mTOR inhibitors for hepatocellular cancer: a forward-moving target

Potential Molecular Targeted Therapy for Unresectable Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is one of the most prevalent and lethal cancers, representing a serious worldwide health concern. The recurrence incidence of hepatocellular carcinoma (HCC) following surgery or ablation is as high as 70%. Thus, the clinical applicability of standard surgery and other locoregional therapy to improve the outcomes of advanced HCC is restricted and far from ideal. The registered trials did not identify a treatment that prolonged recurrence-free survival, the primary outcome of the majority of research. Several investigator-initiated trials have demonstrated that various treatments extend patients' recurrence-free or overall survival after curative therapies. In the past decade, targeted therapy has made significant strides in the treatment of advanced HCC. These targeted medicines produce antitumour effects via specific signals, such as anti-angiogenesis or advancement of the cell cycle. As a typical systemic treatment option, it significantly improves the prognosis of this fatal disease. In addition, the combination of targeted therapy with an immune checkpoint inhibitor is redefining the paradigm of advanced HCC treatment. In this review, we focused on the role of approved targeted medicines and potential therapeutic targets in unresectable HCC.

Immunosuppressive Drugs in Liver Transplant: An Insight

Liver transplantation (LT) is the standard of care for end-stage liver failure and hepatocellular carcinoma. Over the years, immunosuppression regimens have improved, resulting in enhanced graft and patient survival. At present, the side effects of immunosuppressive agents are a significant threat to post-LT quality of life and long-term outcome. The role of personalized immunosuppression is to reach a delicate balance between optimal immunosuppression and minimal side effects. Today, immunosuppression in LT is more of an art than a science. There are no validated markers for overimmunosuppression and underimmunosuppression, only a few drugs have therapeutic drug monitoring and immunosuppression regimens vary from center to center. The immunosuppressive agents are broadly classified into biological agents and pharmacological agents. Most regimens use multiple agents with different modes of action to reduce the dosage and minimize the toxicities. The calcineurin inhibitor (CNI)-related toxicities are reduced by antibody induction or using mTOR inhibitor/antimetabolites as CNI sparing or CNI minimization strategies. Post-liver transplant immunosuppression has an intensive phase in the first three months when alloreactivity is high, followed by a maintenance phase when immunosuppression minimization protocols are implemented. Over time some patients achieve "tolerance," defined as the successful stopping of immunosuppression with good graft function and no indication of rejection. Cell-based therapy using immune cells with tolerogenic potential is the future and may permit complete withdrawal of immunosuppressive agents.

Foremost Concepts in Mechanisms of De Novo Post-Liver Transplantation Malignancy

In liver transplant patients, solid tumors and post-transplant lymphoproliferative disorders (PTLD) have emerged as significant long-term mortality causes. Additionally, it is assumed that de novo malignancy (DNM) after liver transplantation (LT) is the second-leading cause of death after cardiovascular complications. Well-established risk factors for PTLD and solid tumors are calcineurin inhibitors (CNIs), tacrolimus (TAC), and cyclosporine, the cornerstones of all immunosuppressive (IS) therapies used after LT. The loss of immunocompetence facilitated by the host immune system due to prolonged IS therapy leads to cancer development, including in LT patients. Hindering DNA repair mechanisms, promoting tumor cell invasiveness, and hampering apoptosis are critical events in tumorigenesis and tumor growth in LT patients resulting from IS administration. This paper aims to overview the refined mechanisms of IS-induced tumorigenesis after LT and the loss of immunocompetence facilitated by the host immune system due to prolonged IS therapy. In addition, we also discuss in detail the mechanisms of action in different types of IS regimen used after LT, and their putative effect on DNM.

Immunosuppressive regimens for adult liver transplant recipients in real-life practice: consensus recommendations from an Italian Working Group

It is a well-recognized fact that implementing new guidelines in clinical practice may be difficult; therefore the Italian Society for Organ and Tissue Transplantation (SITO) set out to define practical immunosuppression tools for the management of liver transplantation patients. In 2017, an Italian Working Group of liver transplant experts and hepatologists issued a set of consensus statements along with evidence-based recommendations on the use of everolimus after liver transplantation. This article presents the evidence- and consensus-based algorithms developed within the Italian Working Group, which are aimed towards guiding clinicians in the selection of immunosuppressive regimens for the management of adult liver transplant recipients in real-life practice. The liver transplant recipient population, typically managed in clinical practice, was divided into the following categories: (1) standard patients; (2) critically ill patients; (3) patients with a specific etiology; (4) patients with hepatocellular carcinoma; (5) and patients with de novo malignancies. The algorithms are divided into two parts, according to the time from transplantation (0-3 months and > 3 months) and are discussed here along with relevant supporting literature, when available. Ultimately, it is hoped that the evidence- and consensus-based algorithms developed within the Italian Working Group, and presented here, contribute to simplify, personalize, and optimize immunosuppression of liver transplantation recipients in clinical practice.

4-Acetylantrocamol LT3, a New Ubiquinone from Antrodia cinnamomea, Inhibits Hepatocellular Carcinoma HepG2 Cell Growth by Targeting YAP/TAZ, mTOR, and WNT/β-Catenin Signaling

4-acetylantrocamol LT3 (4AALT3), a new ubiquinone from the mycelium of Antrodia cinnamomea (Polyporaceae), has been recently shown to possess anticancer activity. However, the detailed mechanisms of such action remain unclear. In this study, the molecular mechanisms of 4AALT3 on hepatocellular carcinoma cells (HCC) were investigated. Human hepatocellular carcinoma cell line HepG2 cells were treated with concentrations of 4AALT3. Cell viability, colony formation, and the underlying mechanisms were then analyzed by CCK-8, colony formation, qPCR, and Western blotting assays. We found that 4AALT3 significantly decreased cell viability and colony formation in a dose-dependent manner. Accordingly, 4AALT3 significantly decreased protein levels of cyclin B, E1, D1, and D3, thereby facilitating cell cycle arrest. In addition, 4AALT3 significantly suppressed the nuclear localization of Yes-associated protein (YAP)/transcriptional co-activator with PDZ-binding motif (TAZ), mammalian target of rapamycin (mTOR), and WNT/[Formula: see text]-catenin signaling pathways, all of which are well-known signaling pathways that contribute to the malignant properties of HCC. These effects are associated with activation of 5' AMP-activated protein kinase (AMPK) and autophagy. Our findings indicate that 4AALT3 exerts inhibitory effects on HepG2 cell growth via multiple signaling pathways and may be a potential agent for HCC therapy.

Resveratrol potentiates the anti-tumor effects of rapamycin in papillary thyroid cancer: PI3K/AKT/mTOR pathway involved

The phosphatidylinositol 3-kinase (PI3K)/protein kinase B (AKT)/mammalian target of rapamycin (mTOR) signaling pathway plays an important role in the development of papillary thyroid cancer. While rapamycin has been shown to exhibit anti-tumor effects, it may also activate AKT, resulting in increased cell survival and drug resistance, thereby limiting its anti-tumor effects. Resveratrol can also inhibit tumor growth by regulating the PI3K/AKT/mTOR signaling pathway. The present study investigated the anti-tumor effects of the combined use of rapamycin and resveratrol in papillary thyroid cancer. We first treated two human papillary thyroid cancer cell lines (KTC-1 and TPC-1) with single or combined administration, and examined the effects on proliferation, the cell cycle, apoptosis, and invasion/migration of papillary thyroid cancer cells. A mouse xenograft model was induced with KTC-1 and TPC-1 cells followed by treatment with single or combined administration. Body weight and tumor size were monitored to assess the toxicity of each compound. The phosphorylation of AKT and the mTORC1 target p70S6 kinase (p70S6K) in tumors was also examined. Both rapamycin and resveratrol inhibited proliferation, altered the cell cycle, and induced apoptosis of papillary thyroid cancer cells. Invasion and migration were also reduced, as was the tumor growth rate in the xenograft model. Co-administration significantly enhanced the anti-tumor effects than use of any one drug, and significantly reduced the phosphorylation of AKT and p70S6K compared to treatment with rapamycin alone. Overall, compared to single use of rapamycin or resveratrol, co-administration had a synergistic effect in inhibiting proliferation and invasion/migration of papillary thyroid cancer cells and inducing apoptosis. Resveratrol is sensitizing the anti-tumor effects of rapamycin and the PI3K/AKT/mTOR signaling is involved. Although further animal and clinical studies are needed to clarify the mechanism and assess drug safety, the present study suggests that the combination of rapamycin and resveratrol may be a promising strategy for the treatment of papillary thyroid cancer.

Evolving Systemic Therapy in Hepatocellular Carcinoma: Current Management and Opportunities for Integration With Radiotherapy

The majority of patients with hepatocellular carcinoma (HCC) present with advanced disease. While first-line therapy with sorafenib is considered standard of care for patients with advancedHCC, outcomes remain poor. Despite early evidence of antitumor activity from Phase II trials of multiple other tyrosine kinase inhibitors, Phase III trials have largely failed to show an improvement insurvival outcomes over sorafenib. Given the encouraging early results with liver-directed radiotherapy for patients with advanced HCC, there is an increased interest in combination of these therapies tooptimize patient outcomes and improve survival by maximizing both local and distant disease control. Phase II trials of checkpoint inhibitors in HCC have also reported encouraging results, and Phase IIItrials are ongoing. Trials of combining radiotherapy with immunotherapy in solid tumors have shown intriguing results, potentially reflecting the opportunity for synergistic effects with the use of both modalities.

Optimal therapy for patients with hepatocellular carcinoma and resistance or intolerance to sorafenib: challenges and solutions

The only US Food and Drug Administration (FDA)-approved first-line systemic therapy for hepatocellular carcinoma (HCC) is sorafenib; however, resistance or intolerance to sorafenib is unfortunately common. In this review, we briefly describe systemic therapies that can be considered for patients with HCC who show resistance or intolerance to sorafenib. For all patients with HCC who need systemic therapy, we strongly advocate for participation in clinical trials. Cytotoxic chemotherapy plays a minor role in the treatment of advanced HCC, with some data supporting the use of FOLFOX (infusional fluorouracil, leucovorin, and oxaliplatin) and GEMOX (gemcitabine-oxaliplatin). Multi-target kinase inhibitors such as lenvantinib and regorafenib have recently met their primary endpoints as first- and second-line therapy, respectively, with regorafenib now representing the only FDA-approved drug for second-line treatment of HCC. Other targeted therapies remain under investigation, but results so far have not significantly changed clinical practice. Immunotherapy is an interesting area of research in the treatment of HCC with preclinical and early clinical data demonstrating exciting results; thus numerous investigational studies are currently focusing on immunotherapy in the treatment of HCC. While systemic treatment options in HCC remain a challenge for providers, in this review, we summarize the current literature and highlight areas of progress with respect to the treatment of patients with HCC and resistance or intolerance to sorafenib.

Precision medicine for hepatocellular carcinoma: driver mutations and targeted therapy

Hepatocellular carcinoma (HCC) is the third most frequent cause of tumor-related mortality and there are an estimated approximately 850,000 new cases annually. Most HCC patients are diagnosed at middle or advanced stage, losing the opportunity of surgery. The development of HCC is promoted by accumulated diverse genetic mutations, which confer selective growth advantages to tumor cells and are called "driver mutations". The discovery of driver mutations provides a novel precision medicine strategy for late stage HCC, called targeted therapy. In this review, we summarized currently discovered driver mutations and corresponding signaling pathways, made an overview of identification methods of driver mutations and genes, and classified targeted drugs for HCC. The knowledge of mutational landscape deepen our understanding of carcinogenesis and promise future precision medicine for HCC patients.

Use of Everolimus in Liver Transplantation: Recommendations From a Working Group

Immunosuppression after liver transplantation (LT) is presently based on use of calcineurin inhibitors (CNI), although they are associated with an increased incidence of renal dysfunction, cardiovascular complications, and de novo and recurrent malignancies. Over the past decade, mammalian target of rapamycin inhibitors have received considerable attention as immunosuppressants because they are associated with a more favorable renal profile versus CNI, as well as antiproliferative activity in clinical studies. Comprehensive guidelines on use of everolimus (EVR) in LT are still lacking. In Italy, a project, named Everolimus: the road to long-term functioning, was initiated to collect the experience on EVR after LT with the aim of providing guidance for transplant clinicians. Herein, recommendations by this national consensus group, based on Delphi methodology, are presented. Consensus was reached on 20 of the 23 statements proposed, and their level of evidence, grade of recommendation, and percent of agreement are reported. Statements are grouped into 4 areas: (A) renal function; (B) time of EVR introduction, CNI reduction and elimination, and risk for graft rejection; (C) antiproliferative effects of EVR; and (D) management of EVR-related adverse events. The high level of consensus shows that there is good agreement on the routine use of EVR in predefined clinical scenarios, especially in light of posttransplant nephrotoxicity and other adverse events associated with long-term administration of CNIs.

The authors summarize the recommendations reached by an Italian National Consensus group using the Delphi methodology on the use of everolimus in liver transplantation, particularly its role in renal function, antiproliferative effects, adverse events, timing of introduction, and rejection risk.

Mammalian Target of Rapamycin (mTOR) Regulates Transforming Growth Factor-β1 (TGF-β1)-Induced Epithelial-Mesenchymal Transition via Decreased Pyruvate Kinase M2 (PKM2) Expression in Cervical Cancer Cells

BACKGROUND Epithelial-mesenchymal transition (EMT) plays an important role in cancer tumorigenesis. Transforming growth factor β1 (TGF-β1) can induced EMT, which could increase tumor migration and invasion. Moreover, recent studies have been proven that mammalian target of rapamycin (mTOR) is a critical regulator of EMT. We investigated the mechanisms of mTOR in transforming growth factor β1 (TGF-β1)-induced EMT in cervical cancer cells. MATERIAL AND METHODS HeLa and SiHa cells were treated with 10 ng/ml TGF-β1 to induce EMT. Then, they were treated with or without rapamycin. CCK8 assay was performed to determine cell proliferation. Cell migration was detected by wound-healing assay; apoptosis was analyzed by flow cytometry; mTOR inhibitors inhibited mTOR pathway to assess the expression of E-cadherin, Vimentin STAT3, Snail2, p-p70s6k, and PKM2 expression. RESULTS TGF-β1 promoted proliferation and migration, and attenuated apoptosis in cervical carcinoma cells. Rapamycin abolished TGF-β1-induced EMT cell proliferation and migration and reversed TGF-β1-induced EMT. E-cadherin were suppressed, whereas Vimentin and PKM2 were increased in HeLa and SiHa cells after stimulation with TGF-β1. Moreover, mTOR was activated in the process of TGF-β1-induced EMT. Rapamycin inhibited the phosphorylation of p70s6k. Furthermore, inhibition of the mTOR pathway decreased PKM2 expression. CONCLUSIONS Inhibition of the mTOR pathway abolished TGF-β1-induced EMT and reduced mTOR/p70s6k signaling, which downregulated PKM2 expression. Our results provide novel mechanistic insight into the anti-tumor effects of inhibition of mTOR.

Pre-S2 Mutant-Induced Mammalian Target of Rapamycin Signal Pathways as Potential Therapeutic Targets for Hepatitis B Virus-Associated Hepatocellular Carcinoma

Chronic hepatitis B virus (HBV) infection is a major risk factor for hepatocellular carcinoma (HCC). Pre-S2 mutant represents an HBV oncoprotein that is accumulated in the endoplasmic reticulum (ER) and manifests as type II ground glass hepatocytes (GGHs). Pre-S2 mutant can induce ER stress and initiate multiple ER stress-dependent or -independent cellular signal pathways, leading to growth advantage of type II GGH. Importantly, the mammalian target of rapamycin (mTOR) signal pathways are consistently activated throughout the liver tumorigenesis in pre-S2 mutant transgenic mice and in human HCC tissues, leading to hepatocyte proliferation, metabolic disorders, and HCC tumorigenesis. In this review, we summarize the pre-S2 mutant-induced mTOR signal pathways and its implications in HBV-related HCC tumorigenesis. Clinically, the presence of pre-S2 mutant exhibits a high resistance to antiviral treatment and carries a high risk of HCC development in patients with chronic HBV infection. Targeting at pre-S2 mutant-induced mTOR signal pathways may thus provide potential strategies for the prevention or therapy of HBV-associated HCC.

Hepatocellular carcinoma: Will novel targeted drugs really impact the next future?

Cancer treatment has been revolutionized by the advent of new molecular targeted and immunotherapeutic agents. Identification of the role of tumor angiogenesis changed the understanding of many tumors. After the unsuccessful results with chemotherapy, sorafenib, by interfering with angiogenic pathways, has become pivotal in the treatment of hepatocellular carcinoma. Sorafenib is the only systemic treatment to show a modest but statistically significant survival benefit. All novel drugs and strategies for treatment of advanced hepatocellular carcinoma must be compared with the results obtained with sorafenib, but no new drug or drug combination has yet achieved better results. In our opinion, the efforts to impact the natural history of the disease will be directed not only to drug development but also to understanding the underlying liver disease (usually hepatitis B virus- or hepatitis C virus-related) and to interrupting the progression of cirrhosis. It will be important to define the role and amount of mutations in the complex pathogenesis of hepatocellular carcinoma and to better integrate locoregional and systemic therapies. It will be important also to optimize the therapeutic strategies with existing chemotherapeutic drugs and new targeted agents.

MicroRNA-100 promotes the autophagy of hepatocellular carcinoma cells by inhibiting the expression of mTOR and IGF-1R

We found that restoration of miR-100 expression resulted in accumulation of LC3B-II and decrease of p62 in hepatocellular carcinoma (HCC) cells, whereas antagonism of miR-100 reduced the level of LC3B-II. Moreover, a significant correlation between miR-100 downregulation and p62 upregulation was observed in human HCC tissues, suggesting an autophagy-promoting effect of miR-100. Subsequent investigations disclosed that knockdown of Atg7 but not Beclin-1 attenuated the miR-100-induced LC3B-II elevation. Furthermore, miR-100 overexpression caused massive cell death, which was abrogated by both the Atg7 silencing and chloroquine treatment. Simultaneously, miR-100 expression led to increased fraction of cells with Annexin V-staining and loss of mitochondrial potential, implying that miR-100 may promote the Atg7-dependent autophagy and subsequent apoptotic cell death. Consistently, mouse xenograft models revealed that miR-100 inhibited the in vivo growth of HCC cells. We further showed that miR-100 suppressed the expression of mTOR and IGF-1R by binding to their 3′ untranslated region, and knockdown of mTOR or IGF-1R phenocopied the pro-autophagy effect of miR-100, indicating that miR-100 may promote autophagy by reducing mTOR and IGF-1R level. Collectively, our data uncover a new regulatory mechanism of autophagy and a novel function of miR-100, and provide a potential therapeutic target for HCC.

Everolimus in de novo liver transplant recipients: a systematic review

BACKGROUND

Everolimus has no nephrotoxicity and is used to treat patients with post-liver transplant chronic renal insufficiency. The present systematic review was to evaluate the efficacy and safety of everolimus in de novo liver transplant patients.

DATA SOURCES

Randomized controlled trials comparing everolimus for de novo liver transplant in PubMed, the Cochrane Library, and ScienceDirect published up to March 31, 2014 were searched by two independent reviewers. Mean differences and 95% confidence interval (95% CI) for renal function, relative risk (RR) and 95% CI for treated biopsy-proven acute rejection (tBPAR), graft loss, death, neoplasms/tumor recurrence, and adverse events were collected. Meta-analyses were performed with RevMan version 5.10.

RESULTS

A total of four randomized controlled trials covering 1119 cases were included. The meta-analyses revealed that compared with standard exposure of calcineurin inhibitors (CNIs), everolimus combined with reduced CNIs improved creatinine clearance (calculated with the Cockcroft-Gault formula) by 5.13 mL/min at one year (95% CI: 0.42-9.84; P=0.03), and decreased tBPAR (RR: 0.56; 95% CI: 0.35-0.90; P=0.02). Everolimus initiation with CNIs elimination improved glomerular filtration rate (GFR, measured with the modification of diet in renal disease formula) of 10.42 mL/min/1.73 m2 (95% CI: 3.44-17.41; P<0.01) one year after treatment, but increased tBPAR (RR: 1.71; 95% CI: 1.15-2.53; P<0.01). Everolimus decreased the risk of neoplasms/tumor recurrence after liver transplant (RR: 0.60; 95% CI: 0.34-1.03; P=0.06), but was associated with greater risk of adverse events which resulted in drug discontinuation (RR: 1.98; 95% CI: 1.49-2.64; P<0.01).

CONCLUSIONS

Early introduction of everolimus combined with low-dose or no CNI in de novo liver transplant significantly improves renal function one year post treatment. Everolimus combined with low-dose CNI decreases the risk of tBPAR one year after liver transplant, but everolimus administered without CNIs increases tBPAR.

mTORC1 Up-Regulates GP73 to Promote Proliferation and Migration of Hepatocellular Carcinoma Cells and Growth of Xenograft Tumors in Mice

BACKGROUND & AIMS

Levels of the Golgi protein 73 (GP73) increase during development of hepatocellular carcinoma (HCC); GP73 is a serum marker for HCC. However, little is known about the mechanisms or effects of GP73 during hepatic carcinogenesis.

METHODS

GP73 was overexpressed from a retroviral vector in HepG2 cells, which were analyzed in proliferation and migration assays. Xenograft tumors were grown from these cells in nude mice. The effects of monoclonal antibodies against GP73 were studied in mice and cell lines. GP73(-/-), GP73(+/-), and GP73(+/+) mice were given injections of diethylnitrosamine to induce liver injury. Levels of GP73 were reduced in MHCC97H, HCCLM3, and HepG2.215 cell lines using small hairpin RNAs; xenograft tumors were grown in mice from MHCC97H-small hairpin GP73 or MHCC97H-vector cells. We used microarray analysis to compare expression patterns between GP73-knockdown and control MHCC97H cells. We studied the effects of the mechanistic target of rapamycin (mTOR) inhibitor rapamycin on GP73 expression in different cancer cell lines and on growth of tumors in mice. Levels of GP73 and activated mTOR were quantified in human HCC tissues.

RESULTS

Xenograft tumors grown from HepG2 cells that expressed GP73 formed more rapidly and more metastases than control HepG2 cells in mice. A monoclonal antibody against GP73 reduced proliferation of HepG2 cells and growth of xenograft tumors in mice. GP73(-/-) mice had less liver damage after administration of diethylnitrosamine than GP73(+/-) or GP73(+/+) mice. In phosphatase and tensin homolog-null mouse embryonic fibroblasts with constitutively activated mTOR, GP73 was up-regulated compared with control mouse embryonic fibroblasts; this increase was reversed after incubation with rapamycin. Expression of GP73 also was reduced in HCC and other cancer cell lines incubated with rapamycin. mTORC1 appeared to regulate expression of GP73 in cell lines. Activated mTOR correlated with the level of GP73 in human HCC tissues. Injection of rapamycin slowed the growth of xenograft tumors from MHCC97H-vector cells, compared with MHCC97H-short hairpin GP73 cells.

CONCLUSIONS

Increased expression of GP73 promotes proliferation and migration of HCC cell lines and growth of xenograft tumors in mice. mTORC1 regulates the expression of GP73, so GP73 up-regulation can be blocked with rapamycin. mTOR inhibitors or other reagents that reduce the level or activity of GP73 might be developed for the treatment of HCC.

Dissecting signaling pathways in hepatocellular carcinoma: new perspectives in medical therapy

Prognosis of patients with advanced hepatocellular carcinoma (HCC) is poor and is largely influenced by associated liver comorbidities. Moreover, effective treatment alternatives are limited; with the exception of the multitargeted inhibitor sorafenib, established options in the treatment of advanced HCC no longer amenable with ablative or locoregional procedures are lacking. In light of the limited efficacy of chemotherapy in this setting, great efforts have been made in the definition of targetable molecular pathways with a central role in the progression of HCC. Targeting angiogenesis, growth factor receptors, intracellular transduction pathways, or mechanisms of gene-expression regulation represents the main way to improve patient outcome. At the same time, identifying clinical and biological factors, which may help selecting patients with higher chances of benefit, is essential in order to hasten drug development and maximize treatment efficacy.

Role of AMP-activated protein kinase in cancer therapy

Recent advances in AMP-activated protein kinase (AMPK) as a target in cancer waxed and waned over the past decade of cancer research. AMPK is a cellular energy sensor, present in almost all eukaryotic cells. An elevated AMP/ATP ratio activates the AMPK, which in turn inhibits energy-consuming processes and induces catabolic events that generate ATP to restore the energy homeostasis inside the cell. Several reports have indicated that AMPK regulates several metabolic pathways and may be a potential therapeutic target for the treatment of cancer. Cancer cells have specific metabolic changes that differ from normal cells, and AMPK prevents the deregulated processes in cancer. AMPK may also act to inhibit tumor formation through modulation of cell growth, cell proliferation, autophagy, stress responses, and cell polarity. AMPK has been shown to inhibit mammalian target of rapamycin (mTOR) through tuberous sclerosis complex 2 (TSC2) phosphorylation and phosphatase and tensin homolog (PTEN), considered as central cell growth controller signals in diseases. In response to glucose deprivation, AMPK phosphorylates and activates p53, which induces cell cycle arrest in the G1/S phase of the cell cycle. AMPK has also been reported to block cyclin-dependent kinases through phosphorylation of p27(kip1) , promoting its stabilization and allowing cells to survive metabolic stress via induction of autophagy. Additionally, AMPK induces autophagy by phosphorylation and activation of eEF-2 kinase, and prevents the formation of new proteins. AMPK activators are also used for the treatment of type II diabetes and cancer. This review focuses on AMPK activation and its possible therapeutic role in the treatment of cancer.

[Current status of molecular targeted therapies in hepatocellular carcinoma]

Hepatocellular carcinoma (HCC) is one of the leading causes of cancer death in Korea. Curative treatment is only possible when the disease is diagnosed at the early stage. The prognosis of patients with HCC is even dismal in advanced stages. No systemic cytotoxic chemotherapy has proven to be beneficial in overall survival. Recently, the understanding of the molecular pathogenesis led to the development of new therapies. With the evidence of dysregulation of critical genes associated with cellular proliferation, growth factor signaling, cell cycling, apoptosis, and angiogenesis in HCC, a number of molecular target agents are under clinical trials. Sorafenib is the first systemic anticancer drug which has proven to gain survival benefit in the global as well as Asia-Pacific trials. However, the survival gain is still modest, and further efforts to improve outcomes in patients with HCC are necessary by developing novel drugs or combining other forms of therapies. This article will review signaling pathways in HCC and introduce molecular target agents under investigation currently.

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.

Therapeutic potential of the translation inhibitor silvestrol in hepatocellular cancer

BACKGROUND & AIMS

Although hepatocellular cancers (HCC) frequently arise in the setting of fibrosis and a hepatic regenerative response requiring new cell growth, therapeutic strategies for these cancers have not targeted protein synthesis. Silvestrol, a rocaglate isolated from Aglaiafoveolata, can inhibit protein synthesis by modulating the initiation of translation through the eukaryotic initiation factor 4A. In this study, we evaluated the therapeutic efficacy of silvestrol for HCC.

METHODS

The efficacy of silvestrol was examined using human HCC cells in vitro using an orthotopic tumor cell xenograft model in a fibrotic liver. The impact of silvestrol on the liver was assessed in vivo in wild-type mice.

RESULTS

Silvestrol inhibited cell growth with an IC50 of 12.5-86 nM in four different HCC cell lines. In vitro, silvestrol increased apoptosis and caspase 3/7 activity accompanied by loss of mitochondrial membrane potential and decreased expression of Mcl-1 and Bcl-xL. A synergistic effect was observed when silvestrol was combined with other therapeutic agents, with a dose-reduction index of 3.42-fold with sorafenib and 1.75-fold with rapamycin at a fractional effect of 0.5. In vivo, an antitumor effect was observed with 0.4 mg/kg silvestrol compared to controls after one week, and survival of tumor-bearing mice was improved with a median survival time of 42 and 28 days in the silvestrol and control groups, respectively. The effect on survival was not observed in orthotopic xenografts in non-fibrotic livers. Silvestrol treatment in vivo did not alter liver structure.

CONCLUSIONS

These data identify silvestrol as a novel, structurally unique drug with potent anticancer activity for HCC and support the potential value of targeting initiation of translation in the treatment of HCC.

Role of PI3K, mTOR and Akt2 signalling in hepatic tumorigenesis via the control of PKM2 expression

To sustain increased growth, rapidly proliferating cells, such as tumour cells, undergo metabolic adaptations. In recent years, the mechanisms of glycolysis activation as a key metabolic adaptation in proliferating cells became the topic of intense research. Although this phenomenon was described more than 50 years ago by Otto Warburg, the molecular mechanisms remained elusive. Only recently, it was demonstrated that the expression of specific glycolytic enzymes, namely PKM2 (pyruvate kinase M2) and HK2 (hexokinase 2), occurs simultaneously with the glycolytic addiction of cancer cells. The PI3K (phosphoinositide 3-kinase)/mTOR [mammalian (or mechanistic) target of rapamycin] signalling pathway is a central signalling hub co-ordinating the growth in response to growth factor signalling and nutrient availability. Not surprisingly, it is found to be activated in the majority of the tumour cells. In the present article, we discuss the requirement of different PI3K/mTOR downstream effectors for the metabolic adaptation in liver cancer cells driven by this signalling pathway. We provide evidence for a selective involvement of the mTOR target Akt2 in tumoral growth. In addition, PTEN (phosphatase and tensin homologue deleted on chromosome 10)-negative human hepatocellular carcinoma cell lines display an up-regulation of PKM2 expression in an Akt2-dependent manner, providing an advantage for cell proliferation and anchorage-independent growth. Our data have implications on the link between the metabolic action of insulin signal transduction and tumorigenesis, identifying Akt2 as a potential therapeutical target in liver malignancies depending on cancer genotype.

Functional crosstalk between AKT/mTOR and Ras/MAPK pathways in hepatocarcinogenesis: implications for the treatment of human liver cancer

Hepatocellular carcinoma (HCC) is one of the leading causes of cancer-related death worldwide, with limited treatment options. AKT/mTOR and Ras/MAPK pathways are frequently deregulated in human hepatocarcinogenesis. Recently, we generated an animal model characterized by the co-expression of activated forms of AKT and Ras in the mouse liver. We found that concomitant activation of AKT/mTOR and Ras/MAPK cascades leads to rapid liver tumor development in AKT/Ras mice, mainly through mTORC1 induction. To further define the role of mTORC1 cascade in AKT/Ras induced HCC development, the mTORC1 inhibitor Rapamycin was administered to AKT/Ras mice at the time when small tumors started to emerge in the liver. Of note, Rapamycin treatment significantly delayed hepatocarcinogenesis in AKT/Ras mice. However, some microscopic lesions persisted in the livers of AKT/Ras mice despite the treatment and rapidly gave rise to HCC following Rapamycin withdrawal. Mechanistically, Rapamycin inhibited mTORC1 and mTORC2 pathways, lipogenesis and glycolysis, resulting in inhibition of proliferation in the treated livers. However, activated ERK and its downstream effectors, Mnk1 and eIF4E, were strongly upregulated in the residual lesions. Concomitant suppression of AKT/mTOR and Ras/MAPK pathways was highly detrimental for the growth of AKT/Ras cells in vitro. The study indicates the existence of a complex interplay between AKT/mTOR and Ras/MAPK pathways during hepatocarcinogenesis, with important implications for the understanding of HCC pathogenesis as well as for its prevention and treatment.

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.

Reprogramming of the microRNA transcriptome mediates resistance to rapamycin

The mammalian target of rapamycin (mTOR) is a central regulator of cell proliferation that is often deregulated in cancer. Inhibitors of mTOR, including rapamycin and its analogues, are being evaluated as antitumor agents. For their promise to be fulfilled, it is of paramount importance to identify the mechanisms of resistance and develop novel therapies to overcome it. Given the emerging role of microRNAs (miRNAs) in tumorigenesis, we hypothesized that miRNAs could play important roles in the response of tumors to mTOR inhibitors. Long-term rapamycin treatment showed extensive reprogramming of miRNA expression, characterized by up-regulation of miR-17-92 and related clusters and down-regulation of tumor suppressor miRNAs. Inhibition of members of the miR-17-92 clusters or delivery of tumor suppressor miRNAs restored sensitivity to rapamycin. This study identifies miRNAs as new downstream components of the mTOR-signaling pathway, which may determine the response of tumors to mTOR inhibitors. It also identifies potential markers to assess the efficacy of treatment and provides novel therapeutic targets to treat rapamycin-resistant tumors.

Hepatocellular carcinoma biology

Hepatocellular carcinoma (HCC) is the most common primary hepatic malignancy. Its incidence and prevalence is globally heterogeneous with the highest rates in Southeast Asia and Sub-Saharan Africa. In Western Industry nations, its incidence has significantly increased throughout the previous three decades. Its global heterogeneity is in part a reflection of the global distribution of its risk factors. Its prognosis is dismal with a 5-year survival of 11 %. The only potentially curative treatment is surgical with either resection or orthotopic liver transplantation. However, the majority of HCC patients are diagnosed at an advanced stage at which surgical therapies are not feasible. HCC is considered chemotherapy-resistant-a characteristic thought to be mediated in part through stem-like tumor initiating cells (STICs). Recent studies have provided significant insights in the hepatocarcinogenesis and the molecular signaling pathways of this malignancy resulting in the development of novel, molecular targeted therapies with modest therapeutic benefit. Our growing understanding of the biology of this malignancy will help in the development of novel, molecular-targeted therapies.

Targeted agents and systemic therapy in hepatocellular carcinoma

Cytotoxic chemotherapy, hormonal agents, and immunotherapy have been tested in hepatocellular cancer (HCC) with marginal efficacy to date. Recent insights into the molecular pathogenesis of HCC have identified several aberrant signaling pathways that have served as targets for novel therapeutic agents. These discoveries have been translated into the clinical realm with the use of the antiangiogenic and the Raf kinase inhibitor, sorafenib, and have revealed the potential of targeted agents to produce clinically meaningful survival benefits in patients with advanced HCC. Efforts continue in the quest to improve the outcome of HCC patients through the development and evaluation of other targeted agents, and to better understand the interactions between the underlying disease biology and response to therapy. Several pathways are now implicated in hepatocarcinogenesis and agents that target these pathways continue to be developed.

Signaling pathway/molecular targets and new targeted agents under development in hepatocellular carcinoma

Advances in molecular cell biology over the last decade have clarified the mechanisms involved in cancer growth, invasion, and metastasis, and enabled the development of molecular-targeted agents. To date, sorafenib is the only molecular-targeted agent whose survival benefit has been demonstrated in two global phase III randomized controlled trials, and has been approved worldwide. Phase III clinical trials of other molecular targeted agents comparing them with sorafenib as first-line treatment agents are ongoing. Those agents target the vascular endothelial growth factor, platelet-derived growth factor receptors, as well as target the epidermal growth factor receptor, insulin-like growth factor receptor and mammalian target of rapamycin, in addition to other molecules targeting other components of the signal transduction pathways. In addition, the combination of sorafenib with standard treatment, such as resection, ablation, transarterial embolization, and hepatic arterial infusion chemotherapy are ongoing. This review outlines the main pathways involved in the development and progression of hepatocellular carcinoma and the new agents that target these pathways. Finally, the current statuses of clinical trials of new agents or combination therapy with sorafenib and standard treatment will also be discussed.

Antineoplastic effects of mammalian target of rapamycine inhibitors

Cancer after transplantation is the third cause of death and one of the more relevant comorbidities. Aim of this review is to verify the role of different pathogenetic mechanisms in cancer development in transplant patients and in general population as well. In particular has been outlined the different role exerted by two different families of drug as calcineurin inhibitor and mammalian target of rapamycin (mTOR) inhibitor. The role of mTOR pathways in cell homeostasis is complex but enough clear. As a consequence the mTOR pathway deregulation is involved in the genesis of several cancers. Hence the relevant role of mTOR inhibitors. The authors review the complex mechanism of action of mTOR inhibitors, not only for what concerns the immune system but also other cells as endothelial, smooth muscle and epithelial cells. The mechanism of action is still now not completely defined and understood. It implies the inhibition of mTOR pathway at different levels, but mainly at level of the phosphorylation of several intracellular kinases that contribute to activate mTOR complex. Many prospective and retrospective studies in transplant patients document the antineoplastic role of mTOR inhibition. More recently mTOR inhibitors proven to be effective in the treatment of some cancers also in general population. Kidney cancers, neuroendocrine tumors and liver cancers seem to be the most sensitive to these drugs. Best results are obtained with a combination treatment, targeting the mTOR pathway at different levels.

Chronic activation of mTOR complex 1 is sufficient to cause hepatocellular carcinoma in mice

The mammalian target of rapamycin (mTOR) complex 1 (mTORC1) is a nutrient-sensitive protein kinase that is aberrantly activated in many human cancers. Whether dysregulation of mTORC1 signaling in normal tissues increases the risk for cancer, however, is unknown. We focused on hepatocellular carcinoma, which has been linked to environmental factors that affect mTORC1 activity, including diet. Ablation of the gene encoding TSC1 (tuberous sclerosis complex 1), which as part of the TSC1-TSC2 complex is an upstream inhibitor of mTORC1, results in constitutively increased mTORC1 signaling, an effect on this pathway similar to that of obesity. We found that mice with liver-specific knockout of Tsc1 developed sporadic hepatocellular carcinoma with heterogeneous histological and biochemical features. The spontaneous development of hepatocellular carcinoma in this mouse model was preceded by a series of pathological changes that accompany the primary etiologies of this cancer in humans, including liver damage, inflammation, necrosis, and regeneration. Chronic mTORC1 signaling led to unresolved endoplasmic reticulum stress and defects in autophagy, factors that contributed to hepatocyte damage and hepatocellular carcinoma development. Therefore, we conclude that increased activation of mTORC1 can promote carcinogenesis and may thus represent a key molecular link between cancer risk and environmental factors, such as diet.

Obesity, inflammation, and liver cancer

Obesity has become a universal and major public health problem with increasing prevalence in both adults and children in the 21st century, even in developing countries. Extensive epidemiological studies reveal a strong link between obesity and development and progression of various types of cancers. The connection between obesity and liver cancer is particularly strong and obesity often results in liver diseases such as non-alcoholic fatty liver disease (NAFLD) and the more severe non-alcoholic steatohepatitis (NASH). NASH is characterized by fatty liver inflammation and is believed to cause fibrosis and cirrhosis. The latter is a known liver cancer risk factor. In fact due to its much higher prevalence obesity may be a more substantial contributor to overall hepatocellular carcinoma burden than infection with hepatitis viruses. Here we review and discuss recent advances in elucidation of cellular and molecular alterations and signaling pathways associated with obesity and liver inflammation and their contribution to hepatocarcinogenesis.

Effects of STAT3 gene silencing and rapamycin on apoptosis in hepatocarcinoma cells

The PI3K/Akt/mTOR and JAK/STAT3 signaling pathways are important for regulating apoptosis, and are frequently activated in cancers. In this study, we targeted STAT3 and mTOR in human hepatocellular carcinoma Bel-7402 cells and examined the subsequent alterations in cellular apoptosis. The expression of STAT3 was silenced with small interfering RNA (siRNA)-expressing plasmid. The activity of mTOR was inhibited using rapamycin. Following treatment, Annexin V/propidium iodide staining followed by flow cytometry and Hoechst33258 immunofluorescence staining was used to examine cellular apoptosis. JC-1 staining was used to monitor depolarization of mitochondrial membrane (ΔΨm). Furthermore, the expression of activated caspase 3 protein was analyzed by Western blotting. Compared to non-treated or control siRNA-transfected cells, significantly higher levels of apoptosis were detected in siSTAT3-transfected or rapamycin-treated cells (P < 0.05), which was further enhanced in cells targeted for both molecules (P < 0.05). The pro-apoptotic effects were accompanied with concomitant depolarization of mitochondrial membrane and up-regulation of activated caspase 3. Combined treatments using rapamycin and STAT3 gene silencing significantly increases apoptosis in Bel-7402 cells, displaying more dramatic effect than any single treatment. This study provides evidence for targeting multiple molecules in cancer therapy.

Resveratrol inhibits protein translation in hepatic cells

Resveratrol is a plant-derived polyphenol that extends lifespan and healthspan in model organism. Despite extensive investigation, the biological processes mediating resveratrol's effects have yet to be elucidated. Because repression of translation shares many of resveratrol's beneficial effects, we hypothesized that resveratrol was a modulator of protein synthesis. We studied the effect of the drug on the H4-II-E rat hepatoma cell line. Initial studies showed that resveratrol inhibited global protein synthesis. Given the role of the mammalian Target of Rapamycin (mTOR) in regulating protein synthesis, we examined the effect of resveratrol on mTOR signaling. Resveratrol inhibited mTOR self-phosphorylation and the phosphorylation of mTOR targets S6K1 and eIF4E-BP1. It attenuated the formation of the translation initiation complex eIF4F and increased the phosphorylation of eIF2α. The latter event, also a mechanism for translation inhibition, was not recapitulated by mTOR inhibitors. The effects on mTOR signaling were independent of effects on AMP-activated kinase or AKT. We conclude that resveratrol is an inhibitor of global protein synthesis, and that this effect is mediated through modulation of mTOR-dependent and independent signaling.

Sorafenib: complexities of Raf-dependent and Raf-independent signaling are now unveiled

Hepatocellular carcinoma (HCC) is the most common primary cancer worldwide. The only current drug available for clinical treatment of HCC is sorafenib, which inhibits multiple signaling kinases including Raf family members, platelet-derived growth factor receptor, vascular endothelial growth factor receptors 1 and 2, c-Kit, and Fms-like tyrosine kinase 3. Many studies have revealed that the mechanism underlying the antitumor effect of sorafenib is complex. Because sorafenib inhibits C-Raf more potently than B-Raf, the therapeutic efficacy of sorafenib is strongly influenced by the relative expression and activity of B-Raf and C-Raf and the complex interactions between these factors. Moreover, Rafindependent signaling mechanisms have recently emerged as important pathways of sorafenib-induced cell death. Basic research studies have suggested that using sorafenib as part of a combination therapy may improve its effect, although this has yet to be confirmed by clinical evidence. Further studies of the functional mechanism of sorafenib are required to advance the development of targeted therapy for HCC. To aid future work on sorafenib, we here review the current literature pertaining to sorafenib signaling and its clinical efficacy in both monotherapy and combination therapy.

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.

Novel feedback inhibition of surface antigen synthesis by mammalian target of rapamycin (mTOR) signal and its implication for hepatitis B virus tumorigenesis and therapy

Ground glass hepatocytes (GGHs) harboring hepatitis B virus (HBV) pre-S mutants have been recognized as precursor lesions of hepatocellular carcinoma (HCC). Previously, we observed the activation of mammalian target of rapamycin (mTOR) in GGHs and HCCs, together with a decreased expression of HBV surface antigen (HBsAg) in HCC tissues. It is, therefore, hypothesized that the activation of mTOR during HBV tumorigenesis may potentially down-regulate HBsAg expression. In this study, we verified an inverse relationship between the expression of HBsAg and phosphorylated mTOR (p-mTOR) in 13 of 20 paired nontumorous liver and HCC tissues. In vitro, wild-type or mutant pre-S proteins could activate mTOR in the HuH-7 cell line. Interestingly, the up-regulated mTOR, in turn, suppressed HBsAg synthesis at the transcriptional level via the transcription factor, Yin Yang 1 (YY1), which bound to nucleotide 2812-2816 of the pre-S1 promoter. This inhibitory effect by the mTOR signal could be abolished by the knockdown of histone deacetylase 1 (HDAC1). Furthermore, YY1 was physically associated with HDAC1 in a manner dependent on mTOR activation. Collectively, pre-S protein-induced mTOR activation may recruit the YY1-HDAC1 complex to feedback suppress transcription from the pre-S1 promoter.

CONCLUSION

The activation of mTOR signal in GGHs may feedback suppress HBsAg synthesis during HBV tumorigenesis and explain the observed decrease or absence of HBsAg in HCC tissues. Therapy using mTOR inhibitors for HCCs may potentially activate HBV replication in patients with chronic HBV infection.

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.

Hepatocellular carcinoma: locoregional and targeted therapies

HCC is a leading cause of morbidity and mortality worldwide. Advances in cancer screening and surveillance have allowed for earlier detection of tumors, affording greater treatment potential. The advent of locoregional therapies has generated greater treatment options for patients with HCC. Either alone or in combination as an adjuvant or neoadjuvant therapy, these novel approaches continue to hold promise for improving morbidity and/or mortality of patients with HCC. The emergence of systemic molecular targeted therapies increases the role of translational science. Whereas surgical resection and transplantation conventionally form the cornerstone of curative approaches, the advancement of locoregional therapies holds great promise in adding to the curative armamentarium.

Signaling pathway and molecular-targeted therapy for hepatocellular carcinoma

In recent years, molecular-targeted agents have been used clinically to treat various malignant tumors. In May 2009, sorafenib (Nexavar®) was approved in Japan for 'unresectable hepatocellular carcinoma (HCC)', and was the first molecular-targeted agent for use in HCC. To date, sorafenib is the only molecular-targeted agent whose survival benefit has been demonstrated in two global phase III randomized controlled trials, and has now been approved worldwide. Phase III clinical trials of other molecular-targeted agents comparing them with sorafenib as first-line treatment agents are now ongoing. Those agents target the vascular endothelial growth factor, platelet-derived growth factor receptors, as well as target the epidermal growth factor receptor, insulin-like growth factor receptor and mammalian target of rapamycin, in addition to other molecules targeting other components of the signal transduction pathways. This review outlines the main pathways involved in the development and progression of HCC and the agents that target these pathways. Finally, current status and future perspective will also be discussed.

Conversion to everolimus in maintenance liver transplant patients: a multicenter, retrospective analysis

Data on the conversion of patients to everolimus after liver transplantation are sparse. A multicenter, retrospective study followed 240 maintenance liver transplant patients to analyze the current indications for everolimus conversion, the employed regimens and exposure levels, and the impact on efficacy and safety. The mean time from transplantation to the introduction of everolimus was 4.9 ± 5.2 years. The mean everolimus trough level was 7.3 ± 4.1 ng/mL at month 1 and 8.1 ± 4.7 ng/mL at month 12. At 12 months, 61.6% of the patients were no longer receiving calcineurin inhibitor (CNI) therapy. The mean estimated glomerular filtration rate (eGFR) according to the Cockcroft-Gault formula was 64.2 ± 30.0 mL/minute on day 0 and 68.4 ± 32.5 mL/minute at month 12 (P = 0.007). Among patients with baseline serum creatinine levels ≥ 130 μmol/L, the eGFR values were 44.3 ± 15.7 mL/minute on day 0 and 53.7 ± 26.0 mL/minute at month 12 (P = 0.003). Four patients (1.6%) developed mild or moderate biopsy-proven acute rejection. Adverse events led to everolimus discontinuation in 12.9% of the patients. After the initiation of everolimus, the mean white blood cell count decreased significantly, and the total cholesterol and triglyceride levels increased significantly. In this retrospective analysis of the largest cohort of maintenance liver transplant patients analyzed after their conversion to everolimus, more than 60% of the patients were kept free of CNIs with a very low risk of acute rejection and with an acceptable safety profile. Randomized trials in which maintenance liver transplant patients are switched to everolimus in response to clinical indications or preemptively are warranted.

Phase 1/2 study of everolimus in advanced hepatocellular carcinoma

BACKGROUND

The phosphoinositide 3-kinase/Akt/mammalian target of rapamycin pathway plays a critical role in the pathogenesis of hepatocellular carcinoma (HCC). We performed a single-arm, phase 1/2 study of everolimus in patients with advanced HCC.

METHODS

Patients with histologically confirmed measurable advanced HCC, 0-2 prior regimens, and adequate hematologic, hepatic, and renal functions received everolimus at 5 mg/day or 10 mg/day orally (6 weeks/cycle). The primary end points were determination of a safe dosage of everolimus (phase 1) and progression-free survival (PFS) at 24 weeks (phase 2).

RESULTS

Twenty-eight patients were enrolled and evaluable for efficacy and toxicity. No dose-limiting toxicities were observed at the 5 mg/day (n = 3) or 10 mg/day (n = 6) dosage level in phase 1. Twenty-five patients received everolimus at 10 mg/day. Grade 3-4 adverse events included lymphopenia (n = 3), aspartate transaminase (n = 3), hyponatremia (n = 2), and 1 patient each with anemia, alanine transaminase, hyperglycemia, proteinuria, rash, and hypoxia. One patient (4%) had partial response (95% confidence interval [CI], 0.9%-19.6%). The median PFS and overall survival were 3.8 months (95% CI, 2.1-4.6) and 8.4 months (95% CI, 3.9-21.1), respectively. The estimated PFS rate at 24 weeks was 28.6% (95% CI, 7.9%-49.3%).

CONCLUSION

Everolimus was well tolerated in patients with advanced HCC, and 10 mg/day was defined as the phase 2 dosage. Although the study did not proceed to the second stage of phase 2, preliminary antitumor activity was observed with everolimus in patients with advanced HCC, most of whom had prior systemic treatment.

Phase 1/2 study of everolimus in advanced hepatocellular carcinoma

BACKGROUND

The phosphoinositide 3-kinase/Akt/mammalian target of rapamycin pathway plays a critical role in the pathogenesis of hepatocellular carcinoma (HCC). We performed a single-arm, phase 1/2 study of everolimus in patients with advanced HCC.

METHODS

Patients with histologically confirmed measurable advanced HCC, 0-2 prior regimens, and adequate hematologic, hepatic, and renal functions received everolimus at 5 mg/day or 10 mg/day orally (6 weeks/cycle). The primary end points were determination of a safe dosage of everolimus (phase 1) and progression-free survival (PFS) at 24 weeks (phase 2).

RESULTS

Twenty-eight patients were enrolled and evaluable for efficacy and toxicity. No dose-limiting toxicities were observed at the 5 mg/day (n = 3) or 10 mg/day (n = 6) dosage level in phase 1. Twenty-five patients received everolimus at 10 mg/day. Grade 3-4 adverse events included lymphopenia (n = 3), aspartate transaminase (n = 3), hyponatremia (n = 2), and 1 patient each with anemia, alanine transaminase, hyperglycemia, proteinuria, rash, and hypoxia. One patient (4%) had partial response (95% confidence interval [CI], 0.9%-19.6%). The median PFS and overall survival were 3.8 months (95% CI, 2.1-4.6) and 8.4 months (95% CI, 3.9-21.1), respectively. The estimated PFS rate at 24 weeks was 28.6% (95% CI, 7.9%-49.3%).

CONCLUSION

Everolimus was well tolerated in patients with advanced HCC, and 10 mg/day was defined as the phase 2 dosage. Although the study did not proceed to the second stage of phase 2, preliminary antitumor activity was observed with everolimus in patients with advanced HCC, most of whom had prior systemic treatment.

Latest developments in targeted therapy for hepatocellular carcinoma

The advent of sorafenib can be considered as a turning point in the history of advanced hepatocellular carcinoma. After unfortunate attempts at using chemotherapy, drugs targeting key pathways have generated new perspectives in this field. This means not only killing both tumor cells and cirrhotic fragile tissue, but killing them selectively; more than was previously possible. This seems like the Copernican Revolution. However, hepatocellular carcinoma is pathogenetically complicated, resulting from the number of mutations. Until now, there has not been a single drug able to block and reverse abnormally activated signaling in hepatocellular carcinoma cells. In this article, we describe the most promising targeted drugs being studied in hepatocellular carcinoma and depict the possible future scenarios.

The physiology and pathophysiology of rapamycin resistance: implications for cancer

Rapamycin is an inhibitor of the mammalian Target of Rapamycin, mTOR, a nutrient-sensing signaling kinase and a key regulator of cell growth and proliferation. While rapamycin and related compounds have anti-tumor activity, a prevalent characteristic of cancer cells is resistance to their anti-proliferative effects. Our studies on nutrient regulation of fetal development showed that hepatocyte proliferation in the late gestation fetal rat is resistant to rapamycin. Extension of these studies to other tissues in the fetal and neonatal rat indicated that rapamycin resistance is a characteristic of normal cell proliferation in the growing organism. In hepatic cells, ribosomal biogenesis and cap-dependent protein translation were found to be relatively insensitive to the drug even though mTOR signaling was highly sensitive. Cell cycle progression was also resistant at the level of cyclin E-dependent kinase activity. Studies on the effect of rapamycin on gene expression in vitro and in vivo demonstrated that mTOR-mediated regulation of gene expression is independent of effects on cell proliferation and cannot be accounted for by functional regulation of identifiable transcription factors. Genes involved in cell metabolism were overrepresented among rapamycin-sensitive genes. We conclude that normal cellular proliferation in the context of a developing organism can be independent of mTOR signaling, that cyclin E-containing complexes are a critical locus for rapamycin sensitivity, and that mTOR functions as a modulator of metabolic gene expression in cells that are resistant to the anti-proliferative effects of the drug.

A unique P-glycoprotein interacting agent displays anticancer activity against hepatocellular carcinoma through inhibition of GRP78 and mTOR pathways

P-glycoprotein (P-gp) overexpression has been demonstrated in many malignancies being a predominant mechanism by which cancer cells develop multidrug resistance. Several categories of P-gp inhibitors have been demonstrated to potentiate anticancer effect induced by cancer chemotherapeutic drugs through competitive inhibition of P-gp pumping activity. Few studies show the agent that selectively acts on P-gp and, by itself, causes cell apoptosis while remain P-gp-deficient cells unaffected. KNG-I-322, a desmosdumotin B derivative, displayed a direct interaction with P-gp and demonstrated selective anti-proliferative and apoptotic activities in P-gp overexpressed Hep3B/VIN other than P-gp-deficient Hep3B cells. KNG-I-322 induced an inhibitory effect on the phosphorylation of mTOR(Ser2448), p70S6K(Thr389) and 4E-BP(Thr37/46) in Hep3B/VIN but not Hep3B cells. The inhibition was fully blocked by the knockdown of P-gp using siRNA techniques. Notably, the P-gp inhibitor, verapamil, also directly interacted with P-gp but significantly diminished KNG-I-322-induced anti-proliferative activity. After the mechanism study, the data showed that KNG-I-322 induced a dramatic down-regulation of GRP78 expression, which was significantly inhibited by verapamil and completely diminished by the knockdown of P-gp. The protein profile analysis of detergent resistant membranes showed that upon the stimulation by KNG-I-322, the level of P-gp expression in non-raft fractions was dramatically increased and, concomitantly, the GRP78 expression was significantly decreased. Taken together, the data suggest that KNG-I-322 induces anticancer activity in Hep3B/VIN cells through a direct interaction with P-gp, leading to the inhibition of mTOR pathways and the induction of GRP78 down-regulation. The data support that KNG-I-322 is a selective anticancer agent against P-gp-overexpressed other than P-gp-deficient cancer cells.

Mammalian target of rapamycin regulates expression of β-catenin in hepatocellular carcinoma

Although evidence has shown that both the mammalian target of rapamycin and β-catenin are involved in hepatocellular carcinoma, little is known about their relationship in pathogenesis of hepatocellular carcinoma. To investigate the expression of phosphorylated mammalian target of rapamycin and β-catenin and their prognostic impacts, as well as their relationship in hepatocellular carcinoma, we analyzed 63 human hepatocellular carcinoma samples by immunohistochemistry. Phosphorylated mammalian target of rapamycin cytoplasmic and β-catenin cytoplasmic/nuclear-positive immunoreactivities were observed in 63.5% (40/63) and 55.6% (35/63) of the hepatocellular carcinoma specimens, respectively. Significant associations were found between cytoplasmic β-catenin and phosphorylated mammalian target of rapamycin expression and tumor size (both P < .01) and metastasis (P < .01 and P < .05, respectively). In addition, β-catenin expression in the cytoplasm was closely associated with the expression of phosphorylated mammalian target of rapamycin. To further explore the relationship between mammalian target of rapamycin and β-catenin, hepatocellular carcinoma HepG2 and Hep3B cells were treated with β-catenin siRNA and mammalian target of rapamycin inhibitor, rapamycin; and the expression of phosphorylated mammalian target of rapamycin and β-catenin in cells was then measured by Western blot. The activity of Wnt/β-catenin signaling pathway was also assessed by luciferase reporter assay. The cell viability and proliferation were evaluated by thiazolyl blue tetrazolium bromide assay and [(3)H]-thymidine incorporation assay. The results showed that the level of β-catenin protein expression was markedly decreased by rapamycin in HepG2 and Hep3B cells. The reduction of β-catenin and mammalian target of rapamycin resulted in inhibition of cell viability proliferation, but the combination of reduction of β-catenin and mammalian target of rapamycin did not show a synergistic effect on the inhibition of cell viability and proliferation in HepG2 and Hep3B cells. In conclusion, the present study showed that, for the first time, mammalian target of rapamycin regulated the expression level of β-catenin in hepatocellular carcinoma. Both mammalian target of rapamycin and β-catenin play important roles in the growth, metastasis, and prognosis of hepatocellular carcinoma.

Hepatocellular carcinoma: consensus recommendations of the National Cancer Institute Clinical Trials Planning Meeting

Hepatocelluar carcinoma (HCC) is the most common primary malignancy of the liver in adults and the third most common cause of cancer death worldwide. The incidence of HCC in the United States is rising steadily because of the prevalence of hepatitis C viral infection and other causes of hepatic cirrhosis. The majority of patients have underlying hepatic dysfunction, which complicates patient management and the search for safe and effective therapies. The Clinical Trials Planning Meeting (CTPM) in HCC was convened by the National Cancer Institute's Gastrointestinal Cancer Steering Committee to identify the key knowledge gaps in HCC and define clinical research priorities. The CTPM structured its review according to current evidence-based treatment modalities in HCC and prioritized the recommendations on the basis of the patient populations representing the greatest unmet medical need.

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.

Novel inhibitors in development for hepatocellular carcinoma

IMPORTANCE OF THE FIELD

The multikinase inhibitor sorafenib was the first agent to demonstrate a survival benefit for patients with locally advanced or metastatic hepatocellular carcinoma (HCC). Although sorafenib represents a landmark in the treatment of HCC and proved molecularly targeted therapy to be effective in this disease, it represents just the first step towards an improvement in systemic therapy. Since then, novel inhibitors have been evaluated in early clinical trials, showing potential activity.

AREAS COVERED IN THIS REVIEW

This article aims to review novel inhibitors emerging in the field of advanced HCC. An Internet-based search was performed to identify abstracts, clinical trials ( www.clinicaltrials.gov , last accessed 30 November 2009), and original research and review articles.

WHAT THE READER WILL GAIN

Readers will gain a comprehensive survey of current molecularly targeted therapy approaches in advanced HCC. In addition, challenges such as the design of clinical trials, the assessment of radiological response, the role of combination therapy, and future developments in molecularly targeted therapy are discussed.

TAKE HOME MESSAGE

Sorafenib is the standard of care in patients with advanced HCC. However, promising novel inhibitors are under investigation. Combined molecularly targeted therapies according to an individual genomic and proteomic profiling will probably lead to more personalised medicine in advanced HCC.

Future perspectives in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the most common and lethal malignancies worldwide. Due to late diagnosis and advanced underlying liver cirrhosis, only limited treatment options with marginal clinical benefits have been available in up to 70% of patients. However, major progress has been achieved with regard to surveillance, early diagnosis, and multimodal treatment approaches during the last years leading to an improvement in prognosis. Particularly, the increasing knowledge of molecular hepatocarcinogenesis today provides the opportunity for targeted therapy. The multikinase inhibitor sorafenib has broadened the therapeutic horizon for patients with advanced disease and is currently under investigation for patients in early and intermediate stages as adjuvant therapy after resection/local ablation or in combination with transcatheter arterial chemoembolization. Future research will continue to unravel the key signaling cascades in different subclasses of HCC patients according to their genomic and proteomic profiling. These approaches bear the potential to individualize anticancer therapy, in the end allowing treatment of those benefiting most and excluding those who do not. This article shortly reviews the current knowledge in the management of HCC and provides insights into future perspectives with a special focus on recent progress in multidisciplinary treatment modalities.