Apoptosis induced by depsipeptide FK228 coincides with inhibition of survival signaling in lung cancer cells

What we have learnt from Drosophila model organism: the coordination between insulin signaling pathway and tumor cells

Cancer development is related to a variety of signaling pathways which mediate various cellular processes including growth, survival, division and competition of cells, as well as cell-cell interaction. The insulin signaling pathway interacts with different pathways and plays a core role in the regulations of all these processes. In this study, we reviewed recent studies on the relationship between the insulin signaling pathway and tumors using the Drosophila melanogaster model. We found that on one hand, the insulin pathway is normally hyperactive in tumor cells, which promotes tumor growth, and on the other hand, tumor cells can suppress the growth of healthy tissues via inhibition of their insulin pathway. Moreover, systematic disruption in glucose homeostasis also facilitates cancer development by different mechanisms. The studies on how the insulin network regulates the behaviors of cancer cells may help to discover new therapeutic treatments for cancer.

Epigenetic Priming of Bladder Cancer Cells With Decitabine Increases Cytotoxicity of Human EGFR and CD44v6 CAR Engineered T-Cells

Background

Treatment of B-cell malignancies with CD19-directed chimeric antigen receptor (CAR) T-cells marked a new era in immunotherapy, which yet has to be successfully adopted to solid cancers. Epigenetic inhibitors of DNA methyltransferases (DNMTi) and histone deacetylases (HDACi) can induce broad changes in gene expression of malignant cells, thus making these inhibitors interesting combination partners for immunotherapeutic approaches.

Methods

Urothelial carcinoma cell lines (UCC) and benign uroepithelial HBLAK cells pretreated with the DNMTi decitabine or the HDACi romidepsin were co-incubated with CAR T-cells directed against EGFR or CD44v6, and subsequent cytotoxicity assays were performed. Effects on T-cell cytotoxicity and surface antigen expression on UCC were determined by flow cytometry. We also performed next-generation mRNA sequencing of inhibitor-treated UCC and siRNA-mediated knockdown of potential regulators of CAR T-cell killing.

Results

Exposure to decitabine but not romidepsin enhanced CAR T-cell cytotoxicity towards all UCC lines, but not towards the benign HBLAK cells. Increased killing could neither be attributed to enhanced target antigen expression (EGFR and CD44v6) nor fully explained by changes in the T-cell ligands PD-L1, PD-L2, ICAM-1, or CD95. Instead, gene expression analysis suggested that regulators of cell survival and apoptosis were differentially induced by the treatment. Decitabine altered the balance between survival and apoptosis factors towards an apoptosis-sensitive state associated with increased CAR T-cell killing, while romidepsin, at least partially, tilted this balance in the opposite direction. Knockdown experiments with siRNA in UCC confirmed BID and BCL2L1/BCLX as two key factors for the altered susceptibility of the UCC.

Conclusion

Our data suggest that the combination of decitabine with CAR T-cell therapy is an attractive novel therapeutic approach to enhance tumor-specific killing of bladder cancer. Since BID and BCL2L1 are essential determinants for the susceptibility of a wide variety of malignant cells, their targeting might be additionally suitable for combination with immunotherapies, e.g., CAR T-cells or checkpoint inhibitors in other malignancies.

A review on epigenetic effects of environmental factors causing and inhibiting cancer

Epigenetic modifications refer to reversible changes in gene expression. Epigenetic changes include DNA methylation, histone modification, and non-coding RNAs that are collectively called epigenome. Various epigenetic effects account for the main impacts of environment and lifestyle on multifactorial diseases such as cancers. The environment's impacts on cancers act as double-edged swords. While some of them are involved in cancer development, some others contribute to preventing it. In this review article, the keywords 'cancer', 'epigenetic', 'lifestyle', 'carcinogen', ' cancer inhibitors" and related words were searched to finding a link between environmental factors and epigenetic mechanisms influencing cancer in ISI, PUBMED, SCOPUS, and Google Scholar databases. Based on the literature environmental factors that are effective in cancer development or cancer prevention in this review will be divided into physical, chemical, biological, and lifestyle types. Different types of epigenetic mechanisms known for each of these agents will be addressed in this review. Unregulated changes in epigenome play roles in tumorigenicity and cancer development. The action mechanism and genes targeted which are related to the signaling pathway for epigenetic alterations determine whether environmental agents are carcinogenic or prevent cancer. Having knowledge about the effective factors and related mechanisms such as epigenetic on cancer can help to prevent and better cancers treatment.

Targeted Exosomes for Drug Delivery: Biomanufacturing, Surface Tagging, and Validation

Exosomes hold great potential to deliver therapeutic reagents for cancer treatment due to its inherent low antigenicity. However, several technical barriers, such as low productivity and ineffective cancer targeting, need to be overcome before wide clinical applications. The present study aims at creating a new biomanufacturing platform of cancer-targeted exosomes for drug delivery. Specifically, a scalable, robust, high-yield, cell line based exosome production process is created in a stirred-tank bioreactor, and an efficient surface tagging technique is developed to generate monoclonal antibody (mAb)-exosomes. The in vitro characterization using transmission electron microscopy, NanoSight, and western blotting confirm the high quality of exosomes. Flow cytometry and confocal laser scanning microscopy demonstrate that mAb-exosomes have strong surface binding to cancer cells. Furthermore, to validate the targeted drug delivery efficiency, romidepsin, a histone deacetylase inhibitor, is loaded into mAb-exosomes. The in vitro anti-cancer toxicity study shows high cytotoxicity of mAb-exosome-romidepsin to cancer cells. Finally, the in vivo study using tumor xenograft animal model validates the cancer targeting specificity, anti-cancer efficacy, and drug delivery capability of the targeted exosomes. In summary, new techniques enabling targeted exosomes for drug delivery are developed to support large-scale animal studies and to facilitate the translation from research to clinics.

Inhibition of class I HDACs attenuates renal interstitial fibrosis in a murine model

Renal interstitial fibrosis is the most common of all the forms of chronic kidney disease (CKD). Research has shown that histone deacetylases (HDACs) participate in the process leading to renal fibrosis. However, the effects of class I HDAC inhibitors on the mechanisms of onset and progression of renal interstitial fibrosis are still unclear. Here, we present the effects and mechanisms of action of FK228 (a selective inhibitor of class I HDACs) in the murine model of unilateral ureteral obstruction (UUO) and in vitro models. We investigated the antifibrotic role of FK228 in a murine model of UUO. We used two key effector cell populations, rat renal interstitial fibroblasts and renal tubular epithelial cells exposed to recombinant transforming growth factor-beta 1 (TGF-β1), to explore the mechanistic pathways among in vitro models. The results indicated that FK228 significantly suppressed the production of extracellular matrix (ECM) in both in vivo and in vitro models. FK228 inhibited renal fibroblast activation and proliferation and increased the acetylation of histone H3. We found that FK228 also inhibited the small mothers against decapentaplegic (Smad) and non-Smad signaling pathways. So FK228 could significantly suppress renal interstitial fibrosis via Smad and non-Smad pathways. FK228 may be the basis for a new and effective medicine for alleviating renal fibrosis in the future.

FK228 augmented temozolomide sensitivity in human glioma cells by blocking PI3K/AKT/mTOR signal pathways

Temozolomide is a novel cytotoxic agent currently used as first-line chemotherapy for glioblastoma multiforme (GBM). Romidepsin (FK228), a histone deacetylase inhibitor, is a promising new class of antineoplastic agent with the capacity to induce growth arrest and/or apoptosis of cancer cells. However, combination of the two drugs in glioma remains largely unknown. In the present study, we evaluated the combinatory effects of FK228 with TMZ in glioma, and its molecular mechanisms responsible for these effects. Glioma cell lines were treated with TMZ, FK228 or the combination of drugs. The resistance effect including cytotoxicity and apoptosis was determined in glioma cells, respectively. We further evaluated the effects of FK228 in the PI3K/Akt-signaling pathway in vitro. Mice engrafted with 5×10⁶ LN382 cells were treated with TMZ, FK228 or the combination of two drugs, and tumor weights and volumes were measured, respectively. FK228 enhanced the cytotoxic effects of TMZ in glioma cells compared to vehicle-treated controls or each drug alone. The combination of FK228 and TMZ-induced apoptosis was demonstrated by increased expression of cleaved-Caspase 3, Bax, cleaved-PARP, and decreased Bcl-2 expression. Furthermore, the expression of key components of the PI3K/Akt-signaling pathway showed that combination of FK228 and TMZ block PI3K/Akt pathways in vitro. This block effect was also confirmed in vivo in mice models. Mice treated with both FK228 and TMZ drugs showed significantly reduced tumor weights and volumes, compared to each drug alone. Our results suggested that FK228 augmented temozolomide sensitivity in human glioma cells partially by blocking PI3K/AKT/mTOR signal pathways. It thus may provide a promising target for improving the therapeutic outcome of TMZ-resistant gliomas, although further studies will be needed.

Use of class I histone deacetylase inhibitor romidepsin in combination regimens

Histone deacetylase (HDAC) inhibitors are epigenetic-modifying agents that have shown promise as anticancer therapies. Several HDAC inhibitors have been approved by the US Food and Drug Administration (FDA) as single-agent therapies to treat T-cell lymphoma. The synergistic combination of HDAC inhibitors with other anticancer agents has the potential to constitute treatment regimens with enhanced efficacy. Romidepsin is a structurally unique, potent, bicyclic class 1 selective HDAC inhibitor approved by the FDA for the treatment of patients with peripheral T-cell lymphoma who have had at least 1 prior therapy and patients with cutaneous T-cell lymphoma who have had at least 1 prior systemic therapy. Here, we review data that support the use of romidepsin in combination with other anticancer agents for the treatment of various malignancies. Promising results have emerged from early clinical studies, supporting the potential for romidepsin combination regimens to constitute safe and effective treatments for cancer.

Cyclic depsipeptides as potential cancer therapeutics

Cyclic depsipeptides are polypeptides in which one or more amino acid is replaced by a hydroxy acid, resulting in the formation of at least one ester bond in the core ring structure. Many natural cyclic depsipeptides possessing intriguing structural and biological properties, including antitumor, antifungal, antiviral, antibacterial, anthelmintic, and anti-inflammatory activities, have been identified from fungi, plants, and marine organisms. In particular, the potent effects of cyclic depsipeptides on tumor cells have led to a number of clinical trials evaluating their potential as chemotherapeutic agents. Although many of the trials have not achieved the desired results, romidepsin (FK228), a bicyclic depsipeptide that inhibits histone deacetylase, has been shown to have clinical efficacy in patients with refractory cutaneous T-cell lymphoma and has received Food and Drug Administration approval for use in treatment. In this review, we discuss antitumor cyclic depsipeptides that have undergone clinical trials and focus on their structural features, mechanisms, potential applications in chemotherapy, and pharmacokinetic and toxicity data. The results of this study indicate that cyclic depsipeptides could be a rich source of new cancer therapeutics.

CRISPR/Cas9: molecular tool for gene therapy to target genome and epigenome in the treatment of lung cancer

Although varied drugs and therapies have been developed for lung cancer treatment, in the past 5 years overall survival rates have not improved much. It has also been reported that lung cancer is diagnosed in most of the patients when it is already in the advanced stages with heterogeneous tumors where single therapy is mostly ineffective. A combination of therapies are being administered and specific genes in specific tissues are targeted while protecting normal cell, but most of the therapies face drawbacks for the development of resistance against them and tumor progression. Therefore, therapeutic implications for various therapies need to be complemented by divergent strategies. This review frames utilization of CRISPR/Cas9 for molecular targeted gene therapy leading to long-term repression and activation or inhibition of molecular targets linked to lung cancer, avoiding the cycles of therapy.

Phase 1 study of romidepsin plus erlotinib in advanced non-small cell lung cancer

PURPOSE

Preclinical studies demonstrated anti-tumor efficacy of the combination of the histone deacetylase (HDAC) inhibitor romidepsin plus erlotinib in non-small cell lung cancer (NSCLC) models that were insensitive to erlotinib monotherapy. We therefore studied this combination in a phase 1 clinical trial in previously treated advanced NSCLC.

METHODS

Romidepsin (8 or 10mg/m(2)) was administered intravenously on days 1, 8, and 15 every 28 days in combination with erlotinib (150 mg orally daily), with romidepsin monotherapy lead-in during Cycle 1. Correlative studies included peripheral blood mononuclear cell HDAC activity and histone acetylation status, and EGFR pathway activation status in skin biopsies.

RESULTS

A total of 17 patients were enrolled. Median number of prior lines of therapy was 3 (range 1-5). No cases had a sensitizing EGFR mutation. The most common related adverse events were nausea, vomiting, and fatigue (each 82%), diarrhea (65%), anorexia (53%), and rash (41%). Dose-limiting nausea and vomiting occurred at the romidepsin 10 mg/m(2) level despite aggressive antiemetic prophylaxis and treatment. Among 10 evaluable patients, the best response was stable disease (n=7) and progressive disease (n=3). Median progression-free survival (PFS) was 3.3 months (range 1.4-16.5 months). Prolonged PFS (>6 months) was noted in a KRAS mutant adenocarcinoma and a squamous cell cancer previously progressed on erlotinib monotherapy. Romidepsin monotherapy inhibited HDAC activity, increased histone acetylation status, and inhibited EGFR phosphorylation.

CONCLUSIONS

Romidepsin 8 mg/m(2) plus erlotinib appears well tolerated, has evidence of disease control, and exhibits effects on relevant molecular targets in an unselected advanced NSCLC population.

Epigenetics of lung cancer

Lung cancer is the leading cause of cancer-related mortality in the United States. Epigenetic alterations, including DNA methylation, histone modifications, and noncoding RNA expression, have been reported widely in the literature to play a major role in the genesis of lung cancer. The goal of this review is to summarize the common epigenetic changes associated with lung cancer to give some clarity to its etiology, and to provide an overview of the potential translational applications of these changes, including applications for early detection, diagnosis, prognostication, and therapeutics.

Histone deacetylase inhibitor-mediated cell death is distinct from its global effect on chromatin

Romidepsin and vorinostat are histone deacetylase inhibitors (HDACis) that have activity in T-cell lymphomas, but have not gained traction in solid tumors. To gain deeper insight into mechanisms of HDACi efficacy, we systematically surveyed 19 cell lines with different molecular phenotypes, comparing romidepsin and vorinostat at equipotent doses. Acetylation at H3K9 and H4K8 along with 22 other histone lysine acetylation and methylation modifications were measured by reverse phase proteomics array (RPPA), and compared with growth inhibition (IC50), and cell cycle arrest. These assays typically used to assess HDACi effect showed that acetylation and methylation of specific lysine residues in response to HDACis were consistent across cell lines, and not related to drug sensitivity. Using a treatment duration more reflective of the clinical exposure, cell death detected by annexin staining following a 6 h drug exposure identified a subset of cell lines, including the T-cell lymphoma line, that was markedly more sensitive to HDAC inhibition. Kinetic parameters (Km values) were determined for lysine acetylation and for cell cycle data and were themselves correlated following HDACi exposure, but neither parameter correlated with cell death. The impact on cell survival signaling varied with the molecular phenotype. This study suggests that cellular response to HDACis can be viewed as two distinct effects: a chromatin effect and a cell death effect. All cells undergo acetylation, which is necessary but not sufficient for cell death. Cells not primed for apoptosis will not respond with cell death to the impact of altered histone acetylation. The divergent apoptotic responses observed reflect the variable clinical outcome of HDACi treatment. These observations should change our approach to the development of therapeutic strategies that exploit the dual activities of HDACis.

Effects of treatment with histone deacetylase inhibitors in solid tumors: a review based on 30 clinical trials

It has been found that the epigenetic silence of tumor suppressor genes induced by overexpression of histone deacetylases (HDACs) plays an important role in carcinogenesis. HDAC inhibitors (HDACi) that block the activity of specific HDACs have emerged as the accessory therapeutic agents for multiple human cancers. To better understand the effects of HDACi in cancer treatment, we carried out a review based on 30 published clinical trials to determine whether HDACi will benefit patients with solid tumors. Information of complete response, partial response, stable disease, objective responses and objective response rate was collected to assess clinical outcomes. A lack of therapeutic effects was observed when HDACi was used as a single agent. However, when HDACi treatment was combined with other agents, it appeared to increase the anti-tumor activity. High-quality studies are required to better understand the clinical effects of HDACi.

MAPK pathway activation leads to Bim loss and histone deacetylase inhibitor resistance: rationale to combine romidepsin with an MEK inhibitor

To identify molecular determinants of histone deacetylase inhibitor (HDI) resistance, we selected HuT78 cutaneous T-cell lymphoma (CTCL) cells with romidepsin in the presence of P-glycoprotein inhibitors to prevent transporter upregulation. Resistant sublines were 250- to 385-fold resistant to romidepsin and were resistant to apoptosis induced by apicidin, entinostat, panobinostat, belinostat, and vorinostat. A custom TaqMan array identified increased insulin receptor (INSR) gene expression; immunoblot analysis confirmed increased protein expression and a four- to eightfold increase in mitogen-activated protein kinase (MAPK) kinase (MEK) phosphorylation in resistant cells compared with parental cells. Resistant cells were exquisitely sensitive to MEK inhibitors, and apoptosis correlated with restoration of proapoptotic Bim. Romidepsin combined with MEK inhibitors yielded greater apoptosis in cells expressing mutant KRAS compared with romidepsin treatment alone. Gene expression analysis of samples obtained from patients with CTCL enrolled on the NCI1312 phase 2 study of romidepsin in T-cell lymphoma suggested perturbation of the MAPK pathway by romidepsin. Immunohistochemical analysis of Bim expression demonstrated decreased expression in some skin biopsies at disease progression. These findings implicate increased activation of MEK and decreased Bim expression as a resistance mechanism to HDIs, supporting combination of romidepsin with MEK inhibitors in clinical trials.

Targeting epigenetic mediators of gene expression in thoracic malignancies

Lung and esophageal cancers and malignant pleural mesotheliomas are highly lethal neoplasms that are leading causes of cancer-related deaths worldwide. Presently, limited information is available pertaining to epigenetic mechanisms mediating initiation and progression of these neoplasms. The following presentation will focus on the potential clinical relevance of epigenomic alterations in thoracic malignancies mediated by DNA methylation, perturbations in the histone code, and polycomb group proteins, as well as ongoing translational efforts to target epigenetic regulators of gene expression for treatment of these neoplasms. This article is part of a Special Issue entitled: Chromatin in time and space.

Histone deacetylase inhibitors: emerging mechanisms of resistance

The histone deacetylase inhibitors (HDIs) have shown promise in the treatment of a number of hematologic malignancies, leading to the approval of vorinostat and romidepsin for the treatment of cutaneous T-cell lymphoma and romidepsin for the treatment of peripheral T-cell lymphoma by the U.S. Food and Drug Administration. Despite these promising results, clinical trials with the HDIs in solid tumors have not met with success. Examining mechanisms of resistance to HDIs may lead to strategies that increase their therapeutic potential in solid tumors. However, relatively few examples of drug-selected cell lines exist, and mechanisms of resistance have not been studied in depth. Very few clinical translational studies have evaluated resistance mechanisms. In the current review, we summarize many of the purported mechanisms of action of the HDIs in clinical trials and examine some of the emerging resistance mechanisms.

Genetic and epigenetic changes in lung carcinoma and their clinical implications

Lung cancer is the leading cause of cancer deaths worldwide. Recent advance in targeted therapy for lung cancer patients with epidermal growth factor receptor (EGFR) mutations has demonstrated a promising development toward personalized therapy for lung cancer patients. The development of lung cancer is a complex process, involving a series of genetic and epigenetic changes. Tobacco smoke is the predominant etiologic risk factor for lung cancer. However, some lung cancers, especially adenocarcinomas, arise in patients who have never smoked, suggesting the importance of host genetic/epigenetic susceptibility in the occurrence and development of lung cancer. Understanding of these genetic and epigenetic changes will further aid in the biomarker-driven personalized therapy for lung cancer patients. In this review, we summarize the genetic and epigenetic alterations observed in lung cancers, including chromosomal loss of heterozygosity, tumor-suppressor gene mutation, gene methylation, histone modification, and microRNA expression changes. Clinical and preclinical studies have implied specific genetic/epigenetic changes for clinical application in lung cancer patients. However, more efforts are required in validation of the identified molecular markers in lung cancer patients for early detections, assessment for treatment response, and survival predictions.

Interpreting clinical assays for histone deacetylase inhibitors

As opposed to genetics, dealing with gene expressions by direct DNA sequence modifications, the term epigenetics applies to all the external influences that target the chromatin structure of cells with impact on gene expression unrelated to the sequence coding of DNA itself. In normal cells, epigenetics modulates gene expression through all development steps. When "imprinted" early by the environment, epigenetic changes influence the organism at an early stage and can be transmitted to the progeny. Together with DNA sequence alterations, DNA aberrant cytosine methylation and microRNA deregulation, epigenetic modifications participate in the malignant transformation of cells. Their reversible nature has led to the emergence of the promising field of epigenetic therapy. The efforts made to inhibit in particular the epigenetic enzyme family called histone deacetylases (HDACs) are described. HDAC inhibitors (HDACi) have been proposed as a viable clinical therapeutic approach for the treatment of leukemia and solid tumors, but also to a lesser degree for noncancerous diseases. Three epigenetic drugs are already arriving at the patient's bedside, and more than 100 clinical assays for HDACi are registered on the National Cancer Institute website. They explore the eventual additive benefits of combined therapies. In the context of the pleiotropic effects of HDAC isoforms, more specific HDACi and more informative screening tests are being developed for the benefit of the patients.

HDAC inhibition decreases the expression of EGFR in colorectal cancer cells

Epidermal growth factor receptor (EGFR), a receptor tyrosine kinase which promotes cell proliferation and survival, is abnormally overexpressed in numerous tumors of epithelial origin, including colorectal cancer (CRC). EGFR monoclonal antibodies have been shown to increase the median survival and are approved for the treatment of colorectal cancer. Histone deacetylases (HDACs), frequently overexpressed in colorectal cancer and several malignancies, are another attractive targets for cancer therapy. Several inhibitors of HDACs (HDACi) are developed and exhibit powerful antitumor abilities. In this study, human colorectal cancer cells treated with HDACi exhibited reduced EGFR expression, thereby disturbed EGF-induced ERK and Akt phosphorylation. HDACi also decreased the expression of SGLT1, an active glucose transporter found to be stabilized by EGFR, and suppressed the glucose uptake of cancer cells. HDACi suppressed the transcription of EGFR and class I HDACs were proved to be involved in this event. Chromatin immunoprecipitation analysis showed that HDACi caused the dissociation of SP1, HDAC3 and CBP from EGFR promoter. Our data suggested that HDACi could serve as a single agent to block both EGFR and HDAC, and may bring more benefits to the development of CRC therapy.

Enhanced growth inhibition by combined DNA methylation/HDAC inhibitors in lung tumor cells with silenced CDKN2A

Aberrant hypermethylation at CpG sites within the CDKN2A gene is associated with silencing and has been proposed as a target for reactivation using both DNA methylation and histone deacetylation inhibitors. This study investigates the role of selecting tumor samples with a silenced as compared to deleted CDKN2A locus when assessing the efficacy of DNA methyltransferase inhibitor, zebularine, combined with the HDAC inhibitor, depsipeptide. Non-small cell lung cancer cell lines with defined CDKN2A status were analyzed by MTS assay to determine the effect of zebularine or zebularine combined with depsipeptide on tumor cell growth. We observed that zebularine treatment resulted in inhibition of cell growth in 11 out of 12 lung cancer cell lines with silenced CDKN2A, but no cell growth inhibition was detected in the 7 lung cancer cell lines tested with deleted CDKN2A (p>0.001). In addition, we found that the combination of 30 microM zebularine and 6 or 7 nM depsipeptide resulted in a synergistic inhibition of cell growth in tumor cells with silenced CDKN2A (p<0.001, CI=0.70 and 0.57, respectively) but not in tumor cells with deleted CDKN2A. In conclusion, tumor cells with methylated CDKN2A are more sensitive to zebularine than cell lines with deleted CDKN2A and the combination of zebularine/depsipeptide results in a synergistic effect on cell growth inhibition that is also linked with the presence of silenced CDKN2A. Thus, combination of DNA methyltransferase and HDAC inhibitors may be a potential treatment for lung cancer patients, but careful selection of patients will be needed to optimize the benefit of this regimen.

Histone deacetylase inhibitors repress macrophage migration inhibitory factor (MIF) expression by targeting MIF gene transcription through a local chromatin deacetylation

The cytokine macrophage migration inhibitory factor plays a central role in inflammation, cell proliferation and tumorigenesis. Moreover, macrophage migration inhibitory factor levels correlate with tumor aggressiveness and metastatic potential. Histone deacetylase inhibitors are potent antitumor agents recently introduced in the clinic. Therefore, we hypothesized that macrophage migration inhibitory factor would represent a target of histone deacetylase inhibitors. Confirming our hypothesis, we report that histone deacetylase inhibitors of various chemical classes strongly inhibited macrophage migration inhibitory factor expression in a broad range of cell lines, in primary cells and in vivo. Nuclear run on, transient transfection with macrophage migration inhibitory factor promoter reporter constructs and transduction with macrophage migration inhibitory factor expressing adenovirus demonstrated that trichostatin A (a prototypical histone deacetylase inhibitor) inhibited endogenous, but not episomal, MIF gene transcription. Interestingly, trichostatin A induced a local and specific deacetylation of macrophage migration inhibitory factor promoter-associated H3 and H4 histones which did not affect chromatin accessibility but was associated with an impaired recruitment of RNA polymerase II and Sp1 and CREB transcription factors required for basal MIF gene transcription. Altogether, this study describes a new molecular mechanism by which histone deacetylase inhibitors inhibit MIF gene expression, and suggests that macrophage migration inhibitory factor inhibition by histone deacetylase inhibitors may contribute to the antitumorigenic effects of histone deacetylase inhibitors.

Romidepsin inhibits Ras-dependent growth transformation of NIH 3T3 fibroblasts and RIE-1 epithelial cells independently of Ras signaling inhibition

Background

Despite intensive effort, currently no effective anti-Ras therapies have successfully reached clinical application. Previous studies suggest that the histone deacetylatse (HDAC) inhibitor romidepsin, which is currently in clinical trials for the treatment of multiple malignancies, can block Ras-dependent signaling and growth transformation. These studies suggest that mutational activation of Ras may be a useful biomarker for sensitivity to romidepsin and that the anti-tumor activity of this HDAC inhibitor may involve inhibition of Ras effector-mediated signaling.

Results

To rigorously assess romidepsin as an antagonist of Ras, we utilized two well-characterized cell models for Ras transformation. We found that romidepsin blocked the anchorage-dependent and -independent growth of NIH 3T3 fibroblasts and RIE-1 epithelial cells transformed by all three Ras isoforms. However, romidepsin treatment also blocked growth transformation caused by other oncoproteins (B-Raf and ErbB2/Neu), suggesting that romidepsin is not selective for Ras. We also observed striking differences in romidepsin-mediated growth inhibition between transformed NIH 3T3 fibroblasts compared to RIE-1 epithelial cells, suggesting that the mechanism by which romidepsin blocks transformation is dependent on cellular context. Finally, we found that romidepsin did not inhibit Ras activation of the ERK and AKT effector pathways in NIH 3T3 and RIE-1 cells, suggesting that romidepsin does not directly antagonize Ras.

Conclusion

Taken together, our results suggest that romidepsin is not selective for Ras-transformed cells and that the anti-tumor activity of romidepsin is not due to direct inhibition of Ras function.

Enhancing the apoptotic and therapeutic effects of HDAC inhibitors

Histone deacetylase inhibitors (HDACi) are anti-cancer drugs that have moved rapidly through clinical development and in 2006 vorinostat (SAHA, Zolinza) was given FDA approval for the treatment of cutaneous T cell lymphoma. Class I, II and IV HDACs that are targets for these compounds deacetylate histone proteins, resulting in chromatin remodelling and altered gene transcription. In addition, numerous non-histone proteins are modified by acetylation and the inhibition of HDAC activity can therefore affect various molecular processes. This broad effect on protein function may account for the pleiotropic anti-tumor responses elicited by HDACi that include induction of tumor cell apoptosis, cell cycle arrest, differentiation and senescence, modulation of immune responses and altered angiogenesis. The ability of HDACi to selectively induce tumor cells to undergo apoptosis is important for the therapeutic efficacy observed in pre-clinical models. Moreover, HDACi can augment the apoptotic effects of other anti-cancer agents that have diverse molecular targets. While HDACi are promising anti-cancer drugs, particularly given the scope to combine HDACi with other agents, identifying the key molecular events that determine the biological response of cells to HDACi treatment remains a challenge. Herein we focus on HDACi-induced apoptosis and discuss the various proteins and pathways that are affected by HDACi to mediate this programmed cell death response. In addition, we highlight the ability of HDACi to synergise with other anti-cancer agents to potently kill tumor cells and discuss the possible molecular processes that underpin the combination effect.

Targeting histone deacetylases for the treatment of disease

The ‘histone code’ is a well-established hypothesis describing the idea that specific patterns of post-translational modifications to histones act like a molecular ‘code’ recognized and used by non-histone proteins to regulate specific chromatin functions. One modification, which has received significant attention, is that of histone acetylation. The enzymes that regulate this modification are described as lysine acetyltransferases or KATs, and histone deacetylases or HDACs. Due to their conserved catalytic domain HDACs have been actively targeted as a therapeutic target. The pro-inflammatory environment is increasingly being recognized as a critical element for both degenerative diseases and cancer. The present review will discuss the current knowledge surrounding the clinical potential and current development of histone deacetylases for the treatment of diseases for which a pro-inflammatory environment plays important roles, and the molecular mechanisms by which such inhibitors may play important functions in modulating the pro-inflammatory environment.

Epi-drugs to fight cancer: from chemistry to cancer treatment, the road ahead

In addition to genetic events, a variety of epigenetic events have been widely reported to contribute to the onset of many diseases including cancer. DNA methylation and histone modifications (such as acetylation, methylation, sumoylation, and phosphorylation) involving chromatin remodelling are among the most studied epigenetic mechanisms for regulation of gene expression leading, when altered, to some diseases. Epigenetic therapy tries to reverse the aberrations followed to the disruption of the balance of the epigenetic signalling ways through the use of both natural compounds and synthetic molecules, active on specific epi-targets. Such epi-drugs are, for example, inhibitors of DNA methyltransferases, histone deacetylases, histone acetyltransferases, histone methyltransferases, and histone demethylases. In this review we will focus on the chemical aspects of such molecules, joined to their effective (or potential) application in cancer therapy.

Advances in regulation mechanism of hepatocyte apoptosis in nonalcoholic fatty liver disease

The pathogenic mechanism of nonalcoholic fatty liver disease (NAFLD) still remains unclear. In recent years, many studies indicate that abnormal hepatocyte apoptosis exists in NAFLD, confirming the close relationship between NAFLD and hepatocyte apoptosis. The regulation of cell apoptosis includes two: positive or negative. In this paper, we review the research advances in the regulation of hepatocyte apoptosis during the pathogenesis of NAFLD.

Clinical and molecular responses in lung cancer patients receiving Romidepsin

PURPOSE

Our preclinical experiments indicated that Romidepsin (Depsipeptide FK228; DP) mediates growth arrest and apoptosis in cultured lung cancer cells. A phase II trial was done to examine clinical and molecular responses mediated by this histone deacetylase inhibitor in lung cancer patients.

EXPERIMENTAL DESIGN

Nineteen patients with neoplasms refractory to standard therapy received 4-h DP infusions (17.8 mg/m(2)) on days 1 and 7 of a 21-day cycle. Each full course of therapy consisted of two identical 21-day cycles. Plasma DP levels were evaluated by liquid chromatography-mass spectrometry techniques. A variety of molecular end points were assessed in tumor biopsies via immunohistochemistry techniques. Long oligo arrays were used to examine gene expression profiles in laser-captured tumor cells before and after DP exposure, relative to lung cancer cells and adjacent normal bronchial epithelia from patients undergoing pulmonary resections.

RESULTS

Nineteen patients were evaluable for toxicity assessment; 18 were evaluable for treatment response. Myelosuppression was dose limiting in one individual. No significant cardiac toxicities were observed. Maximum steady-state plasma DP concentrations ranged from 384 to 1,114 ng/mL. No objective responses were observed. Transient stabilization of disease was noted in nine patients. DP enhanced acetylation of histone H4, increased p21 expression in lung cancer cells, and seemed to shift global gene expression profiles in these cells toward those detected in normal bronchial epithelia.

CONCLUSION

Although exhibiting minimal clinical efficacy at this dose and schedule, DP mediates biological effects that may warrant further evaluation of this histone deacetylase inhibitor in combination with novel-targeted agents in lung cancer patients.