Current pathogenetic and molecular concepts in viral liver carcinogenesis

Involvement of DNA damage response pathways in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) has been known as one of the most lethal human malignancies, due to the difficulty of early detection, chemoresistance, and radioresistance, and is characterized by active angiogenesis and metastasis, which account for rapid recurrence and poor survival. Its development has been closely associated with multiple risk factors, including hepatitis B and C virus infection, alcohol consumption, obesity, and diet contamination. Genetic alterations and genomic instability, probably resulted from unrepaired DNA lesions, are increasingly recognized as a common feature of human HCC. Dysregulation of DNA damage repair and signaling to cell cycle checkpoints, known as the DNA damage response (DDR), is associated with a predisposition to cancer and affects responses to DNA-damaging anticancer therapy. It has been demonstrated that various HCC-associated risk factors are able to promote DNA damages, formation of DNA adducts, and chromosomal aberrations. Hence, alterations in the DDR pathways may accumulate these lesions to trigger hepatocarcinogenesis and also to facilitate advanced HCC progression. This review collects some of the most known information about the link between HCC-associated risk factors and DDR pathways in HCC. Hopefully, the review will remind the researchers and clinicians of further characterizing and validating the roles of these DDR pathways in HCC.

Occult hepatitis B virus infection and hepatocellular carcinoma: a systematic review

Occult hepatitis B (OHB) infection has been reported to play an important role in the development of hepatocellular carcinoma (HCC). In this systematic review, a significantly higher prevalence of OHB was observed in patients with HCC in the presence or absence of HCV infection when compared with control populations without HCC. Correspondingly, among adequately designed prospective studies, the cumulative probability of developing HCC was significantly greater among patients with OHB than among HBV DNA-negative patients in the presence or absence of HCV infection. Study design, inclusion criteria, treatment options, methodology and potential confounding variables were evaluated, and immunopathogenic mechanisms that could be involved in OHB as a risk factor in HCC were reviewed. From this analysis, we conclude that although OHB is an independent risk factor in HCC development in anti-HCV-negative patients, a synergistic or additive role in the occurrence of HCC in HCV-coinfected patients is more problematic due to the HCC risk attributable to HCV alone, especially in patients with advanced fibrosis and cirrhosis.

Insulin resistance is associated with hepatocellular carcinoma in chronic hepatitis C infection

AIM: To elucidate the role of insulin resistance (IR) and serum adiponectin level in hepatocellular carcinoma (HCC) associated with chronic hepatitis C.

METHODS: Clinical and biochemical characteristics were collected from 165 consecutive patients with newly diagnosed HCC. Homeostasis model assessment of IR (HOMA-IR) and serum adiponectin level were investigated in 188 patients with different stages of hepatitis C virus (HCV) infection.

RESULTS: Among HCC patients, type 2 diabetics (DM) was more prevalent in HCV subjects (35.6%, n = 59) compared to hepatitis B virus (HBV; 12.7%, n = 63) or non-HBV, non-HCV cases (7.1%, n = 28). In patients with chronic hepatitis C, HCC subjects had higher blood sugar (P < 0.001), insulin level (P = 0.003) and HOMA-IR (P = 0.018) than those with chronic hepatitis and advanced fibrosis. Age, male sex and body mass index were significantly associated with serum adiponectin level, whereas HOMA-IR was not. Based on stepwise logistic regression analysis, age (OR: 1.124, P < 0.001), serum insulin level (OR: 1.585, P < 0.001), HOMA-IR (OR: 0.495, P = 0.001), DM (OR: 11.601, P = 0.002) and male sex (OR: 3.877, P = 0.016) were independently associated with HCC. This result was similar even if the diabetic subjects were excluded for analysis.

CONCLUSION: Insulin resistance measured by HOMA-IR, regardless of the presence of diabetes, is significantly associated with HCC development in patients with chronic HCV infection.

[Molecular pathogenesis of hepatocellular carcinoma: new therapeutic approaches and predictive pathology]

Hepatocellular carcinoma is one of the most prevalent malignancies worldwide and its incidence is increasing. Multimodal strategies directed towards this carcinoma include primary (e.g. immunisation) and secondary (e.g. antiviral therapy) prevention, surgical approaches, novel specific systemic therapies (targeted therapy), and the treatment of comorbidity (cirrhosis). New molecular approaches are currently under development. These tackle several specific targets, with pathology being challenged in many aspects: experimental evaluation, the development of valid tumor-relevant diagnostic tests as well as morphological evaluation in the context of clinical studies, and finally in routine diagnosis.

Association of amino acid variations in the NS5A and E2-PePHD region of hepatitis C virus 1b with hepatocellular carcinoma

NS5A and E2 proteins of the hepatitis C virus (HCV) have the potential to repress protein kinase R (PKR) that exerts a tumour suppressor function. We investigated the relationship between amino acid variations in the NS5A-PKR-binding domain and E2-PKR-eIF2alpha phosphorylation homology domain (PePHD) region and the development of hepatocellular carcinoma (HCC) in chronic HCV-1b patients. In a cross-sectional, hospital-based setting, we compared the amino acid sequences of NS5A-PKR-binding domain and E2-PePHD in the sera of 104 chronic hepatitis, 44 cirrhosis and 96 HCC patients. The nucleotide sequences were inferred by direct sequencing of the amplified HCV products and deduced amino acid were compared with the sequence of HCV-J. By univariate analysis, old age, lower viral load, fewer amino acid substitutions in the NS5A-PKR-binding domain (codons 2209-2274) and the interferon sensitivity-determining region (ISDR; codons 2209-2248), and wild-type amino acid at codon 2209 and codon 2240 was significantly correlated with HCC, whereas substitutions in the E2-PePHD was not. Patients with a mutated-type (> or = 4) NS5A-ISDR had a lower prevalence of HCC than those with intermediate or wild type (P < 0.05). Based on stepwise logistic regression analysis, age [odds ratio (OR): 1.132, P < 0.001], viral load (OR: 0.305, P < 0.001) and mutated-type ISDR (OR: 0.137, P = 0.001) were independently associated with HCC. In conclusion, NS5A-ISDR variations may play an important role in the development of HCV-related HCC.

Mutations in the E2-PePHD region of hepatitis C virus type 1b in patients with hepatocellular carcinoma

An interaction between the protein kinase (PKR)-eIF2-alpha phosphorylation homology domain (PePHD) within the E2 protein of hepatitis C virus (HCV) and cell protein kinase (PKR) may affect the control of protein synthesis and cell growth. In an attempt to investigate the genetic variability of the E2-PePHD domain in hepatocellular carcinoma (HCC), we studied sera and liver tissues from HCC patients. The partial E2-PePHD region was analysed by direct sequencing of the sera of 47 HCCs in cirrhotic livers and 31 cases of chronic active hepatitis (CAH), and tumoral and non-tumoral liver tissues from 13 HCC patients. A similar number of mutations was detected within the E2 domain in the HCC and CAH cases, but nine of the 47 HCCs (19%) showed an amino acid (aa) mutation at position 660, eight of which involved a change in the same aa (alanine instead of serine; A/S). No such mutation was detected in any of the PePHD sequences from the CAH patients: this difference was statistically significant (P = 0.008). The aa change at position 660 was also found in two sequences from tumoral but not non-tumoral tissue from the same liver. The analysis of 461 sequences obtained from GenBank supports the conclusion that the observed aa change is an infrequent event in HCV-infected patients, thus suggesting that it could be associated with HCC.

Prevalence of wild-type in NS5A-PKR protein kinase binding domain in HCV-related hepatocellular carcinoma

BACKGROUND/AIMS

Experimental studies have demonstrated that the wild-type PKR-NS5A strain of hepatitis C virus (HCV) may have oncogenic potential through the binding and functional repression of PKR protein kinase. To assess whether the NS5A-PKR-binding domain may be involved in HCV-related liver carcinogenesis, its sequence was analyzed in the sera of 85 patients with hepatocellular carcinoma (HCC) and in 51 patients with chronic active hepatitis (CAH). In 13 HCC cases sequence analysis was also performed in tumor and nontumor liver tissues.

METHODS

The nucleotide sequences of the PKR-binding domain were inferred by direct sequencing of the amplified HCV products and deduced amino acids were compared with the sequence of HCV-J.

RESULTS

A wild-type or single mutated strain which retains PKR-binding activity was found in 88% of HCC and 69% of CAH cases (P=0.0096). All but three HCC cases showed no divergences in amino acid changes between serum and liver tissues. The wild-type strains were equally distributed between the HCC with or without cirrhosis.

CONCLUSIONS

The prevalance of the wild-type NS5A-PKR strain is significantly higher in HCC than in CAH. These data suggest that inhibition of PKR activity by HCV might represent a potential mechanism of HCV-related carcinogenesis.

The facultative stem cell: A new star in liver pathology

Although the unlimited capacity of hepatocytes to divide has been recently proven, more and more evidences support the existence of a primitive stem cell compartment in the liver. These cells probably do not participate in the usual maintenance of the liver mass, but they are activated in case of extensive hepatocyte injury. In vivo the oval cells show deep similarly to the primitive cells of the embryonic liver and seem to be the amplification compartment of the hepatic stem cells. A primitive epithelial cell population can be isolated from the normal liver and maintained in vitro. Studies of these two experimental systems provide most of the data about liver stem cells, which may become important for the clinical practice if we understand how their growth is regulated.

The importance of hepatic resection for hepatocellular carcinoma originating from nonfibrotic liver

BACKGROUND

Our study aimed to clarify the characteristics of hepatocellular carcinoma (HCC) in patients with a nonfibrotic liver and the role of surgical resection for HCC in nonfibrotic liver compared with patients with HCC in fibrotic or cirrhotic livers.

STUDY DESIGN

A total of 516 patients who underwent hepatectomy between April 1985 and June 1999 were classified into two groups: a nonfibrotic liver group (n=65) and a fibrotic liver group (n=451), which included fibrotic or cirrhotic livers. Clinicopathologic variables were then compared between the groups, including disease-free survival rate and patient survival rate.

RESULTS

Only 8 of 65 patients (12.3%) with a nonfibrotic liver showed a histologically completely normal liver. The numbers of men and patients with alcohol abuse in the nonfibrotic liver group were higher than in the fibrotic liver group. The numbers of patients with positive hepatitis B antigen and positive hepatitis C antibody in the nonfibrotic liver group were lower than in the fibrotic liver group. Results of liver function tests in the nonfibrotic liver group were better than those in the fibrotic liver group. The rates of both portal vein and hepatic vein invasion of cancer cells in the nonfibrotic liver group were higher than in the fibrotic liver group. The tumor size in the nonfibrotic liver group was larger than in the fibrotic liver group. The patient survival and disease-free survival rates in the nonfibrotic liver group were better than in the fibrotic liver group.

CONCLUSIONS

Hepatic resection can be beneficial for patients with HCC originating from a nonfibrotic liver when compared with fibrotic or cirrhotic patients with HCC.

Marked genetic similarities between hepatitis B virus-positive and hepatitis C virus-positive hepatocellular carcinomas

Hepatocellular carcinoma (HCC) is one of the most common neoplasms worldwide. Well-established risk factors include infections with two very different viruses: the DNA virus causing hepatitis B (HBV) and the RNA virus inducing hepatitis C (HCV). In order to determine whether genetic differences exist between HBV- and HCV-induced HCC, 41 HCC samples of known vival status were examined by comparative genomic hybridization (CGH). The analysis revealed frequent deletions of 1p (24%), 4q (39%), 6q (41%), 8p (44%), 9p (24%), 11q (24%), 12q (22%), and 13q (39%), as well as common gains of 1q (46%), 6p+ (20%), 8q+ (41%), 11q (27%), and 17q+ (37%). There was no significant difference in the number and type of chromosomal imbalances between 25 HCV- and 16 HBV-infected tumours. This is consistent with models suggesting that HBV and HCV cause cancer through non-specific inflammatory and regenerative processes, rather than through virus-specific interactions with defined target genes. Chromosomal imbalances were also unrelated to the grade and stage of HCC. This may suggest that most gross genomic alterations occur early during HCC development and that further progression of these tumours may be associated with other types of genetic changes, not detectable by CGH. In summary, these data show that characteristic gross genomic changes occur in HCC, but these alterations at present do not appear to have diagnostic or prognostic applications.

2-acetaminofluorene blocks cell cycle progression after hepatectomy by p21 induction and lack of cyclin E expression

In the Solt-Faber model DENA and 2-Acetaminofluorene (AAF) treatment combined with hepatectomy induces hepatocellular carcinoma in rats. In this model AAF blocks proliferation of hepatocytes, while oval cells restore liver mass. Here we studied the molecular mechanism involved in blocking AAF-dependent cell cycle progression of hepatocytes. AAF inhibits cell proliferation of hepatocytes shown by the lack of Cyclin E expression before the G1/S phase restriction point. Immunfluorescence studies revealed that Cyclin E positive signals were restricted to oval cells, while hepatocytes remained negative. Additionally, AAF treatment induces strong nuclear p53 expression which is associated with increased p21 mRNA levels. Inhibition of active Cyclin/CdK (cyclin dependent kinase) complexes is reflected in AAF-treated animals by decreased RB expression and phosphorylation. The decrease in RB expression and phosphorylation, which is essential in triggering DNA synthesis and Cyclin A expression, leads to a deficiency in transcriptionally active E2F complex formation after hepatectomy. Thus, two molecular explanations are evident to account for AAF-dependent cell cycle progression of hepatocytes in vivo: first, induction of p53 expression which leads to higher p21 mRNA levels, and second, a lack of Cyclin E expression at the G1/S phase restriction point after hepatectomy.

Expression of mutant thyroid hormone nuclear receptors in human hepatocellular carcinoma cells

To understand the expression and role of thyroid hormone nuclear receptors (TRs) in hepatocarcinogenesis, we characterized the TRs in 16 human hepatocellular carcinoma (HCC) specimens. The full-length cDNAs for the two TR subtypes, alpha1 and beta1, were cloned from several tumors by reverse transcription-polymerase chain reaction. Southern blot analysis indicated that, in addition to the full-length cDNA, truncated TRalpha1 and TRbeta1 cDNAs were present in nine tumors (53%). In addition, point mutations detected by the mismatch RNase cleavage assay in TRalpha1 and TRbeta1 were found in 65% and 76% of the tumors, respectively. The mutations were confirmed by DNA sequencing. Interestingly, most of the TRalpha1 mutations were in amino acid codons 209-228 and 245-256, two hot-spots in HCC patients. However, no hot-spot was detected in TRbeta1. The expression of TRalpha1 and TRbeta1 proteins was determined in the tissue extracts by western blotting. TRbeta1 protein was expressed or elevated in 10 tumors but not in normal livers, whereas the expression of TRalpha1 was variable among tumors. The mutant TR proteins were translated in vitro, and their hormone- and DNA-binding activities were evaluated. Abnormal binding to the thyroid hormone response elements was observed. The proteins' DNA binding activity was either partially impaired or completely lost. The high prevalence of TR mutations found in the tumors of patients with hepatocellular carcinoma suggests that mutant TRs could play an important role in liver carcinogenesis.

Effects of continuous hepatitis with persistent hepatitis C viremia on outcome after resection of hepatocellular carcinoma

The effect of persistent hepatitis C viremia on the outcome after resection of hepatocellular carcinoma (HCC) was investigated in 59 consecutive patients with a single small HCC (< or = 3.0 cm in diameter). The presence of serum hepatitis C virus (HCV) RNA was evaluated using a reverse transcription polymerase chain reaction method as well as a branched DNA probe method. Clinicopathologic findings were compared between patients with and without viremia and the risk factors for poor outcome were evaluated. Hepatitis C virus (HCV) RNA was not detected in the sera from 7 patients (group 1), but was detected in the sera from the other 52 patients (group 2). Alanine aminotransferase (ALT) activity was significantly higher in group 2 than in group 1. The proportion of patients with active hepatitis was significantly higher in group 2. In group 2, new HCC often developed after the operation and four patients died of liver dysfunction. HCV viremia, high ALT activity, high concentration of total bilirubin, and liver cirrhosis were related to recurrence after the operation. Multivariate analysis indicated that HCV viremia and high ALT activity were independent risk factors for recurrence of HCC. Continuous hepatitis with persistent HCV viremia worsened the outcome after the resection of HCC by causing new development of HCC and deterioration of liver function. In patients with HCV-related HCC, but without HCV viremia, satisfactory results can be expected after liver resection.

Comparison of serum and liver hepatitis C virus quasispecies in HCV-related hepatocellular carcinoma

BACKGROUND/AIMS

The hepatitis C virus (HCV) genome consists of quasispecies populations of heterogeneous variants, especially in the hypervariable region. To assess the profiles of viral quasispecies in HCV-related hepatocellular carcinoma, we studied the viral population patterns in serum and liver tissues of 13 HCV-positive patients with hepatocellular carcinoma developed on cirrhotic and non-cirrhotic livers (5 and 8 cases, respectively).

METHODS

HCV genome heterogeneity was analyzed by polymerase chain reaction-mediated single-strand conformation polymorphism analysis, which showed multiple DNA bands representing different hypervariable region sequences.

RESULTS

The HCV populations were different between tumorous and nontumorous tissues in 3/5 hepatocellular carcinomas with cirrhosis and in 6/8 without cirrhosis. At least one or more than one common band was detected in both compartments in all but one case. No significant differences in the complexity of HCV quasispecies were found in hepatocellular carcinoma with or without underlying cirrhosis. Comparison of the HCV quasispecies profiles in serum and liver tissues showed a different distribution of HCV variants between these two compartments in 6/7 patients. In four cases, both common and compartmentalized sequences were detected, whereas in two cases, both without cirrhosis, the HCV population in serum was completely different from that found in the liver.

CONCLUSIONS

These results suggest that the complexity of HCV populations is influenced by the presence of hepatocellular carcinoma rather than by the severity of the underlying chronic liver disease. The different quasispecies patterns found in serum and liver may reflect different biological properties of circulating and intrahepatic HCV particles or the existence of extrahepatic sites of replication.

Different responses of rat liver adenosine metabolizing enzymes during in vivo and in vitro treatment with interferon-alpha 2b

Interferon-alpha 2b (IFN-alpha 2b) can exert antiproliferative activity in both normal and malignant liver tissue. To study mechanisms of its antiproliferative action, the activity of the enzymes of adenosine metabolism were investigated. We studied 5'-nucleotidase (an adenosine-producing enzyme) and adenosine deaminase (involved in adenosine degradation). Female Wistar rats (3 weeks old) were treated with IFN-alpha 2b for 48 h, as were adult rats (3 months old) and adult rats subjected to partial hepatectomy. During IFN-alpha 2b administration, the activity of 5'-nucleotidase increased in the liver of 3-week-old rats, proportionately more than in adult rats, but the greatest increase was seen in partially hepatectomised rats. The activity of adenosine deaminase decreased in the liver of 3-week-old rats, did not change significantly in 3-month-old rats, but was significantly lower in partially hepatectomised rats. As high adenosine concentrations are toxic for mammalian cells, especially during proliferation, the progressive increase of adenosine production, together with the progressive decrease of its degradation, could be one of the mechanisms of IFN-alpha 2b-induced antiproliferative activity. In vitro studies were performed using collagenase-isolated hepatocytes. They were exposed to IFN-alpha 2b, a cAMP analogue, or both. The incubation of hepatocytes with IFN-alpha 2b did not significantly change the activity of both enzymes, whereas incubation with the cAMP analogue decreased 5'-nucleotidase activity and increased adenosine deaminase activity. The mechanism of IFN-alpha 2b-induced alteration in adenosine metabolism is therefore unclear.

Transforming growth factor alpha (TGFalpha) in hepatocellular carcinomas and adjacent hepatic parenchyma

We examined stage T1 to T4 hepatocellular carcinomas (HCC) to determine whether transforming growth factor alpha (TGFalpha) presence differed between early- and late-stage HCC and between tumors with low and high proliferative rates. Paraffin sections from 36 HCC were evaluated for TGFalpha and the proliferation markers Kiel 67 antigen (Ki67) or proliferating cell nuclear antigen (PCNA) by immunoperoxidase staining. In 12 cases, double staining for TGFalpha and Ki67 was also performed. Eighty-one percent of tumors and 94% of adjacent liver sections contained TGFalpha. A trend toward inverse correlation was seen between the percentage of TGFalpha-positive tumor cells and the proliferative rate as determined by Ki67 staining. No clear correlation of TGFalpha to either tumor stage or percentage of PCNA-positive cells was seen. This study confirms the presence of TGFalpha in the majority of early- and late-stage HCC. Positivity within tumor tissue is consistent with autocrine or paracrine stimulation. A trend toward inverse correlation between TGFalpha-producing cells and the number of cycling cells suggests that rapidly proliferating tumors may consume this growth factor at an accelerated rate. Alternatively, other hepatic mitogens may have more functional significance in these latter tumors. Finally, the presence of TGFalpha in peritumoral hepatocytes suggests these cells as potential sources of paracrine stimulation for HCC.

Clinical relevance of transforming growth factor-beta 1 in the urine of patients with hepatocellular carcinoma

To assess the clinical relevance of transforming growth factor-beta 1 (TGF-beta 1) in the urine of patients with hepatocellular carcinoma (HCC), TGF-beta 1 was measured, by radioimmunoassay, in 140 patients with HCC, 50 cirrhotic patients, 30 patients with chronic active hepatitis, and 50 healthy controls. The results indicate that there were significantly increased urinary TGF-beta 1 levels in patients with HCC. Raised TGF-beta 1 levels were associated, in a dose-related fashion, with increased risk for development of HCC (odds ratio, 1.05, 95% confidence interval, 1.03-1.07). HCC patients with raised TGF-beta 1 levels had shorter survival than those with normal TGF-beta 1 levels (p = 0.038). TGF-beta 1 levels decreased after successful anticancer therapy (p < 0.0001). There was an inverse correlation between TGF-beta 1 and serum alpha-fetoprotein (AFP) (r = -0.199, p < 0.04). Receiver operating characteristics (ROC) curve analysis indicated that parallel determination of TGF-beta 1 and AFP significantly increased the sensitivity and diagnostic accuracy, with a high specificity. In conclusion, raised urinary TGF-beta 1 was associated with HCC development. It is a predictor of poor prognosis, and a tumor marker for diagnosis and therapeutic follow-up of HCC.

Extracellular matrix composition and integrin expression in early hepatocarcinogenesis in human cirrhotic liver

Extracellular matrix (ECM) plays a major role in cell differentiation, proliferation, and gene expression, both in physiological and in pathological conditions. Immunohistochemistry has been used to investigate modifications of ECM and related receptors, the integrins, in 26 small nodular lesions developed in human cirrhotic livers, on the basis that these lesions could represent sequential steps of hepatocarcinogenesis: the lesions were 16 macroregenerative nodules (MRNs), either of ordinary (n = 5) or atypical (n = 11) type, and ten small (< 15 mm) hepatocellular carcinomas (HCCs). Data were compared with those obtained in the surrounding cirrhotic tissue, in large HCCs, and in normal liver. The results indicate similarities between ordinary MRNs and cirrhosis, on the one hand, and between atypical MRNs and small HCCs, on the other. Strong and homogeneous deposition of collagen type IV and laminin in sinusoids and overexpression of alpha 6 integrin by sinusoidal cells and hepatocytes were especially noticeable in dysplastic areas characteristic of atypical MRNs, as in small HCCs. In addition, the staining of alpha 2 and alpha 6 integrins in MRNs revealed the presence of widespread atypical ductular proliferation expanding from periportal and perinodular areas, containing epithelial cells with transitional (hepato-biliary) phenotype. These findings suggest a transition from atypical MRNs to small HCCs and a possible role for liver epithelial precursor cells ('stem cells') in the development and evolution of MRNs.

Additive effect modification of hepatitis B surface antigen and e antigen on the development of hepatocellular carcinoma

To assess the role of hepatitis B e antigen (HBeAg) and its interaction with hepatitis B surface antigen (HBsAg) on the development of hepatocellular carcinoma (HCC), this case-control study included 361 age- and sex-matched pairs of patients with histologically proven HCC and healthy control subjects. HBsAg, HBeAg and antibody to HBeAg (anti-HBe) were detected by radioimmunoassay. Antibodies to hepatitis C virus (anti-HCV) were detected by second-generation enzyme immunoassay. The prevalences of HBeAg (20.2%), HBsAg (80.3%) and anti-HCV (29.5%) in cases were higher than in controls (1.9%, 20.7%, and 2.7% respectively; each P < 0.0001). Using patients negative for HBsAg, HBeAg and anti-HBe as a referent group, univariate analysis indicated that HBsAg alone or HBsAg and HBeAg were risk factors for HCC (P for trend < 0.0001). Calculation of incremental odds ratio indicated that there was additive interaction between HBsAg and HBeAg. Multivariate analysis indicated that HCC development was strongly associated with the presence of HBeAg (odds ratio, 8.1; 95% confidence interval, 2.4-27.1), HBsAg (odds ratio, 68.4; 95% confidence interval, 20.5-227.8) and anti-HCV (odds ratio, 59.3; 95% confidence interval, 13.6-258.4). In conclusion, HBsAg, HBeAg and anti-HCV are independent risk factors for HCC. There is additive and independent effect modification between HBsAg and HBeAg on the development of HCC.

Intracellular accumulation of incompletely processed transforming growth factor-alpha polypeptides in ground glass hepatocytes of chronic hepatitis B virus infection

BACKGROUND

Transforming growth factor-alpha is an intracellularly processed and secreted polypeptide that induces a proliferative response in epithelial target cells and represents a potential regulatory factor in embryonic development, liver regeneration, and also hepatocarcinogenesis. We have observed focal transforming growth factor-alpha expression in liver tissues with chronic hepatitis B virus infection.

METHODS

To further elucidate the nature of this focal transforming growth factor-alpha accumulation we have analyzed overall 23 different liver tissues with chronic hepatitis B virus and hepatitis C virus infection as well as normal liver tissues by immunohistology, ELISA, and Western immunoblot with and without immunoprecipitation.

RESULTS

By immunohistology transforming growth factor-alpha polypeptides showed focal subcellular accumulation in ground glass hepatocytes, the histological hallmark of chronic hepatitis B virus infection, in co-localization with HBV-preS1 antigen. By ELISA and Western immunoblot increased tissue concentrations of transforming growth factor-alpha were demonstrated in chronically hepatitis B virus-infected liver tissues with ground glass hepatocytes, especially a 15-kD polypeptide, most likely representing an incompletely processed transforming growth factor-alpha polypeptide. Transforming growth factor-alpha retention in ground glass hepatocytes is not a general unspecific effect, since it was not observed for several other secretory liver proteins. Accumulated transforming growth factor-alpha in ground glass hepatocytes does not co-localize with Epidermal Growth Factor Receptor expression.

CONCLUSION

Thus evidence is presented that a principally secreted (viral) polypeptide (HBV-preS1) can interfere with the secretion and processing of a second (cellular) protein (transforming growth factor-alpha). Accumulation of transforming growth factor-alpha may result from alteration of the endoplasmic reticulum due to storage of hepatitis B virus surface antigen particles. No evidence was found for transforming growth factor-alpha in ground glass hepatocytes to intracellularly interact with the Epidermal Growth Factor Receptor.

HCV-associated hepatocellular carcinoma without cirrhosis

BACKGROUND/AIMS

Hepatocellular carcinoma is an aggressive malignancy and carries a poor prognosis. Hepatitis B and C virus infection, cirrhosis and aflatoxin B1 exposure are considered major risk factors. The role of hepatitis C virus in the causation of hepatocellular carcinoma has been debated. It is a positive, single-stranded RNA virus without a DNA intermediate in its replicative cycle, so that integration of hepatitis C virus nucleic acid sequences into the host genome seems unlikely. The most plausible explanation of hepatitis C virus-associated hepatocellular carcinoma so far is that the virus causes necroinflammatory hepatic disease with vigorous regeneration, fibrosis, and eventually cirrhosis. The aim of this study was to examine the relationship of hepatitis C, cirrhosis and hepatocellular carcinoma.

METHODS

Sixty-six consecutive patients with hepatocellular carcinoma undergoing resection or transplantation at the Royal Free Hospital were reviewed. A combination of serological data and polymerase chain reaction assay was used to assign hepatitis C virus and hepatitis B virus infection.

RESULTS

We found four HCV-RNA positive patients with hepatocellular carcinoma without cirrhosis. All four cases were positive for HCV-RNA and negative for all markers of hepatitis B virus infection.

CONCLUSIONS

These four cases show that hepatocellular carcinoma may develop in patients with hepatitis C virus without pre-existing cirrhosis. However, the precise role of hepatitis C virus in hepatocarcinogenesis, the carcinogenic potential of the different genotypes and whether this role is influenced by other risk factors still have to be clarified.

p53-mediated cellular response to DNA damage in cells with replicative hepatitis B virus

Wild-type p53 acts as a tumor suppressor gene by protecting cells from deleterious effects of genotoxic agents through the induction of a G1/S arrest or apoptosis as a response to DNA damage. Transforming proteins of several oncogenic DNA viruses inactivate tumor suppressor activity of p53 by blocking this cellular response. To test whether hepatitis B virus displays a similar effect, we studied the p53-mediated cellular response to DNA damage in 2215 hepatoma cells with replicative hepatitis B virus. We demonstrate that hepatitis B virus replication does not interfere with known cellular functions of p53 protein.

Stimulation of proliferation by 3,3',5-triiodo-L-thyronine in poorly differentiated human hepatocarcinoma cells overexpressing beta 1 thyroid hormone receptor

To understand the role of thyroid hormone nuclear receptors (TRs) in hepatocarcinogenesis, we characterized the TRs in nine human hepatocarcinoma cell lines. The expression of TR proteins is receptor subtype- and cell type-dependent. TR alpha 1 protein expresses similarly at a low level in each of the nine cell lines. In contrast, TR beta 1 is overexpressed in hepatocarcinoma cells which are poorly differentiated. Furthermore, thyroid hormone was found to stimulate the proliferation of cells in which TR beta 1 is overexpressed. These results suggest that TR beta 1 is most likely involved in the differentiation and proliferation of hepatocarcinoma cells. Our studies have shed new light in the understanding of the role of TRs in liver carcinogenesis.