Ras pathway activation in hepatocellular carcinoma and anti-tumoral effect of combined sorafenib and rapamycin in vivo

Epigenetic inactivation of the tumor suppressor gene RIZ1 in hepatocellular carcinoma involves both DNA methylation and histone modifications

BACKGROUND & AIMS

The retinoblastoma-interacting zinc finger gene RIZ1 is inactivated in many cancers, but the underlying mechanisms remain unknown. This study aimed to investigate the epigenetic mechanisms of RIZ1 inactivation by analyzing the relationship between DNA methylation and histone modifications during regulation of RIZ1 expression.

METHODS

Methylation-specific PCR, RT-PCR, and immunohistochemistry were performed to examine RIZ1 methylation and expression. Dynamic changes in histone H3 lysine 9 (H3K9) modifications and histone deacetylases (HDACs) associated with the promoter were analyzed by chromatin immunoprecipitation (ChIP).

RESULTS

RIZ1 methylation was detected in 66.7% (32/48) HCC tissues, 6.3% (3/48) corresponding non-cancerous tissues, and 66.7% (4/6) HCC cell lines. All 32 HCC tissues with promoter methylation showed complete loss of RIZ1 protein, whereas RIZ1 protein was present in all the corresponding non-cancerous tissues. Neither 5-aza-2-deoxycitidine (5-Aza-dC) nor Trichostatin A (TSA) reversed promoter methylation, but did restore RIZ1 mRNA and resulted in the downregulation of HDAC1 but not HDAC3. However, 5-Aza-dC+TSA induced a partial reversal of promoter methylation and a markedly synergistic reactivation of RIZ1. Moreover, both HDAC1 and HDAC3 were downregulated. The ChIP assays showed 5-Aza-dC and/or TSA also contributed to the dynamic conversion of trimethylated to acetylated H3K9 at the promoter. Furthermore, a decrease in H3K9 trimethylation preceded an increase in H3K9 acetylation.

CONCLUSIONS

Our results suggest that promoter methylation and H3K9 modifications work together to silence the RIZ1 gene in HCC. 5-Aza-dC can restore the expression of RIZ1, as reflected by its effects on histone modification levels. This finding indicates that cooperative effects between these epigenetic modifications exist.

Prognostic significance of RASSF1A expression and methylation status in esophageal squamous cell carcinoma

AIM: To investigate the expression and methylation status of the RASSF1A gene in esophageal squamous cell carcinoma (ESCC) and to analyze their prognostic significance.

METHODS: The mRNA expression and DNA methylation of the promoter region of the RASSF1A gene in normal esophageal tissue samples and ESCC tissue samples taken from 49 ESCC patients were detected by real-time RT-PCR and real-time methylation-specific PCR (qMSP), respectively.

RESULTS: RASSF1A mRNA expression was down-regulated in 53.06% (26/49) of ESCC tissue samples. The level of RASSF1A mRNA expression in ESCC was significantly lower than that in adjacent normal tissue (P < 0.05). Down-regulation of RASSF1A mRNA expression was correlated with TNM stage, lymph node metastasis and poor prognosis in ESCC patients (all P < 0.05). Hypermethylation of the RASSF1A gene promoter region was detected in 77.60% (38/49) of ESCC patients. RASSF1A gene promoter hypermethylation was correlated with TNM stage, lymph node metastasis and poor prognosis in ESCC patients (all P < 0.05).

CONCLUSION: RASSF1A gene promoter hypermethylation is a very common molecular event in ESCC and may be responsible for the down-regulation of RASSF1A mRNA expression. Down-regulation of RASSF1A mRNA expression and hypermethylation of RASSF1A gene promoter region were significantly correlated with lymph node metastasis, TNM stage and poor prognosis in ESCC patients.

The multikinase inhibitor Sorafenib displays significant antiproliferative effects and induces apoptosis via caspase 3, 7 and PARP in B- and T-lymphoblastic cells

Background

Targeted therapy approaches have been successfully introduced into the treatment of several cancers. The multikinase inhibitor Sorafenib has antitumor activity in solid tumors and its effects on acute lymphoblastic leukemia (ALL) cells are still unclear.

Methods

ALL cell lines (SEM, RS4;11 and Jurkat) were treated with Sorafenib alone or in combination with cytarabine, doxorubicin or RAD001. Cell count, apoptosis and necrosis rates, cell cycle distribution, protein phosphorylation and metabolic activity were determined.

Results

Sorafenib inhibited the proliferation of ALL cells by cell cycle arrest accompanied by down-regulation of CyclinD3 and CDK4. Furthermore, Sorafenib initiated apoptosis by cleavage of caspases 3, 7 and PARP. Apoptosis and necrosis rates increased significantly with most pronounced effects after 96 h. Antiproliferative effects of Sorafenib were associated with a decreased phosphorylation of Akt (Ser473 and Thr308), FoxO3A (Thr32) and 4EBP-1 (Ser65 and Thr70) as early as 0.5 h after treatment. Synergistic effects were seen when Sorafenib was combined with other cytotoxic drugs or a mTOR inhibitor emphasizing the Sorafenib effect.

Conclusion

Sorafenib displays significant antileukemic activity in vitro by inducing cell cycle arrest and apoptosis. Furthermore, it influences PI3K/Akt/mTOR signaling in ALL cells.

Inherited hepatocellular carcinoma

Inherited liver disorders that cause chronic inflammation, fibrosis, and cirrhosis can lead to the development of liver cancer. Because of the rarity and diversity of some of these syndromes, the relative risk of developing HCC in these patients and the age at which tumours typically arise cannot be accurately estimated. Among patients with hereditary hemachromatosis (HH), the annual incidence of HCC is 4% once cirrhosis has been established. Fibrosis and portal hypertension associated with HH can be partially reversed with therapeutic phlebotomy, but it is unclear whether this treatment alters the incidence of HCC in these patients. Importantly, it seems likely that coincidence of these genetic disorders with known HCC risk factors such as alcoholism and viral hepatitis would amplify their oncogenic potential. For this reason, patients with known genetic disorders of the liver should be repeatedly counselled to avoid environmental and toxic injury to the liver. Treatment of HCC in patients with inherited liver disease mirrors that of HCC associated with other etiologies. Unfortunately, there are case series which suggest these patients with inherited liver disease and HCC tend to present at more advanced stages and are therefore not eligible for curative therapies, causing overall decreased survival relative to patients with HCC of viral or other etiologies.

Pilot study: rapamycin in advanced hepatocellular carcinoma

BACKGROUND

The PI3K/Akt/mTOR signal pathway is involved in hepatocarcinogenesis. Rapamycin (=sirolimus), a specific mTOR inhibitor, leads to G(1) arrest of many malignant cell lines and currently, analogues of rapamycin are being investigated as a cancer chemotherapeutic adjuvant.

AIM

To study the toxicity and tolerability of rapamycin therapy in patients with advanced hepatocellular carcinoma (HCC).

METHODS

Between June 2005 and February 2007, patients with advanced HCC, not eligible for any established therapy, were included in the study.

RESULTS

Eighteen patients (F/M: 5/13) with compensated liver cirrhosis (Child A n = 11, Child B n = 5, Child C n = 2) and histologically proven HCC were included in this study. According to the BCLC staging system, most of the patients enrolled had an advanced HCC: BCLC stage B: n = 2, Barcelona Clinic Liver-Cancer (BCLC) stage C: n = 14, BCLC stage D: n = 2. Overall, therapy with rapamycin was well tolerated. Most common toxicities were thrombocytopaenia and anaemia. We did not observe any partial or complete tumour response. At 3 months, two patients had stable disease and at 6 months, all patients had progressed. The median overall survival was 5.27 months, median time to progression was 3 months.

CONCLUSION

Rapamycin is well tolerated in patients with advanced HCC, but only minimally effective.

Management of hepatocellular carcinoma recurrence after liver transplantation

Management of patients with hepatocellular carcinoma (HCC) recurrence after liver transplantation (OLT) is not well established. We conducted a retrospective analysis of our results in the treatment of HCC recurrence after OLT Patients. The 23 HCC recurrences developed after 182 OLT performed for HCC within Milan criteria, had an average follow-up of 60 months.

RESULTS

The median time to recurrence was 23.4 months. Surgical resection of the recurrence was possible in 11 patients, but an R-0 resection was obtained in 8 patients. Four of these 8 patients developed another recurrence, with 3 succumbing due to tumor recurrence and 1 alive at 12 months with recurrence. The other 4 patients without recurrences, include 3 who are alive at 19, 31, and 86 months and 1 who died at 32.6 months due to hepatitis C recurrence. The 3 patients with palliative resections developed recurrences. Twelve patients were rejected for surgery: 8 were treated symptomatically, 2 with systemic chemotherapy, and 2 with everolimus and sorafenib. This last treatment was also prescribed for 2 patients after R-0 surgery who are alive at 19 and 31 months and for 1 patient after R-1 surgery who is alive at 19 months. Of 15 patients who died, 13 succumbed to HCC recurrence. The average survival from transplantation was 61.7 +/- 37.5 and 48 +/- 34.3 months for patients without and with recurrence, respectively (P < .001). The survival from the recurrence was significantly higher among patients with R-0 surgery: 32.3 +/- 21.5 versus 11.9 +/- 6.9 months (P = .006).

CONCLUSIONS

HCC recurrence after OLT of patients within Milan criteria was low but had a great impact on survival. Few cases are amenable to R-0 resection, but when possible it was associated with a significantly increased survival, although with an high incidence of a new recurrence. There is a rationale for the use of sorafenib and mammalian target of rapamycin based immunosuppression, which warrants randomized studies.

Molecular targeted therapy for advanced hepatocellular carcinoma: current status and future perspectives

Sorafenib, a multikinase inhibitor targeting vascular endothelial growth factor (VEGF)-mediated angiogenesis, is the first drug found to prolong survival of patients with advanced hepatocellular carcinoma (HCC). This advance has shifted the paradigm of systemic treatment for HCC toward molecular targeted therapy (MTT). However, the disease-stabilizing effect of VEGF signaling-targeted MTT normally lasts only for a few months, suggesting a rapid emergence of resistance in the majority of patients. To overcome the resistance to VEGF signaling-targeted MTT, strategies incorporating inhibition of either compensatory pro-angiogenic pathways or recruitment of bone marrow-derived circulating endothelial progenitors, as well as suppression of other oncogenic pathways, are currently being investigated. The combination of multiple molecular targeted agents or the use of multi-target agents may enhance the efficacy at the expense of increased toxicities. To facilitate the development of MTT for HCC, current methodologies for pharmacodynamic assessment, patient selection and target identification need to be improved. Patient selection according to the individual molecular signature of the tumor and correlative biomarker studies are encouraged while planning a clinical trial of novel MTT.

Synergistic role of Sprouty2 inactivation and c-Met up-regulation in mouse and human hepatocarcinogenesis

Sprouty2 (Spry2), a negative feedback regulator of the Ras/mitogen-activated protein kinase (MAPK) pathway, is frequently down-regulated in human hepatocellular carcinoma (HCC). We tested the hypothesis that loss of Spry2 cooperates with unconstrained activation of the c-Met protooncogene to induce hepatocarcinogenesis via in vitro and in vivo approaches. We found coordinated down-regulation of Spry2 protein expression and activation of c-Met as well as its downstream effectors extracellular signal-regulated kinase (ERK) and v-akt murine thymoma viral oncogene homolog (AKT) in a subset of human HCC samples with poor outcome. Mechanistic studies revealed that Spry2 function is disrupted in human HCC via multiple mechanisms at both transcriptional and post-transcriptional level, including promoter hypermethylation, loss of heterozygosity, and proteosomal degradation by neural precursor cell expressed, developmentally down-regulated 4 (NEDD4). In HCC cell lines, Spry2 overexpression inhibits c-Met-induced cell proliferation as well as ERK and AKT activation, whereas loss of Spry2 potentiates c-Met signaling. Most importantly, we show that blocking Spry2 activity via a dominant negative form of Spry2 cooperates with c-Met to promote hepatocarcinogenesis in the mouse liver by sustaining proliferation and angiogenesis. The tumors exhibited high levels of activated ERK and AKT, recapitulating the subgroup of human HCC with a clinically aggressive phenotype.

CONCLUSION

The occurrence of frequent genetic, epigenetic, and biochemical events leading to Spry2 inactivation provides solid evidence that Spry2 functions as a tumor suppressor gene in liver cancer. Coordinated deregulation of Spry2 and c-Met signaling may be a pivotal oncogenic mechanism responsible for unrestrained activation of ERK and AKT pathways in human hepatocarcinogenesis.

Molecular approaches to treatment of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) remains a highly complex disease resistant to commonly used chemotherapy and radiotherapy. As the sixth most common cancer worldwide with the third highest mortality rate and very poorly understood molecular pathways driving hepatocarcinogenesis, new treatment strategies are urgently needed for this devastating disease. The multikinase inhibitor sorafenib was the first molecular targeted drug in HCC that led to significant survival benefit in patients with advanced tumors. It is the first drug to be considered standard of care for advanced HCC and supports the importance of molecular therapies in the treatment of this cancer. Analyses of genetic and epigenetic alterations as well as different molecular pathways involved in the development of HCC help to identify potential new druggable targets. A variety of novel compounds are already under preclinical or clinical investigation, and accumulating evidence suggests that combination therapy targeting different pathways will potentiate anti-tumoral effects and will become the future therapeutic approach. In addition the establishment of a robust molecular classification will pave the way for a more personalized treatment scheme in HCC. In this article we review the current knowledge of the molecular pathogenesis of HCC and provide an overview of molecular targeted therapies in the management of HCC.

A seven-gene set associated with chronic hypoxia of prognostic importance in hepatocellular carcinoma

PURPOSE

Hepatocellular carcinomas (HCC) have an unpredictable clinical course, and molecular classification could provide better insights into prognosis and patient-directed therapy. We hypothesized that in HCC, certain microenvironmental regions exist with a characteristic gene expression related to chronic hypoxia which would induce aggressive behavior.

EXPERIMENTAL DESIGN

We determined the gene expression pattern for human HepG2 liver cells under chronic hypoxia by microarray analysis. Differentially expressed genes were selected and their clinical values were assessed. In our hypothesis-driven analysis, we included available independent microarray studies of patients with HCC in one single analysis. Three microarray studies encompassing 272 patients were used as training sets to determine a minimal prognostic gene set, and one recent study of 91 patients was used for validation.

RESULTS

Using computational methods, we identified seven genes (out of 3,592 differentially expressed under chronic hypoxia) that showed correlation with poor prognostic indicators in all three training sets (65/139/73 patients) and this was validated in a fourth data set (91 patients). Retrospectively, the seven-gene set was associated with poor survival (hazard ratio, 1.39; P = 0.007) and early recurrence (hazard ratio, 2.92; P = 0.007) in 135 patients. Moreover, using a hypoxia score based on this seven-gene set, we found that patients with a score of >0.35 (n = 42) had a median survival of 307 days, whereas patients with a score of < or =0.35 (n = 93) had a median survival of 1,602 days (P = 0.005).

CONCLUSIONS

We identified a unique, liver-specific, seven-gene signature associated with chronic hypoxia that correlates with poor prognosis in HCCs.

Cell cycle progression or translation control is not essential for vesicular stomatitis virus oncolysis of hepatocellular carcinoma

The intrinsic oncolytic specificity of vesicular stomatitis virus (VSV) is currently being exploited to develop alternative therapeutic strategies for hepatocellular carcinoma (HCC). Identifying key regulators in diverse transduction pathways that define VSV oncolysis in cancer cells represents a fundamental prerequisite to engineering more effective oncolytic viral vectors and adjusting combination therapies. After having identified defects in the signalling cascade of type I interferon induction, responsible for attenuated antiviral responses in human HCC cell lines, we have now investigated the role of cell proliferation and translation initiation. Cell cycle progression and translation initiation factors eIF4E and eIF2Bε have been recently identified as key regulators of VSV permissiveness in T-lymphocytes and immortalized mouse embryonic fibroblasts, respectively. Here, we show that in HCC, decrease of cell proliferation by cell cycle inhibitors or siRNA-mediated reduction of G(1) cyclin-dependent kinase activities (CDK4) or cyclin D1 protein expression, do not significantly alter viral growth. Additionally, we demonstrate that translation initiation factors eIF4E and eIF2Bε are negligible in sustaining VSV replication in HCC. Taken together, these results indicate that cellular proliferation and the initiation phase of cellular protein synthesis are not essential for successful VSV oncolysis of HCC. Moreover, our observations indicate the importance of cell-type specificity for VSV oncolysis, an important aspect to be considered in virotherapy applications in the future.

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.

Personalized molecular targeted therapy in advanced, recurrent hepatocellular carcinoma after liver transplantation: a proof of principle

BACKGROUND & AIMS

The advent of molecular medicine that targets specific pathways is changing the therapeutic approach to hepatocellular carcinoma. For several aberrantly activated pathways in hepatocarcinoma, surrogate markers of activation can be assessed by immunohistochemistry, although associations with in vivo response to targeted therapies are still lacking.

METHODS

A patient, who presented with hepatic and extra-hepatic hepatocarcinoma recurrence 11 years after liver transplantation, was assessed for beta-catenin, pERK, and pS6 in primary and secondary tumor specimens, in order to define a possible activation of the Wnt, Ras/MAPK and Akt/mTOR pathways and design a personalized targeted therapy in absence of alternative treatment options. Moreover, mutation analysis of the beta-catenin gene (CTNNB1) and DNA microsatellite analyses were performed.

RESULTS

The identification of the same mutation in the beta-catenin gene, as well as the same microsatellite pattern in tumor tissues taken 11 years apart, proved that the observed hepatocarcinoma was a true recurrence. Nuclear beta-catenin and pS6 in tumor cells were positive, whereas pERK was positive only in the peritumoral endothelium. This pattern of immunohistochemistry, after failure of sorafenib alone, lead to the choice to add the mTOR inhibitor, everolimus, to sorafenib. Three months later a 50% tumor reduction was observed, and after 6 months a further reduction of tumor vital components was confirmed, while a grade II gastrointestinal bleeding episode occurred.

CONCLUSIONS

A personalized approach aimed to treat recurrent hepatocarcinoma is possible through analysis of tumoral molecular pathways. Partial success of the selected combination of sorafenib and everolimus supports the pivotal role of mTOR signalling and highlights the importance of reliable biomarkers to route the best molecular-based therapeutic options in HCC.

Functional genomics of endothelial cells treated with anti-angiogenic or angiopreventive drugs

Angiogenesis is a highly regulated physiological process that has been studied in considerable detail given its importance in several chronic pathologies. Many endogenous factors and hormones intervene in the regulation of angiogensis and classical as well as targeted drugs have been developed for its control. Angiogenesis inhibition has come off the bench and entered into clinical application for cancer therapy, particularly for metastatic disease. While the clinical benefit is currently in terms of months, preclinical data suggest that novel drugs and drug combinations could lead to substantial improvement. The many targets of endogenous angiogenesis inhibitors reflect the complexity of the process; in contrast, current clinical therapies mainly target the vascular endothelial growth factor system. Cancer chemopreventive compounds can retard tumor insurgence and delay or prevent metastasis and many of these molecules hinder angiogenesis, a mechanism that we termed angioprevention. Angiopreventive drugs appear to prevalently act through the inhibition of the pro-inflammatory and anti-apoptotic player NFkappaB, thus contrasting inflammation dependent angiogenesis. Relatively little is known concerning the effects of these angiogenesis inhibitors on gene expression of endothelial cells, the main target of many of these molecules. Here we provide an exhaustive list of anti-angiogenic molecules, and summarize their effects, where known, on the transcriptome and functional genomics of endothelial cells. The regulation of specific genes can be crucial to preventive or therapeutic intervention. Further, novel targets might help to circumvent resistance to anti-angiogenic therapy. The studies we review are relevant not only to cancer but also to other chronic degenerative diseases involving endothelial cells, such as cardiovascular disorders, diabetes, rheumatoid arthritis and retinopaties, as well as vessel aging.

Epigenetic mechanisms involved in the pathogenesis of hepatobiliary malignancies

Primary tumors of the liver and biliary tree are increasing in frequency and portend a miserable prognosis. Epigenetic regulation of gene expression has emerged as a fundamental aspect of cancer development and progression. The molecular mechanisms of carcinogenesis in hepatocellular carcinoma and cholangiocarcinoma involve a complex interplay of both genetic and epigenetic factors. Recent studies investigating the possible epigenetic mechanisms induced in the disease have shed new light on the molecular underpinnings of hepatobiliary cancers. In addition, epigenetic modifications of DNA in cancer and precancerous lesions offer hope and the promise of novel biomarkers for early cancer detection, prediction, prognosis and response to treatment. Furthermore, the reversal of epigenetic changes represents a potential target for novel therapeutic strategies and medication design.

Mechanisms of HBV-related hepatocarcinogenesis

The hepatitis B virus (HBV) is a small enveloped DNA virus, which primarily infects hepatocytes and causes acute and persistent liver disease. Epidemiological studies have provided overwhelming evidence for a causal role of chronic HBV infection in the development of hepatocellular carcinoma, but the molecular mechanisms underlying virally-induced tumourigenesis remain largely debated. In the absence of a dominant oncogene encoded by the HBV genome, indirect roles have been proposed, including insertional activation of cellular cancer-related genes by HBV DNA integration, induction of genetic instability by viral integration or by the regulatory protein HBx, and long-term effects of viral proteins in enhancing immune-mediated liver disease. Recent genetic studies indicate that HBV-related tumours display a distinctive profile with a high rate of chromosomal alterations and low frequency of beta-catenin mutations. This review will discuss the evidence implicating chronic HBV infection as a causal risk factor of primary liver cancer. It will also discuss the molecular mechanisms that are critical for the tumourigenic process due to long lasting infection with HBV.

[Treatment of advanced hepatocellular carcinoma]

In the last few years, much progress has been made in the diagnosis and treatment of hepatocellular carcinoma (HCC). Due to these advances, HCC is no longer regarded as a disease with an extremely poor prognosis and has become the focus of some of the most active basic and clinical research in recent years. The most important advance is possibly the demonstration that sorafenib, a multikinase inhibitor with antiproliferative and antiangiogenic properties, is an effective treatment, able to increase survival in patients with advanced-stage HCC. This increased survival has demonstrated that these drugs, which act selectively on the molecular pathways involved in tumoral progression, can be effective in the treatment of HCC and has opened the door to the evaluation of these molecular agents, alone or in combination, in HCC. The present article provides a review of the treatment of advanced-stage HCC, with special emphasis on the distinct agents that are currently under evaluation.

Prognostic markers and putative therapeutic targets for hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the fifth most frequent human cancer and a fatal disease. Therapies with pharmacological agents do not improve the prognosis of patients with unresectable HCC. This emphasizes the need to identify new targets for early diagnosis, chemoprevention, and treatment of the disease. Available evidence indicates that clinical outcome of HCC could reflect the genetic predisposition to cancer development and progression. Numerous loci controlling HCC progression have been identified in rodents. In this review, we describe results of recent studies on effector mechanisms of susceptibility/resistance genes, responsible for HCC progression, aimed at identifying new putative prognostic markers and therapeutic targets of this tumor. Highest c-myc amplification and overexpression, alterations of iNOS crosstalk with IKK/NF-kB and RAS/ERK signaling, ubiquitination of ERK and cell cycle inhibitors, and deregulation of FOXM1 and cell cycle key genes occur in rapidly progressing dysplastic nodules and HCC, induced in genetic susceptible rat strains, compared to the lesions of resistant rats. Notably, alterations of these mechanisms in human HCC subtypes with poorer or better prognosis, are similar to those present in genetically susceptible and resistant rats, respectively, and function as prognostic markers and therapeutic targets. Attempts to cure advanced HCC by molecular therapy directed against specific targets led to modest survival benefit. Thus, efforts are necessary to identify and test, in pre-clinical and clinical studies, new therapeutic targets for combined molecular treatments of HCC. They may take advantage from the comparative analysis of signal transduction in HCCs differently prone to progress, in rats and humans.