The HDAC inhibitor panobinostat (LBH589) inhibits mesothelioma and lung cancer cells in vitro and in vivo with particular efficacy for small cell lung cancer

DrugRepoBank: a comprehensive database and discovery platform for accelerating drug repositioning

In recent years, drug repositioning has emerged as a promising alternative to the time-consuming, expensive and risky process of developing new drugs for diseases. However, the current database for drug repositioning faces several issues, including insufficient data volume, restricted data types, algorithm inaccuracies resulting from the neglect of multidimensional or heterogeneous data, a lack of systematic organization of literature data associated with drug repositioning, limited analytical capabilities and user-unfriendly webpage interfaces. Hence, we have established the first all-encompassing database called DrugRepoBank, consisting of two main modules: the 'Literature' module and the 'Prediction' module. The 'Literature' module serves as the largest repository of literature-supported drug repositioning data with experimental evidence, encompassing 169 repositioned drugs from 134 articles from 1 January 2000 to 1 July 2023. The 'Prediction' module employs 18 efficient algorithms, including similarity-based, artificial-intelligence-based, signature-based and network-based methods to predict repositioned drug candidates. The DrugRepoBank features an interactive and user-friendly web interface and offers comprehensive functionalities such as bioinformatics analysis of disease signatures. When users provide information about a drug, target or disease of interest, DrugRepoBank offers new indications and targets for the drug, proposes new drugs that bind to the target or suggests potential drugs for the queried disease. Additionally, it provides basic information about drugs, targets or diseases, along with supporting literature. We utilize three case studies to demonstrate the feasibility and effectiveness of predictively repositioned drugs within DrugRepoBank. The establishment of the DrugRepoBank database will significantly accelerate the pace of drug repositioning. Database URL:  https://awi.cuhk.edu.cn/DrugRepoBank.

Synergistic activities of Panobinostat and doxorubicin in soft tissue sarcomas

BACKGROUND

Soft tissue sarcomas (STS) are rare diseases typically arising from connective tissues in children and adults. However, chemotherapies involved in the treatment of STS may cause toxic side effects and multi-drug chemoresistance, making the treatment even more challenging. Histone deacetylase inhibitors (HDACi) are epigenetic agents which have shown anti-tumor effects as single agent as well as combination use with other drugs. Our project intends to prove the same effects in STS.

METHODS

Panobinostat (LBH589) plus doxorubicin was selected for investigations based on our previous research. Tumor xenografts were tried in an epithelioid sarcoma model to validate good synergy effects in vivo and a leiomyosarcoma model was used as a negative comparison group. Gene profile changes were studied afterwards. The possible pathway changes caused by HDACi were explored and validated by several assays.

RESULTS

Synergy effect of LBH589 plus doxorubicin was successfully validated in STS cell lines and an epithelioid sarcoma mice model. We tried to reduce the dose of doxorubicin to a lower level and found the drug combination can still inhibit tumor size in mice. Furthermore, gene profile changes caused by LBH589 was studied by RNA-Sequencing analysis. Results showed LBH589 can exert effects on a group of target genes which can regulate potential biological functions especially in the cell cycle pathway.

Phase I trial of panobinostat in children with diffuse intrinsic pontine glioma: A report from the Pediatric Brain Tumor Consortium (PBTC-047)

BACKGROUND

Diffuse intrinsic pontine glioma (DIPG) is a lethal childhood cancer with median survival of less than 1 year. Panobinostat is an oral multihistone deacetylase inhibitor with preclinical activity in DIPG models. Study objectives were to determine safety, tolerability, maximum tolerated dose (MTD), toxicity profile, and pharmacokinetics of panobinostat in children with DIPG.

PATIENTS AND METHODS

In stratum 1, panobinostat was administered 3 days per week for 3 weeks on, 1 week off to children with progressive DIPG, with dose escalation following a two-stage continual reassessment method. After this MTD was determined, the study was amended to evaluate the MTD in children with nonprogressive DIPG/Diffuse midline glioma (DMG) (stratum 2) on an alternate schedule, 3 days a week every other week in an effort to escalate the dose.

RESULTS

For stratum 1, 19 subjects enrolled with 17/19 evaluable for dose-finding. The MTD was 10 mg/m2/dose. Dose-limiting toxicities included thrombocytopenia and neutropenia. Posterior reversible encephalopathy syndrome was reported in 1 patient. For stratum 2, 34 eligible subjects enrolled with 29/34 evaluable for dose finding. The MTD on this schedule was 22 mg/m2/dose. DLTs included thrombocytopenia, neutropenia, neutropenia with grade 4 thrombocytopenia, prolonged intolerable nausea, and increased ALT.

CONCLUSIONS

The MTD of panobinostat is 10 mg/m2/dose administered 3 times per week for 3 weeks on/1 week off in children with progressive DIPG/DMG and 22 mg/m2/dose administered 3 times per week for 1 week on/1 week off when administered in a similar population preprogression. The most common toxicity for both schedules was myelosuppression.

Novel Therapeutic Options for Small Cell Lung Cancer

PURPOSE OF REVIEW

The aim of this review is to focus on the recent advances in the molecular knowledge of small cell lung cancer (SCLC) and potential promising new treatment strategies, like targeting the DNA damage pathway, epigenetics, angiogenesis, and oncogenic drivers.

RECENT FINDINGS

In the last few years, the addition of immunotherapy to chemotherapy has led to significant improvements in clinical outcomes in this complex neoplasia. Nevertheless, the prognosis remains dismal. Recently, numerous genomic alterations have been identified, and they may be useful to classify SCLC into different molecular subtypes (SCLC-A, SCLC-I, SCLC-Y, SCLC-P). SCLC accounts for 10-20% of all lung cancers, most patients have an extensive disease at the diagnosis, and it is characterized by poor prognosis. Despite the progresses in the knowledge of the disease, efficacious targeted treatments are still lacking. In the near future, the molecular characterisation of SCLC will be fundamental to find more effective treatment strategies.

Molecular mechanisms underlying the clinical efficacy of panobinostat involve Stochasticity of epigenetic signaling, sensitization to anticancer drugs, and induction of cellular cell death related to cellular stresses

Panobinostat, also known as Farydak®, LBH589, PNB, or panobinostat lactate, is a hydroxamic acid that has been approved by the Food and Drug Administration (FDA) for its anti-cancer properties. This orally bioavailable drug is classified as a non-selective histone deacetylase inhibitor (pan-HDACi) that inhibits class I, II, and IV HDACs at nanomolar levels due to its significant histone modifications and epigenetic mechanisms. A mismatch between histone acetyltransferases (HATs) and HDACs can negatively affect the regulation of the genes concerned, which in turn can contribute to tumorigenesis. Indeed, panobinostat inhibits HDACs, potentially leading to acetylated histone accumulation, re-establishing normal gene expression in cancer cells, and helping to drive multiple signaling pathways. These pathways include induction of histone acetylation and cytotoxicity for the majority of tested cancer cell lines, increased levels of p21 cell cycle proteins, enhanced amounts of pro-apoptotic factors (such as caspase-3/7 activity and cleaved poly (ADP-ribose) polymerase (PARP)) associated with decreased levels of anti-apoptotic factors [B-cell lymphoma 2 (Bcl-2) and B-cell lymphoma-extra-large (Bcl-XL)], as well as regulation of immune response [upregulated programmed death-ligand 1 (PD-L1) and interferon gamma receptor 1 (IFN-γR1) expression] and other events. The therapeutic outcome of panobinostat is therefore mediated by sub-pathways involving proteasome and/or aggresome degradation, endoplasmic reticulum, cell cycle arrest, promotion of extrinsic and intrinsic processes of apoptosis, tumor microenvironment remodeling, and angiogenesis inhibition. In this investigation, we aimed to pinpoint the precise molecular mechanism underlying panobinostat's HDAC inhibitory effect. A more thorough understanding of these mechanisms will greatly advance our knowledge of cancer cell aberrations and, as a result, provide an opportunity for the discovery of significant new therapeutic perspectives through cancer therapeutics.

Super-enhancers complexes zoom in transcription in cancer

Super-enhancers (SEs) consist of multiple typical enhancers enriched at high density with transcription factors, histone-modifying enzymes and cofactors. Oncogenic SEs promote tumorigenesis and malignancy by altering protein-coding gene expression and noncoding regulatory element function. Therefore, they play central roles in the treatment of cancer. Here, we review the structural characteristics, organization, identification, and functions of SEs and the underlying molecular mechanism by which SEs drive oncogenic transcription in tumor cells. We then summarize abnormal SE complexes, SE-driven coding genes, and noncoding RNAs involved in tumor development. In summary, we believe that SEs show great potential as biomarkers and therapeutic targets.

Arginine Deprivation in SCLC: Mechanisms and Perspectives for Therapy

Arginine deprivation has gained increasing traction as a novel and safe antimetabolite strategy for the treatment of several hard-to-treat cancers characterised by a critical dependency on arginine. Small cell lung cancer (SCLC) displays marked arginine auxotrophy due to inactivation of the rate-limiting enzyme argininosuccinate synthetase 1 (ASS1), and as a consequence may be targeted with pegylated arginine deiminase or ADI-PEG20 (pegargiminase) and human recombinant pegylated arginases (rhArgPEG, BCT-100 and pegzilarginase). Although preclinical studies reveal that ASS1-deficient SCLC cell lines are highly sensitive to arginine-degrading enzymes, there is a clear disconnect with the clinic with minimal activity seen to date that may be due in part to patient selection. Recent studies have explored resistance mechanisms to arginine depletion focusing on tumor adaptation, such as ASS1 re-expression and autophagy, stromal cell inputs including macrophage infiltration, and tumor heterogeneity. Here, we explore how arginine deprivation may be combined strategically with novel agents to improve SCLC management by modulating resistance and increasing the efficacy of existing agents. Moreover, recent work has identified an intriguing role for targeting arginine in combination with PD-1/PD-L1 immune checkpoint inhibitors and clinical trials are in progress. Thus, future studies of arginine-depleting agents with chemoimmunotherapy, the current standard of care for SCLC, may lead to enhanced disease control and much needed improvements in long-term survival for patients.

Deacetylation of YAP1 Promotes the Resistance to Chemo- and Targeted Therapy in FLT3-ITD+ AML Cells

The FLT3-ITD mutation occurs in about 30% of acute myeloid leukemia (AML) and is associated with poor prognosis. However, FLT3 inhibitors are only partially effective and prone to acquired resistance. Here, we identified Yes-associated protein 1 (YAP1) as a tumor suppressor in FLT3-ITD⁺ AML. YAP1 inactivation conferred FLT3-ITD⁺ AML cell resistance to chemo- and targeted therapy. Mass spectrometric assay revealed that DNA damage repair gene poly (ADP-ribose) polymerase 1 (PARP1) might be the downstream of YAP1, and the pro-proliferative effect by YAP1 knockdown was partly reversed via PARP1 inhibitor. Importantly, histone deacetylase 10 (HDAC10) contributed to decreased YAP1 acetylation levels through histone H3 lysine 27 (H3K27) acetylation, leading to the reduced nuclear accumulation of YAP1. Selective HDAC10 inhibitor chidamide or HDAC10 knockdown activated YAP1, enhanced DNA damage, and significantly attenuated FLT3-ITD⁺ AML cell resistance. In addition, combination chidamide with FLT3 inhibitors or chemotherapy agents synergistically inhibited growth and increased apoptosis of FLT3-ITD⁺ AML cell lines and acquired resistant cells from the relapse FLT3-ITD⁺ AML patients. These findings demonstrate that the HDAC10-YAP1-PARP1 axis maintains FLT3-ITD⁺ AML cells and targeting this axis might improve clinical outcomes in FLT3-ITD⁺ AML patients.

Natural compound library screening identifies Sanguinarine chloride for the treatment of SCLC by upregulating CDKN1A

OBJECTIVES

Small cell lung cancer (SCLC) is notorious for aggressive malignancy without effective treatment, and most patients eventually develop tumor progression with a poor prognosis. There is an urgent need for discovering novel antitumor agents or therapeutic strategies for SCLC.

MATERIALS AND METHODS

We performed a screening method based on CCK-8 assay to screen 640 natural compounds for SCLC. The effects of Sanguinarine chloride on SCLC cell proliferation, colony formation, cell cycle, apoptosis, migration and invasion were determined. RNA-seq and bioinformatics analysis was performed to investigate the anti-SCLC mechanism of Sanguinarine chloride. Publicly available datasets and samples were analyzed to investigate the expression level of CDKN1A and its clinical significance. Loss of functional cancer cell models were constructed by shRNA-mediated silencing. Quantitative RT-PCR and Western blot were used to measure gene and protein expression. Immunohistochemistry staining was performed to detect the expression of CDKN1A, Ki67, and Cleaved caspase 3 in xenograft tissues.

RESULTS

We identified Sanguinarine chloride as a potential inhibitor of SCLC, which inhibited cell proliferation, colony formation, cell cycle, cell migration and invasion, and promoted apoptosis of SCLC cells. Sanguinarine chloride played an important role in anti-SCLC by upregulating the expression of CDKN1A. Furthermore, Sanguinarine chloride in combination with panobinostat, or THZ1, or gemcitabine, or (+)-JQ-1 increased the anti-SCLC effect compared with either agent alone treatment.

CONCLUSIONS

Our findings identified Sanguinarine chloride as a potential inhibitor of SCLC by upregulating the expression of CDKN1A. Sanguinarine chloride in combination with chemotherapy compounds exhibited strong synergism anti-SCLC properties, which could be further clinically explored for the treatment of SCLC.

A Glimpse in the Future of Malignant Mesothelioma Treatment

Malignant mesothelioma (MMe) is a rare neoplasm with few therapeutic options available. The landscape of effective therapy for this disease remained unchanged in the last two decades. Recently, however, the introduction of Immune Checkpoint Inhibitors (ICIs) led to small, but nevertheless, promising improvements. However, many efforts are still needed to radically improve the prognosis of MMe. In this review, we analyze all those therapeutic strategies for MMe that are still in a preclinical or early clinical phase of development. In particular, we focus on novel antiangiogenic drugs and their possible combination with immunotherapy. Furthermore, we describe also more complex strategies such as microRNA-loaded vectors, oncolytic viruses, and engineered lymphocytes.

A High-throughput Approach to Identify Effective Systemic Agents for the Treatment of Anaplastic Thyroid Carcinoma

BACKGROUND

Despite the use of aggressive multimodality treatment, most anaplastic thyroid carcinoma (ATC) patients die within a year of diagnosis. Although the combination of BRAF and MEK inhibitors has recently been approved for use in BRAF-mutated ATC, they remain effective in a minority of patients who are likely to develop drug resistance. There remains a critical clinical need for effective systemic agents for ATC with a reasonable toxicity profile to allow for rapid translational development.

MATERIAL AND METHODS

Twelve human thyroid cancer cell lines with comprehensive genomic characterization were used in a high-throughput screening (HTS) of 257 compounds to select agents with maximal growth inhibition. Cell proliferation, colony formation, orthotopic thyroid models, and patient-derived xenograft (PDX) models were used to validate the selected agents.

RESULTS

Seventeen compounds were effective, and docetaxel, LBH-589, and pralatrexate were selected for additional in vitro and in vivo analysis as they have been previously approved by the US Food and Drug Administration for other cancers. Significant tumor growth inhibition (TGI) was detected in all tested models treated with LBH-589; pralatrexate demonstrated significant TGI in the orthotopic papillary thyroid carcinoma model and 2 PDX models; and docetaxel demonstrated significant TGI only in the context of mutant TP53.

CONCLUSIONS

HTS identified classes of systemic agents that demonstrate preferential effectiveness against aggressive thyroid cancers, particularly those with mutant TP53. Preclinical validation in both orthotopic and PDX models, which are accurate in vivo models mimicking tumor microenvironment, may support initiation of early-phase clinical trials in non-BRAF mutated or refractory to BRAF/MEK inhibition ATC.

Synergistic Tumor Cytolysis by NK Cells in Combination With a Pan-HDAC Inhibitor, Panobinostat

Histone deacetylases (HDAC) are frequently overexpressed in tumors, and their inhibition has shown promising anti-tumor effects. However, the synergistic effects of HDAC inhibition with immune cell therapy have not been fully explored. Natural killer (NK) cells are cytotoxic lymphocytes for anti-tumor immune surveillance, with immunotherapy potential. We showed that a pan-HDAC inhibitor, panobinostat, alone demonstrated anti-tumor and anti-proliferative activities on all tested tumors in vitro. Additionally, panobinostat co-treatment or pretreatment synergized with NK cells to mediate tumor cell cytolysis. Mechanistically, panobinostat treatment increased the expression of cell adhesion and tight junction-related genes, promoted conjugation formation between NK and tumor cells, and modulates NK cell-activating receptors and ligands on tumor cells, contributing to the increased tumor cytolysis. Finally, panobinostat therapy led to better tumor control and synergized with anti-PD-L1 therapy. Our data highlights the anti-tumor potential of HDAC inhibition through tumor-intrinsic toxicity and enhancement of NK -based immunotherapy.

Pharmaco-transcriptomic correlation analysis reveals novel responsive signatures to HDAC inhibitors and identifies Dasatinib as a synergistic interactor in small-cell lung cancer

BACKGROUND

Histone acetylation/deacetylase process is one of the most studied epigenetic modifications. Histone deacetylase inhibitors (HDACis) have shown clinical benefits in haematological malignancies but failed in solid tumours due to the lack of biomarker-driven stratification.

METHODS

We perform integrative pharmaco-transcriptomic analysis by correlating drug response profiles of five pan-HDACis with transcriptomes of solid cancer cell lines (n=659) to systematically identify generalizable gene signatures associated with HDACis sensitivity and resistance. The established signatures are then applied to identify cancer subtypes that are potentially sensitive or resistant to HDACis, and drugs that enhance the efficacy of HDACis. Finally, the reproductivity of the established HDACis signatures is evaluated by multiple independent drug response datasets and experimental assays.

FINDINGS

We successfully delineate generalizable gene signatures predicting sensitivity (containing 46 genes) and resistance (containing 53 genes) to all five HDACis, with their reproductivity confirmed by multiple external sources and independent internal assays. Using the gene signatures, we identify low-grade glioma harbouring isocitrate dehydrogenase 1/2 (IDH1/2) mutation and non-YAP1-driven subsets of small-cell lung cancer (SCLC) that particularly benefit from HDACis monotherapy. Further, based on the resistance gene signature, we identify clinically-approved Dasatinib as a synthetic lethal drug with HDACi, synergizing in inducing apoptosis and reactive oxygen species on a panel of SCLC. Finally, Dasatinib significantly enhances the therapeutic efficacy of Vorinostat in SCLC xenografts.

INTERPRETATION

Our work establishes robust gene signatures predicting HDACis sensitivity/resistance in solid cancer and uncovers combined Dasatinib/HDACi as a synthetic lethal combination therapy for SCLC.

FUNDING

This work was supported by the National Natural Science Foundation of China (82072570 to F. Yao; 82002941 to B. Sun).

Targeting Histone Modifications in Bone and Lung Metastatic Cancers

PURPOSE OF REVIEW

Breast cancer frequently metastasizes to the bone and lung, but the ability to treat metastatic tumor cells remains a pressing clinical challenge. Histone deacetylases (HDACs) and histone acetyltransferases (HATs) have emerged as promising targets since these enzymes are aberrantly expressed in numerous cancers and regulate the expression of genes that drive tumorigenesis and metastasis. This review focuses on the abnormal expression of histone-modifying enzymes in cancers that have a high tropism for the bone and lung and explores the clinical use of histone deacetylase inhibitors for the treatment and prevention of metastasis to these sites.

RECENT FINDINGS

Preclinical studies have demonstrated that the role for HDACs is highly dependent on tumor type and stage of disease progression. HDAC inhibitors can induce apoptosis, senescence, cell differentiation, and tumor dormancy genes and inhibit angiogenesis, making these promising therapeutics for the treatment of metastatic disease. HDAC inhibitors are already FDA approved for hematologic malignancies and are in clinical trials with standard-of-care chemotherapies and targeted agents for several solid tumors, including cases of metastatic disease. However, these drugs can negatively impact bone homeostasis. Although HDAC inhibitors are not currently administered for the treatment of bone and lung metastatic disease, preclinical studies have shown that these drugs can reduce distant metastasis by targeting molecular factors and signaling pathways that drive tumor cell dissemination to these sites. Thus, HDAC inhibitors in combination with bone protective therapies may be beneficial in the treatment of bone metastatic cancers.

Inactivation of the Akt/FOXM1 Signaling Pathway by Panobinostat Suppresses the Proliferation and Metastasis of Gastric Cancer Cells

Gastric cancer is the fifth most common cancer and the third leading cause of cancer-related deaths worldwide. Histone deacetylase (HDAC) inhibitors are a new class of cytostatic agents available for the treatment of various cancers and diseases. Although numerous clinical and pre-clinical trials on the anticancer effects of panobinostat have been conducted, only a few reports have investigated its efficacy in gastric cancer. The present study aimed to investigate the effects of panobinostat in gastric cancer cells. Panobinostat significantly inhibited the cell viability and proliferation of the gastric cancer cell lines SNU484 and SNU638 in a dose-dependent manner; it reduced the colony-forming ability of these cells. Moreover, it induced apoptosis as indicated by increased protein levels of cleaved poly ADP-ribose polymerase and cleaved caspase-3. Panobinostat induced the G2/M cell cycle arrest in SNU484 and SNU638 cells and subsequently decreased the G2/M phase regulatory-associated protein expression of p-Wee1, Myt1, and Cdc2. Furthermore, panobinostat significantly inhibited the metastasis of SNU484 and SNU638 cells by regulating the expression of MMP-9 and E-cadherin. Further, it decreased the protein levels of p-Akt and forkhead box protein M1 (FOXM1). These effects were reversed by the Akt agonist SC79 and were accelerated by the Akt inhibitor LY2940002. Moreover, tumor growth in xenograft animal experiments was suppressed by panobinostat. These results indicated that panobinostat inhibits the proliferation, metastasis, and cell cycle progression of gastric cancer cells by promoting apoptosis and inactivating Akt/FOXM1 signaling. Cumulatively, our present study suggests that panobinostat is a potential drug for the treatment of gastric cancer.

Identification of histone deacetylase inhibitors with (arylidene)aminoxy scaffold active in uveal melanoma cell lines

Uveal melanoma (UM) represents an aggressive type of cancer and currently, there is no effective treatment for this metastatic disease. In the last years, histone deacetylase inhibitors (HDACIs) have been studied as a possible therapeutic treatment for UM, alone or in association with other chemotherapeutic agents. Here we synthesised a series of new HDACIs based on the SAHA scaffold bearing an (arylidene)aminoxy moiety. Their HDAC inhibitory activity was evaluated on isolated human HDAC1, 3, 6, and 8 by fluorometric assay and their binding mode in the catalytic site of HDACs was studied by molecular docking. The most promising hit was the quinoline derivative VS13, a nanomolar inhibitor of HDAC6, which exhibited a good antiproliferative effect on UM cell lines at micromolar concentration and a capability to modify the mRNA levels of HDAC target genes similar to that of SAHA.

The dual HDAC-PI3K inhibitor CUDC-907 displays single-agent activity and synergizes with PARP inhibitor olaparib in small cell lung cancer

BACKGROUND

Small cell lung cancer (SCLC) is a deadly neuroendocrine tumor with limited therapeutic options. Recent data suggest that histone deacetylases (HDACs) and the phosphatidylinositol 3-kinase (PI3K) pathway play essential roles in SCLC cell proliferation and survival.

METHODS

The inhibition of the PI3K signaling and HDAC activity by CUDC-907 was analyzed by western blotting. The effect of CUDC-907 on olaparib-induced DNA damage response was assessed by western blotting and Immunofluorescence staining. The cytotoxicity of CUDC-907 alone or in combination with olaparib in a panel of SCLC cell lines were evaluated by the CellTiter-Glo Luminescent Cell Viability Assay and flow cytometry. The in vivo effects of CUDC-907 and olaparib alone or in combination were examined using a patient-derived xenografts (PDX) model of SCLC.

RESULTS

CUDC-907 treatment downregulated MYC paralogs and FoxM1, induced G1 cell-cycle arrest, and impaired DNA double-strand break (DSB) repair capacity in SCLC cells, which produced a potent antiproliferative effect. Furthermore, we showed that CUDC-907 treatment enhanced the therapeutic efficacy of PARP inhibitor olaparib in SCLC cellular models and a PDX model. Mechanistic investigations demonstrated that CUDC-907 synergized with olaparib through the blockade of DSB repair pathways and downregulation of MYC paralogs and FoxM1.

CONCLUSIONS

Our study uncovers that dual PI3K and HDAC inhibition by CUDC-907 exerts significant single-agent activity and strong synergistic effects with PARP inhibitor olaparib in SCLC, which thus provides a rational combination treatment strategy for SCLC clinical investigation.

The Use of Immunohistochemistry, Fluorescence in situ Hybridization, and Emerging Epigenetic Markers in the Diagnosis of Malignant Pleural Mesothelioma (MPM): A Review

Malignant pleural mesothelioma (MPM) is an aggressive asbestos related disease that is generally considered to be difficult to diagnose, stage and treat. The diagnostic process is continuing to evolve and requires highly skilled pathology input, and generally an extensive list of biomarkers for definitive diagnosis. Diagnosis of MPM requires histological evidence of invasion by malignant mesothelial cells often confirmed by various immunohistochemical biomarkers in order to separate it from pleural metastatic carcinoma. Often when invasion of neoplastic mesothelial cells into adjacent tissue is not apparent, further immunohistochemical testing - namely BAP1 and MTAP, as well as FISH testing for loss of p16 (CDKN2A) are used to separate reactive mesothelial proliferation due to benign processes, from MPM. Various combinations of these markers, such as BAP1 and/or MTAP immunohistochemistry alongside FISH testing for loss of p16, have shown excellent sensitivity and specificity in the diagnosis of MPM. Additionally, over the recent years, research into epigenetic marker use in the diagnosis of MPM has gained momentum. Although still in their research stages, various markers in DNA methylation, long non-coding RNA, micro RNA, circular RNA, and histone modifications have all been found to support diagnosis of MPM with generally good sensitivity and specificity. Many of these studies are however, limited by small sample sizes or other study limitations and further research into the area would be beneficial. Epigenetic markers show promise for use in the future to facilitate the diagnosis of MPM.

Targeting Piezo1 unleashes innate immunity against cancer and infectious disease

Piezo1 is a mechanosensitive ion channel that has gained recognition for its role in regulating diverse physiological processes. However, the influence of Piezo1 in inflammatory disease, including infection and tumor immunity, is not well studied. We postulated that Piezo1 links physical forces to immune regulation in myeloid cells. We found signal transduction via Piezo1 in myeloid cells and established this channel as the primary sensor of mechanical stress in these cells. Global inhibition of Piezo1 with a peptide inhibitor was protective against both cancer and septic shock and resulted in a diminution in suppressive myeloid cells. Moreover, deletion of Piezo1 in myeloid cells protected against cancer and increased survival in polymicrobial sepsis. Mechanistically, we show that mechanical stimulation promotes Piezo1-dependent myeloid cell expansion by suppressing the retinoblastoma gene Rb1 We further show that Piezo1-mediated silencing of Rb1 is regulated via up-regulation of histone deacetylase 2. Collectively, our work uncovers Piezo1 as a targetable immune checkpoint that drives immunosuppressive myelopoiesis in cancer and infectious disease.

The Biology of Malignant Mesothelioma and the Relevance of Preclinical Models

Malignant mesothelioma (MM), especially its more frequent form, malignant pleural mesothelioma (MPM), is a devastating thoracic cancer with limited therapeutic options. Recently, clinical trials that used immunotherapy strategies have yielded promising results, but the benefits are restricted to a limited number of patients. To develop new therapeutic strategies and define predictors of treatment response to existing therapy, better knowledge of the cellular and molecular mechanisms of MM tumors and sound preclinical models are needed. This review aims to provide an overview of our present knowledge and issues on both subjects. MM shows a complex pattern of molecular changes, including genetic, chromosomic, and epigenetic alterations. MM is also a heterogeneous cancer. The recently described molecular classifications for MPM could better consider inter-tumor heterogeneity, while histo-molecular gradients are an interesting way to consider both intra- and inter-tumor heterogeneities. Classical preclinical models are based on use of MM cell lines in culture or implanted in rodents, i.e., xenografts in immunosuppressed mice or isografts in syngeneic rodents to assess the anti-tumor immune response. Recent developments are tumoroids, patient-derived xenografts (PDX), xenografts in humanized mice, and genetically modified mice (GEM) that carry mutations identified in human MM tumor cells. Multicellular tumor spheroids are an interesting in vitro model to reduce animal experimentation; they are more accessible than tumoroids. They could be relevant, especially if they are co-cultured with stromal and immune cells to partially reproduce the human microenvironment. Even if preclinical models have allowed for major advances, they show several limitations: (i) the anatomical and biological tumor microenvironments are incompletely reproduced; (ii) the intra-tumor heterogeneity and immunological contexts are not fully reconstructed; and (iii) the inter-tumor heterogeneity is insufficiently considered. Given that these limitations vary according to the models, preclinical models must be carefully selected depending on the objectives of the experiments. New approaches, such as organ-on-a-chip technologies or in silico biological systems, should be explored in MM research. More pertinent cell models, based on our knowledge on mesothelial carcinogenesis and considering MM heterogeneity, need to be developed. These endeavors are mandatory to implement efficient precision medicine for MM.

Anti-leukemic effects of histone deacetylase (HDAC) inhibition in acute lymphoblastic leukemia (ALL) cells: Shedding light on mitigating effects of NF-κB and autophagy on panobinostat cytotoxicity

Identification of the roles of epigenetic alterations in cancers has suggested that different molecules involved in this process are potentially therapeutic targets. Given the role of histone deacetylases (HDACs) enzymes in leukemogenesis, we designed a study to investigate the anti-leukemic property of panobinostat, a HDAC inhibitor, in acute lymphoblastic leukemia (ALL) cells. Our results showed that panobinostat decreased cell viability of pre-B ALL-derived cells. The favorable anti-leukemic effects of the inhibitor was further confirmed by cell cycle analysis, where we found that panobinostat prolonged the transition of the cells from G1 phase probably through c-Myc-mediated up-regulation of cyclin-dependent kinase inhibitors. Unlike the apoptotic effect of panobinostat on Nalm-6 cells, the expression of anti-apoptotic nuclear factor-kappa B (NF-κB) target genes remained unchanged. Accordingly, we found that the inhibition of NF-κB pathway using bortezomib boosted the effect of panobinostat, indicating that panobinostat-induced apoptosis could be attenuated through the activation of the NF-κB pathway. The results of the present study reflected another aspect of autophagy in leukemic cells, as we showed that although Nalm-6 cells could exploit autophagy to override the anti-survival effect of HDAC inhibition, the presence of an autophagy inhibitor could alter the compensatory circumstance to induce cell death. Beyond panobinostat cytotoxicity as a single agent, synergistic experiments outlined that pharmaceutical targeting of HDACs could amplify the cytotoxicity of vincristine in ALL cells, delineating that panobinostat, either as a single agent or in a combined modality, possesses novel promising potentials for the treatment of ALL.

Pan-HDAC inhibitor panobinostat, as a single agent or in combination with PI3K inhibitor, induces apoptosis in APL cells: An emerging approach to overcome MSC-induced resistance

The emergence of the drugs targeting epigenetic alterations has brought an optimistic outlook for cancer patients and probably put an end into the devastating effects of the disease. Given to the prominent involvement of histone deacetylase (HDAC) enzymes in the formation of neoplastic nature of acute promyelocytic leukemia (APL), this study was aimed to evaluate the suppressive effect of pan-HDAC inhibitor panobinostat on both NB4 and primary APL patients cells, either in the context of mono- or co-culture with mesenchymal stem cells (MSC). Panobinostat effectively reduced the survival of APL cells; however, as compared to NB4, the viability of primary cells was inhibited at higher concentrations. Our results also showed that although HDAC inhibition could merely block the survival signals transduced from MSC, the presence of PI3K inhibitor could robustly reinforce panobinostat cytotoxicity; suggesting that MSC-induced activation of PI3K may attenuate, at least partly, the efficacy of HDAC inhibition in APL cells. In addition, cellular and molecular investigations on NB4 revealed that not only panobinostat induced p21-mediated G1 arrest and ROS-mediated apoptosis, but also exerted a superior cytotoxicity when combined with c-Myc and autophagy inhibitors. Last but not least, we found that panobinostat combined with arsenic trioxide (ATO) prompted a synergistic effect and provided an improved therapeutic value in NB4; proposing that the abrogation of HDAC using panobinostat might be a befitting approach in APL, either as a single agent or in a combined-modal strategy.

HDAC inhibitors rescue multiple disease-causing CFTR variants

Understanding the role of the epigenome in protein-misfolding diseases remains a challenge in light of genetic diversity found in the world-wide population revealed by human genome sequencing efforts and the highly variable response of the disease population to therapeutics. An ever-growing body of evidence has shown that histone deacetylase (HDAC) inhibitors (HDACi) can have significant benefit in correcting protein-misfolding diseases that occur in response to both familial and somatic mutation. Cystic fibrosis (CF) is a familial autosomal recessive disease, caused by genetic diversity in the CF transmembrane conductance regulator (CFTR) gene, a cyclic Adenosine MonoPhosphate (cAMP)-dependent chloride channel expressed at the apical plasma membrane of epithelial cells in multiple tissues. The potential utility of HDACi in correcting the phenylalanine 508 deletion (F508del) CFTR variant as well as the over 2000 CF-associated variants remains controversial. To address this concern, we examined the impact of US Food and Drug Administration-approved HDACi on the trafficking and function of a panel of CFTR variants. Our data reveal that panobinostat (LBH-589) and romidepsin (FK-228) provide functional correction of Class II and III CFTR variants, restoring cell surface chloride channel activity in primary human bronchial epithelial cells. We further demonstrate a synergistic effect of these HDACi with Vx809, which can significantly restore channel activity for multiple CFTR variants. These data suggest that HDACi can serve to level the cellular playing field for correcting CF-causing mutations, a leveling effect that might also extend to other protein-misfolding diseases.

Workshop summary: Potential usefulness and feasibility of a US National Mesothelioma Registry

The burden and prognosis of malignant mesothelioma in the United States have remained largely unchanged for decades, with approximately 3200 new cases and 2400 deaths reported annually. To address care and research gaps contributing to poor outcomes, in March of 2019 the Mesothelioma Applied Research Foundation convened a workshop on the potential usefulness and feasibility of a national mesothelioma registry. The workshop included formal presentations by subject matter experts and a moderated group discussion. Workshop participants identified top priorities for a registry to be (a) connecting patients with high-quality care and clinical trials soon after diagnosis, and (b) making useful data and biospecimens available to researchers in a timely manner. Existing databases that capture mesothelioma cases are limited by factors such as delays in reporting, deidentification, and lack of exposure information critical to understanding as yet unrecognized causes of disease. National disease registries for amyotrophic lateral sclerosis (ALS) in the United States and for mesothelioma in other countries, provide examples of how a registry could be structured to meet the needs of patients and the scientific community. Small-scale pilot initiatives should be undertaken to validate methods for rapid case identification, develop procedures to facilitate patient access to guidelines-based standard care and investigational therapies, and explore approaches to data sharing with researchers. Ultimately, federal coordination and funding will be critical to the success of a National Mesothelioma Registry in improving mesothelioma outcomes and preventing future cases of this devastating disease.

1,25-Dihydroxyvitamin D3 Prevents Epithelial-Mesenchymal Transition of HMrSV5 Human Peritoneal Mesothelial Cells by Inhibiting Histone Deacetylase 3 (HDAC3) and Increasing Vitamin D Receptor (VDR) Expression Through the Wnt/β-Catenin Signaling Pathway

Background

Peritoneal dialysis is the most common treatment for end-stage renal disease. However, peritoneal fibrosis resulting from long-term peritoneal dialysis restricts peritoneal ultrafiltration. Previous studies have shown a role for 1,25-dihydroxyvitamin D3 (1,25[OH]₂D3) in preventing fibrosis, but the potential mechanisms remain unknown. This study aimed to investigate the role of 1,25(OH)₂D3 in epithelial-mesenchymal transition (EMT) and the downstream signaling pathway in HMrSV5 human peritoneal mesothelial cells in vitro.

Material/Methods

An in vitro cell model of peritoneal fibrosis was established using the HMrSV5 human peritoneal mesothelial cell line. High glucose and lipopolysaccharide (LPS) culture conditions, with or without 1,25(OH)₂D3, were used. Wnt agonist 1, a Wnt signaling pathway activator, was applied. Quantitative real-time polymerase chain reaction (qRT-PCR) and western blot were used to measure the vitamin D receptor (VDR) and histone deacetylase 3 (HDAC3) gene and protein expression levels, β-catenin, and EMT-associated biomarkers.

Results

High glucose plus LPS culture medium inhibited cell proliferation, induced cell apoptosis and promoted EMT in HMrSV5 cells, which was reversed by 1,25(OH)₂D3 by down-regulation of HDAC3 and upregulation of VDR. HDAC3 inhibited VDR gene expression. The expression of EMT-associated biomarkers was increased by Wnt agonist 1 and inhibited by 1,25(OH)₂D3.

Conclusions

In HMrSV5 human peritoneal mesothelial cells, 1,25(OH)₂D3 reversed EMT by inhibiting the expression of HDAC3 and upregulating VDR gene expression via the Wnt/β-catenin signaling pathway.

Phase I trial of belinostat with cisplatin and etoposide in advanced solid tumors, with a focus on neuroendocrine and small cell cancers of the lung

The standard-of-care for advanced small cell lung cancer (SCLC) is chemotherapy with cisplatin+etoposide (C+E). Most patients have chemosensitive disease at the outset, but disease frequently relapses and limits survival. Efforts to improve therapeutic outcomes in SCLC and other neuroendocrine cancers have focused on epigenetic agents, including the histone deacetylase inhibitor belinostat. The primary objective was to determine the maximum tolerated dose of the combination of belinostat (B) with C+E. Belinostat was administered as a 48-h continuous intravenous infusion on days 1-2; cisplatin was administered as a 1-h intravenous infusion on day 2; and etoposide was administered as a 1-h intravenous infusion on days 2, 3, and 4. Twenty-eight patients were recruited in this single-center study. The maximum tolerated dose was belinostat 500 mg/m/24 h, cisplatin 60 mg/m, and etoposide 80 mg/m. The combination was safe, although some patients were more susceptible to adverse events. Hematologic toxicities were most commonly observed. Objective responses were observed in 11 (39%) of 28 patients and seven (47%) of 15 patients with neuroendocrine tumors (including SCLC). Patients carrying more than three copies of variant UGT1A1 (*28 and *60) had higher serum levels of belinostat because of slower clearance. DNA damage peaked at 36 h after the initiation of belinostat, as did global lysine acetylation, but returned to baseline 12 h after the end of infusion. The combination of B+C+E is safe and active in SCLC and other neuroendocrine cancers. Future phase II studies should consider genotyping patients for UGT1A1*28 and UGT1A1*60 and to identify patients at an increased risk of adverse events.

Sodium butyrate and panobinostat induce apoptosis of chronic myeloid leukemia cells via multiple pathways

Purpose

Histone deacetylase inhibitor (HDACI) is a novel therapeutic option for cancer. However, the effects of HDACIs on chronic myeloid leukemia (CML) and the underlying mechanisms are still unknown. The aim of this study was to investigate the effect and the mechanism‐of‐action of two HDACI members, sodium butyrate (NaBu) and panobinostat (LBH589) in K562 and the adriamycin–resistant cell line K562/ADR.

Methods

Cell viability was assessed using MTT assay. Cell apoptosis was detected with flow cytometry. Cell cycle analysis and western blot were performed to explore the possible molecules related to HDACIs effects.

Results

The effect of NaBu was more powerful on K562/ADR than on K562 cells. LBH589 triggered apoptosis and inhibited the growth of K562 cells. Both HDACIs inhibited K562 and K562/ADR cells via activation of intrinsic/extrinsic apoptotic pathways and inhibition of AKT‐mTOR pathway while NaBu also activated endoplasmic reticulum stress (ERS) mediated apoptotic pathway in K562/ADR cells. LBH589 reduced the expression of drug–resistant related proteins in K562 cells. However, neither NaBu nor LBH589 could significantly influence the expression of the drug–resistant related proteins in K562/ADR cells.

Conclusion

The combination of HDACI and other therapeutic strategies are likely required to overcome drug resistance in CML therapy.

Panobinostat (LBH589) inhibits Wnt/β-catenin signaling pathway via upregulating APCL expression in breast cancer

Breast cancer is the most common malignant disease among women worldwide and the novel therapeutic agents are urgently needed. Panobinostat (LBH589), a pan-HDACs inhibitor, has shown promising anti-tumor effect in recent years. However, the targets of this compound are largely unclear because of its low selectivity. In consideration of the transcription promoting activity of panobinostat, we speculated that specific tumor suppressor genes might be upregulated after panobinostat treatment. In this study, we verified the inhibition effect of panobinostat in different subtypes of breast cancer cells in vivo and in vitro. We found that panobinostat suppressed proliferation, migration as well as invasion, and induced apoptosis in both TNBC and non-TNBC cells. Consistently, panobinostat inhibited breast cancer growth and metastasis in mouse models. Mechanistically, we found APCL transcription and expression was significantly upregulated in panobinostat treated cells by RNA microarray analysis, while knockdown of APCL resulted in reduced sensitivity to panobinostat in breast cancer cells. APCL is a wnt/β-catenin pathway regulator that promotes β-catenin ubiquitylation and degradation. We found that panobinostat inhibited β-catenin expression by increasing its ubiquitylation and thus reducing its half-life. In addition, the expression of β-catenin activated targets including c-Jun, c-Myc, Cyclin D1 and CD44 were also decreased by panobinostat treatment in breast cancer cells. These results suggested that panobinostat inhibited tumor growth and metastasis via upregulating APCL expression in breast cancer cells, which was a novel and crucial mechanism of panobinostat.

Comparison of the antifibrotic effects of the pan-histone deacetylase-inhibitor panobinostat versus the IPF-drug pirfenidone in fibroblasts from patients with idiopathic pulmonary fibrosis

Background

Idiopathic pulmonary fibrosis (IPF) is a devastating lung disease with a poor prognosis. Pirfenidone is the first antifibrotic agent to be approved for IPF-treatment as it is able to slow down disease progression. However, there is no curative treatment other than lung transplantation. Because epigenetic alterations are associated with IPF, histone deacetylase (HDAC)-inhibitors have recently been proven to attenuate fibrotic remodeling in vitro and in vivo. This study compared the effects of pirfenidone with the pan-HDAC-inhibitor panobinostat/LBH589, a FDA-approved drug for the treatment of multiple myeloma, head-to-head on survival, fibrotic activity and proliferation of primary IPF-fibroblasts in vitro.

Methods

Primary fibroblasts from six IPF-patients were incubated for 24h with vehicle (0.25% DMSO), panobinostat (LBH589, 85 nM) or pirfenidone (2.7 mM), followed by assessment of proliferation and expression analyses for profibrotic and anti-apoptosis genes, as well as for ER stress and apoptosis-markers. In addition, the expression status of all HDAC enzymes was examined.

Results

Treatment of IPF-fibroblasts with panobinostat or pirfenidone resulted in a downregulated expression of various extracellular matrix (ECM)-associated genes, as compared to vehicle-treated cells. In agreement, both drugs decreased protein level of phosphorylated (p)-STAT3, a transcription factor mediating profibrotic responses, in treated IPF-fibroblasts. Further, an increase in histone acetylation was observed in response to both treatments, but was much more pronounced and excessive in panobinostat-treated IPF-fibroblasts. Panobinostat, but not pirfenidone, led to a significant suppression of proliferation in IPF-fibroblasts, as indicated by WST1- and BrdU assay and markedly diminished levels of cyclin-D1 and p-histone H3. Furthermore, panobinostat-treatment enhanced α-tubulin-acetylation, decreased the expression of survival-related genes Bcl-XL and BIRC5/survivin, and was associated with induction of ER stress and apoptosis in IPF-fibroblasts. In contrast, pirfenidone-treatment maintained Bcl-XL expression, and was neither associated with ER stress-induction nor any apoptotic signaling. Pirfenidone also led to increased expression of HDAC6 and sirtuin-2, and enhanced α-tubulin-deacetylation. But in line with its ability to increase histone acetylation, pirfenidone reduced the expression of HDAC enzymes HDAC1, -2 and -9.

Conclusions

We conclude that, beside other antifibrotic mechanisms, pirfenidone reduces profibrotic signaling also through STAT3 inactivation and weak epigenetic alterations in IPF-fibroblasts, and permits survival of (altered) fibroblasts. The pan-HDAC-inhibitor panobinostat reduces profibrotic phenotypes while inducing cell cycle arrest and apoptosis in IPF-fibroblasts, thus indicating more efficiency than pirfenidone in inactivating IPF-fibroblasts. We therefore believe that HDAC-inhibitors such as panobinostat can present a novel therapeutic strategy for IPF.

Histone deacetylase inhibitor panobinostat potentiates the anti-cancer effects of mesenchymal stem cell-based sTRAIL gene therapy against malignant glioma

Human adipose tissue-derived mesenchymal stem cells expressing the secreted form of the tumor necrosis factor-related apoptosis-inducing ligand (hAT-MSC.sTRAIL) have demonstrated therapeutic activity against various tumors in preclinical studies. However, the limited expression of TRAIL death receptors remains a challenge. We evaluated the therapeutic efficacy of panobinostat in enhancing the sensitivity of hAT-MSC.sTRAIL-mediated apoptosis in malignant glioma. Panobinostat effectively inhibited all malignant glioma cells (IC₅₀, 0.03-0.23 μM), enhancing the expression of DRs, but not in hAT-MSCs. Combined treatment with hAT-MSC.sTRAIL and panobinostat significantly suppressed cell viability and enhanced apoptosis. In a diffuse intrinsic pontine glioma (DIPG) mouse model, the combined treatment induced decreases in tumor volume and prolonged survival. Our study demonstrates that panobinostat enhances the expression of TRAIL DRs and potentiates the anti-cancer effects of hAT-MSC.sTRAIL.

The histone deacetylase inhibitor panobinostat is a potent antitumor agent in canine diffuse large B-cell lymphoma

Non-Hodgkin lymphoma (NHL) is one of the most common causes of cancer-related death in the United States and Europe. Although the outcome of NHL patients has improved over the last years with current therapies, the rate of mortality is still high. A plethora of new drugs is entering clinical development for NHL treatment; however, the approval of new treatments remains low due in part to the paucity of clinically relevant models for validation. Canine lymphoma shares remarkable similarities with its human counterpart, making the dog an excellent animal model to explore novel therapeutic molecules and approaches. Histone deacetylase inhibitors (HDACis) have emerged as a powerful new class of anti-cancer drugs for human therapy. To investigate HDACi antitumor properties on canine diffuse large B-cell lymphoma, a panel of seven HDACi compounds (CI-994, panobinostat, SBHA, SAHA, scriptaid, trichostatin A and tubacin) was screened on CLBL-1 canine B-cell lymphoma cell line. Our results demonstrated that all HDACis tested exhibited dose-dependent inhibitory effects on proliferation of CLBL-1 cells, while promoting increased H3 histone acetylation. Amongst all HDACis studied, panobinostat proved to be the most promising compound and was selected for further in vitro and in vivo evaluation. Panobinostat cytotoxicity was linked to H3 histone and α-tubulin acetylation, and to apoptosis induction. Importantly, panobinostat efficiently inhibited CLBL-1 xenograft tumor growth, and strongly induced acetylation of H3 histone and apoptosis in vivo. In conclusion, these results provide new data validating HDACis and, especially, panobinostat as a novel anti-cancer therapy for veterinary applications, while contributing to comparative oncology.

Targeting FBPase is an emerging novel approach for cancer therapy

Cancer is a leading cause of death in both developed and developing countries. Metabolic reprogramming is an emerging hallmark of cancer. Glucose homeostasis is reciprocally controlled by the catabolic glycolysis and anabolic gluconeogenesis pathways. Previous studies have mainly focused on catabolic glycolysis, but recently, FBPase, a rate-limiting enzyme in gluconeogenesis, was found to play critical roles in tumour initiation and progression in several cancer types. Here, we review recent ideas and discoveries that illustrate the clinical significance of FBPase expression in various cancers, the mechanism through which FBPase influences cancer, and the mechanism of FBPase silencing. Furthermore, we summarize some of the drugs targeting FBPase and discuss their potential use in clinical applications and the problems that remain unsolved.

Radiosensitization In Vivo by Histone Deacetylase Inhibition with No Increase in Early Normal Tissue Radiation Toxicity

As the population ages, more elderly patients require radiotherapy-based treatment for their pelvic malignancies, including muscle-invasive bladder cancer, as they are unfit for major surgery. Therefore, there is an urgent need to find radiosensitizing agents minimally toxic to normal tissues, including bowel and bladder, for such patients. We developed methods to determine normal tissue toxicity severity in intestine and bladder in vivo, using novel radiotherapy techniques on a small animal radiation research platform (SARRP). The effects of panobinostat on in vivo tumor growth delay were evaluated using subcutaneous xenografts in athymic nude mice. Panobinostat concentration levels in xenografts, plasma, and normal tissues were measured in CD1-nude mice. CD1-nude mice were treated with drug/irradiation combinations to assess acute normal tissue effects in small intestine using the intestinal crypt assay, and later effects in small and large intestine at 11 weeks by stool assessment and at 12 weeks by histologic examination. In vitro effects of panobinostat were assessed by qPCR and of panobinostat, TMP195, and mocetinostat by clonogenic assay, and Western blot analysis. Panobinostat resulted in growth delay in RT112 bladder cancer xenografts but did not significantly increase acute (3.75 days) or 12 weeks' normal tissue radiation toxicity. Radiosensitization by panobinostat was effective in hypoxic bladder cancer cells and associated with class I HDAC inhibition, and protein downregulation of HDAC2 and MRE11. Pan-HDAC inhibition is a promising strategy for radiosensitization, but more selective agents may be more useful radiosensitizers clinically, resulting in fewer systemic side effects. Mol Cancer Ther; 17(2); 381-92. ©2017 AACRSee all articles in this MCT Focus section, "Developmental Therapeutics in Radiation Oncology."

Safety and Efficacy of Intratumoral Injections of Chimeric Antigen Receptor (CAR) T Cells in Metastatic Breast Cancer

Chimeric antigen receptors (CAR) are synthetic molecules that provide new specificities to T cells. Although successful in treatment of hematologic malignancies, CAR T cells are ineffective for solid tumors to date. We found that the cell-surface molecule c-Met was expressed in ∼50% of breast tumors, prompting the construction of a CAR T cell specific for c-Met, which halted tumor growth in immune-incompetent mice with tumor xenografts. We then evaluated the safety and feasibility of treating metastatic breast cancer with intratumoral administration of mRNA-transfected c-Met-CAR T cells in a phase 0 clinical trial (NCT01837602). Introducing the CAR construct via mRNA ensured safety by limiting the nontumor cell effects (on-target/off-tumor) of targeting c-Met. Patients with metastatic breast cancer with accessible cutaneous or lymph node metastases received a single intratumoral injection of 3 × 10⁷ or 3 × 10⁸ cells. CAR T mRNA was detectable in peripheral blood and in the injected tumor tissues after intratumoral injection in 2 and 4 patients, respectively. mRNA c-Met-CAR T cell injections were well tolerated, as none of the patients had study drug-related adverse effects greater than grade 1. Tumors treated with intratumoral injected mRNA c-Met-CAR T cells were excised and analyzed by immunohistochemistry, revealing extensive tumor necrosis at the injection site, cellular debris, loss of c-Met immunoreactivity, all surrounded by macrophages at the leading edges and within necrotic zones. We conclude that intratumoral injections of mRNA c-Met-CAR T cells are well tolerated and evoke an inflammatory response within tumors. Cancer Immunol Res; 5(12); 1152-61. ©2017 AACR.

Mevastatin blockade of autolysosome maturation stimulates LBH589-induced cell death in triple-negative breast cancer cells

Histone deacetylase inhibitors (HDACi) are promising anti-cancer agents, and combining a HDACi with other agents is an attractive therapeutic strategy in solid tumors. We report here that mevastatin increases HDACi LBH589-induced cell death in triple-negative breast cancer (TNBC) cells. Combination treatment inhibited autophagic flux by preventing Vps34/Beclin 1 complex formation and downregulating prenylated Rab7, an active form of the small GTPase necessary for autophagosome-lysosome fusion. This means that co-treatment with mevastatin and LBH589 activated LKB1/AMPK signaling and subsequently inhibited mTOR. Co-treatment also led to cell cycle arrest in G2/M phase and induced corresponding expression changes of proteins regulating the cell cycle. Co-treatment also increased apoptosis both in vitro and in vivo, and reduced tumor volumes in xenografted mice. Our results indicate that disruption of autophagosome-lysosome fusion likely underlies mevastatin-LBH589 synergistic anticancer effects. This study confirms the synergistic efficacy of, and demonstrates a potential therapeutic role for mevastatin plus LBH589 in targeting aggressive TNBC, and presents a novel therapeutic strategy for further clinical study. Further screening for novel autophagy modulators could be an efficient approach to enhance HDACi-induced cell death in solid tumors.

Cooperative effect of chidamide and chemotherapeutic drugs induce apoptosis by DNA damage accumulation and repair defects in acute myeloid leukemia stem and progenitor cells

BACKGROUND

Many conventional chemotherapeutic drugs are known to be involved in DNA damage, thus ultimately leading to apoptosis of leukemic cells. However, they fail to completely eliminate leukemia stem cells (LSCs) due to their higher DNA repair capacity of cancer stem cells than that of bulk cancer cells, which becomes the root of drug resistance and leukemia recurrence. A new strategy to eliminate LSCs in acute myeloid leukemia (AML) is therefore urgently needed.

RESULTS

We report that a low-dose chidamide, a novel orally active benzamide-type histone deacetylase (HDAC) inhibitor, which selectively targets HDACs 1, 2, 3, and 10, could enhance the cytotoxicity of DNA-damaging agents (daunorubicin, idarubicin, and cytarabine) in CD34⁺CD38^- KG1α cells, CD34⁺CD38^- Kasumi cells, and primary refractory or relapsed AML CD34⁺ cells, reflected by the inhibition of cell proliferation, induction of apoptosis, and increase of cell cycle arrest in vitro. Mechanistically, these events were associated with DNA damage accumulation and repair defects. Co-treatment with chidamide and the DNA-damaging agent IDA gave rise to the production of γH2A.X and inhibited posttranslationally but not transcriptionally the repair gene of ATM, BRCA1, and checkpoint kinase 1 (CHK1) and 2 (CHK2) phosphorylation. Finally, the combination of chidamide and IDA initiated caspase-3 and PARP cleavage, but not caspase-8 and caspase-9, and ultimately induced CD34⁺CD38^- KG1α cell apoptosis. Further analysis of AML patients' clinical characteristics revealed that the ex vivo efficacy of chidamide in combination with IDA in primary CD34⁺ samples was significantly correlated to peripheral blood WBC counts at diagnosis, while LDH levels and karyotype status had no effect, indicating that the combination regimen of chidamide and IDA could rapidly diminish tumor burden in patients with R/R AML.

CONCLUSIONS

These findings provide preclinical evidence for low-dose chidamide in combination with chemotherapeutic agents in treating recurrent/resistant AML as an alternative salvage regimen, especially those possessing stem and progenitor cells.

Panobinostat sensitizes KRAS-mutant non-small-cell lung cancer to gefitinib by targeting TAZ

Mutation of KRAS in non-small-cell lung cancer (NSCLC) shows a poor response to epidermal growth factor receptor (EGFR) inhibitors and chemotherapy. Currently, there are no direct anti-KRAS therapies available. Thus, new strategies have emerged for targeting KRAS downstream signaling. Panobinostat is a clinically available histone deacetylase inhibitor for treating myelomas and also shows potentiality in NSCLC. However, the therapeutic efficacy of panobinostat against gefitinib-resistant NSCLC is unclear. In this study, we demonstrated that panobinostat overcame resistance to gefitinib in KRAS-mutant/EGFR-wild-type NSCLC. Combined panobinostat and gefitinib synergistically reduced tumor growth in vitro and in vivo. Mechanistically, we identified that panobinostat-but not gefitinib-inhibited TAZ transcription, and the combination of panobinostat and gefitinib synergistically downregulated TAZ and TAZ downstream targets, including EGFR and EGFR ligand. Inhibition of TAZ by panobinostat or short hairpin RNA sensitized KRAS-mutant/EGFR-wild-type NSCLC to gefitinib through abrogating AKT/mammalian target of rapamycin (mTOR) signaling. Clinically, TAZ was positively correlated with EGFR signaling, and coexpression of TAZ/EGFR conferred a poorer prognosis in lung cancer patients. Our findings identify that targeting TAZ-mediated compensatory mechanism is a novel therapeutic approach to overcome gefitinib resistance in KRAS-mutant/EGFR-wild-type NSCLC.

Synergistic Immunostimulatory Effects and Therapeutic Benefit of Combined Histone Deacetylase and Bromodomain Inhibition in Non-Small Cell Lung Cancer

Effective therapies for non-small cell lung cancer (NSCLC) remain challenging despite an increasingly comprehensive understanding of somatically altered oncogenic pathways. It is now clear that therapeutic agents with potential to impact the tumor immune microenvironment potentiate immune-orchestrated therapeutic benefit. Herein, we evaluated the immunoregulatory properties of histone deacetylase (HDAC) and bromodomain inhibitors, two classes of drugs that modulate the epigenome, with a focus on key cell subsets that are engaged in an immune response. By evaluating human peripheral blood and NSCLC tumors, we show that the selective HDAC6 inhibitor ricolinostat promotes phenotypic changes that support enhanced T-cell activation and improved function of antigen-presenting cells. The bromodomain inhibitor JQ1 attenuated CD4⁺FOXP3⁺ T regulatory cell suppressive function and synergized with ricolinostat to facilitate immune-mediated tumor growth arrest, leading to prolonged survival of mice with lung adenocarcinomas. Collectively, our findings highlight the immunomodulatory effects of two epigenetic modifiers that, together, promote T cell-mediated antitumor immunity and demonstrate their therapeutic potential for treatment of NSCLC.Significance: Selective inhibition of HDACs and bromodomain proteins modulates tumor-associated immune cells in a manner that favors improved T-cell function and reduced inhibitory cellular mechanisms. These effects facilitated robust antitumor responses in tumor-bearing mice, demonstrating the therapeutic potential of combining these epigenetic modulators for the treatment of NSCLC. Cancer Discov; 7(8); 852-67. ©2017 AACR.This article is highlighted in the In This Issue feature, p. 783.

Inhibiting histone deacetylases suppresses glucose metabolism and hepatocellular carcinoma growth by restoring FBP1 expression

Hepatocellular carcinoma (HCC) is one of the most commonly diagnosed cancers in the world. Elevated glucose metabolism in the availability of oxygen, a phenomenon called the Warburg effect, is important for cancer cell growth. Fructose-1,6-bisphosphatase (FBP1) is a rate-limiting enzyme in gluconeogenesis and is frequently lost in various types of cancer. Here, we demonstrated that expression of FBP1 was downregulated in HCC patient specimens and decreased expression of FBP1 associated with poor prognosis. Low expression of FBP1 correlated with high levels of histone deacetylase 1 (HDAC1) and HDAC2 proteins in HCC patient tissues. Treatment of HCC cells with HDAC inhibitors or knockdown of HDAC1 and/or HDAC2 restored FBP1 expression and inhibited HCC cell growth. HDAC-mediated suppression of FBP1 expression correlated with decreased histone H3 lysine 27 acetylation (H3K27Ac) in the FBP1 enhancer. Restored expression of FBP1 decreased glucose reduction and lactate secretion and inhibited HCC cell growth in vitro and tumor growth in mice. Our data reveal that loss of FBP1 due to histone deacetylation associates with poor prognosis of HCC and restored FBP1 expression by HDAC inhibitors suppresses HCC growth. Our findings suggest that repression of FBP1 by HDACs has important implications for HCC prognosis and treatment.

Clinical outcomes and prognostic factors of patients with advanced mesothelioma treated in a phase I clinical trials unit

BACKGROUND

We have previously reported a prognostic score for patients in phase I trials in the Drug Development Unit, treated at the Royal Marsden Hospital (RPS). The RPS is an objective tool used in patient selection for phase I trials based on albumin, number of disease sites and LDH. Patients with mesothelioma are often selected for phase I trials as the disease remains localised for long periods of time. We have now reviewed the clinical outcomes of patients with relapsed malignant mesothelioma (MM) and propose a specific mesothelioma prognostic score (m-RPS) that can help identify patients who are most likely to benefit from early referral.

METHODS

Patients who participated in 38 phase I trials between September 2003 and November 2015 were included in the analysis. Efficacy was assessed by response rate, median overall survival (OS) and progression-free survival (PFS). Univariate (UVA) and multivariate analyses (MVA) were carried out to develop the m-RPS.

RESULTS

A total of 65 patients with advanced MM were included in this retrospective study. The PFS was 2.5 months (95% confidence interval [CI] 2.0-3.1 months) and OS was 8 months (95% CI 5.6-9.8 months). A total of four (6%) patients had RECIST partial responses, whereas 26 (40%) patients had RECIST stable disease >3 months. The m-RPS was developed comprising of three different prognostic factors: a neutrophil: lymphocyte ratio greater than 3, the presence of more than two disease sites (including lymph nodes as a single site of disease) and albumin levels less than 35 from the MVA. Patients each received a score of 1 for the presence of each factor. Patients in group A (m-RPS 0-1; n = 35) had a median OS of 13.4 months (95% CI 8.5-21.6), whereas those in group B (m-RPS 2-3; n = 30) had a median OS of 4.0 months (95% CI 2.9-7.1, P < 0.0001). A total of 56 (86%) patients experienced G1-2 toxicities, whereas reversible G3-4 toxicities were observed in 18 (28%) patients. Only 10 (15%) patients discontinued phase I trials due to toxicity.

CONCLUSIONS

Phase I clinical trial therapies were well tolerated with early signals of antitumour activity in advanced MM patients. The m-RPS is a useful tool to assess MM patient suitability for phase I trials and should now be prospectively validated.

Research Priorities for Endometriosis

The 3rd International Consensus Workshop on Research Priorities in Endometriosis was held in São Paulo on May 4, 2014, following the 12th World Congress on Endometriosis. The workshop was attended by 60 participants from 19 countries and was divided into 5 main sessions covering pathogenesis/pathophysiology, symptoms, diagnosis/classification/prognosis, disease/symptom management, and research policy. This research priorities consensus statement builds on earlier efforts to develop research directions for endometriosis. Of the 56 research recommendations from the 2011 meeting in Montpellier, a total of 41 remained unchanged, 13 were updated, and 2 were deemed to be completed. Fifty-three new research recommendations were made at the 2014 meeting in Sao Paulo, which in addition to the 13 updated recommendations resulted in a total of 66 new recommendations for research. The research recommendations published herein, as well as those from the 2 previous papers from international consensus workshops, are an attempt to promote high-quality research in endometriosis by identifying and agreeing on key issues that require investigation. New areas included in the 2014 recommendations include infertility, patient stratification, and research in emerging nations, in addition to an increased focus on translational research. A revised and updated set of research priorities that builds on this document will be developed at the 13th World Congress on Endometriosis to be held on May 17-20, 2017, in Vancouver, British Columbia, Canada.

Design and synthesis of benzodiazepine analogs as isoform-selective human lysine deacetylase inhibitors

A comprehensive investigation was performed to identify new benzodiazepine (BZD) derivatives as potent and selective human lysine deacetylase inhibitors (hKDACis). A total of 108 BZD compounds were designed, synthesized and from that 104 compounds were biologically evaluated against human lysine deacetylases (hKDACs) 1, 3 and 8 (class I) and 6 (class IIb). The most active compounds showed mid-nanomolar potencies against hKDACs 1, 3 and 6 and micromolar activity against hKDAC8, while a promising compound (6q) showed selectivity towards hKDAC3 among the different enzyme isoforms. An hKDAC6 homology model, refined by molecular dynamics simulation was generated, and molecular docking studies performed to rationalize the dominant ligand-residue interactions as well as to define structure-activity-relationships. Experimental results confirmed the usefulness of the benzodiazepine moiety as capping group when pursuing hKDAC isoform-selectivity inhibition, suggesting its continued use when designing new hKDACis.

Intratumoral Immunization by p19Arf and Interferon-β Gene Transfer in a Heterotopic Mouse Model of Lung Carcinoma

Therapeutic strategies that act by eliciting and enhancing antitumor immunity have been clinically validated as an effective treatment modality but may benefit from the induction of both cell death and immune activation as primary stimuli. Using our AdRGD-PG adenovector platform, we show here for the first time that in situ gene transfer of p19Arf and interferon-β (IFNβ) in the LLC1 mouse model of lung carcinoma acts as an immunotherapy. Although p19Arf is sufficient to induce cell death, only its pairing with IFNβ significantly induced markers of immunogenic cell death. In situ gene therapy with IFNβ, either alone or in combination with p19Arf, could retard tumor progression, but only the combined treatment was associated with a protective immune response. Specifically in the case of combined intratumoral gene transfer, we identified 167 differentially expressed genes when using microarray to evaluate tumors that were treated in vivo and confirmed the activation of CCL3, CXCL3, IL1α, IL1β, CD274, and OSM, involved in immune response and chemotaxis. Histologic evaluation revealed significant tumor infiltration by neutrophils, whereas functional depletion of granulocytes ablated the antitumor effect of our approach. The association of in situ gene therapy with cisplatin resulted in synergistic elimination of tumor progression. In all, in situ gene transfer with p19Arf and IFNβ acts as an immunotherapy involving recruitment of neutrophils, a desirable but previously untested outcome, and this approach may be allied with chemotherapy, thus providing significant antitumor activity and warranting further development for the treatment of lung carcinoma.

Vorinostat enhances the cisplatin-mediated anticancer effects in small cell lung cancer cells

BACKGROUND

Vorinostat, a histone deacetylase (HDAC) inhibitor, is a promising agent for cancer therapy. Combining vorinostat with cisplatin may relax the chromatin structure and facilitate the accessibility of cisplatin, thus enhancing its cytotoxicity. Studies have not yet investigated the effects of the combination of vorinostat and cisplatin on small cell lung cancer (SCLC).

METHODS

We first assessed the efficacy of vorinostat with etoposide/cisplatin (EP; triple combination) and then investigated the effects of cotreatment with vorinostat and cisplatin on H209 and H146 SCLC cell lines. The anticancer effects of various combinations were determined in terms of cell viability, apoptosis, cell cycle distribution, and vorinostat-regulated proteins. We also evaluated the efficacy of vorinostat/cisplatin combination in H209 xenograft nude mice.

RESULTS

Our data revealed that the triple combination engendered a significant reduction of cell viability and high apoptotic cell death. In addition, vorinostat combined with cisplatin enhanced cell growth inhibition, induced apoptosis, and promoted cell cycle arrest. We observed that the acetylation levels of histone H3 and α-tubulin were higher in combination treatments than in vorinostat treatment alone. Moreover, vorinostat reduced the expression of thymidylate synthase (TS), and TS remained inhibited after cotreament with cisplatin. Furthermore, an in vivo study revealed that the combination of vorinostat and cisplatin significantly inhibited tumor growth in xenograft nude mice (tumor growth inhibition T/C% = 20.5 %).

CONCLUSIONS

Combined treatments with vorinostat promote the cytotoxicity of cisplatin and induce the expression of vorinostat-regulated acetyl proteins, eventually enhancing antitumor effects in SCLC cell lines. Triple combinations with a low dosage of cisplatin demonstrate similar therapeutic effects. Such triple combinations, if applied clinically, may reduce the undesired adverse effects of cisplatin. The effects of the combination of vorinostat and cisplatin should be evaluated further before conducting clinical trials for SCLC treatment.

Panobinostat induces apoptosis via production of reactive oxygen species and synergizes with topoisomerase inhibitors in cervical cancer cells

Cervical cancer is the fourth major cause of cancer-related deaths in women worldwide and is the most common cancer in developing countries. Therefore, a search for novel treatment modalities is warranted. The present study is designed to investigate the effect of pan histone deacetylase inhibitor, 'panobinostat', on cervical cancer cells alone and in combination with topoisomerase inhibitors. We assessed the effect of panobinostat on two cervical cancer cell lines, HeLa and SiHa, for cell viability, apoptosis, oxidative stress and mitochondrial function using various assays. The results indicate that panobinostat reduces the viability of cervical cancer cells in a dose- and time-dependent manner; it arrests HeLa cells in G0/G1 and SiHa cells in G2/M phase of the cell cycle. Panobinostat induced apoptosis through an increase in the ROS production and the disruption of mitochondrial membrane potential. Concomitantly the expression of anti-apoptotic gene Bcl-xL was reduced, while levels of CDK inhibitor p21 and caspase-9 were increased. Panobinostat increased the acetylation of histone H3 indicating HDAC inhibition. In addition, panobinostat also showed synergistic effect with topoisomerase inhibitors mediated by increased activation of caspase-3/7 activity compared to that in cells treated with panobinostat alone. These results suggest a combination therapy using inhibitors of histone deacetylase and topoisomerase together could hold the promise for an effective targeted therapeutic strategy.