Hepatocellular carcinoma pathogenesis: from genes to environment

Progression of hypermethylation of the p16(INK4A) gene from normal liver to nontumorous liver and hepatocellular carcinoma: an evaluation using quantitative PCR analysis

The aim of this study was to determine to what extent hypermethylation of the p16(INK4A) (p16) gene promoter is increased in nontumorous liver tissues compared with in normal liver, using two quantitative methylation-specific polymerase chain reaction (MS-PCR) methods and a bisulfite sequencing method. Methylation of the p16 gene was detected more frequently in nontumorous liver than in normal liver using the TaqMan PCR method. Methylation indices also were significantly higher in nontumorous than in normal liver. However, the bisulfite sequencing method did not detect significantly more methylation of the p16 gene in nontumorous than normal liver, nor was there a significant difference in the level of p16 mRNA. There may be a greater proportion of cells which contain methylated p16 in nontumorous than in normal liver. However, the difference was so small that the functional relevance to hepatocarcinogenesis remains elusive.

Molecularly targeted therapy for hepatocellular carcinoma

Accumulated understanding of the molecular pathways regulating cancer progression has led to the development of novel targeted therapies. Hepatocellular carcinoma (HCC) remains a highly lethal disease that is resistant to conventional cytotoxic chemotherapy and radiotherapy. Unlike conventional chemotherapy, molecular-targeted agents offer the potential advantages of a relatively high therapeutic window and use in combination with other anticancer strategies without overlapping toxicity. It is hoped that these drugs will become valuable therapeutic tools within the multimodal approach to treating cancer. A recent clinical trial revealed an oral multikinase inhibitor, sorafenib, as the first agent that has demonstrated improved overall survival in patients with advanced HCC. The present review summarizes molecular abnormalities of HCC with a focus on clinical studies, and current status as well as problems of the targeted strategies for HCC.

An overview of hepatocellular carcinoma study by omics-based methods

Hepatocellular carcinoma (HCC) is one of the most deadly malignancies worldwide. Scientists have been studying the molecular mechanism of HCC for years, but the understanding of it remains incomplete and scattered across the literature at different molecular levels. Chromosomal aberrations, epigenetic abnormality and changes of gene expression have been reported in HCC. High-throughput omics technologies have been widely applied, aiming at the discovery of candidate biomarkers for cancer staging, prediction of recurrence and prognosis, and treatment selection. Large amounts of data on genetic and epigenetic abnormalities, gene expression profiles, microRNA expression profiles and proteomics have been accumulating, and bioinformatics is playing a more and more important role. In this paper, we review the current omics-based studies on HCC at the levels of genomics, transcriptomics and proteomics. Integrating observations from multiple aspects is an essential step toward the systematic understanding of the disease.

New drugs for the treatment of hepatocellular carcinoma

Treatment of hepatocellular carcinoma has dramatically changed in the last years. The better knowledge of the molecular mechanisms responsible of tumor initiation and progression has allowed the development of molecular targeted therapies that specifically block the disrupted pathways. Among all these new agents, Sorafenib is the only one that has shown efficacy in terms of survival in advanced stage in two randomized, double-blind, controlled trials. The positive result of these two trials are the proof of the efficacy of molecular targeted therapies in hepatocellular carcinoma and opens the door to multipathway blockade and the use of these targeted therapies in the adjuvant setting. Other agents have shown promising results in phase 1-2 trials but further studies are needed to demonstrate their efficacy. In the next years, efforts should be directed to identifying genomic and proteomic profiling that will help us to assess the prognosis and to define what treatment benefits whom, ultimately giving way to personalized medicine.

Wnt/beta-catenin pathway in hepatocellular carcinoma pathogenesis and liver physiology

The Wnt/beta-catenin pathway is a key developmental pathway for which alterations have been described in various human cancers. The aberrant activation of this pathway is a major event in human hepatocellular carcinoma. Several laboratories have shown that the Wnt/beta-catenin pathway plays an essential role in all phases of liver development and maturation, and is required for the metabolic function of this organ. In this review, we summarize current knowledge regarding the role of the Wnt/beta-catenin pathway in hepatocellular carcinoma pathogenesis and liver biology, and the possibilities for developing new therapeutic interventions based on this knowledge.

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.

Combination of sorafenib and doxorubicin in patients with advanced hepatocellular carcinoma: results from a phase I extension trial

Sorafenib, an oral multikinase inhibitor, shows efficacy in renal cell and hepatocellular carcinoma (HCC) and is well tolerated when combined with doxorubicin in other solid tumours. Eighteen patients with inoperable HCC received doxorubicin 60 mg/m(2) IV for up to six 3-week cycles. Sorafenib 400mg bid was administered continuously starting day 4. Patients discontinuing doxorubicin were eligible for sorafenib monotherapy. The most frequent grade 3-4 drug-related adverse events were neutropaenia (61%), leukopaenia (45%) and diarrhoea (17%, grade 3). Seven of eight patients who completed six cycles of doxorubicin continued treatment with sorafenib for at least 3 months. Doxorubicin moderately increased AUC (21%) and C(max) (33%) when administered with sorafenib. The disease control rate for 16 evaluable patients was 69%. Sorafenib plus doxorubicin appears to be well tolerated and more effective in the treatment of HCC than doxorubicin alone. Follow-up with single-agent sorafenib in these patients also appears to be well tolerated.

Human hepatocellular carcinoma: expression profiles-based molecular interpretations and clinical applications

Primary liver cancer is the fifth most common cancer worldwide and hepatocellular carcinoma (HCC) accounts for over 85% of all primary liver cancers. The clinical management of advanced and metastatic HCC is challenging on many counts. Besides largely occurs within a background of underlying chronic liver disease and cirrhosis, HCC is a phenotypically and genetically heterogeneous polyclonal disease and resistant to most conventional chemotherapy. Early manifestation of HCC is characteristically slow growing with few symptoms, and HCC is therefore often diagnosed at an advanced stage when potentially curative surgical or local ablative therapy is not feasible. In this review, I have summarized my presentation at the recent HCC workshop at IARC, Lyon, on our knowledge generated from comprehensive molecular studies of primary liver cancer tissues and attempt to translate these results to gain molecular insights, especially on identification of biomarkers that could confer pathological and functional changes associated with the pathogenesis and progression of HCC, hoping to provide important molecular basis for the development of novel diagnosis and treatments to alter clinical outcomes of this disease.

Mouse models in liver cancer research: A review of current literature

Primary liver cancer remains one of the most lethal malignancies worldwide. Due to differences in prevalence of etiological factors the incidence of primary liver cancer varies among the world, with a peak in East-Asia. As this disease is still lethal in most of the cases, research has to be done to improve our understanding of the disease, offering insights for possible treatment options. For this purpose, animal models are widely used, especially mouse models. In this review, we describe the different types of mouse models used in liver cancer research, with emphasis on genetically engineered mice used in this field. We focus on hepatocellular carcinoma (HCC), as this is by far the most common type of primary liver cancer, accounting for 70%-85% of cases.

Predicting survival after liver transplantation in patients with hepatocellular carcinoma beyond the Milan criteria: a retrospective, exploratory analysis

BACKGROUND

Patients undergoing liver transplantation for hepatocellular carcinoma within the Milan criteria (single tumour </=5 cm in size or </=3 tumours each </=3 cm in size, and no macrovascular invasion) have an excellent outcome. However, survival for patients with cancers that exceed these criteria remains unpredictable and access to transplantation is a balance of maximising patients' chances of cure and organ availability. The aim of this study was to explore the survival of patients with tumours that exceed the Milan criteria, to assess whether the criteria could be less restrictive, enabling more patients to qualify as transplant candidates, and to derive a prognostic model based on objective tumour characteristics, to see whether the Milan criteria could be expanded.

METHODS

Data on patients who underwent transplantation for hepatocellular carcinoma despite exceeding Milan criteria at different centres were recorded via a web-based survey completed by specialists from each centre. The survival of these patients was correlated retrospectively with the size of the largest tumour nodule, number of nodules, and presence or absence of microvascular invasion detected at pathology. Contoured multivariable regression Cox models produced survival estimates by means of different combinations of the covariates. The primary aim of this study was to derive a prognostic model of overall survival based on tumour characteristics, according to the main parameters used in the Tumour Node Metastasis classification. The secondary aim was the identification of a subgroup of patients with hepatocellular carcinoma exceeding the Milan criteria, who achieved a 5-year overall survival of at least 70%-ie, similar to the outcome expected for patients who meet the Milan criteria.

FINDINGS

Over a 10-month period, between June 25, 2006, and April 3, 2007, data for 1556 patients who underwent transplantation for hepatocellular carcinoma were entered on the database by 36 centres. 1112 patients had hepatocellular carcinoma exceeding Milan criteria and 444 patients had hepatocellular carcinoma shown not to exceed Milan criteria at post-transplant pathology review. In the group of patients with hepatocellular carcinomas exceeding the criteria, the median size of the largest nodule was 40 mm (range 4-200) and the median number of nodules was four (1-20). 454 of 1112 patients (41%) had microvascular invasion and, for those transplanted outside the Milan criteria, 5-year overall survival was 53.6% (95% CI 50.1-57.0), compared with 73.3% (68.2-77.7) for those that met the criteria. Hazard ratios (HR) associated with increasing values of size and number were 1.34 (1.25-1.44) and 1.51 (1.21-1.88), respectively. The effect was linear for size, whereas for number of tumours, the effect tended to plateau above three tumours. The effect of tumour size and number on survival was mediated by recurrence (b=0.08, SE=0.12, p=0.476). The presence of microvascular invasion doubled HRs in all scenarios. The 283 patients without microvascular invasion, but who fell within the Up-to-seven criteria (hepatocellular carcinomas with seven as the sum of the size of the largest tumour [in cm] and the number of tumours) achieved a 5-year overall survival of 71.2% (64.3-77.0).

INTERPRETATION

More patients with hepatocellular carcinoma could be candidates for transplantation if the current dual (yes/no) approach to candidacy, based on the strict Milan criteria, were replaced with a more precise estimation of survival contouring individual tumour characteristics and use of the up-to-seven criteria.

Proliferation of human HCC cells and chemically induced mouse liver cancers requires JNK1-dependent p21 downregulation

JNK proteins have been shown to be involved in liver carcinogenesis in mice, but the extent of their involvement in the development of human liver cancers is unknown. Here, we show that activation of JNK1 but not JNK2 was increased in human primary hepatocellular carcinomas (HCCs). Further, JNK1 was required for human HCC cell proliferation in vitro and tumorigenesis after xenotransplantation. Importantly, mice lacking JNK1 displayed decreased tumor cell proliferation in a mouse model of liver carcinogenesis and decreased hepatocyte proliferation in a mouse model of liver regeneration. In both cases, impaired proliferation was caused by increased expression of p21, a cell-cycle inhibitor, and reduced expression of c-Myc, a negative regulator of p21. Genetic inactivation of p21 in JNK1-/- mice restored hepatocyte proliferation in models of both liver carcinogenesis and liver regeneration, and overexpression of c-Myc increased proliferation of JNK1-/- liver cells. Similarly, JNK1 was found to control the proliferation of human HCC cells by affecting p21 and c-Myc expression. Pharmacologic inhibition of JNK reduced the growth of both xenografted human HCC cells and chemically induced mouse liver cancers. These findings provide a mechanistic link between JNK activity and liver cell proliferation via p21 and c-Myc and suggest JNK targeting can be considered as a new therapeutic approach for HCC treatment.

HB-EGF is a paracrine growth stimulator for early tumor prestages in inflammation-associated hepatocarcinogenesis

BACKGROUND/AIMS

We studied the impact of heparin-binding epidermal growth factor-like growth factor (HB-EGF) on inflammation-driven hepatocarcinogenesis.

METHODS

HB-EGF expression was determined by qRT-PCR and immunodetection in hepatocellular adenoma and carcinoma and in mesenchymal (MC) and parenchymal liver cells obtained from different models of inflammation. The functions of HB-EGF in early hepatocarcinogenesis were assessed in co-cultures of unaltered and initiated/premalignant hepatocytes.

RESULTS

In human and rat (pre)malignant liver lesions, HB-EGF levels were comparable to that of the surrounding tissue. In inflamed livers HB-EGF was expressed predominantly in MC and was further increased by pro-inflammatory lipopolysaccharide (LPS) or linoleic acid hydroperoxide (LOOH). In culture, DNA-replication occurred rather in initiated/premalignant than unaltered hepatocytes and was further elevated by LOOH- or LPS-stimulated MC-supernatants. The supernatant effects were abrogated by pre-incubation with HB-EGF-neutralizing antisera. HB-EGF itself induced DNA-replication and mitosis preferentially in the initiated/premalignant cells. When transducing hepatocytes with a dominant-negative ErbB1-construct, HB-EGF-induced DNA-replications were blocked completely in unaltered hepatocytes but incompletely in initiated/premalignant cells, which suggests elevated ErbB-mediated signal transduction in first stages of hepatocarcinogenesis.

CONCLUSIONS

Pro-inflammatory stimuli induce the release of HB-EGF from MC, which stimulates DNA-replication in initiated/premalignant hepatocytes. Similar mechanisms may contribute to carcinogenesis in human inflammatory liver diseases.

Interaction of major genes predisposing to hepatocellular carcinoma with genes encoding signal transduction pathways influences tumor phenotype and prognosis

Studies on rodents and humans demonstrate an inherited predisposition to hepatocellular carcinoma (HCC). Analysis of the molecular alterations involved in the acquisition of a phenotype resistant or susceptible to hepatocarcinogenesis showed a deregulation of G1 and S phases in HCC of genetically susceptible F344 rats and a G1-S block in lesions of resistant Brown norway (BN) rats. Unrestrained extracellular signal-regulated kinase (ERK) activity linked to proteasomal degradation of dual-specificity phosphatase 1 (DUSP1), a specific ERK inhibitor, by the CKS1-SKP2 ubiquitin ligase complex occurs in more aggressive HCC of F344 rats and humans. This mechanism is less active in HCC of BN rats and human HCC with better prognosis. Upregulation of iNos cross-talk with IKK/NF-κB and RAS/ERK pathways occurs in rodent liver lesions at higher levels in the most aggressive models represented by HCC of F344 rats and c-Myc-TGF-α transgenic mice. iNOS, IKK/NF-κB, and RAS/ERK upregulation is highest in human HCC with a poorer prognosis and positively correlates with tumor proliferation, genomic instability and microvascularization, and negatively with apoptosis. Thus, cell cycle regulation and the activity of signal transduction pathways seem to be modulated by HCC modifier genes, and differences in their efficiency influence the susceptibility to hepatocarcinogenesis and probably the prognosis of human HCC.

New therapeutic aspects of flavones: the anticancer properties of Scutellaria and its main active constituents Wogonin, Baicalein and Baicalin

Traditional Chinese medicines have been recently recognized as a new source of anticancer drugs and new chemotherapy adjuvant to enhance the efficacy of chemotherapy and to ameliorate the side effects of cancer chemotherapies however their healing mechanisms are still largely unknown. Scutellaria baicalensis is one of the most popular and multi-purpose herb used in China traditionally for treatment of inflammation, hypertension, cardiovascular diseases, and bacterial and viral infections. Accumulating evidence demonstrate that Scutellaria also possesses potent anticancer activities. The bioactive components of Scutellaria have been confirmed to be flavones. The major constituents of Scutellaria baicalensis are Wogonin, Baicalein and Baicalin. These phytochemicals are not only cytostatic but also cytotoxic to various human tumor cell lines in vitro and inhibit tumor growth in vivo. Most importantly, they show almost no or minor toxicity to normal epithelial and normal peripheral blood and myeloid cells. The antitumor functions of these flavones are largely due to their abilities to scavenge oxidative radicals, to attenuate NF-kappaB activity, to inhibit several genes important for regulation of the cell cycle, to suppress COX-2 gene expression and to prevent viral infections. The tumor-selectivity of Wogonin has recently been demonstrated to be due to its ability to differentially modulate the oxidation-reduction status of malignant vs. normal lymphocytic cells and to preferentially induce phospholipase C gamma 1, a key enzyme involved in Ca(2+) signaling, through H(2)O(2) signaling in malignant lymphocytes. This review is aimed to summarize the research results obtained since the last 20 years and to highlight the recently discovered molecular mechanisms.

EF1A1-actin interactions alter mRNA stability to determine differential osteopontin expression in HepG2 and Hep3B cells

Cancer progression depends on an accumulation of metastasis-supporting physiological changes which are regulated by cell signaling molecules. One such molecule, osteopontin (OPN), is a secreted phosphoprotein which mediates increased cellular migratory and invasive behavior, increased metastasis, protection from apoptosis, promotion of colony formation and 3D growth ability, induction of tumor-associated inflammatory cells, and induction of expression of angiogenic factors. Studies show that OPN expression is controlled by complex regulatory pathways at the transcriptional level in several cancers, but the molecular mechanisms which determine expression of OPN in HCC are largely unknown. In HepG2 and Hep3B tumor cell lines that differentially express OPN mRNA and protein, we identify elongation translation factor-1A1 (EF1A1) to be the trans-acting factor regulating differential OPN mRNA stability between HepG2 and Hep3B cell lines and characterize its interactions with G- and F-actin. EF1A1 binds to the OPN 5'-UTR to regulate OPN mRNA half-life. EF1A1 binds to actin in Hep3B cells. Pharmacologic manipulation to increase the G:F actin ratio in Hep3B increases OPN mRNA half-life and protein expression with simultaneous decrease in EF1A1 binding to OPN 5'-UTR. The converse findings were noted in HepG2 cells. Overall, our results suggest that EF1A1 regulation of OPN mRNA stability is actin dependent. EF1A1 has not been previously identified as a regulatory factor in OPN expression in cancer.

Hypoxia-inducible enhancer/alpha-fetoprotein promoter-driven RNA interference targeting STK15 suppresses proliferation and induces apoptosis in human hepatocellular carcinoma cells

STK15 (Aurora A/BTAK) is an oncogenic serine/threonine kinase that plays a role in centrosome separation and in the formation of the mitotic bipolar spindle. It is highly expressed and constitutively activated in various human tumors including hepatocellular carcinoma (HCC). To investigate its possibility as a molecular target for future therapies directed against hepatocellular carcinoma, we constructed a tissue-specific RNA interference (RNAi) system mediated by hypoxia-inducible (HI) enhancer/alpha-fetoprotein (AFP) promoter and employed it to downregulate exogenous reporters (LUC and EGFP) and endogenous STK15 gene expression and analyzed the phenotypical changes in HCC cells. Results showed that the expression of exogenous reporters (LUC and EGFP) was specifically downregulated in hepatoma cells but not in non-hepatoma cells. Moreover, the specific downregulation of STK15 expression in hepatocellular carcinoma cells (HepG2) significantly inhibited in vitro cellular proliferation and in vivo tumorigenicity. Furthermore, we also found that the downregulation of STK15 expression led to cell arrest in the G(2)/M phase and finally apoptosis induction of HepG2 cells. Thus, the HI enhancer/AFP promoter-mediated RNAi targeting STK15 may be a potential therapeutic strategy for the treatment of hepatocellular carcinoma with tumor specificity and high efficacy.

Re-expression of transcription factor ATF5 in hepatocellular carcinoma induces G2-M arrest

Transcription factors represent an important class of genes that play key roles in controlling cellular proliferation, cell cycle modulation, and attractive targets for cancer therapy. Here, we report on the novel finding of common ATF5 down-regulations in hepatocellular carcinoma (HCC), a highly malignant tumor with a dismal clinical course. Array-based mapping in HCC highlighted a high and consistent incidence of transcription factor ATF5 repressions on regional chr.19q13. By quantitative reverse transcription-PCR, profound down-regulations of ATF5 were further suggested in 78% of HCC tumors (60 of 77 cases) compared to their adjacent nontumoral liver (P = 0.0004). Restoration of ATF5 expression in 3 nonexpressing HCC cell lines demonstrated a consistent growth inhibitory effect (P < 0.029) but minimal induction on cellular apoptosis. Subsequent flow cytometric investigations revealed a G(2)-M cell cycle arrest in HCC cells that were ectopically transfected with ATF5 (P < 0.002). The differential expressed genes from the functional effects of ATF5 were examined by array profiling. Over a hundred genes were identified, among which ID1 contains the ATF/CREB target binding sequences within its promoter region. An inverse relationship between ATF5 expressions with ID1 transcriptions was verified in HCC (P = 0.019), and a direct interaction of ATF5 on the promoter of ID1 was further demonstrated from electromobility shift assay. Examination of causal events underlying the silencing of ATF5 in HCC suggested copy number losses, promoter hypermethylation, histone deacetylation, and DNA mutations to be the likely inactivating mechanisms. In conclusion, our finding supports a tumor suppressive role for ATF5 in HCC, and highlighted ID1 as a potential downstream target.

Focal gains of VEGFA and molecular classification of hepatocellular carcinoma

Hepatocellular carcinomas represent the third leading cause of cancer-related deaths worldwide. The vast majority of cases arise in the context of chronic liver injury due to hepatitis B virus or hepatitis C virus infection. To identify genetic mechanisms of hepatocarcinogenesis, we characterized copy number alterations and gene expression profiles from the same set of tumors associated with hepatitis C virus. Most tumors harbored 1q gain, 8q gain, or 8p loss, with occasional alterations in 13 additional chromosome arms. In addition to amplifications at 11q13 in 6 of 103 tumors, 4 tumors harbored focal gains at 6p21 incorporating vascular endothelial growth factor A (VEGFA). Fluorescence in situ hybridization on an independent validation set of 210 tumors found 6p21 high-level gains in 14 tumors, as well as 2 tumors with 6p21 amplifications. Strikingly, this locus overlapped with copy gains in 4 of 371 lung adenocarcinomas. Overexpression of VEGFA via 6p21 gain in hepatocellular carcinomas suggested a novel, non-cell-autonomous mechanism of oncogene activation. Hierarchical clustering of gene expression among 91 of these tumors identified five classes, including "CTNNB1", "proliferation", "IFN-related", a novel class defined by polysomy of chromosome 7, and an unannotated class. These class labels were further supported by molecular data; mutations in CTNNB1 were enriched in the "CTNNB1" class, whereas insulin-like growth factor I receptor and RPS6 phosphorylation were enriched in the "proliferation" class. The enrichment of signaling pathway alterations in gene expression classes provides insights on hepatocellular carcinoma pathogenesis. Furthermore, the prevalence of VEGFA high-level gains in multiple tumor types suggests indications for clinical trials of antiangiogenic therapies.

Molecular targeted therapies in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a complex and heterogeneous tumor with several genomic alterations. There is evidence of aberrant activation of several signaling cascades such as epidermal growth factor receptor (EGFR), Ras/extracellular signal-regulated kinase, phosphoinositol 3-kinase/mammalian target of rapamycin (mTOR), hepatocyte growth factor/mesenchymal-epithelial transition factor, Wnt, Hedgehog, and apoptotic signaling. Recently a multikinase inhibitor, sorafenib, has shown survival benefits in patients with advanced HCC. This advancement represents a breakthrough in the treatment of this complex disease and proves that molecular therapies can be effective in HCC. It is becoming apparent, however, that to overcome the complexity of genomic aberrations in HCC, combination therapies will be critical. Phase II studies have tested drugs blocking EGFR, vascular endothelial growth factor/platelet-derived growth factor receptor, and mTOR signaling. No relevant data has been produced so far in combination therapies. Future research is expected to identify new compounds to block important undruggable pathways, such as Wnt signaling, and to identify new oncogenes as targets for therapies through novel high-throughput technologies. Recent guidelines have established a new frame for the design of clinical trials in HCC. Randomized phase II trials with a time-to-progression endpoint are proposed as pivotal for capturing benefits from novel drugs. Survival remains the main endpoint to measure effectiveness in phase III studies. Patients assigned to the control arm should receive standard-of-care therapy, that is, chemoembolization for patients with intermediate-stage disease and sorafenib for patients with advanced-stage disease. Biomarkers and molecular imaging should be part of the trials, in order to optimize the enrichment of study populations and identify drug responders. Ultimately, a molecular classification of HCC based on genome-wide investigations and identification of patient subclasses according to drug responsiveness will lead to a more personalized medicine.

Infections and cancer: established associations and new hypotheses

Around the world, infection is one of the most important causes of cancer. Almost one in every five malignancies can be attributed to infectious agents. Among infection-related neoplasms, cancers of the stomach, liver and cervix uteri detain the highest incidence figures, and are known to be largely attributable to Helicobacter pylori, hepatitis B and C viruses, and human papilloma virus, respectively. Other infectious organisms can also cause cancer; these include the Epstein-Barr virus (nasopharyngeal carcinoma, and different types of lymphoma), Human herpes virus-8 (Kaposi's Sarcoma), human T-cell leukemia virus type I (leukaemia, lymphoma), liver flukes (cholangiocarcinoma) and schistosomiasis (bladder cancer). Infection with human immunodeficiency virus, although strongly associated with an excess of cancer incidence at many cancer sites, is probably not carcinogenic per se, but acts mainly via immunodeficiency. The burden of infection-related cancers is still underestimated worldwide, due to the use of conservative population prevalence and risk ratio estimates. Furthermore, associations with new infectious agents remain yet to be explored.

Proline-rich tyrosine kinase 2 (Pyk2) promotes proliferation and invasiveness of hepatocellular carcinoma cells through c-Src/ERK activation

The aim of the current study is to elucidate the mechanism of proline-rich tyrosine kinase 2 (Pyk2)-mediated cell proliferation and invasiveness in hepatocellular carcinoma (HCC) cells. Human HCC cell lines PLC and MHCC97L were stably transfected with either full-length Pyk2 or C-terminal non-kinase region of Pyk2 (PRNK). Functional studies on cell proliferation and invasion were conducted in vitro by colony formation assay, adhesion assay, migration assay and wound-healing assay. For the in vivo study, an orthotopic nude mice liver tumor model was applied to investigate the effects of Pyk2 overexpression on tumor growth and metastasis. Overexpression of Pyk2 in PLC cells resulted in an upregulation of colony formation (P = 0.021) and adhesion toward laminin (P = 0.018). Pyk2 promoted wound recovery by stimulation of actin stress fiber polymerization. In the in vivo study, transfection of PRNK in MHCC97L cells significantly decreased tumor volume (P = 0.001) and the incidence of lung metastasis (P = 0.014). Overexpression of Pyk2 promoted the activation of c-Src, formation of Pyk2/c-Src complex and activated the extracellular signal-regulated kinase (ERK)/mitogen-activated protein kinase (MAPK)-signaling pathway. Pyk2 upregulated the activation of ERK1/2 that is insensitive to MAPK/ERK kinase (MEK)1/2 inhibition. On the contrary, PRNK overexpression downregulated the activation of c-Src and ERK/MAPK-signaling pathways. Immunofluorescence staining showed that the focal adhesion localization of Pyk2 is a major determinant for c-Src and ERK/MAPK activation. In conclusion, our results showed that Pyk2 promoted cell proliferation and invasiveness by upregulation of the c-Src and ERK/MAPK-signaling pathways.

Hepatocellular carcinoma in long-term sustained virological responders following antiviral combination therapy for chronic hepatitis C

Antiviral treatment results in a sustained virologic response (SVR) in 50-75% of patients with chronic hepatitis C. Long-term follow up studies have observed ongoing SVR in the overwhelming majority of them. Thus chronic hepatitis C is considered 'cured' if an SVR is achieved. Consequently, it is expected that in sustained virologic responders long-term complications of hepatatic C virus (HCV) related chronic liver disease including hepatocellular carcinoma are eliminated or have a decreased incidence. We report on five patients (three from Austria, two from USA) who developed hepatocellular carcinoma during follow up (3-6 years) after achieving SVR. During follow up and at diagnosis all were HCV-RNA neg. None of the patients had other liver diseases. One patient presented with bilateral adrenal metastasis, the remaining four with large hepatic tumours. Three patients were noncirrhotic at the start of treatment at the time of tumour diagnosis. Successful antiviral treatment in HCV patients does not prevent development of hepatocellular carcinoma even in non-cirrhotic livers. Long-term follow up of patients with SVR is mandatory and should include surveillance for hepatocellular carcinoma.

Clinicopathologic significance of mitotic arrest defective protein 2 overexpression in hepatocellular carcinoma

Mitotic arrest defective protein 2 (MAD2) gene plays a central role in the mitotic checkpoint. Elevated MAD2 expression was observed in a number of human malignancies; its role in the development of hepatocellular carcinoma is still not understood and is controversial. The purpose of this study was to investigate the clinicopathologic significance of MAD2 expression in hepatocellular carcinoma. The MAD2 protein and its messenger RNA levels were measured in hepatocellular carcinomas, high-grade dysplastic nodules, and their paired nontumorous liver tissues by quantitative real-time polymerase chain reaction, Western blot, and immunohistochemistry. The results showed that MAD2 at both messenger RNA and protein levels was overexpressed in 8 of 9 high-grade dysplastic nodules and in 51 of 58 hepatocellular carcinomas, including 12 of 14 unifocal small hepatocellular carcinomas. There was a tendency for MAD2 expression to increase in the process of this multistep carcinogenesis. A significantly high tumor MAD2 immunostaining was associated with the progression of histologic grade and the overall low survival. In conclusion, MAD2 is overexpressed frequently in hepatocellular carcinoma, including high-grade dysplastic nodules and early-stage small hepatocellular carcinoma, indicating that overexpression of MAD2 plays a role in the development and progression of hepatocellular carcinoma. It may be an early event in hepatocarcinogenesis and could be used as a potential prognostic indicator.

Dual-specificity phosphatase 1 ubiquitination in extracellular signal-regulated kinase-mediated control of growth in human hepatocellular carcinoma

Sustained activation of extracellular signal-regulated kinase (ERK) has been detected previously in numerous tumors in the absence of RAS-activating mutations. However, the molecular mechanisms responsible for ERK-unrestrained activity independent of RAS mutations remain unknown. Here, we evaluated the effects of the functional interactions of ERK proteins with dual-specificity phosphatase 1 (DUSP1), a specific inhibitor of ERK, and S-phase kinase-associated protein 2 (SKP2)/CDC28 protein kinase 1b (CKS1) ubiquitin ligase complex in human hepatocellular carcinoma (HCC). Levels of DUSP1, as assessed by real-time reverse transcription-PCR and Western blot analysis, were significantly higher in tumors with better prognosis (as defined by the length of patients' survival) when compared with both normal and nontumorous surrounding livers, whereas DUSP1 protein expression sharply declined in all HCC with poorer prognosis. In the latter HCC subtype, DUSP1 inactivation was due to either ERK/SKP2/CKS1-dependent ubiquitination or promoter hypermethylation associated with loss of heterozygosity at the DUSP1 locus. Noticeably, expression levels of DUSP1 inversely correlated with those of activated ERK, as well as with proliferation index and microvessel density, and directly with apoptosis and survival rate. Subsequent functional studies revealed that DUSP1 reactivation led to suppression of ERK, CKS1, and SKP2 activity, inhibition of proliferation and induction of apoptosis in human hepatoma cell lines. Taken together, the present data indicate that ERK achieves unrestrained activity during HCC progression by triggering ubiquitin-mediated proteolysis of its specific inhibitor DUSP1. Thus, DUSP1 may represent a valuable prognostic marker and ERK, CKS1, or SKP2 potential therapeutic targets for human HCC.

New cellular tools reveal complex epithelial-mesenchymal interactions in hepatocarcinogenesis

To enable detailed analyses of cell interactions in tumour development, new epithelial and mesenchymal cell lines were established from human hepatocellular carcinoma by spontaneous outgrowth in culture. We obtained several hepatocarcinoma (HCC)-, B-lymphoblastoid (BLC)-, and myofibroblastoid (MF)-lines from seven cases. In-depth characterisation included cell kinetics, genotype, tumourigenicity, expression of cell-type specific markers, and proteome patterns. Many functions of the cells of origin were found to be preserved. We studied the impact of the mesenchymal lines on hepatocarcinogenesis by in vitro assays. BLC- and MF-supernatants strongly increased the DNA replication of premalignant hepatocytes. The stimulation by MF-lines was mainly attributed to HGF secretion. In HCC-cells, MF-supernatant had only minor effects on cell growth but enhanced migration. MF-lines also stimulated neoangiogenesis through vEGF release. BLC-supernatant dramatically induced death of HCC-cells, which could be largely abrogated by preincubating the supernatant with TNFβ-antiserum. Thus, the new cell lines reveal stage-specific stimulatory and inhibitory interactions between mesenchymal and epithelial tumour cells. In conclusion, the new cell lines provide unique tools to analyse essential components of the complex interplay between the microenvironment and the developing liver cancer, and to identify factors affecting proliferation, migration and death of tumour cells, neoangiogenesis, and outgrowth of additional malignancy.

Role of Caveolin-1 in Indomethacin-induced Death of Human Hepatoadenocarcinoma SK-Hep1 Cells

Caveolin-1 (CAV1) is an integral membrane protein that may function as a scaffold for plasma membrane proteins and acts as a tumor suppressor protein. One causative factor of chemotherapy-resistant cancers is P-plycoprotein (P-gp), the product of the multidrug resistance-1 gene (MDR1), which is localized in the caveolar structure. Currently, the interactive roles of CAV1 and MDR1 expression in the death of cancer cells remain controversial. In this study, we investigated the effects of indomethacin on the cell viability and the expression levels of MDR1 mRNA and protein in a CAV1-siRNA-mediated gene knockdown hepatoma cell line (SK-Hep1). Cell viability was significantly decreased in CAV1-siRNA-transfected cells compared with that of control-siRNA-transfected cells. Furthermore, the viability of cells pretreated with CAV1 siRNA was markedly decreased by treatment with indomethacin (400microM for 24 h). However, the protein and mRNA levels of MDR1 were unchanged in CAV1-siRNA-transfected cells. These results suggest that CAV1 plays an important role as a major survival enzyme in cancer cells, and indomethacin can sensitively induce cell death under conditions of reduced CAV1 expression, independent of MDR1 expression.

CpG island hypermethylation of SOCS-1 gene is inversely associated with HBV infection in hepatocellular carcinoma

The CpG island hypermethylation of the suppressor of cytokine signaling-1 (SOCS-1) gene is frequently methylated in hepatocellular carcinoma (HCC), but its clinicopathological significance and the potential risk factors for the epigenetic change in HCC remain poorly understood. The methylation status of SOCS-1 CpG island was evaluated in fresh-frozen tissues from 284 HCC patients using the methylation-specific polymerase chain reaction. The expression of SOCS-1 protein was analyzed by immunohistochemical staining. SOCS-1 methylation was found in 163 (57%) of 284 HCCs. SOCS-1 methylation was positively associated with patient age (P=0.002) and HCV infection status (P=0.004), and was inversely associated with HBV infection (P=0.0002). In the multivariate logistic regression analysis, the HB(s)Ag-negative HCCs showed a 2.78 (95% CI=1.31-5.89, P=0.007) times greater risk of SOCS-1 methylation than the HB(s)Ag-positive HCCs. SOCS-1 methylation also occurred at a 4.34 times (95% CI=1.24-14.25, P=0.02) higher prevalence in antiHCV-positive cases than in antiHCV-negative cases. No prognostic effect of SOCS-1 methylation was observed in the HCCs. In conclusion, the present study suggests that SOCS-1 methylation in HCC may be negatively associated with HB(s)Ag status.

Bid exhibits S phase checkpoint activation and plays a pro-apoptotic role in response to etoposide-induced DNA damage in hepatocellular carcinoma cells

Bid has multiple functions in apoptosis, survival, and proliferation. The role of Bid in etoposide-induced-DNA damage in HCC has not been investigated. Here, we report that p53-overexpression led to the notable up-regulation of the expression of Bid protein, whereas the acquired expression of Bid by PLC/PRF/5 cells dramatically decreased the p53 level. Upon the administration of a high dose of etoposide (causing irreparable damage), Bid sensitized cells to apoptosis. However, at a low dose of etoposide (repairable damage), Bid activated the S phase checkpoint through the up-regulation of p21 and p27, which are both p53-independent. While the unrepairable damage was being carried out, Bid was quickly translocated to the mitochondria to release cytochrome c into the cytosol, which activated caspases 9 and 3 and led to cell death. In conclusion, our study demonstrates that Bid both exhibits S phase checkpoint activation and plays a pro-apoptotic role in response to different degrees of etoposide-induced DNA damage in HCC cells. The elucidation of these intricate mechanisms of Bid points to the development of a possible therapeutic option that combines cytotoxic therapies to treat HCC.

Antiproliferative potential of gallic acid against diethylnitrosamine-induced rat hepatocellular carcinoma

One of the focuses in current cancer chemoprevention studies is the search for nontoxic chemopreventive agents that inhibit the initiation of malignant transformation. Cancer biomarkers are quantifiable molecules involved in the physiologic or pathologic events occurring between exposure to carcinogens and the development, progression of cancer. Biomarkers may be the consequence of a continuous process, such as increased cell mass, or a discrete event, such as genetic mutation. Analysis of tumor markers can be used as an indicator of tumor response to therapy. Gallic acid is a naturally available polyphenol, possess strong antioxidant activity with a capacity to inhibit the formation of tumors in several cancer models. In the present study, we investigated the antiproliferative effect of gallic acid during diethylnitrosamine (DEN)-induced hepatocellular carcinoma (HCC) in male wistar albino rats. DEN treatment resulted in increased levels of aspartate transaminase, alanine transaminase, alkaline phosphatase, acid phosphatase, lactate dehydrogenase, gamma-glutamyltransferase, 5'-nucleotidase, bilirubin, alpha-fetoprotein, carcinoembryonic antigen, argyophillic nucleolar organizing regions, and proliferating cell nuclear antigen. Gallic acid treatment significantly attenuated these alterations and decreased the levels of AgNORs and PCNA. These finding suggests that gallic acid is a potent antiproliferative agent against DEN-induced HCC.

Malignancy and biologic therapy in rheumatoid arthritis

PURPOSE OF REVIEW

Owing to the complex functions of the inflammatory response systems--potentially or clearly of importance in human carcinogenesis--that biological therapies interfere with uncertainty regarding their safety profile for malignancy is more or less expected. This uncertainty has been further sparked by the apparent discordance between trial data and observational studies of anti-TNF agents, and the methodological challenges inherent in addressing the safety profile of new drugs for delayed and multifactorial events like cancer.

RECENT FINDINGS

This review provides a summary of the pattern of cancer seen in patients with rheumatoid arthritis not treated with biologics, and the currently published data on cancer risk following treatment with biologics in patients with rheumatoid arthritis, primarily anti-TNF therapy.

SUMMARY

Published data currently do not exclude clinically important increased risks, nor do they refute beneficial effects. As per definition, much of the currently available safety data from trials or clinical practice do not capture the impact of either any effect that biological therapy might have on early events in carcinogenesis, or of sustained exposure to biologics. Beyond the risk of de-novo cancer development, several other clinically important aspects of cancer safety remain to be addressed, including issues of prognosis, progression, and relapse.

Advances in experimental and translational research in the treatment of hepatocellular carcinoma

Hepatocellular cancer (HCC) is the fifth-leading cause of cancer and the third-leading cause of cancer related deaths world-wide. Current treatment options are limited, as HCC has been shown to be a highly resistant type of cancer to most current treatment modalities. Novel approaches are being explored in the fields of gene therapy, viral oncolytics, radioembolization, and several new biologic therapies. This article summarizes these recent clinical findings and discusses what role they will have in the future treatment of HCC.

Hepatitis B virus X protein mutants exhibit distinct biological activities in hepatoma Huh7 cells

The role of the hepatitis B virus X protein (HBx) in hepatocarcinogenesis remains controversial. To investigate the biological impact of hepatitis B virus x gene (HBx) mutation on hepatoma cells, plasmids expressing the full-length HBx or HBx deletion mutants were constructed. The biological activities in these transfectants were analyzed by a series of assays. Results showed that HBx3'-20 and HBx3'-40 amino acid deletion mutants exhibited an increase in cellular proliferation, focus formation, tumorigenicity, and invasive growth and metastasis through promotion of the cell cycle from G0/G1 to the S phase, when compared with the full-length HBx. In contrast, HBx3'-30 amino acid deletion mutant repressed cell proliferation by blocking in G1 phase. The expression of P53, p21(WAF1), p14(ARF), and MDM2 proteins was regulated by expression of HBx mutants. In conclusions, HBx variants showed different effects and functions on cell proliferation and invasion by regulation of the cell cycle progression and its associated proteins expression.

Increased levels of a unique post-translationally modified betaIVb-tubulin isotype in liver cancer

Identifying changes at the molecular level during the development of hepatocellular carcinoma is important for the detection and treatment of the disease. The characteristic structural reorganization of preneoplastic cells may involve changes in the microtubule cytoskeleton. Microtubules are dynamic protein polymers that play an essential role in cell division, maintenance of cell shape, vesicle transport, and motility. They are comprised of multiple isotypes of alpha- and beta-tubulin. Changes in the levels of these isotypes may affect not only microtubule stability and sensitivity to drugs but also interactions with endogenous proteins. We employed a rat liver cancer model that progresses through stages similar to those of human liver cancer, including metastasis to the lung, to identify changes in the tubulin cytoskeleton during carcinogenesis. Tubulin isotypes in both liver and lung tissue were purified and subsequently separated by isoelectric focusing electrophoresis. The C-terminal isotype-defining region from each tubulin was obtained by cyanogen bromide cleavage and identified by mass spectrometry. A novel post-translational modification of betaIVb-tubulin in which two hydrophobic residues are proteolyzed from the C-terminus, thus exposing a charged glutamic acid residue, was identified. The unique form of betaIVb-tubulin was quantified in the liver tissue of all carcinoma stages and found to be approximately 3-fold more abundant in nodular and tumor tissue than in control tissue. The level of this form was also found to be increased in lung tissue with liver metastasis. This modification alters the C-terminal domain of one of the most abundant beta-tubulin isotypes in the liver and therefore may affect the interactions of microtubules with endogenous proteins.

Hepatocellular carcinoma cell-specific peptide ligand for targeted drug delivery

Hepatocellular carcinoma is the fourth leading cause of cancer death worldwide. Novel treatment strategies derived from increased knowledge of molecular oncology are constantly being developed to cure this disease. Here, we used phage display to identify a novel peptide (SP94), which binds specifically to hepatocellular carcinoma cells. In vitro, the phage clone PC94 was shown to bind to hepatocellular carcinoma cell lines by ELISA and flow cytometry analysis. In vivo, PC94 homed specifically to tumor tissues but not to normal visceral organs in severe combined immunodeficient mice bearing human hepatocellular carcinoma xenografts. This homing ability could be competitively inhibited by synthetic peptide, SP94. Immunohistochemical staining confirmed that PC94 localized to tumor tissues and that it could not be detected in SP94-competed tumor tissues. In addition, PC94 recognized the tumor tissue but not nontumor tissue in surgical specimens from hepatocellular carcinoma patients, with a positive rate of 61.3% (19 of 31). With the conjugation of SP94 and liposomal doxorubicin, the targeted drug delivery system enhanced the therapeutic efficacy against hepatocellular carcinoma xenografts through enhanced tumor apoptosis and decreased tumor angiogenesis. Our results indicate that SP94 has the potential to improve the systemic treatment of patients with advanced hepatocellular carcinoma.

Novel advancements in the management of hepatocellular carcinoma in 2008

New advancements have emerged in the field of hepatocellular carcinoma (HCC) in recent years. There has been a switch in the type of presentation of HCC in developed countries, with a clear increase of tumors <2 cm in diameter as a result of the wide implementation of surveillance programs. Non-invasive radiological techniques have been developed and validated for the diagnosis of small and tiny HCCs. Simultaneously, diagnostic criteria based on molecular profiling of early tumors have been proposed. The current clinical classification of HCC divides patients into 5 stages with a specific treatment-oriented schedule. There is no established molecular classification of HCC, although preliminary proposals have already been published. Advancements in the treatment arena have come from well designed trials. Radiofrequency ablation is currently consolidated as providing better local control of the disease compared with percutaneous ethanol injection. New devices are available to improve the anti-tumoral efficacy of conventional chemoembolization. Sorafenib, a multikinase inhibitor, has shown survival benefits in patients at advanced stages of the disease. This advancement represents a breakthrough in the management of this complex disease, and proves that molecular targeted therapies can be effective in this otherwise chemo-resistant tumor. Consequently, sorafenib will become the standard of care in advanced cases, and the control arm for future trials. Now, the research effort faces other areas of unmet need, such as the adjuvant setting of resection/local ablation and combination therapies.

Epigenetic instability is rare in fibrolamellar carcinomas but common in viral-associated hepatocellular carcinomas

Fibrolamellar carcinomas have a unique predilection for younger individuals and arise in livers without recognizable liver disease. In contrast to typical hepatocellular carcinomas, fibrolamellar carcinomas show few chromosomal changes and lack mutation in key genes such as TP53 and CTNNB1. Epigenetic instability, manifesting as methylation of important tumor suppressor gene promoters, has not been investigated in fibrolamellar carcinomas. Thus, the methylation status of 11 tumor suppressor gene promoters was investigated using methylation-specific PCR: RASSF1, CDH1, CDKN2B, HPP1, CDKN2A, GSTP1, P16, RARA, FLJ13081, SOCS1, and TP53. Nine fibrolamellar carcinomas were studied including primary tumors (N=5) and metastatic deposits (N=4) along with control groups of typical hepatocellular carcinoma arising in livers with (N=21) and without cirrhosis (N=10). In fibrolamellar carcinomas, RASSF1A and CDH1 (e-cadherin) were the most commonly methylated genes with 80-100% of tumors methylated. However, overall fibrolamellar carcinomas showed low levels of methylation with no differences between fibrolamellar carcinomas and their paired normal livers. However, fibrolamellar carcinomas showed significantly less methylation than hepatocellular carcinomas that arose in the background of viral cirrhosis. Overall, methylation was most strongly linked to viral cirrhosis. In conclusion, fibrolamellar carcinoma shows low levels of methylation. In contrast, higher levels of promoter methylation are associated with hepatocellular carcinomas that arise in the setting of viral induced cirrhosis.

Aurora kinase B is a predictive factor for the aggressive recurrence of hepatocellular carcinoma after curative hepatectomy

BACKGROUND

Patterns of cancer recurrence hold the key to prognosis after curative resection. This retrospective study aimed to identify a predictor and therapeutic candidate for aggressive recurrence of hepatocellular carcinoma (HCC).

METHODS

Primary HCC tissues from 107 patients who had curative resection were analysed. Genome-wide gene expression profiles were investigated using a microarray technique, and clustering analysis was carried out based on the first diagnosis of recurrence according to the Milan criteria. Immunohistochemical expression and array-based comparative genomic hybridization (array-CGH) were also assessed.

RESULTS

Microarray analysis revealed overexpression of Aurora kinase B, a chromosome passenger protein kinase, as the most significant predictor of the aggressive recurrence of HCC. Aurora kinase B protein expression was significantly associated with aggressive recurrence (P < 0.001) and prognosis (P < 0.001). Multivariable analysis identified Aurora kinase B as the only independent predictor of aggressive recurrence of HCC (P = 0.031). Array-CGH analysis showed that genomic instability was closely related to Aurora kinase B expression (P = 0.011).

CONCLUSION

Aurora kinase B is an effective predictor of aggressive HCC recurrence, in relation to the genomic instability. It might be worth considering as a molecular target for the adjuvant therapy of HCC.

Mutations in the C-terminus of the X protein of hepatitis B virus regulate Wnt-5a expression in hepatoma Huh7 cells: cDNA microarray and proteomic analyses

Background: The hepatitis B virus x gene (HBx) is a promiscuous transactivator implicated in the development of hepatocellular carcinoma (HCC). The present study was designed to investigate the molecular events regulated by HBx. Methods: Genomic and proteomic expression profiling was performed in Huh7 HCC cells transfected with HBx mutants with a C-terminal deletion. The gene and protein expression of wingless-type murine-mammary-tumour virus (MMTV) integration site family, member 5A (Wnt-5a) was validated by analyses of reverse transcription–polymerase chain reaction (RT–PCR), real-time RT–PCR, western blot and immunohistochemistry. Results: Differentially expressed genes and proteins were found in the transfected Huh7 HCC cells; most of them were involved in transcriptional regulation, although others including oncogenes or tumor suppressor genes, and molecules involved in cell junctions, signal transduction pathways, metabolism or the immune response were also observed. The expression of the Wnt-5a gene was elevated >10-fold in Huh7 cells transfected with the HBx3′-30 amino acid deletion mutant. However, the expression was downregulated by the transfection with the HBx3′-40 amino acid deletion mutant. The changes in Wnt-5a expression were also observed in human HCC tissues, compared with corresponding non-cancerous liver tissues. A negative correlation was found between the expression of Wnt-5a and HBx COOH mutations in HCC tissues. Conclusions: HBx mutants may participate in the development and progression of HCC, at least in part through the Wnt-5a pathway.

Experimental models of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a common and deadly cancer whose pathogenesis is incompletely understood. Comparative genomic studies from human HCC samples have classified HCCs into different molecular subgroups; yet, the unifying feature of this tumor is its propensity to arise upon a background of inflammation and fibrosis. This review seeks to analyze the available experimental models in HCC research and to correlate data from human populations with them in order to consolidate our efforts to date, as it is increasingly clear that different models will be required to mimic different subclasses of the neoplasm. These models will be instrumental in the evaluation of compounds targeting specific molecular pathways in future preclinical studies.

Expression of IQGAP2 and its clinical significance in hepatocellular carcinoma

AIM: To investigate the expression of IQ motif containing GTPase activating protein 2 (IQGAP2) and its correlation with the clinicopathological parameters in hepatocellular carcinoma (HCC), and to reveal the potential mechanisms of IQGAP2 underlying human hepatocarcinogenesis.

METHODS: Western blot, immunofluorescence staining and immunohistochemical staining (IHC) were used to detect the expression and subcellular localization of IQGAP2 in 7 liver cancer and normal liver cell lines, as well as in 51 HCC tissue specimens. Meanwhile, the corresponding clinical data were analyzed retrospectively.

RESULTS: Only two liver cancer cell lines, HepG2 and Hep3B, expressed IQGAP2 at the protein level. In addition, immunofluorescence results revealed that IQGAP2 was localized in cytoplasm and nuclei. Apparent nucleolus and karyotheca staining was observed in HepG2 cells. Furthermore, histological validation of clinical samples showed that IQGAP2 expression was significantly down-regulated in tumor tissues (56.9%, 29/51). Meanwhile, the expression of IQGAP2 was associated with tumor size, AJCC staging and alpha-fetoprotein (AFP) expression level (P = 0.020; P = 0.017; P = 0.002). The immunohistochemical staining results from 38 HCC specimens showed that IQGAP2 was mainly localized at cytoplasm in the tumor and adjacent normal liver cells. In addition, partial cells had cell membrane and nuclear localization. However, definite association was not observed between IQGAP2 levels and tumor size, histological degree, AJCC staging or AFP expression status.

CONCLUSION: IQGAP2 expression is down-regulated in tumor tissues of HCC cases, and IQGAP2 may be a potential marker and tumor suppressor gene involved in HCC. These novel findings may provide a basis for the determination of mechanism(s) underlying human hepatocarcinogenesis.

Chemopreventive effect of silymarin on liver pathology in HBV X protein transgenic mice

There are currently limited therapeutic regimens available for effective treatment of hepatocellular carcinoma (HCC). Silymarin is a naturally derived polyphenolic antioxidant with hepatoprotective properties and is very widely used in clinical application; however, effect of silymarin on spontaneous HCC has not been studied. Silymarin was evaluated for its efficacy against spontaneous carcinogenesis using the HBV X protein (HBx) transgenic model. Silymarin was p.o. given to the HBx transgenic mice from 4 to 6 weeks of age. Our data indicated that silymarin has therapeutic effects on the early stages of liver damage, reversing fatty changes and recovering liver histopathology in a dose-dependent manner. To study the chemopreventive effects on the later stages of carcinogenesis, the mice at 13 months were split into a precancerous group and a group with significant liver carcinogenesis. After silymarin was given to the precancerous mice from 13 to 16 months of age, in contrast to an 80% incidence of HCC development in the untreated transgenic mice, no HCC was detected in any of these mice. Nonetheless, small hyperplastic nodules were detected in 86% of these precancerous mice. In the second group with notable HCC, silymarin was unable to block cancer progression. Although silymarin did not affect HBx expression, intracellular reactive oxygen species levels were decreased, cell proliferation was stimulated, and hepatocyte ultrastructure was found to significantly recover. In conclusion, silymarin exerts beneficial effects on the early stages of liver pathogenesis, preventing and delaying liver carcinogenesis. This drug should be considered as a potential chemopreventive agent for HBV-related hepatocarcinogenesis.

Future of molecular profiling of human hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a fatal disease occurring worldwide and developing mainly in chronic liver diseased patients. Despite routine screening of individuals at high risk, most of the patients are diagnosed at late stages of HCC. In addition, the recurrence rate after surgical resection of small tumors is high. Molecular profiling, including expression analysis, comparative genomics and proteomics, provides powerful tools to gain insight into the molecular mechanisms underlying carcinogenesis. Advances in bioinformatics have also allowed for the evaluation of large data sets. Therefore, molecular profiling of HCC using a Biological Expression Network Discovery (BLEND) strategy that integrates global molecular profiling data, including mRNA, miRNA, DNA methylation and DNA copy numbers from both the tumor and the surrounding microenvironment, along with mechanistic studies, may improve the diagnosis, treatment and prognosis of HCC patients. Such an approach will provide mechanistic insight into the pathogenesis of HCC, potentially leading to personalized medicine and the identification of new therapeutic targets.

[Epidemiology, risk factors and molecular pathogenesis of primary liver cancer]

Primary liver cancer is the fifth most common cancer worldwide. Hepatocellular carcinoma accounts for 85-90% of primary liver cancers. Distribution of hepatocellular carcinoma shows variations among geographic regions and ethnic groups. Males have higher liver cancer rates than females. Hepatocellular carcinoma occurs within an established background of chronic liver disease and cirrhosis (70-90%). Major causes (80%) of hepatocellular carcinoma are hepatitis B, C virus infection, and aflatoxin exposition. Its development is a multistep process. We have a growing understanding on the molecular pathogenesis. Genetic and epigenetic changes activate oncogenes, inhibit tumorsuppressor genes, which result in autonomous cell proliferation. The chromosomal instability caused by telomere dysfunction, the growth-retrained environment and the alterations of the micro- and macroenvironment help the expansion of the malignant cells. Understanding the molecular mechanisms could improve the screening of patients with chronic liver disease, or cirrhosis, and the prevention as well as treatment of hepatocellular carcinoma.

Chromosome instability in human hepatocellular carcinoma depends on p53 status and aflatoxin exposure

Hepatocellular carcinoma (HCC) is a heterogeneous disease triggered by various risk factors and frequently characterized by chromosome instability. This instability is considered to be caused primarily by Hepatitis B virus (HBV), although aflatoxin B1 (AFB1), a potent fungal mutagen is also suspected to influence chromosomal repair. We studied 90 HCCs from Italy, the country with the highest incidence of hepatocellular carcinoma in Europe, 81 samples from France and 52 specimens from Shanghai, in a region where intake of AFB1 via the diet is known to be high. All 223 tumours were characterized for 15 different genomic targets, including allelic loss at 13 chromosome arms and mutations of beta-catenin and p53 genes. Despite disparity in risk-factor distribution, Italian and French cases did not significantly differ for 14 of the 15 targets tested. beta-Catenin and p53 displayed moderate and similar mutation rates (18-29% of cases) in European series. By contrast, tumours from Shanghai were significantly different, with a lower mutation rate for beta-catenin (4% vs. 26%, p<0.0003) and a higher mutation rate for p53 (48% vs. 22%, p<0.0001) when compared with tumours of European origin. The Arg249Ser mutation, hallmark of exposure to AFB1, represented half of the changes in p53 in Shanghai. Furthermore, when stratified for the presence of HBV or p53 mutations, chromosome instability was always higher in Chinese than in European patients. This difference was particularly strong in p53-wildtype tumours (fractional allelic loss, 29.4% vs. 16.7%, p<0.0001). We suggest that AFB1-associated mutagenesis represents a plausible cause for the higher chromosome instability observed in Chinese HCCs, when compared with European primary liver carcinomas.