). All the proteins we studied represent the primary hepatic or extrahepatic enzymes, and their polymorphic expression may be implicated in disease risk and the disposition of drugs or endogenous substances. As such, dose requirements of certain drugs may not be optimal for Asian populations, and a second look at the factors responsible for this difference is necessary.

Impact of hepatitis C virus infection on lifestyle

AIM

To evaluate the impact of the diagnosis of hepatitis C infection on lifestyle habits such as smoking, drinking, sports activity and diet.

METHODS

A self-administered, anonymous questionnaire was offered to out-patients with HCV infection consecutively attending three clinical centres in Italy.

RESULTS

Of the 275 respondents, 62.2% (171) were male. Mean age was 51 (range 20-80) years. Overall, after the diagnosis of hepatitis C, 74.5% of drinkers had modified (giving up or reducing) alcohol consumption, 21.3% of smokers had modified their habits and 32.3% of subjects who reported sports activity had either stopped or reduced frequency of activity or chose a less fatiguing sport. Sixty-four percent of the respondents reported having modified their diet, most of them on physician's advice.

CONCLUSION

After the diagnosis of hepatitis C many patients correctly modified their alcohol consumption and a minority their smoking habits. The reason for reported changes in diet and physical activity needs further investigations.

Heavy smoking and liver

Smoking causes a variety of adverse effects on organs that have no direct contact with the smoke itself such as the liver. It induces three major adverse effects on the liver: direct or indirect toxic effects, immunological effects and oncogenic effects. Smoking yields chemical substances with cytotoxic potential which increase necro-inflammation and fibrosis. In addition, smoking increases the production of pro-inflammatory cytokines (IL-1, IL-6 and TNF- alpha) that would be involved in liver cell injury. It contributes to the development of secondary polycythemia and in turn to increased red cell mass and turnover which might be a contributing factor to secondary iron overload disease promoting oxidative stress of hepatocytes. Increased red cell mass and turnover are associated with increased purine catabolism which promotes excessive production of uric acid. Smoking affects both cell-mediated and humoral immune responses by blocking lymphocyte proliferation and inducing apoptosis of lymphocytes. Smoking also increases serum and hepatic iron which induce oxidative stress and lipid peroxidation that lead to activation of stellate cells and development of fibrosis. Smoking yields chemicals with oncogenic potential that increase the risk of hepatocellular carcinoma (HCC) in patients with viral hepatitis and are independent of viral infection as well. Tobacco smoking has been associated with suppression of p53 (tumour suppressor gene). In addition, smoking causes suppression of T-cell responses and is associated with decreased surveillance for tumour cells. Moreover, it has been reported that heavy smoking affects the sustained virological response to interferon (IFN) therapy in hepatitis C patients which can be improved by repeated phlebotomy. Smoker's syndrome is a clinico-pathological condition where patients complain of episodes of facial flushing, warmth of the palms and soles of feet, throbbing headache, fullness in the head, dizziness, lethargy, prickling sensation, pruritus and arthralgia.

Estrogen receptor alpha polymorphisms associated with susceptibility to hepatocellular carcinoma in hepatitis B virus carriers

BACKGROUND & AIMS

Overexpression of estrogen receptors (ESRs) is implicated in the development of hepatocellular carcinoma (HCC) in both animal models and humans. We examined whether the ESR1 polymorphisms were related to HCC risk among chronic hepatitis B virus carriers.

METHODS

Six ESR1 polymorphisms, which are (TA)n repeat in the promoter, T29C at codon 10 in exon 1, PvuII and XbaI site in intron 1, C136474G at codon 325 in exon 4, and A252966G in intron 5, were genotyped in 248 patients with HCC and 239 controls. The associations with the susceptibility to HCC were estimated by logistic regression. Allele-specific transcription difference of ESR1 messenger RNA was performed by real-time quantitative polymerase chain reaction.

RESULTS

We observed a statistically significant increased susceptibility to HCC associated with the homozygous alleles with a high number of TA repeats (assigned as H/H genotype; odds ratio [OR], 2.66; 95% confidence interval [CI], 1.44-4.94; P = .0018), T29C C/C genotype (OR, 2.31; 95% CI, 1.25-4.26; P = .0076), and PvuII C/C genotype (OR, 2.19; 95% CI, 1.27-3.78; P = .0048) compared with the homozygous alleles with a low number of TA repeats (assigned as L/L genotype), T29C T/T, and PvuII T/T genotype, respectively. In accordance, the relative messenger RNA levels of the at-risk C allele of T29C were consistently higher than those of the T allele in heterozygous cells.

CONCLUSIONS

Our findings suggest that the genetic polymorphism in ESR1 may play a role in mediating susceptibility to HCC in Chinese hepatitis B virus carriers.

A p53 polymorphism modifies the risk of hepatocellular carcinoma among non-carriers but not carriers of chronic hepatitis B virus infection

To clarify the modifying effect of the codon 72 p53 polymorphism on hepatocellular carcinoma (HCC) stratified by chronic hepatitis B virus (HBV) infection status, 111 incident cases of HCC and 424 controls in HBV-negative subjects and 135 cases and 125 controls in HBV-positive subjects were identified. No correlation between the polymorphism and HCC risk was found when comparing the HBV-positive cases to controls. However, in HBV-negative subjects, Arg/Pro and Pro/Pro genotypes had a 1.97-fold and a 3.36-fold increased risk for HCC, respectively. In subjects with the Pro allele and family history of HCC yielded an 11.81-fold increased risk of HCC.

Cytochrome P-450 1A1 gene polymorphisms and risk of breast cancer: a HuGE review

Cytochrome P-450 (CYP) 1A1 plays a key role in phase I metabolism of polycyclic aromatic hydrocarbons and in estrogen metabolism. It is expressed predominantly in extrahepatic tissues, including the breast. Four CYP1A1 gene polymorphisms (3801T --> C, Ile462Val, 3205T --> C, and Thr461Asp) have been studied in relation to breast cancer. The 3801C variant is more common than the Val variant. Both variants occur more frequently in Asians than in White populations. The 3205T --> C polymorphism has been observed in African Americans only. Little data are available on the geographic/ethnic distribution of the Thr461Asp polymorphism. The functional significance of the polymorphisms is unclear. In 17 studies, no consistent association between breast cancer and CYP1A1 genotype was found. Meta-analysis found no significant risk for the genotypes 1) 3801C/C (relative risk (RR) = 0.97, 95% confidence interval (CI): 0.52, 1.80) or 3801T/C (RR = 0.91, 95% CI: 0.70, 1.19) versus 3801T/T, 2) Val/Val (RR = 1.04, 95% CI: 0.63, 1.74) or Ile/Val (RR = 0.92, 95% CI: 0.76, 1.10) versus Ile/Ile, or 3) Asp/Asp (RR = 0.95, 95% CI: 0.20, 4.49) or Thr/Asp (RR = 1.12, 95% CI: 0.87, 1.43) versus Thr/Thr. Future studies should explore possible interactions between CYP1A1 and sources of polycyclic aromatic hydrocarbons, markers of estrogen exposure, other lifestyle factors influencing hormonal levels, and other genes involved in polycyclic aromatic hydrocarbon metabolism or hormonal biosynthesis.

Expression of cytochrome P450 1A1 and its contribution to oxidation of a potential human carcinogen 1-phenylazo-2-naphthol (Sudan I) in human livers

Cytochrome P450 1A1 (CYP1A1) is one of the most important enzymes implicated in the metabolic activation of carcinogens. To date, there is still conflicting evidence for the expression of enzymatically functional CYP1A1 in human liver. In the present work, we clearly demonstrate that CYP1A1 capable of metabolizing a carcinogen 1-phenylazo-2-naphthol (Sudan I) is expressed in livers of eight American Caucasian donors. Using two independent methods (immunoblotting and N-terminal sequencing), CYP1A1 protein was detected and quantified in all human hepatic microsomes tested in the study. Its levels, ranging from 0.97 to 3.0 pmol/mg protein, correlated with activities catalyzed by this enzyme [7-ethoxyresorufin O-deethylation (EROD) and oxidation of Sudan I], indicating the presence of enzymatically active CYP1A1. Even though levels of CYP1A1 expression are low, <0.7% of total hepatic CYP, the CYP1A1 contribution to oxidation of carcinogenic Sudan I in the test set of human liver microsomes ranges from 12 to 30%.

Single Nucleotide Polymorphisms Associated with Hepatocellular Carcinoma in Patients with Chronic Hepatitis B Virus Infection

It is estimated that there are millions of single nucleotide polymorphisms (SNPs) within human genome and there are likely to explain much of the genetic diversity of individuals. Hepatocellular carcinoma (HCC) is etiologically associated with hepatitis B virus (HBV) in 80% of cases, and is the dominant cause of death among HBV carriers. Among patients with chronic HBV infection, family history is a known risk factor for the development of HCC; therefore, genetic factors are likely to modify the risk of HCC. However, the genetic factors that determine progression to HCC remain mostly to be investigated. In this review, we discussed that the natural history of HBV infection and host genetic factors related to HCC, study design and target gene selection for the detection of SNPs related to the occurrence of HCC. Also, we reviewed that several SNPs or haplotypes, which were reportedly associated with increased or reduced risk of HCC occurrence in patients with chronic HBV infection. Screening of these polymorphisms might be useful in clinical practice to stratify the lower or higher risk group for HCC and might modify the design of HCC surveillance programs in patients with chronic HBV infection, if further genetic susceptibilities are identified.

Impact of cigarette smoking on response to interferon therapy in chronic hepatitis C Egyptian patients

AIM: Smoking may affect adversely the response rate to interferon-α . Our objective was to verify this issue among chronic hepatitis C patients.

METHODS: Over the year 1998, 138 chronic hepatitis C male Egyptian patients presenting to Cairo Liver Center, were divided on the basis of smoking habit into: group I which comprised 38 smoker patients ( > 30 cigarettes/d) and group II which included 84 non-smoker patients. Irregular and mild smokers (16 patients) were excluded. Non eligible patients for interferon-α therapy were excluded from the study and comprised 3/38 (normal ALT) in group I and 22/84 in group II (normal ALT, advanced cirrhosis and thrombocytopenia). Group I was randomly allocated into 2 sub-groups: group Ia comprised 18 patients who were subjected to therapeutic phlebotomy while sub-group Ib consisted of 17 patients who had no phlebotomy. In sub-group Ia, 3 patients with normal ALT after repeated phlebotomies were excluded from the study. Interferon-α 2b 3 MU/TIW was given for 6 mo to 15 patients in group Ia, 17 patients in group Ib and 62 patients in group II. Biochemical, virological end-of- treatment and sustained responses were evaluated.

RESULTS: At the end of interferon-α treatment, ALT was normalized in 3/15 patients (20%) in group Ia and 2/17 patients (11.8%) in group Ib compared to17/62 patients (27.4%) in group II (P = 0.1). Whereas 2/15 patients (13.3%) in group Ia. and 2/17 patients (11.8%) in group Ib lost viraemia compared to 13/62 patients (26%) in group II (P = 0.3). Six months later, ALT was persistently normal in 2/15 patients (13.3%) in group 1a and 1/17 patients (5.9%) in group Ib compared to 9/62 patients (14.5%) in group II (P = 0.47). Viraemia was eliminated in 1/15 patients (6.7%) in group Ia and 1/17 patients (5.9%) in group Ib compared to 7/62 patients (11.3%) in group II, but the results did not mount to statistical significance (P = 0.4).

CONCLUSION: Smokers suffering from chronic hepatitis C tend to have a lower response rate to interferon-α compared to non-smokers. Therapeutic phlebotomy improves the response rate to interferon-α therapy among this group.

Intraportal nicotine infusion in rats decreases hepatic blood flow through endothelin-1 and both endothelin A and endothelin B receptors

Smoking has been demonstrated to aggravate liver injury. Nicotine, a major pharmacological component of tobacco smoke, affects a multitude of functions. Smoking and nicotine induce synthesis of endothelin (ET)-1. The effect of intraportal infusion of nicotine on hepatic circulation and an involvement of ET-1 and ET receptor in the action of nicotine were investigated in rats. Nicotine (0-100 microg/kg/h) was infused into the portal vein of urethane-anesthetized rats, and changes of hepatic blood flow were evaluated. Intraportal infusion of nicotine dose-dependently decreased hepatic blood flow and increased portal pressure without any alteration of heart rate or arterial blood pressure. This action of intraportal nicotine was completely abolished by pretreatment of ET-1 antibody. Either BQ485 (ET(A) receptor antagonist) or BQ788 (ET(B) receptor antagonist) partially reversed the effect of nicotine, and combination of BQ788 and BQ485 completely abolished it. These findings suggest that nicotine inhibits hepatic circulation through ET-1, and ET(A) and ET(B) receptor.

Cytochrome P450 1A1 and manganese superoxide dismutase genes polymorphisms in reactive arthritis

To investigate the role of cytochrome P450 1A1 (CYP1A1) and manganese superoxide dismutase (Mn SOD) genes polymorphisms in the susceptibility to reactive arthritis, the polymorphisms of CYP1A1 and Mn SOD genes were determined in 43 patients with reactive arthritis following Chlamydia trachomatis infection and 92 healthy controls by polymerase chain reaction (PCR)/restriction fragment length polymorphisms (RFLP) method. The frequencies of CYP1A1 4887C/A and C/A+A/A were significantly higher in patients with reactive arthritis than in controls. Moreover, the increased frequency of CYP1A1 4887A in patients with reactive arthritis is independent of HLA-B27. The frequency of Mn SOD 1183T/T tended to be increased in patients with reactive arthritis. We also found that the frequency of CYP1A1 4887A was significantly increased in Mn SOD 1183T/T(+) reactive arthritis patients compared with 1183T/T(+) controls. CYP1A1 4887A may be a risk factor for the development of reactive arthritis, especially in the presence of Mn SOD 1183T/T.

Impact of N-acetyltransferase polymorphism (NAT2) in hepatocellular carcinoma (HCC)--an investigation in a department of surgical medicine

In the multifactorial aetiology of hepatocellular carcinoma (HCC), an association and interaction between genetic polymorphisms of xenobiotic metabolizing enzymes, lifestyle factors, and cancer risk has been postulated. N-acetyltransferase (NAT2) is involved in the metabolic activation and detoxification of aromatic amines. Aromatic amines are potential hepatocarcinogens in humans. In the present study, we investigated if genetic NAT2 polymorphism is related to HCC. Genotyping of NAT2 was performed in 70 HCC patients and 87 controls using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis. The results of this investigation show that 46 out 70 HCC patients (65.7%) and 50 out of 87 controls (57.5%) were of the slow acetylator genotypes. The frequency of distribution of slow and rapid acetylators (genotypes) was not significantly different between cases and controls (p > 0.05). Slow acetylator genotypes were not associated with a significantly increased HCC risk (odds ratio, 1.4; 95% confidence interval, 0.74-2.72). A significant association between NAT2 genetic polymorphism and HCC was observed among smokers. Slow acetylator genotypes significantly increased the HCC risk in cigarette smokers (odds ratio, 3.5; 95% confidence interval, 1.38-9.05). Our results suggest that genetic NAT2 polymorphism may play a role in lifestyle factors-related hepatocarcinogenesis. NAT2 activity may be particulary critical in smoking related hepatocarcinogenesis.

Polymorphism of the N-acetyltransferase 2 gene, red meat intake, and the susceptibility of hepatocellular carcinoma

OBJECTIVE

Carcinogenic aromatic amines, derived from cooked meat, are activated or inactivated by hepatic N-acetyltransferase (NAT). The aim of this study was to evaluate the relationship of NAT2 genetic polymorphisms with hepatocellular carcinoma (HCC), with special reference to the interaction of dietary habits.

METHODS

Peripheral white blood cell DNA from 185 HCC patients and 185 matched controls were genotyped for NAT2 by a polymerase chain reaction-restriction fragment length polymorphism method. All the subjects studied were chronic viral hepatitis B or C carriers with liver cirrhosis. Dietary habits of the subjects were assessed using a semiquantitative food frequency questionnaire.

RESULTS

There was no association between the susceptibility of HCC and the overall NAT2 genotypes. However, in rapid acetylators (with two wild type NAT2*4 alleles), there was a trend of increased HCC risk from low to intermediate and high red meat intake (OR = 1, 2.66, 3.89; p(trend) = 0.016), even when adjusted for family history of HCC and habitual alcohol drinking. The interaction between red meat intake and the NAT2*4 acetylator status for an increased risk of HCC was significant (p = 0.007).

CONCLUSIONS

Polymorphisms of the NAT2 gene may confer different susceptibilities to the effect of red meat intake on HCC. In rapid acetylators with chronic viral hepatitis-related cirrhosis, red meat intake may play a role in hepatocarcinogenesis.

CYP enzyme polymorphisms and susceptibility to HCV-related chronic liver disease and liver cancer

Cancer risk can be influenced by the exposure to endogenous or environmental toxins. Polymorphic enzymes involved in the metabolic activation/detoxification of carcinogens may account for individual variations of risk. We studied the polymorphisms of five enzymes of the P450 superfamily, CYP1A1, CYP1A2, CYP2D6, CYP2E1 and CY3A4, as risk factors for liver disease progression and cancer in hepatitis C virus-infected patients. CYP genotyping was performed by polymerase chain reaction (PCR) restriction fragment length polymorphism or allele-specific PCR. Different stages of disease were considered, as follows: 90 asymptomatic carriers and 87 chronic hepatitis, 92 cirrhosis and 91 hepatocellular carcinoma (HCC) cases. Reference allele frequencies were obtained from 99 blood donors. Allele distributions among categories were compared using the chi(2) test. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated to express relative risks. Independent associations were modeled by correspondence analysis and logistic regression. Frequencies of the CYP1A1 highly inducible alleles, MspI m2 and Val, were increased in liver disease patients compared with carriers; no specific association with HCC was found. The high-activity CYP2E1 c2 allele was underrepresented among HCC patients with respect to other HCV categories, including cirrhosis. CYP2D6 poor metabolizer (PM) genotypes were significantly more frequent in healthy subjects (7.1%) and carriers (11.1%) than in hepatitis/cirrhosis (4.6%) and HCC (1.2%) patients. This was confirmed by multivariable analysis. PM genotypes protected against progressive disease as ORs reduced proportionally to stage. The age at diagnosis for HCC was anticipated in non-PM individuals. No differences were seen for CYP1A2 and CYP3A4 genes. Polymorphic variants of CYP genes may contribute to the progression of liver disease and HCC risk in HCV-infected subjects.

Increased risk for hepatitis B-related liver cirrhosis in relatives of patients with hepatocellular carcinoma in northern Taiwan

BACKGROUND

There is a tendency for familial aggregation of hepatocellular carcinoma (HCC). The aims of this study were to assess the degree to which familial aggregation of hepatitis B surface antigen (HBsAg) carriers accounts for familiality of HCC in families of hepatitis B-related HCC patients, and whether HCC shares a familial predisposition with liver cirrhosis among HBsAg carriers.

METHODS

A total of 671 first-degree relatives of HBsAg-positive HCC cases were recruited using abdominal ultrasonography and tests for HBsAg and serum aminotransferases. They were from 165 simplex families defined as having only one HCC case and 72 multiplex families with more than one case. In analyses of family history of HCC and cirrhosis, the data set consisted of 4,471 unrelated asymptomatic HBsAg carriers recruited in a prospective study.

RESULTS

There was no significant difference in the HBsAg-positive rate among relatives between multiplex (55.7%) and simplex (48.1%) families. Sonographic evidence of liver cirrhosis was present in 14.4% of HBsAg-positive relatives from multiplex families but in only 7.8% of HBsAg-positive relatives from simplex families (multiplex versus simplex families: adjusted odds ratio [OR] = 2.29; 95% CI: 1.10-4.77). Among unrelated asymptomatic HBsAg carriers, the adjusted OR of liver cirrhosis associated with a first-degree family history of HCC was 2.80 (95% CI: 1.68-4.66). This association was stronger in HBsAg carriers <50 years. No association was seen between family history of HCC and hepatitis activity based on elevated levels of aminotransferases.

CONCLUSIONS

Familial aggregation of HCC in HBsAg carriers is associated with familial clustering of liver cirrhosis.

Overexpression of p28/gankyrin in human hepatocellular carcinoma and its clinical significance

AIM: To investigate the expression of p28/gankyrin gene and its role in the carcinogenetic process of human hepatocellular carcinoma (HCC).

METHODS: 64 specimens of HCC and para-carcinoma tissues, 22 specimens of non-tumor liver tissues (7 normal, 15 cirrhosis), 10 specimens of normal human tissues and 5 hepatoma cell lines were studied for the expression of p28/gankyrin by Northern blot. The expression of p28/gankyrin protein was detected immunohistochemically by using the specific polyclonal antibody.

RESULTS: Northern blot analysis indicated that the expression of p28/gankyrin mRNA was intensively distributed in brain and heart, weakly in lung, spleen and muscle, undetectable in digestive system including liver, pancreas, stomach, small and large intestines. p28/gankyrin mRNA was absent in normal liver, weakly detected in liver cirrhosis and in 18 of 64 para-carcinoma liver tissues. In contrast, the expression of p28/gankyrin mRNA was intensively detected in all 5 hepatoma cell lines tested, markedly increased in 57 of 64 and moderately increased in 5 of 64 HCC samples. In comparison with liver cirrhosis and para-carcinoma liver tissues, the average expression of p28/gankyrin mRNA in HCC was increased 3.6- (2.901 ± 0.507 vs 0.805 ± 0.252, P < 0.05) and 5.2-fold (2.901 ± 0.507 vs 0.557 ± 0.203, P < 0.01), respectively. In addition, p28/gankyrin mRNA expression level was higher in HCC with portal vein tumor thrombus and microscopic hepatic vein involvement (P = 0.021 and P = 0.047, respectively). The overexpression of p28/gankyrin protein in HCC was targeted in hepatic tumor cells, not in bile duct cells and other interstitial cells.

CONCLUSION: Overexpression of p28/gankyrin in HCC plays an important role and contributes to the metastasis potential in the process of carcinogenesis. p28/gankyrin may become a specific biological tissue marker for the pathological diagnosis of HCC.

Androgen receptor exon 1 CAG repeat length and risk of hepatocellular carcinoma in women

The androgen receptor (AR) gene is localized on chromosome X, and shorter CAG repeats in exon 1 of the AR gene were recently suggested to increase hepatitis B virus (HBV)-related hepatocellular carcinoma (HCC) risk among men. To examine whether the relationship between the AR-CAG repeats and HCC was also evident among women, we conducted a case-control study in Taiwan. The number of AR-CAG repeats was determined for 238 women with HCC and 354 unrelated control subjects (comprising 188 first-degree and 166 nonbiological relatives) selected from female relatives of patients with HCC. Women harboring 2 AR alleles with more than 23 CAG repeats had an increased risk of HCC (age-adjusted odds ratio [OR], 1.82; 95% CI, 1.06-3.14), compared with women with only short alleles or a single long allele. The association between harboring 2 AR alleles containing longer CAG repeats and HCC was more striking among HBV carriers (age-adjusted OR for more than 22 repeats, 2.23; 95% CI, 1.14-4.34) and particularly prominent among HBV carriers under age 53 years (age-adjusted OR, 3.16; 95% CI, 1.13-8.82). When CAG repeats were analyzed as a continuous variable, the increase in HCC risk associated with each incremental repeat in the shorter of 2 alleles in a given genotype was statistically significant among women with a first-degree relative with HCC (age-adjusted OR, 1.18; 95% CI, 1.01-1.37). No such relationship was detected among women without the family history. In conclusion, our observations suggest that the AR-CAG alleles may contribute to HCC predisposition among women through a mechanism different from that for men.

Cancer epidemiology and control in Taiwan: a brief review

Malignant neoplasm has become the leading cause of death in Taiwan since 1982. There has been a decreasing trend for cancers of the stomach and cervix uteri, while an increasing trend has been observed for cancers of the lung, liver, oral cavity, colon and rectum, breast and prostate. International comparison and migrant studies have shown an elevated risk of hepatocellular carcinoma, nasopharyngeal carcinoma and cervical neoplasia in Taiwan. The national hepatitis B vaccination program, started in July 1984, has resulted in a significant decrease in childhood hepatocellular carcinoma in Taiwan. A decrease in prevalence of cigarette smoking has been observed among middle-aged men since the control of tobacco hazards was enacted in 1997. Free mass screening of cervical neoplasia and colorectal cancer has been implemented in the national health insurance program since 1995. Project-based screening for hepatocellular carcinoma, nasopharyngeal carcinoma and breast cancer among high-risk groups was started in 1994. Most cancer patients are diagnosed by pathological examinations and treated by surgical operation, chemotherapy and radiotherapy in major teaching hospitals in Taiwan. The Taiwan Collaborative Oncology Group has been organized to assess the efficacy of various treatment modalities through multicentric clinical trials. There has been a striking increase in expenditure for medical care of cancer patients. Cancer researchers mainly sponsored by the National Science Council and Department of Health are engaged in basic, epidemiological and clinical studies on major cancers in Taiwan. Major fields of the research include cancer genomics, gene therapy, molecular epidemiology and DNA vaccine.

Genetic link of hepatocellular carcinoma with polymorphisms of the UDP-glucuronosyltransferase UGT1A7 gene

BACKGROUND & AIMS

Hepatocellular carcinoma is associated with risk factors including hepatitis C, hepatitis B, cirrhosis, genetic liver diseases, and environmental carcinogens. Uridine 5'-diphosphate-glucuronosyltransferases are a superfamily of detoxifying enzymes capable of tobacco-borne carcinogen detoxification and cellular protection. This study examines the association of UGT1A7 and UGT1A9 gene polymorphisms with hepatocellular carcinoma.

METHODS

Genomic DNA from the blood of 59 patients with hepatocellular carcinoma and 70 control subjects without evidence of cancer was analyzed by UGT1A7- and UGT1A9-specific PCR, sequencing analysis, and temperature gradient gel electrophoresis.

RESULTS

Three UGT1A7 missense mutations were detected defining the UGT1A7*2, UGT1A7*3, and UGT1A7*4 alleles. Wild-type UGT1A7 alleles were present in 41.4% of controls but only in 6.8% of cancer patients (P < 0.001; odds ratio [OR], 9.73; 95% confidence interval [CI], 3.17-29.83). UGT1A7 polymorphisms were present in 93.2% of hepatocellular cancer patients, 74.5% carried the UGT1A7*3 allele (P < 0.001; OR, 10.76; 95% CI, 4.75-24.38), which combines the W208R, N129K, and R131K mutations and encodes a protein with low carcinogen detoxification activity. No UGT1A9 polymorphisms were detected.

CONCLUSIONS

The significant association of hepatocellular carcinoma with the UGT1A7*3 allele encoding a low detoxification activity protein is identified and implicates UGT1A7 as a risk gene of hepatocarcinogenesis in addition to a role as potential marker for cancer risk assessment in chronic liver disease.

Role of N-acetyltransferase polymorphisms in hepatitis B related hepatocellular carcinoma: impact of smoking on risk

BACKGROUND

Persistent infection with hepatitis B virus (HBV) causes chronic phasic necroinflammation and regenerative proliferation in the liver. The sustained hepatocellular proliferation may render chronic HBV carriers more susceptible to the effects of environmental carcinogens. Aromatic amines are potential hepatocarcinogens in humans. N-acetyltransferase (NAT) is involved in the metabolic activation and detoxification of these compounds.

AIMS

To investigate if genetic polymorphisms in N-acetylation are related to hepatocellular carcinoma (HCC) among chronic HBV carriers.

METHODS

Genotyping of NAT1 and NAT2 was performed using polymerase chain reaction-restriction fragment length polymorphism on peripheral leucocyte DNA from 151 incident cases of HCC and 211 controls. All subjects were male, and were chronic HBV surface antigen carriers.

RESULTS

A significant association between NAT2 genetic polymorphism and HCC was observed among chronic HBV carriers who were smokers but not among those who were non-smokers. For smoking HBV carriers, the odds ratios of developing HCC for those heterozygous and homozygous for the NAT2*4 functional allele compared with those without any copies of the functional allele (reference group) were 2.67 (95% confidence interval 1.15-6.22) and 2.58 (95% confidence interval 1.04-6.43), respectively. The interaction between cigarette smoking and the presence of the NAT2*4 allele just failed to reach statistical significance (p=0.06). No association between NAT1 genotype and HCC was evident overall or within the smoking stratified subgroups.

CONCLUSIONS

Our results suggest that NAT2 activity may be particularly critical in smoking related hepatocarcinogenesis among chronic HBV carriers. Our data also indirectly support a role for tobacco smoke derived aromatic amines in the aetiology of HCC.

Hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a disease that is extremely difficult to manage and is increasing markedly in incidence. This presents both an opportunity and a challenge. At-risk patients can be identified and early detection of HCC is feasible. New surgical techniques and postoperative therapies, including hepatic intra-arterial radiation, may improve the outlook for some patients with resectable cancer. Unfortunately, the vast majority of patients with HCC will have unresectable cancers. Regional treatments may shrink or necrose tumors, but no clear benefit to such therapies has been demonstrated. Recent evidence suggests combination chemotherapy may help some patients, although this needs validation. Perhaps the best hope is that the further elucidation of the genetic and molecular features of HCC will lend us insight into innovative strategies to manage this difficult cancer.