Sorafenib and rapamycin induce growth suppression in mouse models of hepatocellular carcinoma

Efficacy of perifosine alone and in combination with sorafenib in an HrasG12V plus shp53 transgenic mouse model of hepatocellular carcinoma

PURPOSE

Perifosine has shown antitumor activity via inhibition of Akt phosphorylation in many advanced solid tumors. This study investigated the efficacy of perifosine alone and in combination with sorafenib in a transgenic mouse model of HCC.

METHODS

The mouse model of HCC was generated by hydrodynamic injection of transposons encoding HrasG12V and short-hairpin RNA downregulating p53. The transgenic mice were treated with perifosine alone and in combination with sorafenib to evaluate efficacy of drugs on tumor growth and survival.

RESULTS

Treatment with perifosine for 5 weeks, alone and in combination with sorafenib, strongly inhibited tumor growth and increased survival. Perifosine inhibited HCC cell proliferation, induced apoptosis, and decreased tumor angiogenesis. Furthermore, its combination with sorafenib enhanced these effects. In addition, Akt phosphorylation was decreased by perifosine and further decreased by combination treatment. Although perifosine alone did not appear to activate the caspase pathway, combination treatment increased the cleavage of caspase-3, caspase-9, and poly (ADP-ribose) polymerase.

CONCLUSIONS

The preclinical effect that current study showed represents a strong rationale for clinical trials using perifosine alone and in combination with sorafenib in the treatment of HCC patients.

Evaluation of in vivo responses of sorafenib therapy in a preclinical mouse model of PTEN-deficient of prostate cancer

Background

Despite recent advances in the treatment for advanced prostate cancer, outcomes remain poor. This lack of efficacy has prompted the development of alternative treatment strategies. In the present study we investigate the effects of the multikinase inhibitor sorafenib in a genetically engineered mouse model of prostate cancer and explore the rational combination with the mTOR inhibitor everolimus.

Methods

Conditional prostate specific PTEN-deficient knockout mice were utilized to determine the pharmacodynamic and chemopreventive effects of sorafenib. This mouse model was also used to examine the therapeutic efficacy of sorafenib alone or in combination with everolimus. Preclinical efficacy was assessed by comparing the reduction of tumor burden, proliferation, angiogenesis and the induction of apoptosis. Molecular responses were assessed by immunohistochemical, TUNEL and western blot assays.

Results

Pharmacodynamic analysis revealed that a single dose of sorafenib decreased activation of the PI3K/AKT/mTOR signaling axis at doses of 30–60 mg/kg, but activated JAK/STAT3 signaling. Levels of cleaved casapase-3 increased in a dose dependent manner. Chemoprevention studies showed that chronic sorafenib administration was capable of inhibiting tumor progression through the reduction of cancer cell proliferation, angiogenesis and the induction of apoptosis. In intervention models of established castration-naïve and castration-resistant prostate cancer, treatment with sorafenib provided modest but statistically insignificant reduction in tumor burden. However, sorafenib significantly inhibited cancer cell proliferation and MVD but had minimal effects on the induction of apoptosis. Interestingly, the administration of sorafenib increased the expression levels of the androgen receptor, p-GSK3β and p-ERK1/2 in castration-resistant prostate cancers. In both intervention models, combination therapy demonstrated a clear tendency of enhanced antitumor effects over monotherapy. Notably, the treatment combination of sorafenib and everolimus overcame therapeutic escape from single agent therapy in castration-resistant prostate cancers.

Conclusions

In summary, we provide insights into the molecular responses of sorafenib therapy in a clinically relevant model of prostate cancer and present preclinical evidence for the development of targeted treatment strategies based on the use of multikinase inhibitors in combination with mTOR inhibitors for the treatment of advanced prostate cancer.

Electronic supplementary material

The online version of this article (doi:10.1186/s12967-015-0509-x) contains supplementary material, which is available to authorized users.

Arsenic trioxide potentiates the anti-cancer activities of sorafenib against hepatocellular carcinoma by inhibiting Akt activation

Sorafenib is the standard first-line systemic drug for advanced hepatocellular carcinoma (HCC), but it also induces the activation of Akt, which contributes to the mechanisms for the resistance to sorafenib. Arsenic trioxide (ATO) is a currently clinically used anticancer drug and displays its anticancer activities by inhibiting Akt activation. Therefore, we hypothesized that ATO may potentiate the anti-cancer activities of sorafenib against HCC. The results have demonstrated that ATO synergized with sorafenib to inhibit the proliferation and promote the apoptosis of HCC cells by diminishing the increased activation of Akt by sorafenib. ATO was shown to inhibit the expression or activation of Akt downstream factors, including glycogen synthase kinase (GSK)-3β, mammalian target of rapamycin (mTOR), ribosomal protein S6 kinase (S6K), and eukaryotic translation initiation factor 4E-binding protein 1 (4EBP1), which regulate cell apoptosis and were upregulated or activated by sorafenib. Both sorafenib and ATO downregulated the expression of cyclin D1, resulting in HCC cells arrested at G0/G1 phase. ATO downregulated the expression of Bcl-2 and Bcl-xL and upregulated the expression of Bax, indicating that ATO could induce the apoptosis of HCC cells through the intrinsic pathways; but sorafenib showed little effects on these proteins of Bcl-2 family. ATO synergized with sorafenib to suppress the growth of HCC tumors established in mice by inhibiting the proliferation and inducing the apoptosis of HCC cells in situ. These results indicate that ATO may be a potential agent that given in combination with sorafenib acts synergistically for treating HCC.

Combination of letrozole, metronomic cyclophosphamide and sorafenib is well-tolerated and shows activity in patients with primary breast cancer

PURPOSE

To assess whether the combination of letrozole, metronomic cyclophosphamide and sorafenib (LCS) is well tolerated and shows activity in primary breast cancer (BC).

METHODS

Thirteen oestrogen receptor-positive, postmenopausal, T2-4, N0-1 BC patients received the LCS combination for 6 months. In these patients we examined the pharmacokinetics of sorafenib and cyclophosphamide, toxicity of the regimen, the clinical response to therapy and changes in the levels of biologically relevant biomarkers.

RESULTS

Adequate plasma concentrations of sorafenib were achieved in patients when it was dosed in combination with L+C. The mean plasma concentrations of C were consistently lower following administration of LCS, compared with administration of L+C only. The most common drug-related grade 3/4 adverse events were skin rash (69.3%), hand-foot skin reaction (69.3%) and diarrhoea (46.1%). According to RECIST Criteria, a clinical complete response was observed in 6 of 13 patients. A significant reduction in tumour size, evaluated with MRI, was also observed between baseline and 14 days of treatment in all 13 patients (P=0.005). A significant reduction in SUV uptake, measured by (18)FDG-PET/CT, was observed in all patients between baseline and 30 days of treatment (P=0.015) and between baseline and definitive surgery (P=0.0002). Using modified CT Criteria, a response was demonstrated in 8 out of 10 evaluable patients at 30 days and in 11 out of 13 evaluable patients at the definitive surgery. A significant reduction in Ki67 expression was observed in all patients at day 14 compared with baseline (P<0.00001) and in 9 out of 13 patients at the definitive surgery compared with baseline (P<0.03). There was also a significant suppression of CD31 and VEGF-A expression in response to treatment (P=0.01 and P=0.007, respectively).

CONCLUSIONS

The LCS combination is feasible and tolerable. The tumour response and target biomarker modulation indicate that the combination is clinically and biologically active.

Reciprocal activating crosstalk between c-Met and caveolin 1 promotes invasive phenotype in hepatocellular carcinoma

c-Met, the receptor for Hepatocyte Growth Factor (HGF), overexpressed and deregulated in Hepatocellular Carcinoma (HCC). Caveolin 1 (CAV1), a plasma membrane protein that modulates signal transduction molecules, is also overexpressed in HCC. The aim of this study was to investigate biological and clinical significance of co-expression and activation of c-Met and CAV1 in HCC. We showed that c-Met and CAV1 were co-localized in HCC cells and HGF treatment increased this association. HGF-triggered c-Met activation caused a concurrent rise in both phosphorylation and expression of CAV1. Ectopic expression of CAV1 accelerated c-Met signaling, resulted in enhanced migration, invasion, and branching-morphogenesis. Silencing of CAV1 downregulated c-Met signaling, and decreased migratory/invasive capability of cells and attenuated branching morphogenesis. In addition, activation and co-localization of c-Met and CAV1 were elevated during hepatocarcinogenesis. In conclusion reciprocal activating crosstalk between c-Met and CAV1 promoted oncogenic signaling of c-Met contributed to the initiation and progression of HCC.

Oncogenic signaling pathways and origins of tumor-initiating stem-like cells of hepatocellular carcinomas induced by hepatitis C virus, alcohol and/or obesity

This review article discusses the importance and oncogenic signaling pathways of tumor-initiating cells (TICs) in several etiologies of hepatocellular carcinomas (HCCs) induced by hepatitis C virus (HCV), alcohol, obesity and/or chemicals. Stem cells may be present in cancer tissue, and a hierarchy of cells is formed, as is the case for normal tissue. Tumor formation, growth and propagation are maintained by a small proportion of cells with stem cell-like properties. TICs are present in alcohol-fed HCV transgenic mice, diethylnitrosamine/phenobarbital-treated mice (chemical carcinogenesis) and Spnb2 +/- mice (defective TGF-β signal). Alcohol/obesity-associated endotoxemia induces the stem cell marker Nanog through TLR4 signaling to generate TICs and liver tumors in several HCC models. The oncogenic pathway (such as the STAT3 and TLR4-NANOG pathway) and mechanism of generation of TICs of HCCs associated with HCV, alcohol and obesity are discussed. Understanding the molecular stemness signaling and cellular hierarchy and defining key TIC-specific genes will accelerate the development of novel biomarkers and treatment strategies. This review highlights recent advances in understanding the pathogenesis of liver TICs and discusses unanswered questions about the concept of liver TICs. (This project was supported by NIH grants 1R01AA018857 and P50AA11999).

Inhibition of Akt reverses the acquired resistance to sorafenib by switching protective autophagy to autophagic cell death in hepatocellular carcinoma

Sorafenib is the standard first-line systemic drug for advanced hepatocellular carcinoma (HCC), but the acquired resistance to sorafenib results in limited benefits. Activation of Akt is thought to be responsible for mediating the acquired resistance to sorafenib. The present study aims to examine the underlying mechanism and seek potential strategies to reverse this resistance. Two sorafenib-resistant HCC cell lines, which had been established from human HCC HepG2 and Huh7 cells, were refractory to sorafenib-induced growth inhibition and apoptosis in vitro and in vivo. Sustained exposure to sorafenib activated Akt via the feedback loop of mTOR but independent of protein phosphatase 2A in HCC cells. Autophagy participated in the resistance to sorafenib as inhibition of autophagy reduced the sensitivity of sorafenib-resistant HCC cells to sorafenib, whereas activation of autophagy by rapamycin had the opposite effect. However, rapamycin did not show a synergistic effect with sorafenib to inhibit cell proliferation, while it also activated Akt via a feedback mechanism in sorafenib-resistant HCC cells. Inhibition of Akt reversed the acquired resistance to sorafenib by switching autophagy from a cytoprotective role to a death-promoting mechanism in the sorafenib-resistant HCC cells. Akt inhibition by GDC0068 synergized with sorafenib to suppress the growth of sorafenib-resistant HCC tumors that possessed the sorafenib-resistant feature in vivo. The results have provided evidence for clinical investigation of GDC0068, a novel ATP-competitive pan-Akt inhibitor, as the second-line treatment after the failure of sorafenib-medicated molecular targeted therapy for advanced HCC.

Cabozantinib suppresses tumor growth and metastasis in hepatocellular carcinoma by a dual blockade of VEGFR2 and MET

PURPOSE

MET signaling has been suggested a potential role in hepatocellular carcinoma (HCC) and associated with prometastasis during antiangiogenesis therapy. We investigated the potential association between MET expression and therapeutic response to sorafenib in patients with HCC. Antitumor effects of cabozantinib, a dual inhibitor of MET and VEGFR2, were examined in cultured HCC cells as well as in vivo models.

EXPERIMENTAL DESIGN

Total MET and phosphorylated MET (p-MET) were measured in 29 resected HCC specimens, and correlated with response to sorafenib as postoperative adjuvant therapy. In the second set of experiments using cultured HCC cells, and mouse xenograft and metastatic models, effects of cabozantinib were examined.

RESULTS

High level of p-MET in resected HCC specimens was associated with resistance to adjuvant sorafenib therapy. In cultured HCC cells that expressed p-MET, cabozantinib inhibited the activity of MET and its downstream effectors, leading to G1-phase arrest. Cabozantinib inhibited tumor growth in p-MET-positive and p-MET-negative HCC by decreasing angiogenesis, inhibiting proliferation, and promoting apoptosis, but it exhibited more profound efficacy in p-MET-positive HCC xenografts. Cabozantinib blocked the hepatocyte growth factor (HGF)-stimulated MET pathway and inhibited the migration and invasion of the HCC cells. Notably, cabozantinib reduced the number of metastatic lesions in the lung and liver in the experimental metastatic mouse model.

CONCLUSIONS

Patients with HCC with high level of p-MET are associated with resistance to adjuvant sorafenib treatment. The dual blockade of VEGFR2 and MET by cabozantinib has significant antitumor activities in HCC, and the activation of MET in HCC may be a promising efficacy-predicting biomarker. Clin Cancer Res; 20(11); 2959-70. ©2014 AACR.

Sorafenib continuation after first disease progression could reduce disease flares and provide survival benefits in patients with hepatocellular carcinoma: a pilot retrospective study

BACKGROUND

Sorafenib is a promising drug for advanced hepatocellular carcinoma (HCC); however, treatment may be discontinued for multiple reasons, such as progressive disease, adverse events, or the cost of treatment. The consequences of sorafenib discontinuation and continuation are uncertain.

MATERIALS AND METHODS

We retrospectively analyzed 88 HCC patients treated with sorafenib from July 2007 to January 2013. Overall survival (OS), post-disease progression overall survival (pOS), and time to disease progression (TTP) were compared for survival analysis. Cox proportional hazard regression was performed to assess the effect of important factors on OS in the overall patient population and on pOS in patients who continued sorafenib treatment.

RESULTS

Sorafenib was discontinued and continued in 24 and 64 patients, respectively. The median OS (355 vs 517 days respectively; p=0.015) and median post-PD OS (260 vs 317 days, respectively; p=0.020) were statistically different between the discontinuation and continuation groups. Neither the median time to first PD nor the time to second PD were significantly different between the 2 groups. In the discontinuation group, 3 of the 24 patients (12.5%) suffered disease outbreaks. In Cox proportional hazard regression analysis after correction for confounding factors, BCLC stage (p=0.002) and PD site (p=0.024) were significantly correlated with pOS in patients who continued sorafenib treatment.

CONCLUSIONS

Sorafenib discontinuation may cause HCC flares or outbreaks. It is advisable to continue sorafenib treatment after first PD, particularly in patients with Barcelona Clinic Liver Cancer stage B disease or only intrahepatic PD.

Sorafenib induces endometrial carcinoma apoptosis by inhibiting Elk-1-dependent Mcl-1 transcription and inducing Akt/GSK3β-dependent protein degradation

Endometrial carcinoma (EC) is one of the main gynecologic malignancies affecting women, but effective treatments are currently lacking. In the present study, we investigated the effect of sorafenib, a general kinase inhibitor, on several EC cell lines (HEC1A, HEC1B, and RL95-2). Sorafenib induced cell death in EC cells with the following order of sensitivity: HEC1A > HEC1B > RL95-2. Sorafenib suppressed several anti-apoptotic proteins in HEC1A cells, including myeloid cell leukemia 1 (Mcl-1). Ectopic overexpression of Mcl-1 prevented the cell killing effect of sorafenib. Sorafenib suppressed Mcl-1 at the gene transactivation level by inactivating the ERK/Elk-1 pathway. Accordingly, the inhibitory effect of sorafenib on Mcl-1 expression decreased following knockdown of Elk-1 using short-hairpin RNA (shRNA). Elk-1 overexpression rescued both the inhibitory effect of sorafenib on Mcl-1 expression and the cell killing effect of sorafenib. Furthermore, sorafenib reduced the stability of the Mcl-1 protein by enhancing its ubiquitination and degradation by the proteasome via the AKT/GSK3β and the ERK pathways. Similar results were detected in other EC cell lines. These results indicate that sorafenib induces apoptosis in EC cells by down-regulating the anti-apoptotic protein Mcl-1 via transcriptional inhibition and protein degradation. Our results thus support the notion that sorafenib may be used in endometrial cancer therapy.

Additive effect of sirolimus and anti-death receptor 5 agonistic antibody against hepatocellular carcinoma

BACKGROUND & AIMS

Despite careful patient selection, hepatocellular carcinoma (HCC) recurs in 10-20% of cases after liver transplantation, and the use of potent adjuvant anticancer drugs would be welcome. The aim of this study was to evaluate the efficiency of a combined therapy of rapamycin (sirolimus) and anti-death receptor (DR)5 monoclonal antibody (mAb) on HCC.

METHODS

We first assessed the side effects of anti-DR5 mAb administration in vivo by giving various doses of anti-DR5 mAb. Cell proliferation assays were then performed using mouse Hepa1-6 cells or human Huh7 cells to quantify the relative cell viability under various concentrations of sirolimus, anti-DR5 mAb or a combination. Next, one million Hepa1-6 cells were transplanted into C.B17-SCID-beige mice subcutaneously, and four groups were created: (1) untreated, (2) anti-DR5 mAb alone, (3) sirolimus alone and (4) anti-DR5 mAb + sirolimus.

RESULTS

Anti-DR5 mAb (200 and 300 μg/day) induced liver dysfunction with partial necrosis of the liver, but 100 μg/day was well tolerated with transaminitis, but normal bilirubin and only minor histological liver damage. In vitro, anti-DR5 mAb lysed Hepa1-6 and Huh7 cells in a dose-dependent manner, and combinations of sirolimus and anti-DR5 mAb demonstrated an additive effect. In vivo studies demonstrated that tumour sizes were significantly smaller in the combined therapy group than in the monotherapy groups.

CONCLUSIONS

Combining sirolimus and low-dose anti-DR5 mAb has a significant effect against HCC. This strategy represents a potential novel approach for the management of HCC.

Effects of sorafenib on energy metabolism in breast cancer cells: role of AMPK-mTORC1 signaling

In this study, we investigated the effects and the underlying molecular mechanisms of the multi-kinase inhibitor sorafenib in a panel of breast cancer cell lines. Sorafenib inhibited cell proliferation and induced apoptosis through the mitochondrial pathway. These effects were neither correlated with modulation of MAPK and AKT pathways nor dependent on the ERα status. Sorafenib promoted an early perturbation of mitochondrial function, inducing a deep depolarization of mitochondrial membrane, associated with drop of intracellular ATP levels and increase of ROS generation. As a response to this stress condition, the energy sensor AMPK was rapidly activated in all the cell lines analyzed. In MCF-7 and SKBR3 cells, AMPK enhanced glucose uptake by up-regulating the expression of GLUT-1 glucose transporter, as also demonstrated by AMPKα1 RNA interference, and stimulated aerobic glycolysis thus increasing lactate production. Moreover, the GLUT-1 inhibitor fasentin blocked sorafenib-induced glucose uptake and potentiated its cytotoxic activity in SKBR3 cells. Persistent activation of AMPK by sorafenib finally led to the impairment of glucose metabolism both in MCF-7 and SKBR3 cells as well as in the highly glycolytic MDA-MB-231 cells, resulting in cell death. This previously unrecognized long-term effect of sorafenib was mediated by AMPK-dependent inhibition of the mTORC1 pathway. Suppression of mTORC1 activity was sufficient for sorafenib to hinder glucose utilization in breast cancer cells, as demonstrated by the observation that the mTORC1 inhibitor rapamycin induced a comparable down-regulation of GLUT-1 expression and glucose uptake. The key role of AMPK-dependent inhibition of mTORC1 in sorafenib mechanisms of action was confirmed by AMPKα1 silencing, which restored mTORC1 activity conferring a significant protection from cell death. This study provides insights into the molecular mechanisms driving sorafenib anti-tumoral activity in breast cancer, and supports the need for going on with clinical trials aimed at proving the efficacy of sorafenib for breast cancer treatment.

Mechanisms of resistance to sorafenib and the corresponding strategies in hepatocellular carcinoma

Sorafenib, the unique drug as first-line treatment for advanced hepatocellular carcinoma (HCC), has opened a window of hope after searching for effective agents to combat HCC for decades. However, the overall outcomes are far from satisfactory. One of the explanations is the genetic heterogeneity of HCC, which has led to identifying predictive biomarkers for primary resistance to sorafenib, and then applying the concept of personalized medicine, or seeking therapeutic strategies such as combining sorafenib with other anticancer agents. Some of the combinations have demonstrated a better effectiveness than sorafenib alone, with good tolerance. The acquired resistance to sorafenib has also drawn attention. As a multikinase inhibitor, sorafenib targets several cellular signaling pathways but simultaneously or sequentially the addiction switches and compensatory pathways are activated. Several mechanisms are involved in the acquired resistance to sorafenib, such as crosstalks involving PI3K/Akt and JAK-STAT pathways, hypoxia-inducible pathways, epithelial-mesenchymal transition, etc. Based on the investigated mechanisms, some other molecular targeted drugs have been applied as second-line treatment for treat HCC after the failure of sorafenib therapy and more are under evaluation in clinical trials. However, the exact mechanisms accounting for sorafenib resistance remains unclear. Further investigation on the crosstalk and relationship of associated pathways will better our understanding of the mechanisms and help to find effective strategies for overcoming sorafenib resistance in HCC.

Temsirolimus combined with sorafenib in hepatocellular carcinoma: a phase I dose-finding trial with pharmacokinetic and biomarker correlates

BACKGROUND

Based upon preclinical evidence for improved antitumor activity in combination, this phase I study investigated the maximum-tolerated dose (MTD), safety, activity, pharmacokinetics (PK), and biomarkers of the mammalian target of rapamycin inhibitor, temsirolimus, combined with sorafenib in hepatocellular carcinoma (HCC).

PATIENTS AND METHODS

Patients with incurable HCC and Child Pugh score ≤B7 were treated with sorafenib plus temsirolimus by 3 + 3 design. The dose-limiting toxicity (DLT) interval was 28 days. The response was assessed every two cycles. PK of temsirolimus was measured in a cohort at MTD.

RESULTS

Twenty-five patients were enrolled. The MTD was temsirolimus 10 mg weekly plus sorafenib 200 mg twice daily. Among 18 patients at MTD, DLT included grade 3 hand-foot skin reaction (HFSR) and grade 3 thrombocytopenia. Grade 3 or 4 related adverse events at MTD included hypophosphatemia (33%), infection (22%), thrombocytopenia (17%), HFSR (11%), and fatigue (11%). With sorafenib, temsirolimus clearance was more rapid (P < 0.05). Two patients (8%) had a confirmed partial response (PR); 15 (60%) had stable disease (SD). Alpha-fetoprotein (AFP) declined ≥50% in 60% assessable patients.

CONCLUSION

The MTD of sorafenib plus temsirolimus in HCC was lower than in other tumor types. HCC-specific phase I studies are necessary. The observed efficacy warrants further study.

Actionable gene expression-based patient stratification for molecular targeted therapy in hepatocellular carcinoma

Background

The effectiveness of molecular targeted agents is modest in hepatocellular carcinoma (HCC). Efficacy of molecular targeted therapies has been better in cancer patients with high expression of actionable molecules defined as cognate target molecules. However, patient stratification based on the actionable molecules dictating the effectiveness of targeted drugs has remained understudied in HCC.

Experimental Design & Results

Paired tumor and non-tumoral tissues derived from a total of 130 HCC patients were studied. Real-time RT-PCR was used to analyze the mRNA expression of actionable molecules in the tissues. mRNA levels of EGFR, VEGFR2, PDGFRβ, FGFR1, and mTOR were up-regulated in tumors compared to non-tumors in 35.4, 42.3, 61.5, 24.6, and 50.0% of patients, respectively. Up-regulation of EGFR was observed at early stage and tended to gradually decrease toward late stages (BCLC stage A: 41.9%; B: 30.8%; C: 17.6%). Frequency of VEGFR2 expression in tumors at stage C was lower than that in the other stages (BCLC stage A: 45.9%; B: 41.0%; C: 29.4%). PDGFRβ and mTOR were observed to be up-regulated in more than 50% of tumors in all the stages whereas FGFR1 was up-regulated in only about 20% of HCC irrespective of stages. A cluster analysis of actionable gene expression revealed that HCC can be categorized into different subtypes that predict the effectiveness of molecular targeted agents and combination therapies in clinical trials. Analysis of in vitro sensitivity to sorafenib demonstrated that HCC cells with up-regulation of PDGFRβ and c-Raf mRNA are more susceptible to sorafenib treatment in a dose and time-dependent manner than cells with low expression of the genes.

Conclusions

mRNA expression analysis of actionable molecules could provide the rationale for new companion diagnostics-based therapeutic strategies in the treatment of HCC.

Impact of genetic targets on cancer therapy: hepatocellular cancer

Understanding cancer at the genetic level had gained significant attention over the last decade since the human genome was first sequenced in 2001. For hepatocellular carcinoma (HCC) a number of genome-wide profiling studies have been published. These studies have provided us with gene sets, based on which we can now classify tumors and have an idea about the likely clinical outcomes. In addition to that, genomic profiling for HCC has provided us a better understanding of the carcinogenesis process and identifies key steps at multiple levels (i.e. Genetics, molecular pathways) that can be potential targets for treatment and prevention. Although still an incurable disease, unresectable HCC has one proven systemic therapy, sorafenib, and many under active investigation. With advancement in technology and understanding of hepatocarcinogenesis, scientists hope to provide true personalized treatment for this disease in the near future. In this review article we discuss advances in understanding genetics and pathogenesis of HCC and the currently available and ongoing trials for targeted therapies. These emerging therapies may guide the development of more effective treatments or possibly a cure for HCC.

The evolving landscape of therapeutic drug development for hepatocellular carcinoma

Currently, only one drug, sorafenib, is FDA approved for the treatment of advanced hepatocellular carcinoma (HCC), achieving modest objective response rates while still conferring an overall survival benefit. Unlike other solid tumors, no oncogenic addiction loops have been validated as clinically actionable targets in HCC. Outcomes of HCC could potentially be improved if critical molecular subclasses with distinct therapeutic vulnerabilities can be identified, biomarkers that predict recurrence or progression early can be determined and key epigenetic, genetic or microenvironment drivers that determine best response to a specific targeting treatment can be uncovered. Our group and others have examined the molecular heterogeneity of hepatocellular carcinoma. We have developed a panel of patient derived xenograft models to enable focused pre-clinical drug development of rationally designed therapies in specific molecular subgroups. We observed unique patterns, including synergies, of drug activity across our molecularly diverse HCC xenografts, pointing to specific therapeutic vulnerabilities for individual tumors. These efforts inform clinical trial designs and catalyze therapeutic development. It also argues for efficient strategic allocation of patients into appropriate enriched clinical trials. Here, we will discuss some of the recent important therapeutic studies in advanced HCC and also some of the potential strategies to optimize clinical therapeutic development moving forward.

Antiangiogenic therapies for advanced hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a significant cause of death worldwide. HCC is a highly vascular tumor, and proangiogenic cytokines such as vascular endothelial growth factor (VEGF), platelet-derived growth factor (PDGF), and fibroblast growth factor may play crucial roles in this disease. Sorafenib, a multikinase inhibitor that blocks VEGF and PDGF signaling, was the first systemic therapy to demonstrate improved survival in patients with advanced HCC. Several other drugs targeting VEGF are in development. Because of the anticipation of eventual resistance to anti-VEGF therapies, drugs that also target alternative proangiogenic pathways are being investigated. Recent clinical and preclinical data along with ongoing studies are reviewed.

Deregulation of signalling pathways in prognostic subtypes of hepatocellular carcinoma: novel insights from interspecies comparison

Hepatocellular carcinoma is a frequent and fatal disease. Recent researches on rodent models and human hepatocarcinogenesis contributed to unravel the molecular mechanisms of hepatocellular carcinoma dedifferentiation and progression, and allowed the discovery of several alterations underlying the deregulation of cell cycle and signalling pathways. This review provides an interpretive analysis of the results of these studies. Mounting evidence emphasises the role of up-regulation of RAS/ERK, P13K/AKT, IKK/NF-kB, WNT, TGF-ß, NOTCH, Hedgehog, and Hippo signalling pathways as well as of aberrant proteasomal activity in hepatocarcinogenesis. Signalling deregulation often occurs in preneoplastic stages of rodent and human hepatocarcinogenesis and progressively increases in carcinomas, being most pronounced in more aggressive tumours. Numerous changes in signalling cascades are involved in the deregulation of carbohydrate, lipid, and methionine metabolism, which play a role in the maintenance of the transformed phenotype. Recent studies on the role of microRNAs in signalling deregulation, and on the interplay between signalling pathways led to crucial achievements in the knowledge of the network of signalling cascades, essential for the development of adjuvant therapies of liver cancer. Furthermore, the analysis of the mechanisms involved in signalling deregulation allowed the identification of numerous putative prognostic markers and novel therapeutic targets of specific hepatocellular carcinoma subtypes associated with different biologic and clinical features. This is of prime importance for the selection of patient subgroups that are most likely to obtain clinical benefit and, hence, for successful development of targeted therapies for liver cancer.

Combination of sorafenib and everolimus impacts therapeutically on adrenocortical tumor models

Treatment options are insufficient in patients with adrenocortical carcinoma (ACC). Based on the efficacy of sorafenib, a tyrosine kinase inhibitor, and everolimus, an inhibitor of the mammalian target of rapamycin in tumors of different histotype, we aimed at testing these drugs in adrenocortical cancer models. The expression of vascular endothelial growth factor and its receptors (VEGFR1-2) was studied in 18 ACCs, 33 aldosterone-producing adenomas, 12 cortisol-producing adenomas, and six normal adrenal cortex by real-time PCR and immunohistochemistry and by immunoblotting in SW13 and H295R cancer cell lines. The effects of sorafenib and everolimus, alone or in combination, were tested on primary adrenocortical cultures and SW13 and H295R cells by evaluating cell viability and apoptosis in vitro and tumor growth inhibition of tumor cell line xenografts in immunodeficient mice in vivo. VEGF and VEGFR1-2 were detected in all samples and appeared over-expressed in two-thirds of ACC specimens. Dose-dependent inhibition of cell viability was observed particularly in SW13 cells after 24 h treatment with either drug; drug combination produced markedly synergistic growth inhibition. Increasing apoptosis was observed in tumor cells treated with the drugs, particularly with sorafenib. Finally, a significant mass reduction and increased survival were observed in SW13 xenograft model undergoing treatment with the drugs in combination. Our data suggest that an autocrine VEGF loop may exist within ACC. Furthermore, a combination of molecularly targeted agents may have both antiangiogenic and direct antitumor effects and thus could represent a new therapeutic tool for the treatment of ACC.

Detection of eukaryotic translation initiation factor 4E and its clinical significance in hepatocellular carcinoma

AIM: To study the expression of eukaryotic translation initiation factor 4E (eIF4E), which is closely correlated with malignant tumors, and its relationship to prognosis in hepatocellular carcinoma.

METHODS: Western blotting was performed to quantify the elF4E protein expression in the normal human liver cell line L02 and the hepatoma cell lines Hep3B, HepG2, and Huh7. Forty-six hepatocellular carcinoma samples with complete clinical data were obtained from Changzheng Hospital during the period of December 2008 to July 2009. The expression of eIF4E in the tumor samples and their adjacent tissues were detected by immunohistochemistry. The relationship between the test results and hepatocellular carcinoma (HCC) prognosis was statistically analysed by using a COX proportional hazard model.

RESULTS: Western blotting analysis showed that there were distinct eIF4E protein bands in all three of the hepatoma cell lines. In particular, the HepG2 cell line had the highest level of eIF4E protein expression. The L02 cell group had a low eIF4E expression. Immunohistochemical assay showed that there were 32 cases in which the tumour tissue expression was higher than their adjacent tissues, accounting for 69.57%. There were also 14 cases in which the tumour tissue expression was lower or no significant difference was found, accounting for 30.43%. COX proportional hazards model analysis showed that HCC prognosis was related to the depth of invasion, the overexpression of eIF4E and p53, possibly as independent HCC prognostic predictors.

CONCLUSION: In summary, eIF4E expression is associated with liver cancer, and patients with high eIF4E expression levels have a higher risk of recurrence.

Sorafenib for recurrence of hepatocellular carcinoma after liver transplantation

BACKGROUND

Recurrence of hepatocellular carcinoma after orthotopic liver transplantation not amenable to surgical approaches is associated with poor outcome.

AIMS

Retrospective evaluation of the safety and efficacy of sorafenib in patients with post-transplant hepatocellular carcinoma recurrence.

METHODS

Patients with post-transplant hepatocellular carcinoma recurrence were treated with sorafenib. Adverse events were assessed using National Cancer Institute Common Toxicity Criteria of AEs version 3.0, tumour response was evaluated according to Response Evaluation Criteria in Solid Tumours.

RESULTS

First-line therapy after recurrence was surgery (n=6), radiation therapy (n=1), chemotherapy (n=1), and sorafenib (n=3). Finally, 11 patients were treated with sorafenib. Nine patients (82%) received an additionally targeted therapy with sirolimus as part of their immunosuppressive regimen. Most common grade 3 adverse events included diarrhoea (46%), hand-foot skin reaction (27%), nausea, fatigue, and leucopoenia (all 18%). Sorafenib had to be discontinued in two patients due to adverse events and six additional patients required a dose adjustment. No deterioration of liver graft function occurred. Median time to progression was 4.1 months; however, patients were treated with ongoing sorafenib in case of clinical benefit (median 8.9 months). Median overall survival after initiation of sorafenib treatment was 20.1 months.

CONCLUSION

Sorafenib in combination with immunosuppression including sirolimus may be administered to patients with post-transplant hepatocellular carcinoma recurrence with acceptable toxicity and without deterioration of liver graft function.

Receptor tyrosine kinases and targeted cancer therapeutics

The majority of growth factor receptors are composed of extracellular, transmembrane, and cytoplasmic tyrosine kinase (TK) domains. Receptor tyrosine kinase (RTK) activation regulates many key processes including cell growth and survival. However, dysregulation of RTK has been found in a wide range of cancers, and it has been shown to correlate with the development and progression of numerous cancers. Therefore, RTK has become an attractive therapeutic target. One way to effectively block signaling from RTK is inhibition of its catalytic activity with small-molecule inhibitors. Low-molecular-weight TK inhibitors (TKIs), such as imatinib, targeting tumors with mutant c-Kit, and gefitinib, targeting non-small cell lung cancer with mutant epidermal growth factor receptor (EGFR), have received marketing approval in Japan. MET, fibroblast growth factor receptor (FGFR), and insulin-like growth factor-I receptor (IGF-IR) are frequently genetically altered in advanced cancers. TKIs of these receptors have not yet appeared on the market, but many anticancer drug candidates are currently undergoing clinical trials. Most of these TKIs were designed to compete with ATP at the ATP-binding site within the TK domain. This review will focus on small-molecule TKIs targeting MET, FGFR, and IGF-IR and discuss the merits and demerits of two types of agents, i.e., those with only one or a few targets and those directed at multiple targets. Targeting agents specifically inhibiting the target kinase were previously searched for based on the hypothesis that a narrow target window might reduce unexpected side effects, but agents with multiple targets have been recently developed to overcome tumors resistant against a single-targeting agent.

Activation of PI3K/AKT and MAPK pathway through a PDGFRβ-dependent feedback loop is involved in rapamycin resistance in hepatocellular carcinoma

BACKGROUND

Rapamycin is an attractive approach for the treatment and prevention of HCC recurrence after liver transplantation. However, the objective response rates of rapamycin achieved with single-agent therapy were modest, supporting that rapamycin resistance is a frequently observed characteristic of many cancers. Some studies have been devoted to understanding the mechanisms of rapamycin resistance, however, the mechanisms are cell-type-dependent and studies on rapamycin resistance in HCC are extremely limited.

METHODOLOGY/PRINCIPAL FINDINGS

The anti-tumor sensitivity of rapamycin was modest in vitro and in vivo. In both human and rat HCC cells, rapamycin up-regulated the expression and phosphorylation of PDGFRβ in a time and dose-dependent manner as assessed by RT-PCR and western blot analysis. Using siRNA mediated knockdown of PDGFRβ, we confirmed that subsequent activation of AKT and ERK was PDGFRβ-dependent and compromised the anti-tumor activity of rapamycin. Then, blockade of this PDGFRβ-dependent feedback loop by sorafenib enhanced the anti-tumor sensitivity of rapamycin in vitro and in an immunocompetent orthotopic rat model of HCC.

CONCLUSIONS

Activation of PI3K/AKT and MAPK pathway through a PDGFRβ-dependent feedback loop compromises the anti-tumor activity of rapamycin in HCC, and blockade of this feedback loop by sorafenib is an attractive approach to improve the anti-tumor effect of rapamycin, particularly in preventing or treating HCC recurrence after liver transplantation.

Sorafenib, a multikinase inhibitor, is effective in vitro against non-Hodgkin lymphoma and synergizes with the mTOR inhibitor rapamycin

Non-Hodgkin lymphoma (NHL) represents a heterogenous group of neoplasias originating from lymphoid cells. Increased angiogenesis and expression of Vascular Endothelial Growth Factor (VEGF) and its receptors (VEGFR) have been found to be associated with NHL disease progression. Increase in VEGF and other cytokines stimulate signaling cascades, including the Ras/Raf/Mek/Erk pathway, resulting in increased proliferation and decreased apoptosis. Here, we report the in vitro antilymphoma activity of sorafenib, an inhibitor of VEGFR and Raf kinase. Sorafenib induced potent cytotoxicity in NHL cell lines and patient samples. This induction of cytotoxicity was associated with a corresponding increase in apoptotic cell death. Mechanism of action of sorafenib was investigated in follicular (DoHH2) and Burkitt lymphoma (Raji) cell lines. pStat3, pAkt, Mcl1, and Xiap were downregulated in both cell lines, whereas pErk decreased in Raji but not in DoHH2 cells following sorafenib treatment. IL6 was unable to prevent sorafenib induced repression of pStat3, pAkt, Mcl1, and Bcl-Xl. Sorafenib in combination with an mTORC1 inhibitor rapamycin demonstrated synergy in inducing cytotoxicity in NHL cells. Sorafenib/rapamycin combination resulted in downregulation of pAkt, pmTOR, p-p70S6K, p4EBP1, pGSK3β, Mcl1, and Bcl-Xl. On the basis of our results, a clinical trial is underway using sorafenib with everolimus in NHL patients.

Multiplexed quantum dot labeling of activated c-Met signaling in castration-resistant human prostate cancer

The potential application of multiplexed quantum dot labeling (MQDL) for cancer detection and prognosis and monitoring therapeutic responses has attracted the interests of bioengineers, pathologists and cancer biologists. Many published studies claim that MQDL is effective for cancer biomarker detection and useful in cancer diagnosis and prognosis, these studies have not been standardized against quantitative biochemical and molecular determinations. In the present study, we used a molecularly characterized human prostate cancer cell model exhibiting activated c-Met signaling with epithelial to mesenchymal transition (EMT) and lethal metastatic progression to bone and soft tissues as the gold standard, and compared the c-Met cell signaling network in this model, in clinical human prostate cancer tissue specimens and in a castration-resistant human prostate cancer xenograft model. We observed c-Met signaling network activation, manifested by increased phosphorylated c-Met in all three. The downstream survival signaling network was mediated by NF-κB and Mcl-1 and EMT was driven by receptor activator of NF-κB ligand (RANKL), at the single cell level in clinical prostate cancer specimens and the xenograft model. Results were confirmed by real-time RT-PCR and western blots in a human prostate cancer cell model. MQDL is a powerful tool for assessing biomarker expression and it offers molecular insights into cancer progression at both the cell and tissue level with high degree of sensitivity.

PKI-587 and sorafenib targeting PI3K/AKT/mTOR and Ras/Raf/MAPK pathways synergistically inhibit HCC cell proliferation

BACKGROUND

Deregulated Ras/Raf/MAPK and PI3K/AKT/mTOR signaling pathways are found in hepatocellular carcinoma (HCC). This study aimed to test the inhibitory effects of PKI-587 and sorafenib as single agents or in combination on HCC (Huh7 cell line) proliferation.

MATERIALS AND METHODS

(3)H-thymidine incorporation and MTT assay were used to assess Huh7 cell proliferation. Phosphorylation of the key enzymes in the Ras/Raf/MAPK and PI3K/AKT/mTOR pathways was detected by Western blot.

RESULTS

We found that PKI-587 is a more potent PI3K/mTOR inhibitor than PI-103. Combination of PKI-587 and sorafenib was a more effective inhibitor of Huh7 proliferation than the combination of PI-103 and sorafenib. Combination of PKI-587 and sorafenib synergistically inhibited epidermal growth factor (EGF)-stimulated Huh7 proliferation compared with monodrug therapy. EGF increased phosphorylation of Ras/Raf downstream signaling proteins MEK and ERK; EGF-stimulated activation was inhibited by sorafenib. However, sorafenib, as a single agent, increased AKT (Ser473) phosphorylation. EGF-stimulated AKT (ser473) activation was inhibited by PKI-587. PKI-587 is a potent inhibitor of AKT (Ser473), mTOR (Ser2448), and S6K (Thr389) phosphorylation; in contrast, rapamycin stimulated mTOR complex 2 substrate AKT(Ser473) phosphorylation although it inhibited mTOR complex 1 substrate S6K phosphorylation. PKI-587, as a single agent, stimulated MEK and ERK phosphorylation. However, when PKI-587 and sorafenib were used in combination, they inhibited all the tested kinases in the Ras/Raf /MAPK and PI3K/AKT/mTOR pathways.

CONCLUSION

The combination of PKI-587 and sorafenib has the advantage over monodrug therapy on inhibition of HCC cell proliferation by blocking both PI3K/AKT/mTOR and Ras/Raf/MAPK signaling pathways.

The metabolic and toxicological considerations for mTOR inhibitors in the treatment of hepatocarcinoma

INTRODUCTION

Hepatocellular carcinoma (HCC) is a major health problem worldwide. Several molecular pathways involved in HCC growth and progression have recently been identified. Rapamycin analogs are able to inhibit one of the most active oncogenic molecular pathways in HCC cells: the mammalian target of rapamycin (mTOR) pathway.

AREAS COVERED

In this review, the authors analyze the principal molecular features of the mTOR pathway and the use of rapamycin analogs in the treatment of hepatocarcinoma. The article also looks at the reoccurrence of HCC following liver transplantation as well as after the treatment of de novo neoplasms. Finally, the authors discuss the advantage of using a combined HCC pharmacological therapy to obtain a synergistic effect on tumor mass.

EXPERT OPINION

Among the available options for the treatment of advanced-stage HCC, mTOR pathway inhibitors show great promise. Once these agents have their safety and efficacy confirmed, in the treatment of liver disease, their use should be considered in patients affected by HCC. This should especially be the case for those who have had liver transplants or suffered with de novo tumors. Moreover, the authors believe that mTOR inhibitors could be used in a combined pharmacological approach to improve HCC molecular-targeted therapy by producing a multiple-level block of tumor intracellular signaling.

Hepatocellular carcinoma: insight from animal models

Hepatocellular carcinoma (HCC) ranks as the third most common cause of death from cancer worldwide. Although major risk factors for the development of HCC have been defined, many aspects of the evolution of hepatocellular carcinogenesis and metastasis are still unknown. Suitable animal models are, therefore, essential to promote our understanding of the molecular, cellular and pathophysiological mechanisms of HCC and for the development of new therapeutic strategies. This Review provides an overview of animal models that are relevant to HCC development, metastasis and treatment. For HCC development, this Review focuses on transgenic mouse models of HBV and HCV infection, which provide experimental evidence that viral genes could initiate or promote liver carcinogenesis. Animal models of HCC metastasis provide platforms to elucidate the mechanisms of HCC metastasis, to study the interaction between the microenvironment and HCC invasion and to conduct intervention studies. In addition, animal models have been developed to investigate the effects of new treatment modalities. The criteria for establishing ideal HCC animal models are also discussed.

Hepatocellular carcinoma and liver transplantation: clinical perspective on molecular targeted strategies

Hepatocellular carcinoma (HCC) has an aggressive clinical course with frequent recurrence and metastasis. Orthotopic liver transplantation has been the only curative tool for unresectable HCC; therefore, recent advances in molecular targeted therapy may improve the prognosis of HCC. The multiple kinase inhibitor sorafenib and the macrolide antibiotic rapamycin are currently the most promising agents for treating unresectable HCC. A large population-based clinical trial revealed that sorafenib significantly prolonged the overall survival of HCC patients. However, subsequent clinical studies showed that sorafenib rarely reduced tumor volume and inadequately prolonged survival of patients with severe liver damage. To improve its therapeutic effect, the development of a predictive biomarker and a sorafenib-based combination is awaited. Another molecular targeting agent, rapamycin, has now been considered as a putative agent for preventing tumor recurrence in post-liver transplantation HCC patients, because it not only has immunosuppressive activity but also exerts an anti-tumor effect. In the near future, a combination of molecular targeting agents, such as sorafenib and rapamycin, may become a standard protocol for treating unresectable HCC. For specifying cases with more effective and less harmful modalities, further investigation in clinical and basic research to identify unexpected effects are needed.

Baicalein inhibits the migration and invasive properties of human hepatoma cells

Flavonoids have been demonstrated to exert health benefits in humans. We investigated whether the flavonoid baicalein would inhibit the adhesion, migration, invasion, and growth of human hepatoma cell lines, and we also investigated its mechanism of action. The separate effects of baicalein and baicalin on the viability of HA22T/VGH and SK-Hep1 cells were investigated for 24h. To evaluate their invasive properties, cells were incubated on matrigel-coated transwell membranes in the presence or absence of baicalein. We examined the effect of baicalein on the adhesion of cells, on the activation of matrix metalloproteinases (MMPs), protein kinase C (PKC), and p38 mitogen-activated protein kinase (MAPK), and on tumor growth in vivo. We observed that baicalein suppresses hepatoma cell growth by 55%, baicalein-treated cells showed lower levels of migration than untreated cells, and cell invasion was significantly reduced to 28%. Incubation of hepatoma cells with baicalein also significantly inhibited cell adhesion to matrigel, collagen I, and gelatin-coated substrate. Baicalein also decreased the gelatinolytic activities of the matrix metalloproteinases MMP-2, MMP-9, and uPA, decreased p50 and p65 nuclear translocation, and decreased phosphorylated I-kappa-B (IKB)-β. In addition, baicalein reduced the phosphorylation levels of PKCα and p38 proteins, which regulate invasion in poorly differentiated hepatoma cells. Finally, when SK-Hep1 cells were grown as xenografts in nude mice, intraperitoneal (i.p.) injection of baicalein induced a significant dose-dependent decrease in tumor growth. These results demonstrate the anticancer properties of baicalein, which include the inhibition of adhesion, invasion, migration, and proliferation of human hepatoma cells in vivo.

Targeted therapy in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the commonest cancers worldwide, as well as a common cause of cancer-related death. HCC frequently occurs in the setting of a diseased cirrhotic liver and many patients present at an advanced stage of disease. Together with a poor functional status, this often precludes the use of systemic therapy, especially conventional cytotoxic drugs. Moreover, HCC is known to be a relatively chemo-refractory tumor. There have been many targeted drugs that have shown potential in the treatment of HCC. Many clinical trials have been carried out with many more in progress. They include trials evaluating a single targeted therapy alone, two or more targeted therapy in tandem or a combination of targeted therapy and conventional chemotherapy. In this article, we seek to review some of the more important trials examining the use of targeted therapy in HCC and to look into what the future holds in terms of targeted treatment of HCC.

The tyrosine kinase inhibitor sorafenib sensitizes hepatocellular carcinoma cells to taxol by suppressing the HURP protein

The hepatoma upregulated protein (HURP) represents a putative oncogene that is overexpressed in many human cancers, especially hepatocellular carcinoma (HCC). HURP plays an important role during mitotic spindle formation, a process that is targeted by various anti-cancer drugs like taxol. However, the role of HURP during the establishment of taxol chemoresistance in HCC remains unclear. In this study, we observed that high HURP protein level correlates with taxol resistance in HCC cells. Following HURP knockdown, HCC cells show a more sensitive response to taxol treatment. Notably, sorafenib, a tyrosine kinase inhibitor approved for the treatment of HCC, inhibits HURP expression primarily at the transcriptional level and sensitizes HCC cells to sub-lethal doses of taxol. By using real-time PCR and chromatin immunoprecipitation assays, we observed that the NF-κB family member c-Rel represents a putative transcription factor that activates HURP gene expression. In addition, the inhibitory effect of sorafenib on HURP expression was attributed to a reduced translation and nuclear translocation of c-Rel. Accordingly, downregulation of c-Rel using short-hairpin RNA was shown to reduce HURP protein level and enhance taxol-induced cell death. Taken together, our results indicate that HURP acts as a novel survival protein that protects HCC cells against taxol-induced cell death. In addition, the regulation of HURP gene expression by NF-κB signaling appears to be critical for the response of HCC cells to taxol.

Everolimus augments the effects of sorafenib in a syngeneic orthotopic model of hepatocellular carcinoma

Sorafenib targets the Raf/mitogen-activated protein kinase, VEGF, and platelet-derived growth factor pathways and prolongs survival patients in advanced hepatocellular carcinoma (HCC). Everolimus inhibits the mammalian target of rapamycin, a kinase overactive in HCC. To investigate whether the antitumor effects of these agents are additive, we compared a combined and sequential treatment regimen of everolimus and sorafenib with monotherapy. After hepatic implantation of Morris Hepatoma (MH) cells, rats were randomly allocated to everolimus (5 mg/kg, 2×/week), sorafenib (7.5 mg/kg/d), combined everolimus and sorafenib, sequential sorafenib (2 weeks) then everolimus (3 weeks), or control groups. MRI quantified tumor volumes. Erk1/2, 4E-BP1, and their phosphorylated forms were quantified by immunoblotting. Angiogenesis was assessed in vitro by aortic ring and tube formation assays, and in vivo with Vegf-a mRNA and vascular casts. After 35 days, tumor volumes were reduced by 60%, 85%, and 55%, relative to controls, in everolimus, the combination, and sequential groups, respectively (P < 0.01). Survival was longest in the combination group (P < 0.001). Phosphorylation of 4E-BP1 and Erk1/2 decreased after everolimus and sorafenib, respectively. Angiogenesis decreased after all treatments (P < 0.05), although sorafenib increased Vegf-a mRNA in liver tumors. Vessel sprouting was abundant in control tumors, lower after sorafenib, and absent after the combination. Intussusceptive angiogenic transluminal pillars failed to coalesce after the combination. Combined treatment with everolimus and sorafenib exerts a stronger antitumoral effect on MH tumors than monotherapy. Everolimus retains antitumoral properties when administered sequentially after sorafenib. This supports the clinical use of everolimus in HCC, both in combination with sorafenib or after sorafenib.

Mechanisms of mTOR inhibitor resistance in cancer therapy

Mammalian target of rapamycin (mTOR) is a conserved serine/threonine kinase that regulates cell cycle progression, protein translation, metabolism, and cellular proliferation. The mTOR pathway promotes cell proliferation under energy or nutrient-rich conditions by increasing ribosomal biogenesis and protein synthesis. Since enhanced activity of the mTOR pathway is frequently observed in malignant cells, inhibition of this kinase has become an attractive strategy to treat cancer. Rapamycin and its analogs temsirolimus, everolimus, and ridaforolimus referred to as "rapalogs" have demonstrated promising efficacy against renal cell carcinoma and are under investigation for the treatment of other malignancies. However, the emergence of drug resistance may ultimately limit the utility of rapalog therapy. Here we summarize the known mechanisms of resistance to mTOR-inhibitor therapy and describe potential strategies to overcome these for the current agents that target this pathway.

Liver cancer: Targeted future options

Hepatocellular carcinoma (HCC) has a poor prognosis and systemic chemotherapies have disappointing results. The increasing knowledge of the molecular biology of HCC has resulted in novel targets, with the vascular endothelial growth factor and epidermal growth factor receptor (EGFR)-related pathways being of special interest. New blood vessel formation (angiogenesis) is essential for the growth of solid tumors. Anti-angiogenic strategies have become an important therapeutic modality for solid tumors. Several agents targeting angiogenesis-related pathways have entered clinical trials or have been already approved for the treatment of solid tumors. These include monoclonal antibodies, receptor tyrosine kinase inhibitors and immunomodulatory drugs. HCC is a highly vascular tumor, and angiogenesis is believed to play an important role in its development and progression. This review summarizes recent advances in the basic understanding of the role of angiogenesis in HCC as well as clinical trials with novel therapeutic approaches targeting angiogenesis and EGFR-related pathways.

Angiogenesis in chronic liver disease and its complications

Nowadays, liver cancer, cirrhosis and other liver-related diseases are the fifth most common cause of mortality in the UK. Furthermore, chronic liver diseases (CLDs) are one of the major causes of death, which are still increasing year-on-year. Therefore, knowledge about the pathophysiology of CLDs and its complications is of uttermost importance. The goal of this review is to clarify the role of angiogenesis in the disease progression of various liver diseases. Looking closer at the pathophysiology of portal hypertension (PH), fibrosis, cirrhosis, non-alcoholic steatohepatitis (NASH) and hepatocellular carcinoma (HCC), we find that angiogenesis is a recurring factor in the disease progression. In PH, several factors involved in its pathogenesis, such as hypoxia, oxidative stress, inflammation and shear stress are potential mediators for the angiogenic response. The progression from fibrosis to cirrhosis, the end-point of CLDs, is distinguished by a prolonged inflammatory and fibrogenic process that leads to an abnormal angioarchitecture distinctive for cirrhosis. In several stages of NASH, a link might be made between the disease progression and hepatic microvasculature changes. HCC is one of the most vascular solid tumours in which angiogenesis plays an important role in its development, progression and metastasis. The close relationship between the progression of CLDs and angiogenesis emphasises the need for anti-angiogenic therapy as a tool for blocking or slowing down the disease progression. The fact that angiogenesis plays a pivotal role in CLDs gives rise to new opportunities for treating CLDs and its complications.

Novel molecular therapies in hepatocellular carcinoma

The approval of sorafenib as the standard of care (SOC) for advanced hepatocellular carcinoma (HCC) fostered interest to further evaluate several other targeted therapies and extend the positioning of sorafenib alone and in combination with other drugs and local therapies at earlier stages and in an adjuvant setting. This review highlights current research using targeted therapies in HCC. Information for this review was compiled by searching PubMed and MEDLINE databases for articles published until September 2010. Several small molecules and humanized antibodies with anti-angiogenic and antiproliferative properties are currently being investigated in preclinical and/or clinical trials. Results are awaited from these clinical trials and offer promise for extending the current treatment options in HCC. Currently published data suggest that substantial progress may be achieved in the treatment of patients with HCC in the next 10 years.

PI-103 and sorafenib inhibit hepatocellular carcinoma cell proliferation by blocking Ras/Raf/MAPK and PI3K/AKT/mTOR pathways

BACKGROUND

Aberrant Ras/Raf/MAPK and PI3K/AKT/mTOR signaling pathways are found in hepatocellular carcinoma (HCC). This study reports how sorafenib (a multi-kinase inhibitor) and PI-103 (a dual PI3K/mTOR inhibitor) alone and in combination inhibit the proliferation of the HCC cell line, Huh7.

MATERIALS AND METHODS

Huh7 proliferation was assayed by 3H-thymidine incorporation and by MTT assay. Western blot was used to detect phosphorylation of the key enzymes in the Ras/Raf and PI3K pathways.

RESULTS

Sorafenib and PI-103, as single agents inhibited Huh7 proliferation and epidermal growth factor (EGF)-stimulated Huh7 proliferation in a dose-dependent fashion; the combination of sorafenib and PI-103 produced synergistic effects. EGF increased phosphorylation of MEK and ERK, key Ras/Raf downstream signaling proteins; this activation was inhibited by sorafenib. However, sorafenib as a single agent increased AKT(Ser473) and mTOR phosphorylation. EGF-stimulated activation of PI3K/AKT/mTOR pathway components was inhibited by PI-103. PI-103 is a potent inhibitor of AKT(Ser473) phosphorylation; in contrast, rapamycin stimulated AKT(Ser473) phosphorylation. It was found that PI-103, as a single agent, stimulated MEK and ERK phosphorylation. However, the combination of sorafenib and PI-103 caused inhibition of all the tested kinases in the Ras/Raf and PI3K pathways.

CONCLUSION

The combination of sorafenib and PI-103 can significantly inhibit EGF-stimulated Huh7 proliferation by blocking both Ras/Raf/MAPK and PI3K/AKT/mTOR pathways.

Sorafenib: rays of hope in thyroid cancer

BACKGROUND

Sorafenib (BAY 43-9006) is an inhibitor of multiple-receptor tyrosine kinases involved in tumor growth and angiogenesis, which can be advantageously administered orally. Initially used as monotherapy in advanced renal cell carcinoma, sorafenib was proven to increase progression-free survival while enhancing disease control. Clinical trials on sorafenib are at present ongoing for the treatment of various malignancies, including thyroid cancer (TC).

SUMMARY

Specifically, in two phase II studies recently conducted on papillary TC, although the respective results were not entirely compatible as regard partial response rate and progression-free survival, sorafenib demonstrated a relatively favorable benefit/risk profile. In another more recent phase II study, whose primary endpoint was the reinduction of radioactive iodine uptake at 26 weeks, although no reinduction of radioactive iodine uptake was observed, 59% had a beneficial response and 34% had stable disease. Sorafenib hence appears to be a valid alternative to conventional treatment of metastatic papillary TC refractory to radioiodine therapy.

CONCLUSIONS

Further prospective investigations are required to define the characteristics of tumor response to the drug and the factors inducing resistance to treatment. A major issue demanding immediate attention involves optimization of sorafenib treatment: this concerns multidrug combination with different tyrosine kinase inhibitors or immunomodulating agents with the aim of reducing doses and thereby improving drug tolerability and antineoplastic capability.

Sirolimus plus sorafenib in treating HCC recurrence after liver transplantation: A case report

A case of hepatocellular carcinoma (HCC) with pulmonary recurrence after liver transplantation for HCC is presented in this report. The patient showed disease progression on sorafenib therapy demonstrated by computed tomography scans as well as serial serum α-fetoprotein (AFP) elevation. After his immunosuppression therapy was successfully transitioned to sirolimus and a continuation of sorafenib, he achieved partial remission based on RECIST criteria and normalization of AFP. Mammalian target of rapamycin inhibitors including sirolimus alone or in conjunction with sorafenib may be useful in the treatment of post transplant HCC.

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.

New insights into the antifibrotic effects of sorafenib on hepatic stellate cells and liver fibrosis

BACKGROUND & AIMS

During the process of liver fibrosis, hepatic stellate cells (HSCs) play a critical role in the excessive production of extracellular matrix (ECM). We evaluated the therapeutic effects of sorafenib, a multiple receptor tyrosine kinase inhibitor, targeting platelet-derived growth factor (PDGF) receptor and the Raf/extracellular-signal-regulated kinase (ERK) signaling pathway, on liver fibrosis and HSC proliferation.

METHODS

The in vivo effects of sorafenib were monitored in the livers of rats with liver fibrosis, and simultaneously proliferation assays, apoptosis induction studies, and collagen synthesis measurement were conducted in vitro in rat and human HSCs and primary HSCs.

RESULTS

Sorafenib treatment attenuated liver fibrosis and was associated with a significant decrease in intrahepatic fibrogenesis, hydroxyproline accumulation and collagen deposition. Sorafenib reduced HSC proliferation and resulted in significantly higher levels of apoptosis. Moreover, sorafenib downregulated Cyclin D1 and Cyclin-dependent kinase 4 (Cdk-4), simultaneously increased expression of Fas, Fas-L, and Caspase-3, and decreased the ratio of Bcl-2 to Bax. Sorafenib treatment increased the ratio of matrix metalloproteinases (MMPs) to tissue inhibitor of matrix metalloproteinases (TIMPs) and reduced collagen synthesis in HSCs. Sorafenib inhibited the phosphorylation of ERK, Akt and 70-kDa ribosomal S6 kinase (p70S6K), both in vitro and in vivo.

CONCLUSIONS

Sorafenib induces the suppression of collagen accumulation and HSC growth warranting the use of sorafenib as a potential therapeutic agent in the treatment of liver fibrosis.

Sorafenib: where do we go from here?

The approval of sorafenib as the first effective drug for the treatment of hepatocellular carcinoma (HCC) represents a milestone in the treatment of this disease. A better understanding of HCC pathogenesis has led to the development of several novel targeted treatments. HCC is treated in a uniquely multidisciplinary way requiring surgeons, hepatologists, interventional radiologists, and oncologists. This review describes the molecular pathogenesis of HCC, explores current and future treatments based on these pathways, and describes how these new therapies may augment existing approaches to HCC treatment.

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.

Synergistic activity of letrozole and sorafenib on breast cancer cells

Estrogens induce breast tumor cell proliferation by directly regulating gene expression via the estrogen receptor (ER) transcriptional activity and by affecting growth factor signaling pathways such as mitogen-activated protein kinase (MAPK) and AKT/mammalian target of rapamycin Complex1 (mTORC1) cascades. In this study we demonstrated the preclinical therapeutic efficacy of combining the aromatase inhibitor letrozole with the multi-kinase inhibitor sorafenib in aromatase-expressing breast cancer cell lines. Treatment with letrozole reduced testosterone-driven cell proliferation, by inhibiting the synthesis of estrogens. Sorafenib inhibited cell proliferation in a concentration-dependent manner; this effect was not dependent on sorafenib-mediated inhibition of Raf1, but involved the down-regulation of mTORC1 and its targets p70S6K and 4E-binding protein 1 (4E-BP1). At concentrations of 5-10 μM the growth-inhibitory effect of sorafenib was associated with the induction of apoptosis, as indicated by release of cytochrome c and Apoptosis-Inducing Factor into the cytosol, activation of caspase-9 and caspase-7, and PARP-1 cleavage. Combination of letrozole and sorafenib produced a synergistic inhibition of cell proliferation associated with an enhanced accumulation of cells in the G(0)/G(1) phase of the cell cycle and with a down-regulation of the cell cycle regulatory proteins c-myc, cyclin D1, and phospho-Rb. In addition, longer experiments (12 weeks) demonstrated that sorafenib may be effective in preventing the acquisition of resistance towards letrozole. Together, these results indicate that combination of letrozole and sorafenib might constitute a promising approach to the treatment of hormone-dependent breast cancer.