Experimental models of hepatocellular carcinoma

Prognostic significance and therapeutic potential of eukaryotic translation initiation factor 5A (eIF5A) in hepatocellular carcinoma

Using comparative proteomic and genomic approaches, the authors identified eukaryotic translation initiation factor 5A (eIF5A) as an oncofetal molecule highly abundant in mouse embryonic livers and human hepatocellular carcinoma (HCC) cell lines. To evaluate the oncogenic role and prognostic significance of eIF5A in HCC, we investigate the expression patterns of the two isoforms (eIF5A1 and eIF5A2) in a cohort of 258 HCC cases by cDNA microarray. Both eIF5A isoforms were expressed in the tumors, and clinically correlated eIF5A1 with more numbers of tumor nodules and eIF5A2 with tumor venous infiltration in HCC. In a separate cohort of 50 HCCs, high level of eIF5A2, but not eIF5A1, was associated with elevated levels of deoxyhypusine synthase and deoxyhypusine hydroxylase that catalyze post-translational hypusination of eIF5A protein. Interestingly, N1-guanyl-1,7-diaminoheptane (GC7), which is an inhibitor for the first step of eIF5A hypusination, was shown to significantly impair the cell proliferation and invasion of primary HCC cells (HepG2 and Hep3B). To further demonstrate the tumorigenic role associated with eIF5A, a drastic reduction of cell proliferation was associated with suppression of eIF5A2 by transfecting Hep3B, H2-P and H2-M HCC cells expressing high level of this isoform using small interfering RNA (siRNA) against eIF5A2. For these assays, a milder response was usually observed in normal hepatocyte cell line. Therefore, these findings suggest that eIF5A plays an important role in HCC tumorigenesis and metastasis, and targeting eIF5A hypusination by GC7 inhibitor or eIF5A2 by RNA interference (RNAi) may offer new therapeutic alternatives to HCC patients.

Serum N-glycome biomarker for monitoring development of DENA-induced hepatocellular carcinoma in rat

BACKGROUND

There is a demand for serum markers for the routine assessment of the progression of liver cancer. We previously found that serum N-linked sugar chains are altered in hepatocellular carcinoma (HCC). Here, we studied glycomic alterations during development of HCC in a rat model.

RESULTS

Rat HCC was induced by the hepatocarcinogen, diethylnitrosamine (DENA). N-glycans were profiled using the DSA-FACE technique developed in our laboratory.In comparison with control rats, DENA rats showed a gradual but significant increase in two glycans (R5a and R5b) in serum total N-glycans during progression of liver cirrhosis and cancer, and a decrease in a biantennary glycan (P5). The log of the ratio of R5a to P1 (NGA2F) and R5b to P1 [log(R5a/P1) and log(R5b/P1)] were significantly (p < 0.0001) elevated in HCC rats, but not in rats with cirrhosis or fibrosis or in control rats. We thus propose a GlycoTest model using the above-mentioned serum glycan markers to monitor the progression of cirrhosis and HCC in the DENA-treated rat model. When DENA-treated rats were subsequently treated with farnesylthiosalicyclic acid, an anticancer drug, progression to HCC was prevented and GlycoTest markers (P5, R5a and R5b) reverted towards non-DENA levels, and the HCC-specific markers, log(R5a/P1) and log(R5b/P1), normalized completely.

CONCLUSIONS

We found an increase in core-alpha-1,6-fucosylated glycoproteins in serum and liver of rats with HCC, which demonstrates that fucosylation is altered during progression of HCC. Our GlycoTest model can be used to monitor progression of HCC and to follow up treatment of liver tumors in the DENA rat. This GlycoTest model is particularly important because a rapid non-invasive diagnostic procedure for tumour progression in this rat model would greatly facilitate the search for anticancer drugs.

Cancer gene discovery in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a deadly cancer, whose incidence is increasing worldwide. Albeit the main risk factors for HCC development have been clearly identified, such as hepatitis B and C virus infection and alcohol abuse, there is still preliminary understanding of the key drivers of this malignancy. Recent data suggest that genomic analysis of cirrhotic tissue - the pre-neoplastic carcinogenic field - may provide a read-out to identify at risk populations for cancer development. Given this contextual complexity, it is of utmost importance to characterize the molecular pathogenesis of this disease, and pinpoint the dominant pathways/drivers by integrative oncogenomic approaches and/or sophisticated experimental models. Identification of the dominant proliferative signals and key aberrations will allow for a more personalized therapy. Pathway-based approaches and functional experimental studies have aided in identifying the activation of different signaling cascades in HCC (e.g. epidermal growth factor, insulin-like growth factor, RAS, MTOR, WNT-betacatenin, etc.). However, the introduction of new high-throughput genomic technologies (e.g. microarrays, deep sequencing, etc.), and increased sophistication of computational biology (e.g. bioinformatics, biomodeling, etc.), opens the field to new strategies in oncogene and tumor suppressor discovery. These oncogenomic approaches are framed within emerging new disciplines such as systems biology, which integrates multiple inputs to explain cancer onset and progression. In addition, the consolidation of sophisticated animal models, such as mosaic cancer mouse models or the use of transposons for mutagenesis screens, have been instrumental for the identification of novel tumor drivers. We herein review some classical as well as some recent fast track approaches for oncogene discovery in HCC, and provide a comprehensive landscape of the currently known spectrum of molecular aberrations involved in hepatocarcinogenesis.

Viral hepatocarcinogenesis

Hepatocellular carcinoma (HCC) is the fifth most common cancer and the third leading cause of cancer death worldwide. Despite recent advances in the diagnosis and treatment of HCC, its prognosis remains dismal. Infection with hepatitis B virus (HBV) and hepatitis C virus (HCV) are the major risk factors for HCC. Although both are hepatotropic viral infections, there are important differences between the oncogenic mechanisms of these two viruses. In addition to the oncogenic potential of its viral proteins, HBV, as a DNA virus, can integrate into host DNA and directly transform hepatocytes. In contrast, HCV, an RNA virus, is unable to integrate into the host genome, and viral protein expression has a more critical function in hepatocarcinogenesis. Both HBV and HCV proteins have been implicated in disrupting cellular signal transduction pathways that lead to unchecked cell growth. Most HCC develops in the cirrhotic liver, but the linkage between cirrhosis and HCC is likely multifactorial. In this review, we summarize current knowledge regarding the pathogenetic mechanisms of viral HCC.

Prediction of progression-free survival in patients presenting with hepatocellular carcinoma within the Milan criteria

Transplantation is the treatment of choice for hepatocellular carcinoma (HCC) meeting the Milan criteria. HCC and chronic liver diseases have distinct natural histories for which an equitable transplant policy must account. We enrolled and prospectively followed at a single center 206 consecutive HCC patients that presented within the Milan criteria. Patients were treated per the Barcelona Clinic Liver Cancer (BCLC) algorithm; 95% received resection, ablation, or transarterial chemoembolization. The median follow-up was 16 months. Progression occurred in 84 patients, and 8 patients died. Risk factors for the time to disease progression (death or progression beyond T2) were analyzed in 170 patients with a complete data set. Risk factors with the strongest relationship to progression included tumor diameter and tumor persistence/recurrence after local therapy (hazard ratios of 1.51 and 2.75, respectively, when transplanted patients were censored at the time of transplantation and hazard ratios of 1.53 and 3.66, respectively, when transplantation was counted as an event; P < or = 0.0001). To evaluate the current Model for End-Stage Liver Disease (MELD) exception, we compared the expected progression rate (PR) with our observed PR in 133 stage T2 patients. The current policy resulted in a large overestimation of the PR for T2 HCC and an unsatisfactory performance [Harrell's concordance index (C index) = 0.60, transplant censored; C index = 0.55, transplant as progression]. Risk factors for progression that were identified by univariate analysis were considered for multivariate analysis. With these risk factors and the patients' natural MELD scores, an adjusted model applicable to organ allocation was generated, and this decreased the discrepancy between the expected and observed PRs (C index = 0.66, transplant censored; C index = 0.69, transplant as progression). In conclusion, the current MELD exception largely overestimates progression in T2 patients treated according to the BCLC guidelines. The tumor response to resective or ablative treatment can predict tumor progression beyond the Milan criteria, and it should be taken into account in models designed to prioritize organ allocation.

Carbogen gas-challenge BOLD MR imaging in a rat model of diethylnitrosamine-induced liver fibrosis

PURPOSE

To investigate the relationship between gas-challenge blood oxygen level-dependent (BOLD) magnetic resonance (MR) imaging measurements and hepatic disease progression in a rat model of diethylnitrosamine (DEN)-induced liver fibrosis.

MATERIALS AND METHODS

The institutional animal care and use committee approved all experiments. Liver fibrosis was induced in 27 male Wistar rats by means of weekly oral gavage with 5 mL of 1.5% DEN solution per kilogram of body weight for 3-11 weeks, which produced varying degrees of liver fibrosis. Eight rats developed nonsubstantial fibrosis; eight rats, substantial fibrosis; and 15 rats, cirrhosis. Four nontreated healthy rats served as controls. Multiple-gradient-echo MR images were acquired in the rats at steady-state normoxia and hyperoxia and then during dynamic gas challenges. The change in R2* (DeltaR2*) during the gas challenge and the ratio of number of activated voxels to total number of voxels in the liver were quantified. Masson trichrome staining of liver tissue was used to identify collagen tissue. Liver fibrosis was assessed by using a semiquantitative METAVIR scoring system and quantitative analysis of the percentage of liver fibrosis. Hepatic hemodynamic responses at BOLD MR imaging were compared across the fibrosis stages at independent-sample t test and linear regression analyses.

RESULTS

DeltaR2* was well correlated with gas-challenge interval. Mean DeltaR2* decreased during liver fibrosis progression, from 19.60 sec(-1) +/- 4.47 (standard deviation) in animals without substantial fibrosis to 14.02 sec(-1) +/- 2.88 and 6.26 sec(-1) +/- 7.40 in animals with substantial fibrosis and cirrhosis, respectively (P = .006 for rats without vs rats with substantial fibrosis, P = .001 for rats with substantial fibrosis vs rats with cirrhosis, P < .001 for rats without substantial fibrosis vs rats with cirrhosis). Mean DeltaR2* (r = -0.773) and liver activation (r = -0.691) were inversely correlated with liver fibrosis (P < .001).

CONCLUSION

Carbogen gas-challenge BOLD MR imaging can depict hepatic hemodynamic alterations during the progression of fibrosis and has the potential to serve as a noninvasive, nonenhanced imaging method for liver fibrosis diagnosis and staging.

The effect of Scutellaria baicalensis on the signaling network in hepatocellular carcinoma cells

Scutellaria baicalensis is an anti-inflammatory and antineoplastic Chinese herbal therapy. We have previously shown that S. baicalensis can inhibit hepatocellular carcinoma (HCC) cell growth in vitro. In this study, we sought to determine the effect of S. baicalensis on the cell signaling network using our newly developed Pathway Array technology, which screens cell signaling pathways involved in cell cycle regulation. The HCC cell line (HepG2) was treated with S. baicalensis extract in vitro. The effect on the cell cycle was analyzed by flow cytometry, and the expression of various signaling proteins was assayed with Pathway Array. Our results indicate that S. baicalensis exerts a strong growth inhibition of the HepG2 cells via G(2)/M phase arrest. The Pathway Array analysis of 56 proteins revealed a total of 14 differentially expressed proteins or phosphorylations after treatment. Of these, 9 showed a dose-dependent decrease (p53, ETS1, Cdc25B, p63, EGFR, ERK1/2, XIAP, HIF-2alpha, and Cdc25C) whereas one demonstrated a dose-dependent increase (Cyclin E) after treatment with 200 microg/ml of S. baicalensis. Using computer simulation software, we identified additional hubs in the signaling network activated by S. baicalensis. These results indicate that S. baicalensis exerts a broad effect on cell signaling networks leading to a collective inhibition of cell proliferation.

Expression of stem cell factor and its receptor c-Kit during the development of intrahepatic cholangiocarcinoma

Stem cell factor (SCF) and its receptor, c-Kit, constitute an important signal transduction system with proliferative and anti-apoptotic functions. Besides regulating hemopoietic stem cell proliferation and liver regeneration, it has been implicated in the regulation of human malignancies. However, the cellular expression of the SCF-c-Kit gene system in the liver during cholangiocarcinogenesis has not been studied to date. The protein- and mRNA-expression levels of SCF and c-Kit genes were examined in normal rat liver, in isolated normal rat liver cells and in a thioacetamide-induced rat model of intrahepatic cholangiocarcinoma (CC). Immunohistochemical analysis of the normal liver showed that SCF is expressed in the wall of the hepatic artery and in some cells, which were located along the sinusoids, although it was absent from hepatocytes and biliary epithelial cells. The mRNA analysis of isolated normal liver cell populations revealed a co-expression of SCF- and c-Kit-mRNA in sinusoidal endothelial cells and in Kupffer cells, whereas passaged and cultured liver myofibroblasts (MFs) expressed only SCF. Low levels of the SCF- and c-Kit-mRNA expression could be detected in isolated hepatocytes of the normal liver. Immunohistochemical analysis of the CC tissue showed SCF positivity in proliferating biliary cells (CK-19(+)), in macrophages (ED-1(+)) and in MFs (alpha-smooth-muscle-actin, alpha-SMA(+)) of the tumoral microenvironment. c-Kit-positivity could be detected on hepatocytes of the regenerating nodules and on the proliferating bile ducts of CC. Compared with the normal liver tissue, SCF-mRNA from the CC tissue was upregulated up to 20-fold, whereas c-Kit-mRNA was upregulated up to fivefold. These data indicate that several cell populations may become able to express SCF and/or c-Kit during cholangiocarcinogenesis. Therefore, the SCF-c-Kit system may contribute to tumor development, for instance, by inducing proliferation of hepatocytes and of biliary cells and by acting as a surviving factor for CC cells.

Challenging issues in molecular-targeted therapy

There are variety of anticancer treatments including chemotherapeutic drugs, which are known to induce cell growth arrest and apoptosis through DNA damage and cytoskeleton toxicity. Meanwhile, histone deacetylase (HDAC) inhibitors could apply their antitumor activity through chromatin remodeling and gene expression modulation that affect the cell cycle and survival pathways. This paper proposes an anticancer three-drug compound and discusses several challenging issues in relation to designing multidrug compounds that could possibly lead to molecular-targeted therapies.

Rho GTPases in hepatocellular carcinoma

Rho GTPases are major regulators of signal transduction pathways and play key roles in processes including actin dynamics, cell cycle progression, cell survival and gene expression, whose deregulation may lead to tumorigenesis. A growing number of in vitro and in vivo studies using tumor-derived cell lines, primary tumors and animal cancer models strongly suggest that altered Rho GTPase signaling plays an important role in the initiation as well as in the progression of hepatocellular carcinoma (HCC), one of the deadliest human cancers in the world. These alterations can occur at the level of the GTPases themselves or of one of their regulators or effectors. The participation into the tumorigenic process can occur either through the over-expression of one of these components which presents an oncogenic activity as illustrated with RhoA and C or through the attenuation of the expression of a component presenting tumor suppressor activity as for Cdc42 or the RhoGAP, DLC-1. Consequently, these observations reflect the heterogeneity and the complexity of liver carcinogenesis. Recently, pharmacological approaches targeting Rho GTPase signaling have been used in HCC-derived models with relative success but remain to be validated in more physiologically relevant systems. Therefore, therapeutic approaches targeting Rho GTPase signaling may provide a novel alternative for anti-HCC therapy.

A rodent model of NASH with cirrhosis, oval cell proliferation and hepatocellular carcinoma

BACKGROUND/AIMS

Hepatocellular carcinoma (HCC) is a well recognized complication of advanced NASH (non-alcoholic steatohepatitis). We sought to produce a rat model of NASH, cirrhosis and HCC.

METHODS

Adult Sprague-Dawley rats, weighing 250-300g, were fed a choline-deficient, high trans-fat diet and exposed to DEN in drinking water. After 16 weeks, the animals underwent liver ultrasound (US), sacrifice and assessment by microscopy, immunohistochemistry and transmission electron microscopy (TEM).

RESULTS

US revealed steatosis and focal lesions in 6 of 7. All had steatohepatitis defined as inflammation, advanced fibrosis and ballooning with Mallory-Denk bodies (MDB) with frank cirrhosis in 6. Areas of more severe injury were associated with anti-CK19 positive ductular reaction. HCC, present in all, were macro-trabecullar or solid with polyhedral cells with foci of steatosis and ballooned cells. CK19 was positive in single or solid nests of oval cells and in neoplastic hepatocytes. TEM showed ballooning with small droplet fat, dilated endoplasmic reticulum and MDB in non-neoplastic hepatocytes and small droplet steatosis in some cancer cells.

CONCLUSIONS

This model replicated many features of NASH including steatohepatitis with ballooning, fibrosis, cirrhosis and hepatocellular carcinoma. Oval cell proliferation was evident and the presence anti-CK 19 positivity in the cancer suggests oval cell origin of the malignancy.

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.