Phase II trial of the histone deacetylase inhibitor pivaloyloxymethyl butyrate (Pivanex, AN-9) in advanced non-small cell lung cancer

Butyrate as a potential therapeutic agent for neurodegenerative disorders

Maintaining an optimum microbial community within the gastrointestinal tract is intricately linked to human metabolic, immune and brain health. Disturbance to these microbial populations perturbs the production of vital bioactive compounds synthesised by the gut microbiome, such as short-chain fatty acids (SCFAs). Of the SCFAs, butyrate is known to be a major source of energy for colonocytes and has valuable effects on the maintenance of intestinal epithelium and blood brain barrier integrity, gut motility and transit, anti-inflammatory effects, and autophagy induction. Inducing endogenous butyrate production is likely to be beneficial for gut-brain homeostasis and for optimal neuronal function. For these reasons, butyrate has gained interest as a potential therapy for not only metabolic and immunological disorders, but also conditions related to the brain, including neurodegenerative diseases. While direct and indirect sources of butyrate, including prebiotics, probiotics, butyrate pro-drugs and glucosidase inhibitors, offer a promising therapeutic avenue, their efficacy and dosage in neurodegenerative conditions remain largely unknown. Here, we review current literature on effects of butyrate relevant to neuronal function, the impact of butyrate in a range of neurodegenerative diseases and related treatments that may have potential for the treatment of neurodegenerative diseases.

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.

Harnessing and delivering microbial metabolites as therapeutics via advanced pharmaceutical approaches

Microbial metabolites have emerged as key players in the interplay between diet, the gut microbiome, and host health. Two major classes, short-chain fatty acids (SCFAs) and tryptophan (Trp) metabolites, are recognized to regulate inflammatory, immune, and metabolic responses within the host. Given that many human diseases are associated with dysbiosis of the gut microbiome and consequent reductions in microbial metabolite production, the administration of these metabolites represents a direct, multi-targeted treatment. While a multitude of preclinical studies showcase the therapeutic potential of both SCFAs and Trp metabolites, they often rely on high doses and frequent dosing regimens to achieve systemic effects, thereby constraining their clinical applicability. To address these limitations, a variety of pharmaceutical formulations approaches that enable targeted, delayed, and/or sustained microbial metabolite delivery have been developed. These approaches, including enteric encapsulations, esterification to dietary fiber, prodrugs, and nanoformulations, pave the way for the next generation of microbial metabolite-based therapeutics. In this review, we first provide an overview of the roles of microbial metabolites in maintaining host homeostasis and outline how compromised metabolite production contributes to the pathogenesis of inflammatory, metabolic, autoimmune, allergic, infectious, and cancerous diseases. Additionally, we explore the therapeutic potential of metabolites in these disease contexts. Then, we provide a comprehensive and up-to-date review of the pharmaceutical strategies that have been employed to enhance the therapeutic efficacy of microbial metabolites, with a focus on SCFAs and Trp metabolites.

Acetyl-CoA metabolism as a therapeutic target for cancer

Acetyl-coenzyme A (acetyl-CoA), an essential metabolite, not only takes part in numerous intracellular metabolic processes, powers the tricarboxylic acid cycle, serves as a key hub for the biosynthesis of fatty acids and isoprenoids, but also serves as a signaling substrate for acetylation reactions in post-translational modification of proteins, which is crucial for the epigenetic inheritance of cells. Acetyl-CoA links lipid metabolism with histone acetylation to create a more intricate regulatory system that affects the growth, aggressiveness, and drug resistance of malignancies such as glioblastoma, breast cancer, and hepatocellular carcinoma. These fascinating advances in the knowledge of acetyl-CoA metabolism during carcinogenesis and normal physiology have raised interest regarding its modulation in malignancies. In this review, we provide an overview of the regulation and cancer relevance of main metabolic pathways in which acetyl-CoA participates. We also summarize the role of acetyl-CoA in the metabolic reprogramming and stress regulation of cancer cells, as well as medical application of inhibitors targeting its dysregulation in therapeutic intervention of cancers.

Exploring Therapeutic Avenues in Lung Cancer: The Epigenetic Perspective

Lung cancer, primarily non-small cell lung carcinoma (NSCLC) and small cell lung carcinoma (SCLC), is distinguished by its high prevalence and marked mortality rates. Traditional therapeutic approaches, encompassing chemotherapy, radiation, and targeted therapies, frequently show limited efficacy due to acquired resistance and notable side effects. The objective of this review is to introduce a fresh perspective on the therapeutic strategies for lung cancer, emphasizing interventions targeting the epigenetic alterations often seen in this malignancy. This review presents the most recent advancements in the field, focusing on both past and current clinical trials related to the modulation of methylation patterns using diverse molecular agents. Furthermore, an in-depth analysis of the challenges and advantages of these methylation-modifying drugs will be provided, assessing their efficacy as individual treatments and their potential for synergy when integrated with prevailing therapeutic regimens.

The roles and applications of short-chain fatty acids derived from microbial fermentation of dietary fibers in human cancer

Dietary fibers (DFs) and their metabolites attract significant attention in research on health and disease, attributing to their effects on regulating metabolism, proliferation, inflammation, and immunity. When fermented by gut microbiota, DFs mainly produce short-chain fatty acids (SCFAs), such as acetic acid, propionic acid, and butyric acid. As the essential nutrients for intestinal epithelial cells, SCFAs maintain intestinal homeostasis and play essential roles in a wide range of biological functions. SCFAs have been found to inhibit histone deacetylase, activate G protein-coupled receptors, and modulate the immune response, which impacts cancer and anti-cancer treatment. Notably, while extensive studies have illuminated the roles of SCFAs in colorectal cancer development, progression, and treatment outcomes, limited evidence is available for other types of cancers. This restricts our understanding of the complex mechanisms and clinical applications of SCFAs in tumors outside the intestinal tract. In this study, we provide a comprehensive summary of the latest evidence on the roles and mechanisms of SCFAs, with a focus on butyric acid and propionic acid, derived from microbial fermentation of DFs in cancer. Additionally, we recapitulate the clinical applications of SCFAs in cancer treatments and offer our perspectives on the challenges, limitations, and prospects of utilizing SCFAs in cancer research and therapy.

Potential of Synthetic and Natural Compounds as Novel Histone Deacetylase Inhibitors for the Treatment of Hematological Malignancies

Histone deacetylases (HDACs) and histone acetyltransferases (HATs) are enzymes that remove or add acetyl groups to lysine residues of histones, respectively. Histone deacetylation causes DNA to more snugly encircle histones and decreases gene expression, whereas acetylation has the opposite effect. Through these small alterations in chemical structure, HATs and HDACs regulate DNA expression. Recent research indicates histone deacetylase inhibitors (HDACis) may be used to treat malignancies, including leukemia, B-cell lymphoma, virus-associated tumors, and multiple myeloma. These data suggest that HDACis may boost the production of immune-related molecules, resulting in the growth of CD8-positive T-cells and the recognition of nonreactive tumor cells by the immune system, thereby diminishing tumor immunity. The argument for employing epigenetic drugs in the treatment of acute myeloid leukemia (AML) patients is supported by evidence that both epigenetic changes and mutations in the epigenetic machinery contribute to AML etiology. Although hypomethylating drugs have been licensed for use in AML, additional epigenetic inhibitors, such as HDACis, are now being tested in humans. Preclinical studies evaluating the efficacy of HDACis against AML have shown the ability of specific agents, such as anobinostat, vorinostat, and tricostatin A, to induce growth arrest, apoptosis, autophagy and cell death. However, these inhibitors do not seem to be successful as monotherapies, but instead achieve results when used in conjunction with other medications. In this article, we discuss the mounting evidence that HDACis promote extensive histone acetylation, as well as substantial increases in reactive oxygen species and DNA damage in hematological malignant cells. We also evaluate the potential of various natural product-based HDACis as therapeutic agents to combat hematological malignancies.

An Update of Epigenetic Drugs for the Treatment of Cancers and Brain Diseases: A Comprehensive Review

Epigenetics has long been recognized as a significant field in biology and is defined as the investigation of any alteration in gene expression patterns that is not attributed to changes in the DNA sequences. Epigenetic marks, including histone modifications, non-coding RNAs, and DNA methylation, play crucial roles in gene regulation. Numerous studies in humans have been carried out on single-nucleotide resolution of DNA methylation, the CpG island, new histone modifications, and genome-wide nucleosome positioning. These studies indicate that epigenetic mutations and aberrant placement of these epigenetic marks play a critical role in causing the disease. Consequently, significant development has occurred in biomedical research in identifying epigenetic mechanisms, their interactions, and changes in health and disease conditions. The purpose of this review article is to provide comprehensive information about the different types of diseases caused by alterations in epigenetic factors such as DNA methylation and histone acetylation or methylation. Recent studies reported that epigenetics could influence the evolution of human cancer via aberrant methylation of gene promoter regions, which is associated with reduced gene function. Furthermore, DNA methyltransferases (DNMTs) in the DNA methylation process as well as histone acetyltransferases (HATs)/histone deacetylases (HDACs) and histone methyltransferases (HMTs)/demethylases (HDMs) in histone modifications play important roles both in the catalysis and inhibition of target gene transcription and in many other DNA processes such as repair, replication, and recombination. Dysfunction in these enzymes leads to epigenetic disorders and, as a result, various diseases such as cancers and brain diseases. Consequently, the knowledge of how to modify aberrant DNA methylation as well as aberrant histone acetylation or methylation via inhibitors by using epigenetic drugs can be a suitable therapeutic approach for a number of diseases. Using the synergistic effects of DNA methylation and histone modification inhibitors, it is hoped that many epigenetic defects will be treated in the future. Numerous studies have demonstrated a link between epigenetic marks and their effects on brain and cancer diseases. Designing appropriate drugs could provide novel strategies for the management of these diseases in the near future.

Short-chain fatty acid-releasing nano-prodrugs for attenuating growth and metastasis of melanoma

Low-molecular-weight (LMW) short-chain fatty acids (SCFAs), such as propionic and butyric acids, have been reported to possess anti-neoplastic effects; however, rapid renal clearance and high dose-based side effects limit their clinical translation. Hence, in this study, we have designed a new self-assembling nano-prodrugs that can effectively supply SCFAs: endogenous enzyme-metabolizable block copolymer poly(ethylene glycol)block-poly(vinyl ester) possessing several units of SCFAs conjugated as side chains via ester linkages. These amphiphilic polymers spontaneously self-assemble into nanostructures under aqueous conditions to form orally administrable nano-prodrugs (butyric acid: Nano^BA and propionic acid: Nano^PA). Herein, we show the therapeutic efficacy of SCFA nanoparticles (Nano^SCFA) in a mouse model of metastasis (melanoma). Ad libitum intake of our Nano^SCFA markedly demonstrated a decrease in the metastatic tumor nodules in the lungs compared with the effect observed after LMW SCFA administration with no discernible toxicity to the GI tract. In contrast, LMW SCFAs, even at a lower concentration than that of the Nano^SCFA, facilitated villus atrophy. Taken together, our work suggests that the use of Nano^SCFA as a therapeutic intervention for metastatic cancer is preferable over typical LMW SCFAs. STATEMENT OF SIGNIFICANCE: Low-molecular-weight (LMW) short-chain fatty acids (SCFAs) have shown versatile therapeutic effects on various diseases, including anti-tumorigenesis effects. However, their clinical translation is limited due to their poor pharmacokinetic profile and adverse effects. To overcome these limitations, we have developed new amphiphilic block copolymer-based SCFA-prodrugs, which self-assemble into nanoparticles in aqueous media (Nano^SCFA). SCFAs are covalently conjugated to the hydrophobic polymer segment via ester linkage, which can be enzymatically metabolized after oral administration. In the present study, we confirmed that ad libitum intake of Nano^SCFAs retarded the growth and metastatic potential of B16-F10 tumors compared to the LMW SCFAs with negligible discernible toxicity, reflecting Nano^SCFA as a preferable therapeutic intervention to LMW SCFA counterparts.

Epimutations and Their Effect on Chromatin Organization: Exciting Avenues for Cancer Treatment

The three-dimensional architecture of genomes is complex. It is organized as fibers, loops, and domains that form high-order structures. By using different chromosome conformation techniques, the complex relationship between transcription and genome organization in the three-dimensional organization of genomes has been deciphered. Epigenetic changes, such as DNA methylation and histone modification, are the hallmark of cancers. Tumor initiation, progression, and metastasis are linked to these epigenetic modifications. Epigenetic inhibitors can reverse these altered modifications. A number of epigenetic inhibitors have been approved by FDA that target DNA methylation and histone modification. This review discusses the techniques involved in studying the three-dimensional organization of genomes, DNA methylation and histone modification, epigenetic deregulation in cancer, and epigenetic therapies targeting the tumor.

Do biological activities of selective histone deacetylase 6 (HDAC6) inhibitors rely on the modification of cap group?

Nowadays, significant progress has been made in the development of selective histone deacetylase 6 (HDAC6) inhibitors, exerting great potential in the treatment of various malignant tumors and neurodegenerative diseases. Previously, selective inhibitory activities of HDAC inhibitors were generally considered sensitive to the interactions between the Cap group and the binding site of HDAC6, and a large number of selective HDAC6 inhibitors have been designed and synthesized based on the strategy. However, some inhibitors without Cap group could also exhibit excellent potency and selective inhibition towards HDAC6, and in this study, BRD9757 and compound 8, as capless selective HDAC6 inhibitors, were selected as molecular probes to explore the difference of their binding interactions in HDAC1&6. Through the analysis of binding-free energies and conformational rearrangements after 1 μs molecular dynamics simulation, it could be learned that although the residues in the binding site remained highly consistent, the binding mechanisms of BRD9757 and compound 8 in HDAC1&6 were different, which will provide valuable hints for the discovery of novel selective HDAC6 inhibitors.

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.

An evaluation of the interaction of pixantrone with formaldehyde-releasing drugs in cancer cells

PURPOSE

Pixantrone is a synthetic aza-anthracenedione currently used in the treatment of non-Hodgkin's lymphoma. The drug is firmly established as a poison of the nuclear enzyme topoisomerase II, however, pixantrone can also generate covalent drug-DNA adducts following activation by formaldehyde. While pixantrone-DNA adducts form proficiently in vitro, little evidence is presently at hand to indicate their existence within cells. The molecular nature of these lesions within cancer cells exposed to pixantrone and formaldehyde-releasing prodrugs was characterized along with the cellular responses to their formation.

METHODS

In vitro crosslinking assays, [¹⁴C] scintillation counting analyses and alkaline comet assays were applied to characterize pixantrone-DNA adducts. Flow cytometry, cell growth inhibition and clonogenic assays were used to measure cancer cell kill and survival.

RESULTS

Pixantrone-DNA adducts were not detectable in MCF-7 breast cancer cells exposed to [¹⁴C] pixantrone (10-40 µM) alone, however the addition of the formaldehyde-releasing prodrug AN9 yielded readily measurable levels of the lesion at ~ 1 adduct per 10 kb of genomic DNA. Co-administration with AN9 completely reversed topoisomerase II-associated DNA damage induction by pixantrone yet potentiated cell kill by the drug, suggesting that pixantrone-DNA adducts may promote a topoisomerase II-independent mechanism of cell death. Pixantrone-DNA adduct-forming treatments generally conferred mild synergism in multiple cell lines in various cell death and clonogenic assays, while pixantrone analogues either incapable or relatively defective in forming DNA adducts demonstrated antagonism when combined with AN9.

CONCLUSIONS

The features unique to pixantrone-DNA adducts may be leveraged to enhance cancer cell kill and may be used to guide the design of pixantrone analogues that generate adducts with more favorable anticancer properties.

LCDR regulates the integrity of lysosomal membrane by hnRNP K-stabilized LAPTM5 transcript and promotes cell survival

Here, we report that the long noncoding RNA lysosome cell death regulator (LCDR) mediates the survival of cancer cells, counteracting the effects of apoptosis triggered by lysosomal cell death pathways. Mechanistically, LCDR, as a cofactor for heterogenous nuclear ribonucleoprotein K (hnRNP K) to potentiate the stabilization of lysosomal membrane protein lysosomal-associated protein transmembrane 5 (LAPTM5), prevents lysosomal membrane permeabilization and promotes cancer cell survival. Clinically, LCDR, hnRNP K, and LAPTM5 are significantly up-regulated in lung adenocarcinoma (LUAD) patients. Targeting LCDR via nanoparticles-mediated RNA interference technology increases cell death in vitro and inhibits the growth of patient-derived xenografts of LUAD in vivo. Our study demonstrates that LCDR contributes to cancer pathology by regulating LCDR-mediated apoptosis.

Lysosome plays important roles in cellular homeostasis, and its dysregulation contributes to tumor growth and survival. However, the understanding of regulation and the underlying mechanism of lysosome in cancer survival is incomplete. Here, we reveal a role for a histone acetylation–regulated long noncoding RNA termed lysosome cell death regulator (LCDR) in lung cancer cell survival, in which its knockdown promotes apoptosis. Mechanistically, LCDR binds to heterogenous nuclear ribonucleoprotein K (hnRNP K) to regulate the stability of the lysosomal-associated protein transmembrane 5 (LAPTM5) transcript that maintains the integrity of the lysosomal membrane. Knockdown of LCDR, hnRNP K, or LAPTM5 promotes lysosomal membrane permeabilization and lysosomal cell death, thus consequently resulting in apoptosis. LAPTM5 overexpression or cathepsin B inhibitor partially restores the effects of this axis on lysosomal cell death in vitro and in vivo. Similarly, targeting LCDR significantly decreased tumor growth of patient-derived xenografts of lung adenocarcinoma (LUAD) and had significant cell death using nanoparticles (NPs)-mediated systematic short interfering RNA delivery. Moreover, LCDR/hnRNP K/LAPTM5 are up-regulated in LUAD tissues, and coexpression of this axis shows the increased diagnostic value for LUAD. Collectively, we identified a long noncoding RNA that regulates lysosome function at the posttranscriptional level. These findings shed light on LCDR/hnRNP K/LAPTM5 as potential therapeutic targets, and targeting lysosome is a promising strategy in cancer treatment.

Valproic Acid Prodrug Affects Selective Markers, Augments Doxorubicin Anticancer Activity and Attenuates Its Toxicity in a Murine Model of Aggressive Breast Cancer

We studied the unique inhibitor of the histone deacetylases (HDAC) valproate-valpromide of acyclovir (AN446) that upon metabolic degradation release the HDAC inhibitor (HDACI) valproic acid (VPA). Among the HDAC inhibitors that we have tested, only AN446, and to a lesser extent VPA, synergized with doxorubicin (Dox) anti-cancer activity. Romidepsin (Rom) was additive and the other HDACIs tested were antagonistic. These findings led us to test and compare the anticancer activities of AN446, VPA, and Rom with and without Dox in the 4T1 triple-negative breast cancer murine model. A dose of 4 mg/kg once a week of Dox had no significant effect on tumor growth. Rom was toxic, and when added to Dox the toxicity intensified. AN446, AN446 + Dox, and VPA + Dox suppressed tumor growth. AN446 and AN446 + Dox were the best inhibitory treatments for tumor fibrosis, which promotes tumor growth and metastasis. Dox increased fibrosis in the heart and kidneys, disrupting their function. AN446 most effectively suppressed Dox-induced fibrosis in these organs and protected their function. AN446 and AN446 + Dox treatments were the most effective inhibitors of metastasis to the lungs, as measured by the gap area. Genes that control and regulate tumor growth, DNA damage and repair, reactive oxygen production, and generation of inflammation were examined as potential therapeutic targets. AN446 affected their expression in a tissue-dependent manner, resulting in augmenting the anticancer effect of Dox while reducing its toxicity. The specific therapeutic targets that emerged from this study are discussed.

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.

Recent developments of HDAC inhibitors: Emerging indications and novel molecules

The histone deacetylase (HDAC) enzymes, a class of epigenetic regulators, are historically well established as attractive therapeutic targets. During investigation of trends within clinical trials, we have identified a high number of clinical trials involving HDAC inhibitors, prompting us to further evaluate the current status of this class of therapeutic agents. In total, we have identified 32 agents with HDAC-inhibiting properties, of which 29 were found to interact with the HDAC enzymes as their primary therapeutic target. In this review, we provide an overview of the clinical drug development highlighting the recent advances and provide analysis of specific trials and, where applicable, chemical structures. We found haematologic neoplasms continue to represent the majority of clinical indications for this class of drugs; however, it is clear that there is an ongoing trend towards diversification. Therapies for non-oncology indications including HIV infection, muscular dystrophies, inflammatory diseases as well as neurodegenerative diseases such as Alzheimer's disease, frontotemporal dementia and Friedreich's ataxia are achieving promising clinical progress. Combinatory regimens are proving to be useful to improve responsiveness among FDA-approved agents; however, it often results in increased treatment-related toxicities. This analysis suggests that the indication field is broadening through a high number of clinical trials while several fields of preclinical development are also promising.

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.

A phase 1 trial of the histone deacetylase inhibitor AR-42 in patients with neurofibromatosis type 2-associated tumors and advanced solid malignancies

PURPOSE

Given clinical activity of AR-42, an oral histone deacetylase inhibitor, in hematologic malignancies and preclinical activity in solid tumors, this phase 1 trial investigated the safety and tolerability of AR-42 in patients with advanced solid tumors, including neurofibromatosis type 2-associated meningiomas and schwannomas (NF2). The primary objective was to define the maximum tolerated dose (MTD) and dose-limiting toxicities (DLTs). Secondary objectives included determining pharmacokinetics and clinical activity.

METHODS

This phase I trial was an open-label, single-center, dose-escalation study of single-agent AR-42 in primary central nervous system and advanced solid tumors. The study followed a 3 + 3 design with an expansion cohort at the MTD.

RESULTS

Seventeen patients were enrolled with NF2 (n = 5), urothelial carcinoma (n = 3), breast cancer (n = 2), non-NF2-related meningioma (n = 2), carcinoma of unknown primary (n = 2), small cell lung cancer (n = 1), Sertoli cell carcinoma (n = 1), and uveal melanoma (n = 1). The recommended phase II dose is 60 mg three times weekly, for 3 weeks of a 28-day cycle. DLTs included grade 3 thrombocytopenia and grade 4 psychosis. The most common treatment-related adverse events were cytopenias, fatigue, and nausea. The best response was stable disease in 53% of patients (95% CI 26.6-78.7). Median progression-free survival (PFS) was 3.6 months (95% CI 1.2-9.1). Among evaluable patients with NF2 or meningioma (n = 5), median PFS was 9.1 months (95% CI 1.9-not reached).

CONCLUSION

Single-agent AR-42 is safe and well tolerated. Further studies may consider AR-42 in a larger cohort of patients with NF2 or in combination with other agents in advanced solid tumors.

TRIAL REGISTRATION

NCT01129193, registered 5/24/2010.

Small Molecules Targeting HATs, HDACs, and BRDs in Cancer Therapy

Evidence for research over the past decade shows that epigenetic regulation mechanisms run through the development and prognosis of tumors. Therefore, small molecular compounds targeting epigenetic regulation have become a research hotspot in the development of cancer therapeutic drugs. According to the obvious abnormality of histone acetylation when tumors occur, it suggests that histone acetylation modification plays an important role in the process of tumorigenesis. Currently, as a new potential anti-cancer therapeutic drugs, many active small molecules that target histone acetylation regulatory enzymes or proteins such as histone deacetylases (HDACs), histone acetyltransferase (HATs) and bromodomains (BRDs) have been developed to restore abnormal histone acetylation levels to normal. In this review, we will focus on summarizing the changes of histone acetylation levels during tumorigenesis, as well as the possible pharmacological mechanisms of small molecules that target histone acetylation in cancer treatment.

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.

Histone deacetylase inhibitor based prodrugs

Histone deacetylases (HDACs) are a family of enzymes which play important roles in the development and progression of cancers. Inhibition of HDACs has been widely studied as a therapeutic strategy in the discovery of anticancer drugs. HDAC inhibitors (HDACIs) have exhibited potency against a variety of cancer types, and four of them have been approved by the US FDA for cancer treatment. However, the clinical benefits of current HDACIs is limited by the insufficient physicochemical property, selectivity and potency. To improve the clinical potential of HDACIs, the prodrug strategy had been utilized to improve the in vivo pharmacokinetic and pharmacodynamic performances of HDACIs. Enhancements in the stability, water solubility, lipophilicity, oral bioavailability and tumor cell selectivity were reported by various studies. Herein, the development of different kinds of HDACI-based prodrug is summarized for the further structural modification of HDACIs with high potential to be drug candidates.

Histone deacetylase inhibitor OBP‑801 and amrubicin synergistically inhibit the growth of squamous cell lung carcinoma by inducing mitochondrial ASK1‑dependent apoptosis

Squamous cell lung carcinoma (SQCLC) is an aggressive type of lung cancer. In contrast with the marked advances that have been achieved in the treatment of lung adenocarcinoma, there are currently no effective targeted therapies for SQCLC, for with cytotoxic drugs are still the main treatment strategy. Therefore, the present study aimed to develop novel combination therapies for SQCLC. The results demonstrated that a combined treatment with the potent histone deacetylase (HDAC) inhibitor OBP‑801 and the third‑generation anthracycline amrubicin synergistically inhibited the viability of SQCLC cell lines by inducing apoptosis signal‑regulating kinase 1 (ASK1)‑dependent, as well as JNK‑ and p38 mitogen‑activated protein kinase (MAPK)‑independent apoptosis. OBP‑801 treatment strongly induced the protein expression levels of thioredoxin‑interacting protein (TXNIP), and amrubicin treatment increased the levels of intracellular reactive oxygen species (ROS), which suggested that this combination oxidized and dissociated thioredoxin 2 (Trx2) from mitochondrial ASK1 and activated ASK1. Moreover, mouse xenograft experiments using human H520 SQCLC cells revealed that the co‑treatment potently suppressed tumor growth in vivo. These results suggested that a combined treatment with OBP‑801 and amrubicin may have potential as a therapeutic strategy for SQCLC.

The timeline of epigenetic drug discovery: from reality to dreams

The flexibility of the epigenome has generated an enticing argument to explore its reversion through pharmacological treatments as a strategy to ameliorate disease phenotypes. All three families of epigenetic proteins—readers, writers, and erasers—are druggable targets that can be addressed through small-molecule inhibitors. At present, a few drugs targeting epigenetic enzymes as well as analogues of epigenetic modifications have been introduced into the clinic use (e.g. to treat haematological malignancies), and a wide range of epigenetic-based drugs are undergoing clinical trials. Here, we describe the timeline of epigenetic drug discovery and development beginning with the early design based solely on phenotypic observations to the state-of-the-art rational epigenetic drug discovery using validated targets. Finally, we will highlight some of the major aspects that need further research and discuss the challenges that need to be overcome to implement epigenetic drug discovery into clinical management of human disorders. To turn into reality, researchers from various disciplines (chemists, biologists, clinicians) need to work together to optimise the drug engineering, read-out assays, and clinical trial design.

Nuclear Glycogenolysis Modulates Histone Acetylation in Human Non-Small Cell Lung Cancers

Nuclear glycogen was first documented in the early 1940s, but its role in cellular physiology remained elusive. In this study, we utilized pure nuclei preparations and stable isotope tracers to define the origin and metabolic fate of nuclear glycogen. Herein, we describe a key function for nuclear glycogen in epigenetic regulation through compartmentalized pyruvate production and histone acetylation. This pathway is altered in human non-small cell lung cancers, as surgical specimens accumulate glycogen in the nucleus. We demonstrate that the decreased abundance of malin, an E3 ubiquitin ligase, impaired nuclear glycogenolysis by preventing the nuclear translocation of glycogen phosphorylase and causing nuclear glycogen accumulation. Re-introduction of malin in lung cancer cells restored nuclear glycogenolysis, increased histone acetylation, and decreased growth of cancer cells transplanted into mice. This study uncovers a previously unknown role for glycogen metabolism in the nucleus and elucidates another mechanism by which cellular metabolites control epigenetic regulation.

Structure-based design generated novel hydroxamic acid based preferential HDAC6 lead inhibitor with on-target cytotoxic activity against primary choroid plexus carcinoma

Histone deacetylase 6 (HDAC6) is an attractive target for cancer therapeutic intervention. Selective HDAC6 inhibitors is important to minimise the side effects of pan inhibition. Thus, new class of hydroxamic acid-based derivatives were designed on structural basis to perform preferential activity against HDAC6 targeting solid tumours. Interestingly, 1-benzylbenzimidazole-2-thio-N-hydroxybutanamide 10a showed impressive preference with submicromolar potency against HDAC6 (IC₅₀ = 510 nM). 10a showed cytotoxic activity with interesting profile against CCHE-45 at (IC₅₀ = 112.76 µM) when compared to standard inhibitor Tubacin (IC₅₀ = 20 µM). Western blot analysis of acetylated-α-tubulin verified the HDAC6 inhibiting activity of 10a. Moreover, the insignificant difference in acetylated-α-tubulin induced by 10a and Tubacin implied the on-target cytotoxic activity of 10a. Docking of 10a in the binding site of HDAC6 attributed the activity of 10a to π-π stacking with the amino acids of the hydrophobic channel of HDAC6 and capture of zinc metal in bidentate fashion. The therapeutic usefulness besides the on-target activity may define 10a as an interesting safe-lead inhibitor for future development.

Evaluation of WO2017018805: 1,3,4-oxadiazole sulfamide derivatives as selective HDAC6 inhibitors

INTRODUCTION

There are great potential in the development of selective HDAC6 inhibitors for the treatment of infectious diseases, neoplasms, endocrine diseases, and other diseases associated with HDAC6 activity. Areas covered: The application claims 1,3,4-oxadiazole sulfamide derivatives as selective HDAC6 inhibitors for the treatment of infectious diseases, neoplasms, endocrine, nutritional, and metabolic diseases; mental and behavioral disorders; neurological diseases; diseases of the eye and adnexa; cardiovascular diseases; respiratory diseases; digestive diseases; diseases of the skin and subcutaneous tissue; disease of the musculoskeletal system and connective tissue; or congenital malformations, deformations and chromosomal abnormalities. Many of the exemplified compounds showed nanomole potency against HDAC6 and were more than 5000-fold selectivity for HDAC6 over HDAC1. Expert opinion: These 1,3,4-oxadiazole sulfamide derivatives have a unique zinc-binding group (ZBG) that provide good leads for the discovery of potent selective HDAC6 inhibitors for the treatment of a variety of diseases associated with HDAC6 activity.

Human ATP-binding cassette transporters ABCB1 and ABCG2 confer resistance to histone deacetylase 6 inhibitor ricolinostat (ACY-1215) in cancer cell lines

Ricolinostat is the first orally available, selective inhibitor of histone deacetylase 6 (HDAC6), currently under evaluation in clinical trials in patients with various malignancies. It is likely that the inevitable emergence of resistance to ricolinostat is likely to reduce its clinical effectiveness in cancer patients. In this study, we investigated the potential impact of multidrug resistance-linked ATP-binding cassette (ABC) transporters ABCB1 and ABCG2 on the efficacy of ricolinostat, which may present a major hurdle to its development as an anticancer drug in the future. We demonstrated that the overexpression of ABCB1 or ABCG2 reduces the intracellular accumulation of ricolinostat, resulting in reduced efficacy of ricolinostat to inhibit the activity of HDAC6 in cancer cells. Moreover, the efficacy of ricolinostat can be fully restored by inhibiting the drug efflux function of ABCB1 and ABCG2 in drug-resistant cancer cells. In conclusion, our results provide some insights into the basis for the development of resistance to ricolinostat and suggest that co-administration of ricolinostat with a modulator of ABCB1 or ABCG2 could overcome ricolinostat resistance in human cancer cells, which may be relevant to its use in the clinic.

A Cross-Talk Between Microbiota-Derived Short-Chain Fatty Acids and the Host Mucosal Immune System Regulates Intestinal Homeostasis and Inflammatory Bowel Disease

Gut microbiota has a fundamental role in the energy homeostasis of the host and is essential for proper "education" of the immune system. Intestinal microbial communities are able to ferment dietary fiber releasing short-chain fatty acids (SCFAs). The SCFAs, particularly butyrate (BT), regulate innate and adaptive immune cell generation, trafficing, and function. For example, BT has an anti-inflammatory effect by inhibiting the recruitment and proinflammatory activity of neutrophils, macrophages, dendritic cells, and effector T cells and by increasing the number and activity of regulatory T cells. Gut microbial dysbiosis, ie, a microbial community imbalance, has been suggested to play a role in the development of inflammatory bowel disease (IBD). The relationship between dysbiosis and IBD has been difficult to prove, especially in humans, and is probably complex and dynamic, rather than one of a simple cause and effect relationship. However, IBD patients have dysbiosis with reduced numbers of SCFAs-producing bacteria and reduced BT concentration that is linked to a marked increase in the number of proinflammatory immune cells in the gut mucosa of these patients. Thus, microbial dysbiosis and reduced BT concentration may be a factor in the emergence and severity of IBD. Understanding the relationship between microbial dysbiosis and reduced BT concentration to IBD may lead to novel therapeutic interventions.

Histone deacetylase inhibitors upregulate Snail via Smad2/3 phosphorylation and stabilization of Snail to promote metastasis of hepatoma cells

Hepatocellular carcinoma (HCC) remains the third most common cause of cancer-related mortality. Resection and transplantation are the only curative treatments available, but are greatly hampered by high recurrence rates. Histone deacetylase inhibitors (HDACIs) are considered to be promising anticancer agents in drug development. Currently, four HDACIs have been granted Food and Drug Administration (FDA) approval for cancer. HDACIs have shown significant efficacy in hematological malignancies. However, they have limited effects in epithelial cell-derived cancers, including HCC, and the mechanisms of these are not elucidated. In this study, our results demonstrated that HDACIs were able to induce epithelial-mesenchymal transitions (EMT) in hepatoma cells which are believed to trigger tumor cell invasion and metastasis. We found that HDACIs promoted the expression of Snail and Snail-induced EMT was critical for HDACI-initiated invasion and metastasis. We indicated that HDACIs upregulated Snail in two ways. Firstly, HDACIs upregulated Snail at the transcriptional level by promoting Smad2/3 phosphorylation and nuclear translocation, then combined with the promoter to activate the transcription of Snail. Secondly, we showed that HDACIs regulated the stabilization of Snail via upregulating the expression of COP9 signalosome 2 (CSN2), which combined with Snail and exposed its acetylation site, then promoted acetylation of Snail, thereby inhibiting its phosphorylation and ubiquitination to repress the degradation of Snail. All these results highlighted that HDACIs have limited effects in HCC, and the use of HDACIs combined with other targeted strategies to inhibit EMT, which explored in this study is a promising treatment method for treating HCC.

Comparison of the anticancer properties of a novel valproic acid prodrug to leading histone deacetylase inhibitors

The HDAC inhibitory activity of valproic acid (VPA) has led to on-going evaluation of it as an anticancer agent. The histone deacetylase (HDAC) inhibitor AN446, a prodrug of VPA, releases the acid upon metabolic degradation. AN446 is >60-fold more potent than VPA in killing cancer cells in vitro. Herein, we compare the activities of AN446, as an anticancer agent, to those of representative types from each of the four major classes of HDAC inhibitors (HDACIs): vorinostat, romidepsin, entinostat, and VPA. AN446 exhibited the greatest selectivity and HDAC inhibitory activity against cancer cells. In glioblastoma cells only AN446, and in MDA-MB-231 cells only AN446 and VPA interacted in synergy with doxorubicin (Dox). AN446 was superior to the studied HDACIs in inducing DNA-damage in cancer cells, while in normal astrocytes and cardiomyoblasts AN446 was the least toxic. AN446 was the only HDACI tested that exhibited selective HDAC inhibitory activity that was high in cancer cells and low in noncancerous cells. This discriminating inhibition correlated with the toxicity of the HDACIs, suggesting that their effects could be attributed to HDAC inhibition. In cardiomyoblasts, the HDACIs tested, except for AN446, hampered DNA repair by reducing the level of Rad 51. VPA and AN446 were the most effective HDACIs in inhibiting in vitro migration and invasion. The advantages of AN446 shown here, position it as a potentially improved HDACI for treatment of glioblastoma and triple negative breast cancer.

Role of short-chain fatty acids in colonic inflammation, carcinogenesis, and mucosal protection and healing

Short-chain fatty acids (SCFAs), mainly acetate, propionate, and butyrate, produced by microbial fermentation of undigested food substances are believed to play a beneficial role in human gut health. Short-chain fatty acids influence colonic health through various mechanisms. In vitro and ex vivo studies show that SCFAs have anti-inflammatory and anticarcinogenic effects, play an important role in maintaining metabolic homeostasis in colonocytes, and protect colonocytes from external harm. Animal studies have found substantial positive effects of SCFAs or dietary fiber on colonic disease, but convincing evidence in humans is lacking. Most human intervention trials have been conducted in the context of inflammatory bowel disease. Only a limited number of those trials are of high quality, showing little or no favorable effect of SCFA treatment over placebo. Opportunities for future research include exploring the use of combination therapies with anti-inflammatory drugs, prebiotics, or probiotics; the use of prodrugs in the setting of carcinogenesis; or the direct application of SCFAs to improve mucosal healing after colonic surgery.

Recent advances in the discovery of potent and selective HDAC6 inhibitors

Histone deacetylase HDAC6, a member of the class IIb HDAC family, is unique among HDAC enzymes in having two active catalytic domains, and has unique physiological function. In addition to the modification of histone, HDAC6 targets specific substrates including α-tubulin and HSP90, and are involved in protein trafficking and degradation, cell shape and migration. Selective HDAC6 inhibitors are an emerging class of pharmaceuticals due to the involvement of HDAC6 in different pathways related to neurodegenerative diseases, cancer, and immunology. Therefore, extensive investigations have been made in the discovery of selective HDAC6 inhibitors. Based on their different zinc binding groups (ZBGs), in this review, HDAC6 inhibitors are grouped as hydroxamic acids, a sulfur containing ZBG based derivatives and other ZBG-derived compounds, and their enzymatic inhibitory activity, selectivity and other biological activities are introduced and summarized.

Targeting Epigenetics in Cancer

Alterations of genes regulating epigenetic processes are frequently found as cancer drivers and may cause widespread alterations of DNA methylation, histone modification patterns, or chromatin structure that disrupt normal patterns of gene expression. Because of the inherent reversibility of epigenetic changes, inhibitors targeting these processes are promising anticancer strategies. Small molecules targeting epigenetic regulators have been developed recently, and clinical trials of these agents are under way for hematologic malignancies and solid tumors. In this review, we describe how the writers, readers, and erasers of epigenetic marks are dysregulated in cancer and summarize the development of therapies targeting these mechanisms.

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.

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

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

Development of Allosteric Hydrazide-Containing Class I Histone Deacetylase Inhibitors for Use in Acute Myeloid Leukemia

One of the biggest hurdles yet to be overcome for the continued improvement of histone deacetylase (HDAC) inhibitors is finding alternative motifs equipotent to the classic and ubiquitously used hydroxamic acid. The N-hydroxyl group of this motif is highly subject to sulfation/glucoronidation-based inactivation in humans; compounds containing this motif require much higher dosing in clinic to achieve therapeutic concentrations. With the goal of developing a second generation of HDAC inhibitors lacking this hydroxamate, we designed a series of potent and selective class I HDAC inhibitors using a hydrazide motif. These inhibitors are impervious to glucuronidation and demonstrate allosteric inhibition. In vitro and ex vivo characterization of our lead analogues' efficacy, selectivity, and toxicity profiles demonstrate that they possess low nanomolar activity against models of acute myeloid leukemia (AML) and are at least 100-fold more selective for AML than solid immortalized cells such as HEK293 or human peripheral blood mononuclear cells.

HDACs and HDAC Inhibitors in Cancer Development and Therapy

Over the last several decades, it has become clear that epigenetic abnormalities may be one of the hallmarks of cancer. Posttranslational modifications of histones, for example, may play a crucial role in cancer development and progression by modulating gene transcription, chromatin remodeling, and nuclear architecture. Histone acetylation, a well-studied posttranslational histone modification, is controlled by the opposing activities of histone acetyltransferases (HATs) and histone deacetylases (HDACs). By removing acetyl groups, HDACs reverse chromatin acetylation and alter transcription of oncogenes and tumor suppressor genes. In addition, HDACs deacetylate numerous nonhistone cellular substrates that govern a wide array of biological processes including cancer initiation and progression. This review will discuss the role of HDACs in cancer and the therapeutic potential of HDAC inhibitors (HDACi) as emerging drugs in cancer treatment.

Epigenetic treatment of solid tumours: a review of clinical trials

Epigenetic treatment has been approved by regulatory agencies for haematological malignancies. The success observed in cutaneous lymphomas represents a proof of principle that similar results may be obtained in solid tumours. Several agents that interfere with DNA methylation-demethylation and histones acetylation/deacetylation have been studied, and some (such as azacytidine, decitabine, valproic acid and vorinostat) are already in clinical use.

The aim of this review is to provide a brief overview of the molecular events underlying the antitumour effects of epigenetic treatments and to summarise data available on clinical trials that tested the use of epigenetic agents against solid tumours. We not only list results but also try to indicate how the proper evaluation of this treatment might result in a better selection of effective agents and in a more rapid development.

We divided compounds in demethylating agents and HDAC inhibitors. For each class, we report the antitumour activity and the toxic side effects. When available, we describe plasma pharmacokinetics and pharmacodynamic evaluation in tumours and in surrogate tissues (generally white blood cells).

Epigenetic treatment is a reality in haematological malignancies and deserves adequate attention in solid tumours. A careful consideration of available clinical data however is required for faster drug development and possibly to re-evaluate some molecules that were perhaps discarded too early.

Discovery of Selective Histone Deacetylase 6 Inhibitors Using the Quinazoline as the Cap for the Treatment of Cancer

Novel selective histone deacetylase 6 (HDAC6) inhibitors using the quinazoline as the cap were designed, synthesized, and evaluated for HDAC enzymatic assays. N-Hydroxy-4-(2-methoxy-5-(methyl(2-methylquinazolin-4-yl)amino)phenoxy)butanamide, 23bb, was the most potent selective inhibitor for HDAC6 with an IC50 of 17 nM and showed 25-fold and 200-fold selectivity relative to HDAC1 and HDAC8, respectively. In vitro, 23bb presented low nanomolar antiproliferative effects against panel of cancer cell lines. Western blot analysis further confirmed that 23bb increased acetylation level of α-tubulin in vitro. 23bb has a good pharmacokinetic profile with oral bioavailability of 47.0% in rats. In in vivo efficacy evaluations of colorectal HCT116, acute myelocytic leukemia MV4-11, and B cell lymphoma Romas xenografts, 23bb more effectively inhibited the tumor growth than SAHA even at a 4-fold reduced dose or ACY-1215 at the same dose. Our results indicated that 23bb is a potent oral anticancer candidate for selective HDAC6 inhibitor and deserves further investigation.

Effects of deranged metabolism on epigenetic changes in cancer

The concept of epigenetics is now providing the mechanisms by which cells transfer their new environmental-change-induced phenotypes to their daughter cells. However, how extracellular or cytoplasmic environmental cues are connected to the nuclear epigenome remains incompletely understood. Recently emerging evidence suggests that epigenetic changes are correlated with metabolic changes via chromatin remodeling. As many human complex diseases including cancer harbor both epigenetic changes and metabolic dysregulation, understanding the molecular processes linking them has huge implications for disease pathogenesis and therapeutic intervention. In this review, the impacts of metabolic changes on cancer epigenetics are discussed, along with the current knowledge on cancer metabolism and epigenetics.

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.