Combination of the deacetylase inhibitor panobinostat and the multi-kinase inhibitor sorafenib for the treatment of metastatic hepatocellular carcinoma - review of the underlying molecular mechanisms and first case report

Histone deacetylase inhibitor resminostat in combination with sorafenib counteracts platelet-mediated pro-tumoral effects in hepatocellular carcinoma

In hepatocellular carcinoma (HCC), blood platelets have been linked to tumor growth, epithelial-to-mesenchymal transition (EMT), extrahepatic metastasis and a limited therapeutic response to the multikinase inhibitor (MKi) sorafenib, the standard of care in advanced HCC for the last decade. Recent clinical data indicated an improved overall survival for sorafenib in combination with the HDAC inhibitor resminostat in a platelet count dependent manner. Here, the impact of platelets on the sorafenib and resminostat drug effects in HCC cells was explored. In contrast to sorafenib, resminostat triggered an anti-proliferative response in HCC cell lines independent of platelets. As previously described, platelets induced invasive capabilities of HCC cells, a prerequisite for extravasation and metastasis. Importantly, the resminostat/sorafenib drug combination, but not the individual drugs, effectively blocked platelet-induced HCC cell invasion. Exploration of the molecular mechanism revealed that the combined drug action led to a reduction of platelet-induced CD44 expression and to the deregulation of several other epithelial and mesenchymal genes, suggesting interference with cell invasion via EMT. In addition, the drug combination decreased phosphorylated ERK level, indicating inhibition of the mitogenic signaling pathway MEK/ERK. Taken together, the resminostat plus sorafenib combination counteracts platelet-mediated cancer promoting effects in HCC cells.

Inhibition of Hepatic CYP2D6 by the Active N-Oxide Metabolite of Sorafenib

The multikinase inhibitor sorafenib (SOR) is used to treat patients with hepatocellular and renal carcinomas. SOR undergoes CYP-mediated biotransformation to a pharmacologically active N-oxide metabolite (SNO) that has been shown to accumulate to varying extents in individuals. Kinase inhibitors like SOR are frequently coadministered with a range of other drugs to improve the efficacy of anticancer drug therapy and to treat comorbidities. Recent evidence has suggested that SNO is more effective than SOR as an inhibitor of CYP3A4-mediated midazolam 1'-hydroxylation. CYP2D6 is also reportedly inhibited by SOR. The present study assessed the possibility that SNO might contribute to CYP2D6 inhibition. The inhibition kinetics of CYP2D6-mediated dextromethorphan O-demethylation were analyzed in human hepatic microsomes, with SNO found to be ~ 19-fold more active than SOR (K_is 1.8 ± 0.3 μM and 34 ± 11 μM, respectively). Molecular docking studies of SOR and SNO were undertaken using multiple crystal structures of CYP2D6. Both molecules mediated interactions with key amino acid residues in putative substrate recognition sites of CYP2D6. However, a larger number of H-bonding interactions was noted between the N-oxide moiety of SNO and active site residues that account for its greater inhibition potency. These findings suggest that SNO has the potential to contribute to pharmacokinetic interactions involving SOR, perhaps in those individuals in whom SNO accumulates.

Hepatocellular carcinoma: Therapeutic advances in signaling, epigenetic and immune targets

Hepatocellular carcinoma (HCC) remains a global medical burden with rising incidence due to chronic viral hepatitis and non-alcoholic fatty liver diseases. Treatment of advanced disease stages is still unsatisfying. Besides first and second generation tyrosine kinase inhibitors, immune checkpoint inhibitors have become central for the treatment of HCC. New modalities like epigenetic therapy using histone deacetylase inhibitors (HDACi) and cell therapy approaches with chimeric antigen receptor T cells (CAR-T cells) are currently under investigation in clinical trials. Development of such novel drugs is closely linked to the availability and improvement of novel preclinical and animal models and the identification of predictive biomarkers. The current status of treatment options for advanced HCC, emerging novel therapeutic approaches and different preclinical models for HCC drug discovery and development are reviewed here.

Modification of Epigenetic Histone Acetylation in Hepatocellular Carcinoma

Cells respond to various environmental factors such as nutrients, food intake, and drugs or toxins by undergoing dynamic epigenetic changes. An imbalance in dynamic epigenetic changes is one of the major causes of disease, oncogenic activities, and immunosuppressive effects. The aryl hydrocarbon receptor (AHR) is a unique cellular chemical sensor present in most organs, and its dysregulation has been demonstrated in multiple stages of tumor progression in humans and experimental models; however, the effects of the pathogenic mechanisms of AHR on epigenetic regulation remain unclear. Apart from proto-oncogene activation, epigenetic repressions of tumor suppressor genes are involved in tumor initiation, procession, and metastasis. Reverse epigenetic repression of the tumor suppressor genes by epigenetic enzyme activity inhibition and epigenetic enzyme level manipulation is a potential path for tumor therapy. Current evidence and our recent work on deacetylation of histones on tumor-suppressive genes suggest that histone deacetylase (HDAC) is involved in tumor formation and progression, and treating hepatocellular carcinoma with HDAC inhibitors can, at least partially, repress tumor proliferation and transformation by recusing the expression of tumor-suppressive genes such as TP53 and RB1.

Panbinostat decreases cFLIP and enhances killing of cancer cells by immunotoxin LMB-100 by stimulating the extrinsic apoptotic pathway

LMB-100 (RG7787) is a recombinant immunotoxin, which kills mesothelin-expressing cancer cells and now being evaluated in phase 1 trials. To enhance the anti-tumor activity of LMB-100, we have searched for agents, already approved for cancer therapy, that can be combined with LMB-100 to increase its efficacy. Panbinostat is a pan-histone deacetylase inhibitor that is used to treat multiple myeloma. We incubated different types of cancer cells with panbinostat and LMB-100 and found that they interacted synergistically to cause cell death. We found that panbinostat and the combination increased levels of mRNAs encoding TNF/TNFR family members, as well as BNIP3L and CASP-9, and markedly decreased mRNA levels for c-FLIP and BID. Western blots confirmed a fall in levels of cFLIP protein and a rise in BNIP3L and caspase-9. The combination also increased levels of cleaved BID (t-BID), cleaved-capsase-3 and −8 and PARP. To assess the importance of the fall in cFLIP levels, we treated cells with the cFLIP inhibitor, Rocaglamide, and found it also enhanced killing of tumor cells by LMB-100. LMB-100, which activates the intrinsic pathway of apoptosis, and panbinostat, which activates the extrinsic pathway, work in a synergistic manner to kill cancer cell lines.

Functions of endothelin-1 in apoptosis and migration in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the second leading cause of cancer mortality in China and the third leading cause of cancer mortality worldwide. The mechanisms involved in the development and progression of HCC are not well understood. In the present study, the functions of endothelin-1 (ET-1) in HCC were studied and its underlying mechanisms were investigated. ET-1, B-cell lymphoma 2 (Bcl-2), Bcl-2 related protein 4 (Bax), matrix metalloproteinase (MMP)-2 and MMP-9 expression was measured by reverse transcription-quantitative polymerase chain reaction and western blotting. Cell proliferation was measured via Cell Counting kit-8 assay. Flow cytometry was performed for cell cycle and apoptosis analysis. Migration was measured via Transwell assay. The results demonstrated that ET-1 expression significantly increased in HCC tissues compared with the normal tissues of patients in The Cancer Genome Atlas dataset (P<0.01). Furthermore, downregulation of ET-1 was able to significantly inhibit cell proliferation and growth in vitro (P<0.01) and in vivo (P<0.01), and induce cell cycle arrest (P<0.05) and apoptosis (P<0.01) in the HCC SMMC-7721 cell line. Bioinformatics analysis demonstrated that the cell apoptosis signaling pathway was activated by ET-1. The ratio of B-cell lymphoma (Bcl-2) -related protein 4 (Bax)/Bcl-2 was significantly increased by downregulation of ET-1 (P<0.01). ET-1 downregulation also inhibited migration of SMMC-7721 cells (P<0.05) via decreasing levels of matrix metalloproteinase (MMP) -2 (P<0.05) and MMP-9 (P>0.05). These results suggest that ET-1 may be able to affect the apoptosis and migration of HCC cells via modulation of the Bax/Bcl-2 ratio and expression levels of MMP-2 and MMP-9, which indicates that ET-1 maybe a potential novel target for HCC treatment.

Angiogenesis inhibitors as therapeutic agents in cancer: Challenges and future directions

Angiogenesis has become an attractive target for cancer therapy since the US Food and Drug Administration (FDA) approved the first angiogenesis inhibitor (bevacizumab) for the treatment of metastatic colorectal cancer in 2004. In following years, a large number of angiogenesis inhibitors have been discovered and developed, ranging from monoclonal antibodies, endogenous peptides, to small organic molecules and microRNAs. Many of them are now entering the clinical trial, or achieving approval for clinical use. However, major limitations have been observed about angiogenesis inhibitors by continued clinical investigations, such as resistance, enhancing tumor hypoxia and reducing delivery of chemotherapeutic agents, which might be the main reason for poor improvement in overall survival after angiogenesis inhibitor administration in clinic. Therefore, optimal anti-angiogenic therapy strategies become critical. The present review summarizes recent researches in angiogenesis inhibitors, and proposes a perspective on future directions in this field.

A Systematic Review of Metastatic Hepatocellular Carcinoma to the Spine

BACKGROUND

Hepatocellular carcinoma (HCC) frequently metastasizes to the spine. The impact of medical and/or surgical intervention on overall survival has been examined in a limited number of clinical studies, and herein we systematically review these data.

METHODS

We performed a literature review using PubMed, Embase, CINAHL, and Web of Science to identify articles that reported survival, clinical outcomes, and/or prognostic factors associated with patients diagnosed with spinal metastases. The methodologic quality of each review was assessed using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses tool.

RESULTS

There were 26 articles (152 patients) that met the inclusion criteria and were treated with either surgery, radiotherapy, chemotherapy, and/or observation. There were 3 retrospective cohort studies, 17 case reports, 5 case series, and 1 longitudinal observational study. Of the patients with known overall survival after diagnosis of spinal metastasis, survival at 3 months, 6 months, 1 year, 2 years, and 5 years was 95.2%, 83.0%, 28.6%, 2.0%, and 1.4%, respectively. The median survival after diagnosis of the metastasis was 0.7 months in the patients who received no treatment, 7 months in the patients treated with surgical intervention alone, 6 months for patients who received chemotherapy and/or radiation, and 13.5 months in the patients treated with a combination of surgery and medical management. All other clinical or prognostic parameters were of low or insufficient strength.

CONCLUSIONS

Patients diagnosed with HCC spinal metastasis have a 10.6-month overall survival. Further analysis of patients in prospective controlled trials will be essential to the development of treatment algorithms for these patients in the future.

Sorafenib-based combined molecule targeting in treatment of hepatocellular carcinoma

Sorafenib is the only and standard systematic chemotherapy drug for treatment of advanced hepatocellular carcinoma (HCC) at the current stage. Although sorafenib showed survival benefits in large randomized phase III studies, its clinical benefits remain modest and most often consist of temporary tumor stabilization, indicating that more effective first-line treatment regimens or second-line salvage therapies are required. The molecular pathogenesis of HCC is very complex, involving hyperactivated signal transduction pathways such as RAS/RAF/MEK/ERK and PI3K/AKT/mTOR and aberrant expression of molecules such as receptor tyrosine kinases and histone deacetylases. Simultaneous or sequential abrogation of these critical pathways or the functions of these key molecules involved in angiogenesis, proliferation, and apoptosis may yield major improvements in the management of HCC. In this review, we summarize the emerging sorafenib-based combined molecule targeting for HCC treatment and analyze the rationales of these combinations.

The pan-deacetylase inhibitor panobinostat affects angiogenesis in hepatocellular carcinoma models via modulation of CTGF expression

Post-translational modifications of chromatin components are significantly involved in the regulation of tumor suppressor gene and oncogene expression. Connective tissue growth factor (CTGF) is an epigenetically regulated growth factor with functions in angiogenesis and cell-matrix interactions and plays a pivotal role in hepatocellular carcinoma (HCC). The pharmacologic inhibition of histone and protein deacetylases represents a new approach to interfere with pathways of apoptosis and angiogenesis. We investigated the effect of the pan-deacetylase inhibitor panobinostat (LBH589) on human HCC cell lines HepG2 (p53wt) and Hep3B (p53null) and in a subcutaneous xenograft model and explored the influence on angiogenesis. Specimens were characterized by quantitative real-time PCR. Protein was separated for western blotting against CTGF, VEGF, VEGF receptor-1 (VEGFR-1/FLT-1), VEGF receptor-2 (VEGFR-2/KDR), MAPK and phospho-MAPK. In vivo, HepG2 cells were xenografted to NMRI mice and treated with daily i.p. injections of 10 mg/kg panobinostat. After 1, 7 and 28 days, real-time PCR was performed. Immunohistochemistry and western blotting were examined after 28 days. An increased significant expression of CTGF was only seen after 24 h treatment with 0.1 µM panobinostat in HepG2 cells and Hep3B cells, whereas after 72 h treatment CTGF expression clearly decreased. In the xenografts, treatment with panobinostat showed a minimal CTGF expression after 1 day and 4 weeks, respectively. In vitro as well as in vivo, VEGF was not affected by panobinostat treatment at any time. In conclusion, panobinostat influences extracellular signaling cascades via CTGF-dependent pathways.

The pan-deacetylase inhibitor panobinostat suppresses the expression of oncogenic miRNAs in hepatocellular carcinoma cell lines

Deacetylase inhibitors (DACi) are a new class of drugs with a broad spectrum of mechanisms that favor their application in cancer therapy. Currently, the exact mechanisms and cellular effects of DACi have not been fully elucidated. In addition to their effects on histone acetylation, DACi can interfere with gene expression via miRNA pathways. Treatment with panobinostat (LBH589), a novel potent DACi, led to the highly aberrant modulation of several miRNAs in hepatocellular carcinoma (HCC) cell lines as shown by miRNA array analysis. Among them, hsa-miR-19a, hsa-miR-19b1 and the corresponding precursors were down-regulated by panobinostat in TP53(-/-) Hep3B and TP53(+/+) HepG2 cell lines; hsa-miR30a-5p mature form only was suppressed in both HCC cell lines, as confirmed by further RT-qPCR analysis. In HCC cell lines, panobinostat caused the upregulation of the predicted miRNA targets APAF1 and Beclin1 protein levels. Transfection with oligonucleotides mimicking these miRNAs led to an increase in the viability rate of both cell lines as analyzed by impedance-based real-time cell analysis. In addition, transfecting miRNA mimicking oligonucleotides resulted in the decrease of APAF1, Beclin1 and PAK6 at the protein level, proving the regulating influence of the investigated miRNAs on gene final products. The overexpression of the above mentioned oncomiRs in Hep3B and HepG2 cell lines leads to cell proliferation and downregulation of cell death associated proteins. In our model, panobinostat exerts its anti-cancer effect by suppressing these miRNAs and restoring the expression of their corresponding tumor suppressor targets.

Minnelide, a novel drug for pancreatic and liver cancer

BACKGROUND

Pancreatic cancer is the 10th leading cause of all new cancer cases for men and the fourth leading cause of death across genders, having very poor prognosis and survival rates. The current standard of care Gemcitabine fails to add any survival benefit for this disease (www.cancer.gov). Though the incidence of pancreatic cancer is found to be higher in developed countries, the aggressive biology of the cancer, its high rate of recurrence and chemo-resistance make it a formidable disease in all parts of the globe. Hepatocellular carcinoma (HCC) or liver cancer, on the other hand affects almost 750,000 people world wide with 84% of the cases coming from underdeveloped or developing countries

RESULTS

Our studies show that Minnelide, a water soluble pro-drug of triptolide (active compound from a chinese herb) is very effective against a number of malignant diseases.

CONCLUSION

The current study discusses the efficacy of this compound in pancreatic and liver cancer.

Epigenetic therapy as a novel approach in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the most common type of liver malignancy and one with high fatality. Its 5-year survival rate remains low and thus, there is a need for improvement of current treatment strategies as well as development of novel targeted methodologies in order to optimize existing therapeutic protocols. To this end, only recently, it was discovered that its pathophysiology also involves epigenetic alterations in DNA methylation, histone modifications and/or non-coding microRNA patterns. Unlike genetic events, epigenetic alterations are reversible and thus potentially considered to be an alternative option in cancer treatment protocols. In this review, we describe the general characteristics and resulted major alterations of the epigenetic machinery as well as current state of progress of epigenetic therapy (via different single or combinatorial experimental approaches) in HCC.

Profile of panobinostat and its potential for treatment in solid tumors: an update

The histone deacetylase (HDAC) inhibitors have emerged as novel therapies for cancer. Panobinostat (LBH 589, Novartis Pharmaceuticals) is a pan-deacetylase inhibitor that is being evaluated in both intravenous and oral formulations across multiple tumor types. Comparable to the other HDACs, panobinostat leads to hyperacetylation of histones and other intracellular proteins, allowing for the expression of otherwise repressed genes, leading to inhibition of cellular proliferation and induction of apoptosis in malignant cells. Panobinostat, analogous to other HDAC inhibitors, also induces apoptosis by directly activating cellular death receptor pathways. Preclinical data suggests that panobinostat has inhibitory activity at nanomolar concentrations and appears to be the most potent clinically available HDAC inhibitor. Here we review the current status of panobinostat and discuss its role in the treatment of solid tumors.

Sorafenib inhibits epithelial-mesenchymal transition through an epigenetic-based mechanism in human lung epithelial cells

The epithelial to mesenchymal transition (EMT) has been well recognized for many decades as an essential early step in the progression of primary tumors towards metastases. Widespread epigenetic reprogramming of DNA and histone modifications tightly regulates gene expression and cellular activity during carcinogenesis, and epigenetic therapy has been developed to design efficient strategies for cancer treatment. As the first oral agent approved for the clinical treatment of cancer, sorafenib has significant inhibitory effects on tumor growth and EMT. However, a detailed understanding of the underlying epigenetic mechanism remains elusive. In this manuscript, we performed a ChIP-seq assay to evaluate the activity of sorafenib on the genome-wide profiling of histone modifications. We demonstrate that sorafenib largely reverses the changes in histone modifications that occur during EMT in A549 alveolar epithelial cells. Sorafenib also significantly reduces the coordinated epigenetic switching of critical EMT-associated genes in accordance with their expression levels. Furthermore, we show that sorafenib potentiates histone acetylation by regulating the expression levels of histone-modifying enzymes. Collectively, these findings provide the first evidence that sorafenib inhibits the EMT process through an epigenetic mechanism, which holds enormous promise for identifying novel epigenetic candidate diagnostic markers and drug targets for the treatment of human malignancies.

Endoplasmic reticulum stress plays a pivotal role in cell death mediated by the pan-deacetylase inhibitor panobinostat in human hepatocellular cancer cells

Panobinostat, a pan-deacetylase inhibitor, represents a novel therapeutic option for cancer diseases. Besides its ability to block histone deacetylases (HDACs) by promoting histone hyperacetylation, panobinostat interferes with several cell death pathways providing a potential efficacy against tumors. We have previously demonstrated that panobinostat has a potent apoptotic activity in vitro and causes a significant growth delay of hepatocellular carcinoma (HCC) tumor xenografts in nude mice models. Here, we show that treatment with panobinostat is able to induce noncanonical apoptotic cell death in HepG2 and in Hep3B cells, involving the endoplasmic reticulum (ER) stress by up-regulation of the molecular chaperone binding immunoglobulin protein/glucose-regulated protein 78, activation of eukaryotic initiation factor 2α-activating transcription factor 4 (tax-responsive enhancer element B67) and inositol requiring 1α-X-box binding protein 1 factors, strong increase and nuclear translocation of the transcription factor C/EBP homologous protein/growth arrest and DNA damage-inducible gene 153, and involvement of c-Jun N-terminal kinase. These signaling cascades culminate into the activation of the ER-located caspase-4/12 and of executioner caspases, which finally lead to cell demise. Our results clearly show that panobinostat induces an alternative ER stress-mediated cell death pathway in HCC cells, independent of the p53 status.

Antitumor effect of SIRT1 inhibition in human HCC tumor models in vitro and in vivo

Sirtuins (SIRT1-7) are a highly conserved family of NAD(+)-dependent enzymes that control the activity of histone and nonhistone regulatory proteins. SIRT1 is purposed to promote longevity and to suppress the initiation of some cancers. Nevertheless, SIRT1 is reported to function as a tumor suppressor as well as an oncogenic protein. Our data show that compared with normal liver or surrounding tumor tissue, SIRT1 is strongly overexpressed in human hepatocellular carcinoma (HCC). In addition, human HCC cell lines (Hep3B, HepG2, HuH7, HLE, HLF, HepKK1, skHep1) were screened for the expression of the sirtuin family members and only SIRT1 was consistently overexpressed compared with normal hepatocytes. To determine its effect on HCC growth, SIRT1 activity was inhibited either with lentiviruses expressing short hairpin RNAs or with the small molecule inhibitor, cambinol. Knockdown or inhibition of SIRT1 activity had a cytostatic effect, characterized by an altered morphology, impaired proliferation, an increased expression of differentiation markers, and cellular senescence. In an orthotopic xenograft model, knockdown of SIRT1 resulted in 50% fewer animals developing tumors and cambinol treatment resulted in an overall lower tumor burden. Taken together, our data show that inhibition of SIRT1 in HCC cells impairs their proliferation in vitro and tumor formation in vivo. These data suggest that SIRT1 expression positively influences the growth of HCC and support further studies aimed to block its activity alone or in combination as a novel treatment strategy.

Quantification of dynamic contrast-enhanced ultrasound in HCC: prediction of response to a new combination therapy of sorafenib and panobinostat in advanced hepatocellular carcinoma

Here, we report the case of a patient, who showed an antitumour response to a new combination therapy of sorafenib and the histon deacetylase inhibitor panobinostat (LBH-589). D-CEUS (Dynamic contrast-enhanced ultrasonography) was able to predict response to the new therapy regime and may be an interesting tool in the early evaluation of response to therapy. It might be especially useful to differentiate between responders and non-responders of new-targeted pharmaceuticals like multikinase inhibitors in hepatocellular carcinomas.

Inhibition of DNA methyltransferase activity and expression by treatment with the pan-deacetylase inhibitor panobinostat in hepatocellular carcinoma cell lines

BACKGROUND

Hepatocellular carcinoma (HCC) still represents an unmet medical need. Epigenetic inactivation of tumor suppressor genes like RASSF1A or APC by overexpression of DNA methyltransferases (DNMTs) has been shown to be common in HCC and to be linked to the overall prognosis of patients. Inhibitors of protein and histone deacetylases (DACi) have been demonstrated to possess strong anti-tumor effects in HCC models.

METHODS

We therefore investigated whether DACi also has any influence on the expression and activity of DNMTs and methylated target genes in HepG2 and Hep3B cell culture systems and in a xenograft model by immunohistochemistry, westernblotting, RT-qPCR and methylation-specific PCR.

RESULTS

Our findings demonstrate a rapid inhibition of DNMT activity 6 h after treatment with 0.1 μM of the pan-DACi panobinostat. A downregulation of DNMT mRNAs and protein were also observed at later points in time. This loss of DNMT activity and expression was paralleled by a diminished methylation of the target genes RASSF1A and APC and a concomitant re-expression of APC mRNA and protein. Analysis of HepG2 xenograft specimens confirmed these results in vivo.

CONCLUSION

We suggest a dual mode of action of DACi on DNA methylation status: a rapid inhibition of enzyme activity due to interference with posttranslational acetylation and a delayed effect on transcriptional control of DNMT genes by HDAC or miRNA mechanisms.