Clinical and molecular responses in lung cancer patients receiving Romidepsin

CAMSAP3-mediated regulation of HMGB1 acetylation and subcellular localization in lung cancer cells: Implications for cell death modulation

BACKGROUND

Deregulation of cell death is a common characteristic of cancer, and resistance to this process often occurs in lung cancer. Understanding the molecular mechanisms underlying an aberrant cell death is important. Recent studies have emphasized the involvement of calmodulin-regulated spectrin-associated protein 3 (CAMSAP3) in lung cancer aggressiveness, its influence on cell death regulation remains largely unexplored.

METHODS

CAMSAP3 was knockout in lung cancer cells using CRISPR-Cas9 system. Cell death and autophagy were evaluated using MTT and autophagic detection assays. Protein interactions were performed by proteomic analysis and immunoprecipitation. Protein expressions and their cytoplasmic localization were analyzed through immunoblotting and immunofluorescence techniques.

RESULTS

This study reveals a significant correlation between low CAMSAP3 expression and poor overall survival rates in lung cancer patients. Proteomic analysis identified high mobility group box 1 (HMGB1) as a candidate interacting protein involved in the regulation of cell death. Treatment with trichostatin A (TSA), an inhibitor of histone deacetylases (HDACs) resulted in increased HMGB1 acetylation and its translocation to the cytoplasm and secretion, thereby inducing autophagic cell death. However, this process was diminished in CAMSAP3 knockout lung cancer cells. Mechanistically, immunoprecipitation indicated an interaction between CAMSAP3 and HMGB1, particularly with its acetylated form, in which this complex was elevated in the presence of TSA.

CONCLUSIONS

CAMSAP3 is prerequisite for TSA-mediated autophagic cell death by interacting with cytoplasmic acetylated HMGB1 and enhancing its release.

SIGNIFICANT

This finding provides molecular insights into the role of CAMSAP3 in regulating cell death, highlighting its potential as a therapeutic target for lung cancer treatment.

Lineage-specific proteome remodeling of diverse lung cancer cells by targeted epigenetic inhibitors

Epigenetic inhibitors exhibit powerful antiproliferative and anticancer activities. However, cellular responses to small-molecule epigenetic inhibition are heterogenous and dependent on factors such as the genetic background, metabolic state, and on-/off-target engagement of individual small-molecule drugs. To determine the mechanisms that drive these heterogeneous cellular responses, we quantified chromatin, proteome, and transcriptome remodeling due to histone deacetylase inhibitor (HDACi) -treated cells derived from diverse genetic backgrounds. We utilized high-throughput sample multiplexed proteomics and integrated intelligent data acquisition methods to map proteomes of cancer cell lines in response to HDACi. We determined cell type-specific and ubiquitous cellular responses based on the quantification of 10,621 total proteins. We then established how coordinated remodeling of the proteome, transcriptome and chromatin state of HDACi treated cancer cells revealed convergent (JUN, MAP2K3, CDKN1A) and divergent (CCND3, ASF1B, BRD7) molecular phenotypes. HDACi-regulated proteins differ greatly across cell lines owing to heterogeneous molecular states of these cell lines. Finally, we demonstrated that HDACi treatment drove a highly cell-type specific response that may in part be explained by cell line-specific off-target drug engagement.

DDCM: A Computational Strategy for Drug Repositioning Based on Support-Vector Regression Algorithm

Computational drug-repositioning technology is an effective tool for speeding up drug development. As biological data resources continue to grow, it becomes more important to find effective methods to identify potential therapeutic drugs for diseases. The effective use of valuable data has become a more rational and efficient approach to drug repositioning. The disease-drug correlation method (DDCM) proposed in this study is a novel approach that integrates data from multiple sources and different levels to predict potential treatments for diseases, utilizing support-vector regression (SVR). The DDCM approach resulted in potential therapeutic drugs for neoplasms and cardiovascular diseases by constructing a correlation hybrid matrix containing the respective similarities of drugs and diseases, implementing the SVR algorithm to predict the correlation scores, and undergoing a randomized perturbation and stepwise screening pipeline. Some potential therapeutic drugs were predicted by this approach. The potential therapeutic ability of these drugs has been well-validated in terms of the literature, function, drug target, and survival-essential genes. The method's feasibility was confirmed by comparing the predicted results with the classical method and conducting a co-drug analysis of the sub-branch. Our method challenges the conventional approach to studying disease-drug correlations and presents a fresh perspective for understanding the pathogenesis of diseases.

S100a9 might act as a modulator of the Toll-like receptor 4 transduction pathway in chronic rhinosinusitis with nasal polyps

Chronic rhinosinusitis with nasal polyp (CRSwNP) is a highly prevalent disorder characterized by persistent nasal and sinus mucosa inflammation. Despite significant morbidity and decreased quality of life, there are limited effective treatment options for such a disease. Therefore, identifying causal genes and dysregulated pathways paves the way for novel therapeutic interventions. In the current study, a three-way interaction approach was used to detect dynamic co-expression interactions involved in CRSwNP. In this approach, the internal evolution of the co-expression relation between a pair of genes (X, Y) was captured under a change in the expression profile of a third gene (Z), named the switch gene. Subsequently, the biological relevancy of the statistically significant triplets was confirmed using both gene set enrichment analysis and gene regulatory network reconstruction. Finally, the importance of identified switch genes was confirmed using a random forest model. The results suggested four dysregulated pathways in CRSwNP, including "positive regulation of intracellular signal transduction", "arachidonic acid metabolic process", "spermatogenesis" and "negative regulation of cellular protein metabolic process". Additionally, the S100a9 as a switch gene together with the gene pair {Cd14, Tpd52l1} form a biologically relevant triplet. More specifically, we suggested that S100a9 might act as a potential upstream modulator in toll-like receptor 4 transduction pathway in the major CRSwNP pathologies.

The RELT Family of Proteins: An Increasing Awareness of Their Importance for Cancer, the Immune System, and Development

This review highlights Receptor Expressed in Lymphoid Tissues (RELT), a Tumor Necrosis Factor Superfamily member, and its two paralogs, RELL1 and RELL2. Collectively, these three proteins are referred to as RELTfms and have gained much interest in recent years due to their association with cancer and other human diseases. A thorough knowledge of their physiological functions, including the ligand for RELT, is lacking, yet emerging evidence implicates RELTfms in a variety of processes including cytokine signaling and pathways that either promote cell death or survival. T cells from mice lacking RELT exhibit increased responses against tumors and increased inflammatory cytokine production, and multiple lines of evidence indicate that RELT may promote an immunosuppressive environment for tumors. The relationship of individual RELTfms in different cancers is not universal however, as evidence indicates that individual RELTfms may be risk factors in certain cancers yet appear to be protective in other cancers. RELTfms are important for a variety of additional processes related to human health including microbial pathogenesis, inflammation, behavior, reproduction, and development. All three proteins have been strongly conserved in all vertebrates, and this review aims to provide a clearer understanding of the current knowledge regarding these interesting proteins.

Molecular mechanistic pathways underlying the anticancer therapeutic efficiency of romidepsin

Romidepsin, also known as NSC630176, FR901228, FK-228, FR-901228, depsipeptide, or Istodax®, is a natural molecule produced by the Chromobacterium violaceum bacterium that has been approved for its anti-cancer effect. This compound is a selective histone deacetylase (HDAC) inhibitor, which modifies histones and epigenetic pathways. An imbalance between HDAC and histone acetyltransferase can lead to the down-regulation of regulatory genes, resulting in tumorigenesis. Inhibition of HDACs by romidepsin indirectly contributes to the anticancer therapeutic effect by causing the accumulation of acetylated histones, restoring normal gene expression in cancer cells, and promoting alternative pathways, including the immune response, p53/p21 signaling cascades, cleaved caspases, poly (ADP-ribose) polymerase (PARP), and other events. Secondary pathways mediate the therapeutic action of romidepsin by disrupting the endoplasmic reticulum and proteasome and/or aggresome, arresting the cell cycle, inducing intrinsic and extrinsic apoptosis, inhibiting angiogenesis, and modifying the tumor microenvironment. This review aimed to highlight the specific molecular mechanisms responsible for HDAC inhibition by romidepsin. A more detailed understanding of these mechanisms can significantly improve the understanding of cancer cell disorders and pave the way for new therapeutic approaches using targeted therapy.

DNA and histone modifications as potent diagnostic and therapeutic targets to advance non-small cell lung cancer management from the perspective of 3P medicine

Lung cancer has a very high mortality in females and males. Most (~ 85%) of lung cancers are non-small cell lung cancers (NSCLC). When lung cancer is diagnosed, most of them have either local or distant metastasis, with a poor prognosis. In order to achieve better outcomes, it is imperative to identify the molecular signature based on genetic and epigenetic variations for different NSCLC subgroups. We hypothesize that DNA and histone modifications play significant roles in the framework of predictive, preventive, and personalized medicine (PPPM; 3P medicine). Epigenetics has a significant impact on tumorigenicity, tumor heterogeneity, and tumor resistance to chemotherapy, targeted therapy, and immunotherapy. An increasing interest is that epigenomic regulation is recognized as a potential treatment option for NSCLC. Most attention has been paid to the epigenetic alteration patterns of DNA and histones. This article aims to review the roles DNA and histone modifications play in tumorigenesis, early detection and diagnosis, and advancements and therapies of NSCLC, and also explore the connection between DNA and histone modifications and PPPM, which may provide an important contribution to improve the prognosis of NSCLC. We found that the success of targeting DNA and histone modifications is limited in the clinic, and how to combine the therapies to improve patient outcomes is necessary in further studies, especially for predictive diagnostics, targeted prevention, and personalization of medical services in the 3P medicine approach. It is concluded that DNA and histone modifications are potent diagnostic and therapeutic targets to advance non-small cell lung cancer management from the perspective of 3P medicine.

Histone deacetylases modulate resistance to the therapy in lung cancer

The acetylation status of histones located in both oncogenes and tumor suppressor genes modulate cancer hallmarks. In lung cancer, changes in the acetylation status are associated with increased cell proliferation, tumor growth, migration, invasion, and metastasis. Histone deacetylases (HDACs) are a group of enzymes that take part in the elimination of acetyl groups from histones. Thus, HDACs regulate the acetylation status of histones. Although several therapies are available to treat lung cancer, many of these fail because of the development of tumor resistance. One mechanism of tumor resistance is the aberrant expression of HDACs. Specific anti-cancer therapies modulate HDACs expression, resulting in chromatin remodeling and epigenetic modification of the expression of a variety of genes. Thus, HDACs are promising therapeutic targets to improve the response to anti-cancer treatments. Besides, natural compounds such as phytochemicals have potent antioxidant and chemopreventive activities. Some of these compounds modulate the deregulated activity of HDACs (e.g. curcumin, apigenin, EGCG, resveratrol, and quercetin). These phytochemicals have been shown to inhibit some of the cancer hallmarks through HDAC modulation. The present review discusses the epigenetic mechanisms by which HDACs contribute to carcinogenesis and resistance of lung cancer cells to anticancer therapies.

Histone Modification in NSCLC: Molecular Mechanisms and Therapeutic Targets

Lung cancer is the leading cause of cancer mortality in both genders, with non-small cell lung cancer (NSCLC) accounting for about 85% of all lung cancers. At the time of diagnosis, the tumour is usually locally advanced or metastatic, shaping a poor disease outcome. NSCLC includes adenocarcinoma, squamous cell carcinoma, and large cell lung carcinoma. Searching for novel therapeutic targets is mandated due to the modest effect of platinum-based therapy as well as the targeted therapies developed in the last decade. The latter is mainly due to the lack of mutation detection in around half of all NSCLC cases. New therapeutic modalities are also required to enhance the effect of immunotherapy in NSCLC. Identifying the molecular signature of NSCLC subtypes, including genetics and epigenetic variation, is crucial for selecting the appropriate therapy or combination of therapies. Epigenetic dysregulation has a key role in the tumourigenicity, tumour heterogeneity, and tumour resistance to conventional anti-cancer therapy. Epigenomic modulation is a potential therapeutic strategy in NSCLC that was suggested a long time ago and recently starting to attract further attention. Histone acetylation and deacetylation are the most frequently studied patterns of epigenetic modification. Several histone deacetylase (HDAC) inhibitors (HDIs), such as vorinostat and panobinostat, have shown promise in preclinical and clinical investigations on NSCLC. However, further research on HDIs in NSCLC is needed to assess their anti-tumour impact. Another modification, histone methylation, is one of the most well recognized patterns of histone modification. It can either promote or inhibit transcription at different gene loci, thus playing a rather complex role in lung cancer. Some histone methylation modifiers have demonstrated altered activities, suggesting their oncogenic or tumour-suppressive roles. In this review, patterns of histone modifications in NSCLC will be discussed, focusing on the molecular mechanisms of epigenetic modifications in tumour progression and metastasis, as well as in developing drug resistance. Then, we will explore the therapeutic targets emerging from studying the NSCLC epigenome, referring to the completed and ongoing clinical trials on those medications.

Randomized phase II trial of a first-in-human cancer cell lysate vaccine in patients with thoracic malignancies

BACKGROUND

Although most malignancies express cancer-testis antigens (CTA), immune responses to these proteins are limited in thoracic oncology patients. This trial was undertaken to examine if a cancer cell lysate vaccine could induce immunity to CTA, and to ascertain if metronomic cyclophosphamide and celecoxib enhances vaccine-induced immune responses.

METHODS

Eleven patients with primary thoracic malignancies and 10 patients with extrathoracic neoplasms metastatic to the chest rendered NED by conventional therapies were randomized to receive H1299 lung cancer cell lysates (10 mg protein/vaccine) with Iscomatrix™ adjuvant via deep intradermal injection q 4 weeks ×6 with or without daily oral metronomic cyclophosphamide/celecoxib. The primary endpoint was serologic response to purified CTA assessed 1 month after the 6th vaccination. Secondary endpoints included assessment of the effects of cyclophosphamide and celecoxib on frequency and magnitude of vaccine-induced immune responses to CTA. Exploratory endpoints included evaluation of the effects of the vaccine regimens on peripheral immune subsets. Standard of care imaging studies were obtained at baseline and 1 month after the 3rd and 6th vaccinations.

RESULTS

All patients exhibited local and systemic inflammatory responses lasting 72-96 hours following vaccinations. There were no dose limiting treatment related toxicities. Fourteen patients (67%) completed all six vaccinations. Eight of 14 patients (57%) exhibited serologic responses to NY-ESO-1. One patient developed antibodies to GAGE7; several patients exhibited reactivity to XAGE and MAGE-C2. Vaccine therapy decreased the percent of Tregs (P=0.0068), PD-1 expression on Tregs (P=0.0027), PD-L1 expression on CD14+ monocytes (P=0.0089), PD-L1 expression on classical monocytes (P=0.016), and PD-L1 expression on intermediate monocytes (P=0.0031). Cyclophosphamide/celecoxib did not appear to increase immune responses or enhance vaccine-induced alterations in peripheral immune subsets.

CONCLUSIONS

H1299 lysate vaccines with Iscomatrix™ induce immune responses to CTA and modulate peripheral immune subsets in a manner that may enhance antitumor immunity in patients with thoracic malignancies.

Romidepsin (FK228), A Histone Deacetylase Inhibitor and its Analogues in Cancer Chemotherapy

BACKGROUND

Human HDACs represent a group of enzymes able to modify histone and non-histone proteins, which interact with DNA to generate chromatin. The correlation between irregular covalent modification of histones and tumor development has been proved over the last decades. Therefore, HDAC inhibitors are considered as potential drugs in cancer treatment. Romidepsin (FK228), Belinostat (PXD-101), Vorinostat (SAHA), Panobinostat (LBH-589) and Chidamide were approved by FDA as novel antitumor agents.

OBJECTIVE

The aim of this review article is to highlight the structure-activity relationships of several FK228 analogues as HDAC inhibitors. In addition, the synergistic effects of a dual HDAC/PI3K inhibition by some derivatives have been investigated.

MATERIALS AND METHODS

PubMed, MEDLINE, CAPLUS, SciFinder Scholar database were considered by selecting articles which fulfilled the objectives of this review, dating from 2015 till present time.

RESULTS

HDAC inhibitors have a significant role in cancer pathogenesis and evolution. Class I HDAC isoforms are expressed in many tumor types, therefore, potent and selective Class I HDAC inhibitors are of great interest as candidate therapeutic agents with limited side effects. By structurebased optimization, several FK228 analogues [15 (FK-A5), 22, 23 and 26 (FK-A11)] were identified, provided with significant activity against Class I HDAC enzymes and dose dependent antitumor activity. Compound 26 was recognized as an interesting HDAC/PI3K dual inhibitor (IC₅₀ against p110α of 6.7 μM while for HDAC1 inhibitory activity IC₅₀ was 0.64 nM).

CONCLUSION

Romidepsin analogues HDAC inhibitors have been confirmed as useful anticancer agents. In addition, dual HDAC/PI3K inhibition showed by some of them exhibited synergistic effects in inducing apoptosis in human cancer cells. Further studies on FK228 analogues may positively contribute to the availability of potent agents in tumor treatment.

Bioinformatics-Based Identification of HDAC Inhibitors as Potential Drugs to Target EGFR Wild-Type Non-Small-Cell Lung Cancer

Patients with EGFR-mutant non-small-cell lung cancer (NSCLC) greatly benefit from EGFR-tyrosine kinase inhibitors (EGFR-TKIs) while the prognosis of patients who lack EGFR-sensitive mutations (EGFR wild type, EGFR-WT) remains poor due to a lack of effective therapeutic strategies. There is an urgent need to explore the key genes that affect the prognosis and develop potentially effective drugs in EGFR-WT NSCLC patients. In this study, we clustered functional modules related to the survival traits of EGFR-WT patients using weighted gene co-expression network analysis (WGCNA). We used these data to establish a two-gene prognostic signature based on the expression of CYP11B1 and DNALI1 by combining the least absolute shrinkage and selection operator (LASSO) algorithms and Cox proportional hazards regression analysis. Following the calculation of risk score (RS) based on the two-gene signature, patients with high RSs showed a worse prognosis. We further explored targeted drugs that could be effective in patients with a high RS by the connectivity map (CMap). Surprisingly, multiple HDAC inhibitors (HDACis) such as trichostatin A (TSA) and vorinostat (SAHA) that may have efficacy were identified. Also, we proved that HDACis could inhibit the proliferation and metastasis of NSCLC cells in vitro. Taken together, our study identified prognostic biomarkers for patients with EGFR-WT NSCLC and confirmed a novel potential role for HDACis in the clinical management of EGFR-WT patients.

Beyond regulations at DNA levels: A review of epigenetic therapeutics targeting cancer stem cells

In the past few years, the paramount role of cancer stem cells (CSCs), in terms of cancer initiation, proliferation, metastasis, invasion and chemoresistance, has been revealed by accumulating studies. However, this level of cellular plasticity cannot be entirely explained by genetic mutations. Research on epigenetic modifications as a complementary explanation for the properties of CSCs has been increasing over the past several years. Notably, therapeutic strategies are currently being developed in an effort to reverse aberrant epigenetic alterations using specific chemical inhibitors. In this review, we summarize the current understanding of CSCs and their role in cancer progression, and provide an overview of epigenetic alterations seen in CSCs. Importantly, we focus on primary cancer therapies that target the epigenetic modification of CSCs by the use of specific chemical inhibitors, such as histone deacetylase (HDAC) inhibitors, DNA methyltransferase (DNMT) inhibitors and microRNA‐based (miRNA‐based) therapeutics.

Histone Deacetylase Inhibition in Non-small Cell Lung Cancer: Hype or Hope?

Epigenetic modulation, including acetylation, methylation, phosphorylation, and ubiquitination, plays a pivotal role in regulation of gene expression. Histone acetylation-a balance between the activities of histone acetyltransferases (HATs) and histone deacetylases (HDACs)-is one of the key epigenetic events. Our understanding of the role of HDACs in cancer is evolving. A number of HDAC isoenzymes are overexpressed in a variety of malignancies. Aberrant histone acetylation is associated with dysregulation of tumor suppressor genes leading to development of several solid tumors and hematologic malignancies. Pre-clinical studies have demonstrated that HDAC-1 gene expression is associated with lung cancer progression. Histone hypoacetylation is associated with more aggressive phenotype in adenocarcinoma of the lung. HDAC inhibitors (HDACi) have pleiotropic cellular effects and induce the expression of pro-apoptotic genes/proteins, cause cellular differentiation and/or cell cycle arrest, inhibit angiogenesis, and inhibit transition to a mesenchymal phenotype. Consequently, treatment with HDACi has shown anti-proliferative activity in non-small cell lung cancer (NSCLC) cell lines. Despite promising results in pre-clinical studies, HDACi have shown only modest single agent activity in lung cancer clinical trials. HDAC activation has been implicated as one of the mechanisms causing resistance to chemotherapy, molecularly targeted therapy, and immune checkpoint inhibition. Therefore, there is a growing interest in combining HDACi with these agents to enhance their efficacy or reverse resistance. In this paper, we review the available preclinical and clinical evidence for the use of HDACi in NSCLC. We also review the challenges precluding widespread clinical utility of HDACi as a cancer therapy and future directions.

Inhibitors of DNA Methylation and Histone Deacetylation as Epigenetically Active Drugs for Anticancer Therapy

Gene expression is regulated and tightly controlled by epigenetic mechanisms. Alterations of these mechanisms are frequently observed in various diseases, particularly, in various types of cancer. Malignant transformation is caused by the impairment of the mechanisms of cell differentiation and cell cycle control associated with epigenetic changes. Altered patterns of epigenetic modification associated with malignancies can potentially be reversed by some agents that act on the key proteins responsible for DNA/histone modification and chromatin remodelling. Examples of such substances include the inhibitors of DNA methyltransferases or histone deacetylase. During the recent years, a number of such substances have been evaluated as potential therapeutic agents against certain types of cancer in preclinical and clinical studies, and some of them have been approved for treatment of hematological cancers. Application of epidrugs for therapy of solid tumors remains, however, more challenging. In this review, we summarize the current knowledge on the most studied mechanisms of epigenetic modification and the available epigenetically active drugs.

Epigenetic Metalloenzymes

Epigenetics controls the expression of genes and is responsible for cellular phenotypes. The fundamental basis of these mechanisms involves in part the post-translational modifications (PTMs) of DNA and proteins, in particular, the nuclear histones. DNA can be methylated or demethylated on cytosine. Histones are marked by several modifications including acetylation and/or methylation, and of particular importance are the covalent modifications of lysine. There exists a balance between addition and removal of these PTMs, leading to three groups of enzymes involved in these processes: the writers adding marks, the erasers removing them, and the readers able to detect these marks and participating in the recruitment of transcription factors. The stimulation or the repression in the expression of genes is thus the result of a subtle equilibrium between all the possibilities coming from the combinations of these PTMs. Indeed, these mechanisms can be deregulated and then participate in the appearance, development and maintenance of various human diseases, including cancers, neurological and metabolic disorders. Some of the key players in epigenetics are metalloenzymes, belonging mostly to the group of erasers: the zinc-dependent histone deacetylases (HDACs), the iron-dependent lysine demethylases of the Jumonji family (JMJ or KDM) and for DNA the iron-dependent ten-eleven-translocation enzymes (TET) responsible for the oxidation of methylcytosine prior to the demethylation of DNA. This review presents these metalloenzymes, their importance in human disease and their inhibitors.

A Peptide Probe Enables Photoacoustic-Guided Imaging and Drug Delivery to Lung Tumors in K-rasLA2 Mutant Mice

The lack of molecular targets and targeting probes remains a major drawback for targeted imaging and drug delivery in lung cancer. In this study, we exploited in vivo phage display to identify a novel targeting probe that homes to the tumor in a K-ras^LA2 mutant mouse lung cancer model. Compared with other candidate peptides selected from 5 rounds of phage display, the CRQTKN peptide homed to tumor nodules in the lung of mutant mice at higher levels. Photoacoustic tomography of mutant mice detected lung tumors via tumor homing of the near-infrared fluorescence dye-labeled CRQTKN peptide. Ex vivo photoacoustic images of isolated organs further demonstrated tumor homing of the CRQTKN peptide, whereas minimal accumulation was observed in control organs, such as the liver. Compared with untargeted liposomes and doxorubicin, doxorubicin-loaded liposomes whose surface was modified with the CRQTKN peptide more efficiently delivered doxorubicin and reduced the number or size of tumor lesions in K-ras^LA2 mutant mice. Analysis of hematologic parameters and liver and kidney function showed no significant systemic side effects by the treatments. Affinity-based identification was used to detect TNF receptor superfamily member 19L (TNFRSF19L), which was upregulated in lung tumors of mutant mice, as the receptor for the CRQTKN peptide. In conclusion, these results suggest that the CRQTKN peptide is a promising targeting probe for photoacoustic-guided detection and drug delivery to lung cancer, and acts by binding to TNFRSF19L. SIGNIFICANCE: These findings present a new tumor-targeting probe for photoacoustic-guided detection and drug delivery.

Epigenetic modulators hydralazine and sodium valproate act synergistically in VEGI-mediated anti-angiogenesis and VEGF interference in human osteosarcoma and vascular endothelial cells

Vascular endothelial growth inhibitor (VEGI; also referred to as TNFSF15 or TL1A) is involved in the modulation of vascular homeostasis. VEGI is known to operate via two receptors: Death receptor‑3 (DR3) and decoy receptor‑3 (DcR3). DR3, which is thus far the only known functional receptor for VEGI, contains a death domain and induces cell apoptosis. DcR3 is secreted as a soluble protein and antagonizes VEGI/DR3 interaction. Overexpression of DcR3 and downregulation of VEGI have been detected in a number of cancers. The aim of the present study was to investigate the effects of sodium valproate (VPA), a histone deacetylase inhibitor, in combination with hydralazine hydrochloride (Hy), a DNA methylation inhibitor, on the expression of VEGI and its related receptors in human osteosarcoma (OS) cell lines and human microvascular endothelial (HMVE) cells. Combination treatment with Hy and VPA synergistically induced the expression of VEGI and DR3 in both OS and HMVE cells, without inducing DcR3 secretion. In addition, it was observed that the combination of VPA and Hy significantly enhanced the inhibitory effect on vascular tube formation by VEGI/DR3 autocrine and paracrine pathways. Furthermore, the VEGI/VEGF‑A immune complex was pulled down by immunoprecipitation. Taken together, these findings suggest that DNA methyltransferase and histone deacetylase inhibitors not only have the potential to induce the re‑expression of tumor suppressor genes in cancer cells, but also exert anti‑angiogenic effects, via enhancement of the VEGI/DR3 pathway and VEGI/VEGF‑A interference.

The histone deacetylase inhibitor, romidepsin, as a potential treatment for pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a progressive disease that usually affects elderly people. It has a poor prognosis and there are limited therapies. Since epigenetic alterations are associated with IPF, histone deacetylase (HDAC) inhibitors offer a novel therapeutic strategy to address the unmet medical need. This study investigated the potential of romidepsin, an FDA-approved HDAC inhibitor, as an anti-fibrotic treatment and evaluated biomarkers of target engagement that may have utility in future clinical trials. The anti-fibrotic effects of romidepsin were evaluated both in vitro and in vivo together with any harmful effect on alveolar type II cells (ATII). Bronchoalveolar lavage fluid (BALF) from IPF or control donors was analyzed for the presence of lysyl oxidase (LOX). In parallel with an increase in histone acetylation, romidepsin potently inhibited fibroblast proliferation, myofibroblast differentiation and LOX expression. ATII cell numbers and their lamellar bodies were unaffected. In vivo, romidepsin inhibited bleomycin-induced pulmonary fibrosis in association with suppression of LOX expression. LOX was significantly elevated in BALF of IPF patients compared to controls. These data show the anti-fibrotic effects of romidepsin, supporting its potential use as novel treatment for IPF with LOX as a companion biomarker for evaluation of early on-target effects.

Advances and Challenges of HDAC Inhibitors in Cancer Therapeutics

Since the identification and cloning of human histone deacetylases (HDACs) and the rapid approval of vorinostat (Zolinza®) for the treatment of cutaneous T-cell lymphoma, the field of HDAC biology has met many initial successes. However, many challenges remain due to the complexity involved in the lysine posttranslational modifications, epigenetic transcription regulation, and nonepigenetic cellular signaling cascades. In this chapter, we will: review the discovery of the first HDAC inhibitor and present discussion regarding the future of next-generation HDAC inhibitors, give an overview of different classes of HDACs and their differences in lysine deacylation activity, discuss different classes of HDAC inhibitors and their HDAC isozyme preferences, and review HDAC inhibitors' preclinical studies, their clinical trials, their pharmacokinetic challenges, and future direction. We will also discuss the likely reason for the failure of multiple HDAC inhibitor clinical trials in malignancies other than lymphoma and multiple myeloma. In addition, the potential molecular mechanism(s) that may play a key role in the efficacy and therapeutic response rate in the clinic and the likely patient population for HDAC therapy will be discussed.

Crosstalk among the proteome, lysine phosphorylation, and acetylation in romidepsin-treated colon cancer cells

Romidepsin (FK228) is one of the most promising histone-deacetylase inhibitors due to its potent antitumor activity, and has been used as a practical option for cancer therapy. However, FK228-induced changes in protein modifications and the crosstalk between different modifications has not been reported. To better understand the underlying mechanisms of FK228-related cancer therapy, we investigated the acetylome, phosphorylation, and crosstalk between modification datasets in colon cancer cells treated with FK228 by using stable-isotope labeling with amino acids in cell culture and affinity enrichment, followed by high-resolution liquid chromatography tandem mass spectrometry analysis. In total, 2728 protein groups, 1175 lysine-acetylation sites, and 4119 lysine-phosphorylation sites were quantified. When the quantification ratio thresholds were set to > 2.0 and < 0.5, respectively, a total of 115 and 38 lysine-acetylation sites in 85 and 32 proteins were quantified as increased and decreased targets, respectively, and 889 and 370 lysine-phosphorylation sites in 599 and 289 proteins were quantified as increased and decreased targets, respectively. Furthermore, we identified 274 proteins exhibiting both acetylation and phosphorylation modifications. These findings indicated possible involvement of these proteins in FK228-related treatment of colon cancer, and provided insight for further analysis of their biological function.

Epigenetic Therapeutics and Their Impact in Immunotherapy of Lung Cancer

Lung cancer is the leading cause of cancer-related death in the United States and worldwide. Novel therapeutic developments are critically necessary to improve outcomes for this disease. Aberrant epigenetic change plays an important role in lung cancer development and progression. Therefore, drugs targeting the epigenome are being investigated in the treatment of lung cancer. Monotherapy of epigenetic therapeutics such as DNA methyltransferase inhibitors (DNMTi) and histone deacetylase inhibitors (HDACi) have so far not shown any apparent benefit while one of the clinical trials with the combinations of DNMTi and HDACi showed a small positive signal for treating lung cancer. Combinations of DNMTi and HDACi with chemotherapies have some efficacy but are often limited by increased toxicities. Preclinical data and clinical trial results suggest that combining epigenetic therapeutics with targeted therapies might potentially improve outcomes in lung cancer patients. Furthermore, several clinical studies suggest that the HDACi vorinostat could be used as a radiosensitizer in lung cancer patients receiving radiation therapy. Immune checkpoint blockade therapies are revolutionizing lung cancer management. However, only a minority of lung cancer patients experience long-lasting benefits from immunotherapy. The role of epigenetic reprogramming in boosting the effects of immunotherapy is an area of active investigation. Preclinical studies and early clinical trial results support this approach which may improve lung cancer treatment, with potentially prolonged survival and tolerable toxicity. In this review, we discuss the current status of epigenetic therapeutics and their combination with other antineoplastic therapies, including novel immunotherapies, in lung cancer management.

Lung cancer epigenetics: From knowledge to applications

Lung cancer is the leading cause of cancer-related mortality worldwide. Advances in our understanding of the genomics of lung cancer have led to substantial progress in the treatment of specific molecular subsets. Immunotherapy also emerges as a major breakthrough in lung cancer treatment. However, challenges remain as a consensual approach for early lung cancer detection remains elusive while primary or secondary drug resistance eventually leads to treatment failure in all patients with advanced disease. Furthermore, a large portion of patients are still treated with conventional chemotherapy that is only modestly effective. The last two decades have seen exponential developments in the epigenetic understanding of lung cancer. Epigenetic alterations in DNA methylation, non-coding RNA expression, chromatin modeling and post transcriptional regulators are key events in each step of lung cancer pathogenesis. Here, we review the central role epigenetic disruptions play in lung cancer carcinogenesis and the acquisition of cancerous phenotype and aggressive behavior as well as in the resistance to therapy. Epigenetic disruptions could represent reliable biomarkers for lung cancer risk assessment, early diagnosis, prognosis stratification, molecular classification and prediction of treatment efficacy. The therapeutic potential of epigenetics targeted drugs in combination with chemotherapy, targeted therapy and/or immunotherapy is currently being intensively investigated. We suggest that integration of tissue-derived or circulating epigenetic biomarkers and epidrugs in clinical trial design will translate epigenetic knowledge of lung cancer into the clinic and improve lung cancer patient outcomes.

Romidepsin induces caspase-dependent cell death in human neuroblastoma cells

Neuroblastoma is the most common extracranial pediatric solid tumor, arising from the embryonic sympathoadrenal lineage of the neural crest, and is responsible for 15% of childhood cancer deaths. Although survival rates are good for some patients, those children diagnosed with high-risk neuroblastoma have survival rates as low as 35%. Thus, neuroblastoma remains a significant clinical challenge and the development of novel therapeutic strategies is essential. Given that there is widespread epigenetic dysregulation in neuroblastoma, epigenetic pharmacotherapy holds promise as a therapeutic approach. In recent years, histone deacetylase (HDAC) inhibitors, which cause selective activation of gene expression, have been shown to be potent chemotherapeutics for the treatment of a wide range of cancers. Here we examined the ability of the FDA-approved drug Romidepsin, a selective HDAC1/2 inhibitor, to act as a cytotoxic agent in neuroblastoma cells. Treatment with Romidepsin at concentrations in the low nanomolar range induced neuroblastoma cell death through caspase-dependent apoptosis. Romidepsin significantly increased histone acetylation, and significantly enhanced the cytotoxic effects of the cytotoxic agent 6-hydroxydopamine, which has been shown to induce cell death in neuroblastoma cells through increasing reactive oxygen species. Romidepsin was also more potent in MYCN-amplified neuroblastoma cells, which is an important prognostic marker of poor survival. This study has thus demonstrated that the FDA-approved chemotherapeutic drug Romidepsin has a potent caspase-dependent cytotoxic effect on neuroblastoma cells, whose effects enhance cell death induced by other cytotoxins, and suggests that Romidepsin may be a promising chemotherapeutic candidate for the treatment of neuroblastoma.

Epigenetics in cancer stem cells

Compelling evidence have demonstrated that bulk tumors can arise from a unique subset of cells commonly termed "cancer stem cells" that has been proposed to be a strong driving force of tumorigenesis and a key mechanism of therapeutic resistance. Recent advances in epigenomics have illuminated key mechanisms by which epigenetic regulation contribute to cancer progression. In this review, we present a discussion of how deregulation of various epigenetic pathways can contribute to cancer initiation and tumorigenesis, particularly with respect to maintenance and survival of cancer stem cells. This information, together with several promising clinical and preclinical trials of epigenetic modulating drugs, offer new possibilities for targeting cancer stem cells as well as improving cancer therapy overall.

Deletion of ADP Ribosylation Factor-Like GTPase 13B Leads to Kidney Cysts

The gene for ADP ribosylation factor-like GTPase 13B (Arl13b) encodes a small GTPase essential for cilia biogenesis in multiple model organisms. Inactivation of arl13b in zebrafish leads to a number of phenotypes indicative of defective cilia, including cystic kidneys. In mouse, null mutation in Arl13b results in severe patterning defects in the neural tube and defective Hedgehog signaling. Human mutations of ARL13B lead to Joubert syndrome, a ciliopathy. However, patients with mutated ARL13B do not develop kidney cysts. To investigate whether Arl13b has a role in ciliogenesis in mammalian kidney and whether loss of function of Arl13b leads to cystic kidneys in mammals, we generated a mouse model with kidney-specific conditional knockout of Arl13b Deletion of Arl13b in the distal nephron at the perinatal stage led to a cilia biogenesis defect and rapid kidney cyst formation. Additionally, we detected misregulation of multiple pathways in the cystic kidneys of this model. Moreover, valproic acid, a histone deacetylase inhibitor that we previously showed slows cyst progression in a mouse cystic kidney model with neonatal inactivation of Pkd1, inhibited the early rise of Wnt7a expression, ameliorated fibrosis, slowed cyst progression, and improved kidney function in the Arl13b mutant mouse. Finally, in rescue experiments in zebrafish, all ARL13B allele combinations identified in patients with Joubert syndrome provided residual Arl13b function, supporting the idea that the lack of cystic kidney phenotype in human patients with ARL13B mutations is explained by the hypomorphic nature of the mutations.

Recent advances in epigenomics in NSCLC: real-time detection and therapeutic implications

NSCLC is an aggressive disease with one of the poorer prognosis among cancers. The disappointing response to chemotherapy drives the search for genetic biomarkers aimed at both attaining an earlier diagnosis and choosing the most appropriate chemotherapy. In this scenario, epigenomic markers, such as DNA methylation, histone acetylation and the expression of noncoding RNAs, have been demonstrated to be reliable for the stratification of NSCLC patients. Newest techniques with increased sensitivity and the isolation of nucleic acids from plasma may allow an early diagnosis and then monitoring the efficacy over time. However, prospective confirmatory studies are still lacking. This article presents an overview of the epigenetic markers evaluated in NSCLC and discusses the role of their real-time detection in the clinical management of the disease.

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.

Valproic acid improves second-line regimen of small cell lung carcinoma in preclinical models

With 5-year survival rates below 5%, small cell lung carcinoma (SCLC) has very poor prognosis and requires improved therapies. Despite an excellent overall response to first-line therapy, relapses are frequent and further treatments are disappointing. The goal of the study was to improve second-line therapy of SCLC.

The effect of chemotherapeutic agents was evaluated in cell lines (apoptosis, reactive oxygen species, and RNA and protein expression) and in mouse models (tumour development).

We demonstrate here that valproic acid, a histone deacetylase inhibitor, improves the efficacy of a second-line regimen (vindesine, doxorubicin and cyclophosphamide) in SCLC cells and in mouse models.

Transcriptomic profiling integrating microRNA and mRNA data identifies key signalling pathways in the response of SCLC cells to valproic acid, opening new prospects for improved therapies.

Valproic acid improves second-line regimen of SCLC response in preclinical modelshttp://ow.ly/Rsyd8

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.

Epigenetic Therapy for Solid Tumors: Highlighting the Impact of Tumor Hypoxia

In the last few decades, epigenetics has emerged as an exciting new field in development and disease, with a more recent focus towards cancer. Epigenetics has classically referred to heritable patterns of gene expression, primarily mediated through DNA methylation patterns. More recently, it has come to include the reversible chemical modification of histones and DNA that dictate gene expression patterns. Both the epigenetic up-regulation of oncogenes and downregulation of tumor suppressors have been shown to drive tumor development. Current clinical trials for cancer therapy include pharmacological inhibition of DNA methylation and histone deacetylation, with the aim of reversing these cancer-promoting epigenetic changes. However, the DNA methyltransferase and histone deacetylase inhibitors have met with less than promising results in the treatment of solid tumors. Regions of hypoxia are a common occurrence in solid tumors. Tumor hypoxia is associated with increased aggressiveness and therapy resistance, and importantly, hypoxic tumor cells have a distinct epigenetic profile. In this review, we provide a summary of the recent clinical trials using epigenetic drugs in solid tumors, discuss the hypoxia-induced epigenetic changes and highlight the importance of testing the epigenetic drugs for efficacy against the most aggressive hypoxic fraction of the tumor in future preclinical testing.

Epigenetic therapy for solid tumors: from bench science to clinical trials

The cancer epigenome is characterized by global DNA methylation and chromatin changes, such as the hypermethylation of specific CpG island promoters. Epigenetic agents like DNA methyltransferase or histone deacetylase inhibitors induce phenotype changes by reactivation of epigenetically silenced tumor suppressor genes. Despite initial promise in hematologic malignancies, epigenetic agents have not shown significant efficacy as monotherapy against solid tumors. Recent trials showed that epigenetic agents exert favorable modifier effects when combined with chemotherapy, hormonal therapy, or other epigenetic agents. Due to the novel nature of their mechanism, it is important to reconsider the optimal patient selection, drug regimen, study design, and outcome measures when pursuing future trials in order to discover the full potential of this new therapeutic modality.

Romidepsin in peripheral and cutaneous T-cell lymphoma: mechanistic implications from clinical and correlative data

Romidepsin is an epigenetic agent approved for the treatment of patients with cutaneous or peripheral T-cell lymphoma (CTCL and PTCL). Here we report data in all patients treated on the National Cancer Institute 1312 trial, demonstrating long-term disease control and the ability to retreat patients relapsing off-therapy. In all, 84 patients with CTCL and 47 with PTCL were enrolled. Responses occurred early, were clinically meaningful and of very long duration in some cases. Notably, patients with PTCL receiving romidepsin as third-line therapy or later had a comparable response rate (32%) of similar duration as the total population (38%). Eight patients had treatment breaks of 3.5 months to 10 years; in four of six patients, re-initiation of treatment led to clear benefit. Safety data show slightly greater haematological and constitutional toxicity in PTCL. cDNA microarray studies show unique individual gene expression profiles, minimal overlap between patients, and both induction and repression of gene expression that reversed within 24 h. These data argue against cell death occurring as a result of an epigenetics-mediated gene induction programme. Together this work supports the safety and activity of romidepsin in T-cell lymphoma, but suggests a complex mechanism of action.

Histone deacetylase inhibitors in clinical studies as templates for new anticancer agents

Histone dacetylases (HDACs) are a group of enzymes that remove acetyl groups from histones and regulate expression of tumor suppressor genes. They are implicated in many human diseases, especially cancer, making them a promising therapeutic target for treatment of the latter by developing a wide variety of inhibitors. HDAC inhibitors interfere with HDAC activity and regulate biological events, such as cell cycle, differentiation and apoptosis in cancer cells. As a result, HDAC inhibitor-based therapies have gained much attention for cancer treatment. To date, the FDA has approved three HDAC inhibitors for cutaneous/peripheral T-cell lymphoma and many more HDAC inhibitors are in different stages of clinical development for the treatment of hematological malignancies as well as solid tumors. In the intensifying efforts to discover new, hopefully more therapeutically efficacious HDAC inhibitors, molecular modeling-based rational drug design has played an important role in identifying potential inhibitors that vary in molecular structures and properties. In this review, we summarize four major structural classes of HDAC inhibitors that are in clinical trials and different computer modeling tools available for their structural modifications as a guide to discover additional HDAC inhibitors with greater therapeutic utility.

HDAC Inhibitors: A New Radiosensitizer for Non-small-cell Lung Cancer

For many decades, lung cancer has been the most common cancer and the leading cause of cancer death worldwide. More than 50% of non-small-cell lung cancer patients receive radiotherapy (alone or in combination with chemotherapy or surgery) during their treatment. The intrinsic radiosensitivity of tumors and dose-limiting toxicity restrict the curative potential of radiotherapy. Histone deacetylase inhibitors (HDACis) are an emerging class of agents that target histone deacetylase and represent promising radiosensitizers that affect various biological processes, such as cell growth, apoptosis, DNA repair, and terminal differentiation. Histone deacetylase inhibitors have been found to suppress many important DNA damage responses by downregulating proteins in the homologous recombination and nonhomologous end joining repair pathways in vitro. In this review, we describe the rationale for using HDACis as radiosensitizers and the clinical evidence regarding the use of HDACis for the treatment of non-small-cell lung cancer.

New strategies in lung cancer: epigenetic therapy for non-small cell lung cancer

Recent discoveries that non-small cell lung cancer (NSCLC) can be divided into molecular subtypes based on the presence or absence of driver mutations have revolutionized the treatment of many patients with advanced disease. However, despite these advances, a majority of patients are still dependent on modestly effective cytotoxic chemotherapy to provide disease control and prolonged survival. In this article, we review the current status of attempts to target the epigenome, heritable modifications of DNA, histones, and chromatin that may act to modulate gene expression independently of DNA coding alterations, in NSCLC and the potential for combinatorial and sequential treatment strategies.

Romidepsin for the treatment of T-cell lymphomas

PURPOSE

The pharmacology, pharmacokinetic and pharmacodynamic properties, and clinical data on a novel therapy for the treatment of cutaneous or peripheral T-cell lymphoma (CTCL, PTCL) are summarized.

SUMMARY

Romidepsin is the only bicyclic histone deacetylase (HDAC) inhibitor to undergo clinical development. A potent and specific inhibitor of class 1 HDACs, romidepsin has linear pharmacokinetics and is primarily metabolized by cytochrome P-450 isoenzyme 3A4. In two Phase II studies involving patients with relapsed or refractory CTCL, romidepsin therapy produced overall response rates of 34-35% (including patients with advanced and heavily pretreated disease), with a complete response seen in about 6% of patients in both studies; romidepsin responses were seen across all evaluated disease sites (skin, blood, lymph, viscera). In two Phase II studies in patients with relapsed or refractory PTCL, romidepsin produced overall response rates of 25-38%, and 15-18% of patients experienced a complete response; therapeutic responses were seen across major PTCL subtypes regardless of the number or types of previous therapies or refractoriness to the last prior therapy. In clinical trials to date, romidepsin therapy was generally well tolerated, with nausea, fatigue, and vomiting reported as the most common nonhematologic adverse events. However, thrombocytopenia and neutropenia are relatively common events, especially in patients with PTCL.

CONCLUSION

Romidepsin, a class 1-specific HDAC inhibitor, induces durable responses, with a manageable toxicity profile, in patients with relapsed or refractory CTCL or PTCL who have few therapeutic options.

Histone deacetylase inhibitors with enhanced enzymatic inhibition effects and potent in vitro and in vivo antitumor activities

In the present work, a series of small molecules were designed and synthesized based on structural optimization. A significant improvement in the enzyme inhibitory activity of these compounds was discovered. Moreover, the tested compounds have moderate preference for class I HDACs over HDAC6, as demonstrated by enzyme selectivity assays. In vitro antiproliferation assay results show that representative compounds can selectively inhibit the growth of non-solid lymphoma and leukemic cells such as U937, K562, and HL60. In the in vivo antitumor assay, (S)-4-(2-(5-(dimethylamino)naphthalene-1-sulfonamido)-2-phenylacetamido)-N-hydroxybenzamide (D17) showed better performance than SAHA in blocking U937 tumor growth. Western blot analysis revealed that representative molecules can block the function of both class I HDACs and HDAC6. More importantly, our western blot results reveal that the levels of some oncogenic proteins (p-Akt in the PI3K/AKT/mTOR signal pathway, c-Raf and p-Erk in the MAPK signal pathway) were dramatically down-regulated by our compounds in the U937 cell line rather than MDA-MB-231 cells. This distinction in cellular mechanism might be an important reason why the U937 cell line was found to more sensitive to our HDAC inhibitors than the MDA-MB-231 cell line.

Targeting the epigenome in lung cancer: expanding approaches to epigenetic therapy

Epigenetic aberrations offer dynamic and reversible targets for cancer therapy; increasingly, alteration via overexpression, mutation, or rearrangement is found in genes that control the epigenome. Such alterations suggest a fundamental role in carcinogenesis. Here, we consider three epigenetic mechanisms: DNA methylation, histone tail modification and non-coding, microRNA regulation. Evidence for each of these in lung cancer origin or progression has been gathered, along with evidence that epigenetic alterations might be useful in early detection. DNA hypermethylation of tumor suppressor promoters has been observed, along with global hypomethylation and hypoacetylation, suggesting an important role for tumor suppressor gene silencing. These features have been linked as prognostic markers with poor outcome in lung cancer. Several lines of evidence have also suggested a role for miRNA in carcinogenesis and in outcome. Cigarette smoke downregulates miR-487b, which targets both RAS and MYC; RAS is also a target of miR-let-7, again downregulated in lung cancer. Together the evidence implicates epigenetic aberration in lung cancer and suggests that targeting these aberrations should be carefully explored. To date, DNA methyltransferase and histone deacetylase inhibitors have had minimal clinical activity. Explanations include the possibility that the agents are not sufficiently potent to invoke epigenetic reversion to a more normal state; that insufficient time elapses in most clinical trials to observe true epigenetic reversion; and that doses often used may provoke off-target effects such as DNA damage that prevent epigenetic reversion. Combinations of epigenetic therapies may address those problems. When epigenetic agents are used in combination with chemotherapy or targeted therapy it is hoped that downstream biological effects will provoke synergistic cytotoxicity. This review evaluates the challenges of exploiting the epigenome in the treatment of lung cancer.

A novel hydroxysuberamide derivative potentiates MG132-mediated anticancer activity against human hormone refractory prostate cancers--the role of histone deacetylase and endoplasmic reticulum stress

BACKGROUND

Histone deacetylase (HDAC) inhibitors are successful for treatment of advanced cutaneous T-cell lymphoma but only show modest effect in solid tumors. Approaches for HDAC inhibitors to improve activity against solid tumors are necessary.

METHODS

Sulforhodamine B assay and flow cytometric analysis detected cell proliferation and cell-cycle progression, respectively. Protein expression was determined by Western blotting. Comet assay and DNA end-binding activity of Ku proteins detected DNA damage and DNA repair activity, respectively. siRNA technique was used for knockdown of specific cellular target.

RESULTS

WJ25591 displayed inhibitory activity against HDAC1 and cell proliferation in human hormone-refractory prostate cancers PC-3 and DU-145. WJ25591 caused an arrest of cell-cycle at both G1- and G2-phase and increased protein expressions of p21 and cyclin E, followed by cell apoptosis. WJ25591-induced Bcl-2 down-regulation and activation of caspase-9, -8, and -3, suggesting apoptotic execution through both intrinsic and extrinsic apoptotic pathways. WJ25591 also significantly inhibited DNA repair activity but not directly induced DNA damage. Moreover, the proteasome inhibitor MG-132 dramatically sensitized WJ25591-induced cell apoptosis. The siRNA technique demonstrated that endoplasmic reticulum (ER) stress, in particular CHOP/GADD153 up-regulation, contributed to the synergistic effect.

CONCLUSIONS

The data suggest that WJ25591 inhibited HDAC activity, leading to cell-cycle arrest and inhibition of DNA repair. Caspase cascades are subsequently triggered to execute cell apoptosis. MG-132 dramatically sensitizes WJ25591-mediated apoptosis, at least partly, through ER stress response. The data also reveal that combination of HDAC inhibitors and proteasome inhibitors may be a potential strategy against hormone-refractory prostate cancers.

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.

Epigenetic therapy in non-small-cell lung cancer: targeting DNA methyltransferases and histone deacetylases

INTRODUCTION

Epigenetics refers to heritable modifications of DNA and associated chromatin components that influence gene expression without altering DNA coding sequence. Epigenetic dysregulation is a central contributor to oncogenesis and is increasingly a focus of interest in cancer therapeutic research. Two key levels of aberrant epigenetic control are DNA methylation and histone acetylation. Primary regulators of these epigenetic changes include DNA methyltransferases (DNMTs) and histone deacetylases (HDACs).

AREAS COVERED

This review focuses on epigenetic changes in non-small-cell lung cancer and recent preclinical and clinical studies targeting these changes. DNMT inhibitors were previously explored at or near maximally tolerated doses, levels at which these agents are cytotoxic but have suboptimal effects on DNA methylation. Use of these inhibitors at substantially lower doses, in combination with HDAC inhibitors, can promote re-expression of silenced tumor suppressor genes, can result in major clinical responses and may alter tumor responsiveness to subsequent cytotoxic therapies.

EXPERT OPINION

Combinatorial epigenetic therapy has demonstrated encouraging clinical activity, but many relevant questions remain. Global strategies influencing the epigenome may have both positive and potential negative long-term effects on cancer progression. Further clinical investigation of this approach, including exploratory studies to define predictive biomarkers, is warranted.

Phase I trial of a new schedule of romidepsin in patients with advanced cancers

PURPOSE

Romidepsin is a potent histone deacetylase inhibitor (HDI) with activity in T-cell lymphoma. Given preclinical data showing greater induction of gene expression with longer exposures to HDIs, a phase I study of a day 1, 3, and 5 romidepsin schedule was evaluated. A secondary objective was to assess the effect of romidepsin on radioactive iodine (RAI) uptake in thyroid cancers.

EXPERIMENTAL DESIGN

Open-label, single-arm, phase I, 3 + 3 dose escalation study. Romidepsin was administered as a 4-hour infusion on days 1, 3, and 5 of a 21-day cycle. Pharmacokinetics (PK) and pharmacodynamics (PD) were assessed, including histone acetylation in peripheral blood mononuclear cells (PBMC), RAI uptake in refractory thyroid cancer, and HDI-related ECG changes.

RESULTS

Twenty-eight patients with solid tumors, including 11 patients with thyroid cancer were enrolled. Six dose levels were explored, and 7 mg/m(2) on days 1, 3, and 5 was identified as tolerable. No Response Evaluation Criteria In Solid Tumors-defined objective responses were recorded although 9 patients had stable disease a median 30 weeks (range, 21-112) including 6 with thyroid cancer a median of 33 weeks. PD studies detected acetylated histones in PBMCs and ECG changes beginning at low dose levels. Follow-up RAI scans in patients with RAI refractory thyroid cancer did not detect meaningful increases.

CONCLUSIONS

A romidepsin dose of 7 mg/m(2) administered on days 1, 3, and 5 was found tolerable and resulted in histone acetylation in PBMCs. Although there were no objective responses with romidepsin alone, this schedule may be useful for developing combination studies in solid tumors.

A focus on the preclinical development and clinical status of the histone deacetylase inhibitor, romidepsin (depsipeptide, Istodax(®))

Romidepsin (Istodax(®), depsipeptide, FR901228, FK228, NSC 630176) is a cyclic peptide, broad-spectrum, potent histone deacetylase inhibitor, with activity mainly against class I histone deacetylase enzymes. In this article, we give an overview of the putative modes of action, such as effects on gene expression, cell cycle regulation, apoptosis induction, DNA repair, protein acetylation and induction of autophagy. Romidepsin has mainly been developed as a therapy for hematologic malignancies and is approved by the US FDA for the treatment of cutaneous T-cell lymphomas. This report outlines the laboratory and clinical development of the compound as a single agent that has more recently been evaluated in combination with other anticancer therapeutics, such as proteasome inhibitors.

Epigenetic therapy: use of agents targeting deacetylation and methylation in cancer management

The emergence of epigenetic mechanisms as key regulators of gene expression has led to dramatic advances in understanding cancer biology. Driven by complex layers that include aberrant DNA methylation and histone modification, epigenetic aberrations have emerged as critical processes that disrupt cellular machinery and homeostasis. Recent discoveries have already translated into successful clinical trials and improved patient care, with several agents approved for hematologic disease and others undergoing study. As the field matures, substantial challenges persist that will require resolution. These include the need to decipher more fully the interplay between the epigenetic and genetic machinery, patient selection and improving treatment efficacy in solid tumors, and optimizing combination therapies to counteract chemoresistance and minimize adverse effects. Here, we review recent progress in epigenetic treatments and consider their implications for future cancer therapy.

Histone deacetylase inhibitors (HDACIs): multitargeted anticancer agents

Histone deacetylase (HDAC) inhibitors are an emerging class of therapeutics with potential as anticancer drugs. The rationale for developing HDAC inhibitors (and other chromatin-modifying agents) as anticancer therapies arose from the understanding that in addition to genetic mutations, epigenetic changes such as dysregulation of HDAC enzymes can alter phenotype and gene expression, disturb homeostasis, and contribute to neoplastic growth. The family of HDAC inhibitors is large and diverse. It includes a range of naturally occurring and synthetic compounds that differ in terms of structure, function, and specificity. HDAC inhibitors have multiple cell type-specific effects in vitro and in vivo, such as growth arrest, cell differentiation, and apoptosis in malignant cells. HDAC inhibitors have the potential to be used as monotherapies or in combination with other anticancer therapies. Currently, there are two HDAC inhibitors that have received approval from the US FDA for the treatment of cutaneous T-cell lymphoma: vorinostat (suberoylanilide hydroxamic acid, Zolinza) and depsipeptide (romidepsin, Istodax). More recently, depsipeptide has also gained FDA approval for the treatment of peripheral T-cell lymphoma. Many more clinical trials assessing the effects of various HDAC inhibitors on hematological and solid malignancies are currently being conducted. Despite the proven anticancer effects of particular HDAC inhibitors against certain cancers, many aspects of HDAC enzymes and HDAC inhibitors are still not fully understood. Increasing our understanding of the effects of HDAC inhibitors, their targets and mechanisms of action will be critical for the advancement of these drugs, especially to facilitate the rational design of HDAC inhibitors that are effective as antineoplastic agents. This review will discuss the use of HDAC inhibitors as multitargeted therapies for malignancy. Further, we outline the pharmacology and mechanisms of action of HDAC inhibitors while discussing the safety and efficacy of these compounds in clinical studies to date.

Aberrant epigenetic regulation: a central contributor to lung carcinogenesis and a new therapeutic target

Carcinogenesis is driven by a combination of genetic and epigenetic abnormalities. Aberrancies in gene promoter methylation patterns and histone acetylation are associated with silencing of tumor suppressor genes in lung cancer and other solid tumors. Identification of key epigenetic modifications has been shown to be prognostic in early-stage non-small cell lung cancer. Previous clinical trials aimed at modifying the epigenome with single-agent demethylating agents or histone deacetylase inhibitors given at maximally tolerated doses have provided disappointing results. A recent clinical trial using a combination of a demethylating agent and a histone deacetylase inhibitor at "epigenetically targeted" doses concomitantly has shown promising results, including a patient with a complete objective response. Biomarkers associated with this clinical trial suggest that patients who undergo robust demethylation, as detected in the peripheral blood after a month on treatment, identifies those who gain the most benefit from this novel treatment strategy. Based on observations of unusually durable responses to subsequent therapy after administration of combined epigenetic therapy, epigenetic therapy may also play a role in "priming" patients to better respond to standard cytotoxic therapy or immunotherapy. This manuscript will review the data on the role of epigenetics in lung cancer and the history of epigenetic treatments in lung cancer spanning over the last 40 years.

Phase I study of 5-aza-2'-deoxycytidine in combination with valproic acid in non-small-cell lung cancer

PURPOSE

Non-small-cell lung cancer (NSCLC) accounts for the majority of lung cancer and is the most common cause of cancer death in industrialized countries. Epigenetic modifications are observed universally during the tumorigenesis of lung cancer. The development of epigenetic-modulating agents utilizing the synergism between hypomethylating agents and histone deacetylase (HDAC) inhibitors provides a novel therapeutic approach in treating NSCLC.

METHODS

We performed a phase I trial combining 5-aza-2'-deoxycytidine (decitabine) and valproic acid (VPA), in patients with advanced stage NSCLC. Patients were treated with escalating doses of decitabine (5-15 mg/m(2)) IV for 10 days in combination with VPA (10-20 mg/kg/day) PO on days 5-21 of a 28-day cycle. Pharmacokinetic and pharmacodynamic analysis included decitabine pharmacokinetics and fetal hemoglobin expression.

RESULTS

Eight patients were accrued to this phase I study. All patients had advanced NSCLC and had received prior chemotherapy. Eastern Cooperative Oncology Group performance status was 0-2. Major toxicities included myelosuppression and neurotoxicity. Dose-limiting toxicity was seen in two patients suffering grade 3 neurotoxicity during cycle one including disorientation, lethargy, memory loss, and ataxia at dose level 1. One patient had grade 3 neutropenia at the de-escalated dose. No objective response was observed, and stable disease was seen in one patient. Fetal hemoglobin levels increased after cycle one in all seven patients with evaluable results.

CONCLUSIONS

We observed that decitabine and valproic acid are an effective combination in reactivating hypermethylated genes as demonstrated by re-expressing fetal hemoglobin. This combination in patients with advanced stage IV NSCLC, however, is limited by unacceptable neurological toxicity at a relatively low dosage. Combining hypomethylating agents with alternative HDAC inhibitors that lack the toxicity of VPA should be explored further.