Safety and Tolerability of Histone Deacetylase (HDAC) Inhibitors in Oncology. Drug Saf. 2019;42:235-245. [PMID: 30649740 DOI: 10.1007/s40264-018-0773-9]

Synergistic strategies: histone deacetylase inhibitors and platinum-based drugs in cancer therapy

INTRODUCTION

The synergistic combination of histone deacetylase inhibitors and platinum-based medicines represents a promising therapeutic strategy to efficacy and overcome drug resistance in cancer therapy, necessitating a comprehensive understanding on their molecular interactions and clinical potential.

AREAS COVERED

The objective of presented review is to investigate the molecular pathways of platinum medicines and HDAC inhibitors. A comprehensive literature review from 2011 to 2024 was conducted across multiple databases like MEDLINE, PubMed, Google Scholar, Science Direct, Scopus and official websites of ClinicalTrial.gov to explore publications on HDAC inhibitors, platinum drugs, and combination cancer therapies, revealing preliminary evidence of innovative treatment strategies involving HDAC inhibitors and platinum chemotherapeutics. Several new platinum (IV) complexes, with HDAC inhibitory moieties and better cytotoxicity profiles than conventional platinum drugs, are also reviewed here.

EXPERT OPINION

The above combination has great potential in cancer treatment, however managing toxicity, dosage regimens, and patient selection biomarkers are problematic. More selective HDAC inhibitors and innovative delivery techniques are potential areas for future research. An adaptation toward changing cancer therapeutic landscapes, highlights combining HDAC inhibitors with platinum-based medicines serves as a new concept for personalized medicine, however, a deeper research is still needed at this time.

Exploring the potential of Andrographis paniculata for developing novel HDAC inhibitors: an in silico approach

Cancer is one of the dreaded diseases of the twentieth century, emerging the major global causes of human morbidity. Cancer research in the last 15 years has provided unprecedented information on the role of epigenetics in cancer initiation and progression. Histone deacetylases (HDACs) are recognized as important epigenetic markers in cancer, whose overexpression leads to increased metastasis and angiogenesis. In the current study, thirty-four (34) compounds from Andrographis paniculata were screened for the identification of potential candidate drugs, targeting three Class I HDACs (Histone deacetylases), namely HDAC1 (PDB id 5ICN), HDAC3 (PDB id 4A69) and HDAC8 (PDB id 5FCW) through computer-assisted drug discovery study. Results showed that some of the phytochemicals chosen for this study exhibited significant drug-like properties. In silico molecular docking study further revealed that out of 34 compounds, the flavonoid Andrographidine E had the highest binding affinities towards HDAC1 (-9.261 Kcal mol-1) and 3 (-9.554 Kcal mol-1) when compared with the control drug Givinostat (-8.789 and -9.448 Kcal mol-1). The diterpenoid Andrographiside displayed the highest binding affinity (-9.588 Kcal mol-1) to HDAC8 compared to Givinostat (-8.947 Kcal mol-1). Statistical analysis using Principal Component Analysis tool revealed that all 34 phytocompounds could be clustered in four statistical groups. Most of them showed high or comparable inhibitory potentials towards HDAC target protein. Finally, the stability of top-ranked complexes (Andrographidine E-HDAC1 and HDAC3; Andrographiside-HDAC8) at the physiological condition was validated by Molecular Dynamic Simulation and MM-PBSA study.Communicated by Ramaswamy H. Sarma.

Treatment with TNFα and lipolysis-stimulated lipoprotein receptor (LSR) antibody in the presence of HDAC inhibitors promotes apoptosis in human salivary duct adenocarcinoma

Lipolysis-stimulated lipoprotein receptor (LSR), a lipid metabolism-related factor localized in tricellular tight junctions (tTJs), plays an important role in maintaining the epithelial homeostasis. LSR is highly expressed in well-differentiated cancers, and its expression decreases during malignancy. The LSR antibody inhibits cell growth and promotes apoptosis in some cancers. Histone deacetylases (HDACs) are thought to play a crucial role in carcinogenesis, and HDAC inhibitors promote differentiation and prevent cell proliferation and migration in cancers. HDAC inhibitors together with TNFα also induce apoptosis via TNFα-related apoptosis-inducing ligand (TRAIL) in some cancers. In this study, we investigated the apoptosis signaling induced by an anti-LSR antibody in human salivary duct adenocarcinoma (SDC) cell line A253, compared to TRAIL-induced apoptosis. A253 cells were treated with human recombinant TNFα with or without HDAC inhibitor trichostatin A (TSA) and quisinostat (JNJ-26481585). Treatment using TNFα with HDAC inhibitors markedly induced apoptosis in A253 cells and the anti-TNFα antibody prevented the induced apoptosis. A253 cells were treated with an antibody against the extracellular N-terminal domain of human LSR (LSR-N-ab) with or without HDAC inhibitors. Treatment with HDAC inhibitors induced LSR expression in the membranes of A253 cells. Treatment using LSR-N-ab with HDAC inhibitors markedly promoted apoptosis in A253 cells. The tricellular signaling pathway JNK inhibitor SP600125 and Hippo pathway MST1/2 inhibitor XMU-MP-1 prevented the apoptosis induced by treatment using TNFα or LSR-N-ab with HDAC inhibitors. Our findings indicated that treatment with TNFα or LSR-N-ab with HDAC inhibitors might be useful in the therapy for human SDC by enhancing apoptosis.

Histone Deacetylase (HDAC) Inhibitors as a Novel Therapeutic Option Against Fibrotic and Inflammatory Diseases

Histone deacetylases (HDACs) are enzymes that play an essential role in the onset and progression of cancer. As a consequence, a variety of HDAC inhibitors (HDACis) have been developed as potent anticancer agents, several of which have been approved by the FDA for cancer treatment. However, recent accumulated research results have suggested that HDACs are also involved in several other pathophysiological conditions, such as fibrotic, inflammatory, neurodegenerative, and autoimmune diseases. Very recently, the HDAC inhibitor givinostat has been approved by the FDA for an indication beyond cancer: the treatment of Duchenne muscular dystrophy. In recent years, more and more HDACis have been developed as tools to understand the role that HDACs play in various disorders and as a novel therapeutic approach to fight various diseases other than cancer. In the present perspective article, we discuss the development and study of HDACis as anti-fibrotic and anti-inflammatory agents, covering the period from 2020-2024. We envision that the discovery of selective inhibitors targeting specific HDAC isozymes will allow the elucidation of the role of HDACs in various pathological processes and will lead to the development of promising treatments for such diseases.

Epigenetics-targeted drugs: current paradigms and future challenges

Epigenetics governs a chromatin state regulatory system through five key mechanisms: DNA modification, histone modification, RNA modification, chromatin remodeling, and non-coding RNA regulation. These mechanisms and their associated enzymes convey genetic information independently of DNA base sequences, playing essential roles in organismal development and homeostasis. Conversely, disruptions in epigenetic landscapes critically influence the pathogenesis of various human diseases. This understanding has laid a robust theoretical groundwork for developing drugs that target epigenetics-modifying enzymes in pathological conditions. Over the past two decades, a growing array of small molecule drugs targeting epigenetic enzymes such as DNA methyltransferase, histone deacetylase, isocitrate dehydrogenase, and enhancer of zeste homolog 2, have been thoroughly investigated and implemented as therapeutic options, particularly in oncology. Additionally, numerous epigenetics-targeted drugs are undergoing clinical trials, offering promising prospects for clinical benefits. This review delineates the roles of epigenetics in physiological and pathological contexts and underscores pioneering studies on the discovery and clinical implementation of epigenetics-targeted drugs. These include inhibitors, agonists, degraders, and multitarget agents, aiming to identify practical challenges and promising avenues for future research. Ultimately, this review aims to deepen the understanding of epigenetics-oriented therapeutic strategies and their further application in clinical settings.

Discovery of a Novel and Potent Dual-Targeting Inhibitor of ATM and HDAC2 Through Structure-Based Virtual Screening for the Treatment of Testicular Cancer

Purpose

Dual inhibition of ataxia telangiectasia mutated (ATM) and histone deacetylase 2 (HDAC2) may be a potential strategy to improve antitumor efficacy in testicular cancer.

Methods

A combined virtual screening protocol including pharmacophore modeling and molecular docking was used for screening potent dual-target ATM/HDAC2 inhibitors. In order to obtain the optimal lead compound, the dual ATM/HDAC2 inhibitory activity of the screened compounds was further evaluated using enzyme inhibition methods. The binding stability of the optimal compound to the dual targets was verified by molecular dynamics (MD) simulation. MTT assay and in vivo antitumor experiment were performed to validate antitumor efficacy of the optimal compound in testicular cancer.

Results

Here, we successfully discovered six potent dual-target ATM/HDAC2 inhibitors (AMHs 1-6), which exhibited good inhibitory activity against both ATM and HDAC2. Among them, AMH-4 showed strong inhibitory activity against both ATM (IC50 = 1.12 ± 0.03 nM) and HDAC2 (IC50 = 3.04 ± 0.08 nM). MD simulation indicated that AMH-4 binds to ATM and HDAC2 with satisfactory stability. Importantly, AMH-4 had significant antiproliferative activity on human testicular tumor cells, especially NTERA-2 cL.D1 cells, and no inhibitory effect on normal human testicular cells. In vivo experiments exhibited that AMH-4 was more effective than lartesertib and vorinostat in inhibiting the growth of NTERA-2 cL.D1 xenograft tumors with low toxicity.

Conclusion

Overall, these results suggest that AMH-4 is an effective and low toxicity candidate for the treatment of testicular germ cell tumors.

Targeting Relevant HDACs to Support the Survival of Cone Photoreceptors in Inherited Retinal Diseases: Identification of a Potent Pharmacological Tool with In Vitro and In Vivo Efficacy

Inherited retinal diseases, which include retinitis pigmentosa, are a family of genetic disorders characterized by gradual rod-cone degeneration and vision loss, without effective pharmacological treatments. Experimental approaches aim to delay disease progression, supporting cones' survival, crucial for human vision. Histone deacetylases (HDACs) mediate the activation of epigenetic and nonepigenetic pathways that modulate cone degeneration in RP mouse models. We developed new HDAC inhibitors (5a-p), typified by a tetrahydro-γ-carboline scaffold, characterized by high HDAC6 inhibition potency with balanced physicochemical properties for in vivo studies. Compound 5d (repistat, IC50 HDAC6 = 6.32 nM) increased the levels of acetylated α-tubulin compared to histone H3 in ARPE-19 and 661W cells. 5d promoted vision rescue in the atp6v0e1-/- zebrafish model of photoreceptor dysfunction. A single intravitreal injection of 5d in the rd10 mouse model of RP supported morphological and functional preservation of cone cells and maintenance of the retinal pigment epithelium array.

Therapeutic indications for HDAC6 inhibitors in the peripheral and central nervous disorders

INTRODUCTION

Inhibition of the enzymatic function of HDAC6 is currently being explored in clinical trials ranging from peripheral neuropathies to cancers. Advances in selective HDAC6 inhibitor discovery allowed studying highly efficacious brain penetrant and peripheral restrictive compounds for treating PNS and CNS indications.

AREAS COVERED

This review explores the multifactorial role of HDAC6 in cells, the common pathological hallmarks of PNS and CNS disorders, and how HDAC6 modulates these mechanisms. Pharmacological inhibition of HDAC6 and genetic knockout/knockdown studies as a therapeutic strategy in PNS and CNS indications were analyzed. Furthermore, we describe the recent developments in HDAC6 PET tracers and their utility in CNS indications. Finally, we explore the advancements and challenges with HDAC6 inhibitor compounds, such as hydroxamic acid, fluoromethyl oxadiazoles, HDAC6 degraders, and thiol-based inhibitors.

EXPERT OPINION

Based on extensive preclinical evidence, pharmacological inhibition of HDAC6 is a promising approach for treating both PNS and CNS disorders, given its involvement in neurodegeneration and aging-related cellular processes. Despite the progress in the development of selective HDAC6 inhibitors, safety concerns remain regarding their chronic administration in PNS and CNS indications, and the development of novel compound classes and modalities inhibiting HDAC6 function offer a way to mitigate some of these safety concerns.

Discovery of Novel Imidazo[1,2-a]pyridine-Based HDAC6 Inhibitors as an Anticarcinogen with a Cardioprotective Effect

Cardiotoxicity associated with chemotherapy has gradually become the major cause of death in cancer patients. The development of bifunctional drugs with both cardioprotective and antitumor effects has become the future direction. HDAC6 plays important roles in the progression, treatment, and prognosis of cancer and cardiovascular diseases, but bifunctional inhibitors have not been reported. Herein, structure-activity relationship studies driven by pharmacophore-based remodification and fragment-based design were performed to yield highly potent HDAC6 inhibitor I-c4 containing imidazo[1,2-a]pyridine. Importantly, I-c4 effectively suppressed the growth of MGC-803 xenografts in vitro and in vivo by inhibiting the deacetylation pathway without causing myocardial damage after long-term administration. Meanwhile, I-c4 could mitigate severe myocardial damage against H2O2 or myocardial ischemia/reperfusion in vitro and in vivo. Further studies revealed that the cardioprotective effect of I-c4 was associated with reduction of inflammatory cytokines. Taken together, I-c4 may represent a novel lead compound for further development of an anticarcinogen with a cardioprotective effect.

HDAC3 genetic and pharmacologic inhibition radiosensitizes fusion positive rhabdomyosarcoma by promoting DNA double-strand breaks

Radiotherapy (RT) plays a critical role in the management of rhabdomyosarcoma (RMS), the prevalent soft tissue sarcoma in childhood. The high risk PAX3-FOXO1 fusion-positive subtype (FP-RMS) is often resistant to RT. We have recently demonstrated that inhibition of class-I histone deacetylases (HDACs) radiosensitizes FP-RMS both in vitro and in vivo. However, HDAC inhibitors exhibited limited success on solid tumors in human clinical trials, at least in part due to the presence of off-target effects. Hence, identifying specific HDAC isoforms that can be targeted to radiosensitize FP-RMS is imperative. We, here, found that only HDAC3 silencing, among all class-I HDACs screened by siRNA, radiosensitizes FP-RMS cells by inhibiting colony formation. Thus, we dissected the effects of HDAC3 depletion using CRISPR/Cas9-dependent HDAC3 knock-out (KO) in FP-RMS cells, which resulted in Endoplasmatic Reticulum Stress activation, ERK inactivation, PARP1- and caspase-dependent apoptosis and reduced stemness when combined with irradiation compared to single treatments. HDAC3 loss-of-function increased DNA damage in irradiated cells augmenting H2AX phosphorylation and DNA double-strand breaks (DSBs) and counteracting irradiation-dependent activation of ATM and DNA-Pkcs as well as Rad51 protein induction. Moreover, HDAC3 depletion hampers FP-RMS tumor growth in vivo and maximally inhibits the growth of irradiated tumors compared to single approaches. We, then, developed a new HDAC3 inhibitor, MC4448, which showed specific cell anti-tumor effects and mirrors the radiosensitizing effects of HDAC3 depletion in vitro synergizing with ERKs inhibition. Overall, our findings dissect the pro-survival role of HDAC3 in FP-RMS and suggest HDAC3 genetic or pharmacologic inhibition as a new promising strategy to overcome radioresistance in this tumor.

The Antioxidant and HDAC-Inhibitor α-Lipoic Acid Is Synergistic with Exemestane in Estrogen Receptor-Positive Breast Cancer Cells

Anti-estrogenic therapy is established in the management of estrogen receptor (ER)-positive breast cancer. However, to overcome resistance and improve therapeutic outcome, novel strategies are needed such as targeting widely recognized aberrant epigenetics. The study aims to investigate the combination of the aromatase inhibitor exemestane and the histone deacetylase (HDAC) inhibitor and antioxidant α-lipoic acid in ER-positive breast cancer cells. First, the enantiomers and the racemic mixture of α-lipoic acid, and rac-dihydro-lipoic acid were investigated for HDAC inhibition. We found HDAC inhibitory activity in the 1-3-digit micromolar range with a preference for HDAC6. Rac-dihydro-lipoic acid is slightly more potent than rac-α-lipoic acid. The antiproliferative IC50 value of α-lipoic acid is in the 3-digit micromolar range. Notably, the combination of exemestane and α-lipoic acid resulted in synergistic behavior under various incubation times (24 h to 10 d) and readouts (MTT, live-cell fluorescence microscopy, caspase activation) analyzed by the Chou-Talalay method. α-lipoic acid increases mitochondrial fusion and the expression of apoptosis-related proteins p21, APAF-1, BIM, FOXO1, and decreases expression of anti-apoptotic proteins survivin, BCL-2, and c-myc. In conclusion, combining exemestane with α-lipoic acid is a promising novel treatment option for ER-positive breast cancer.

Dual-targeted NAMPT inhibitors as a progressive strategy for cancer therapy

In mammals, nicotinamide phosphoribosyltransferase (NAMPT) is a crucial enzyme in the nicotinamide adenine dinucleotide (NAD+) synthesis pathway catalyzing the condensation of nicotinamide (NAM) with 5-phosphoribosyl-1-pyrophosphate (PRPP) to produce nicotinamide mononucleotide (NMN). Given the pivotal role of NAD+ in a range of cellular functions, including DNA synthesis, redox reactions, cytokine generation, metabolism, and aging, NAMPT has become a promising target for many diseases, notably cancer. Therefore, various NAMPT inhibitors have been reported and classified as first and second-generation based on their chemical structures and design strategies, dual-targeted being one. However, most NAMPT inhibitors suffer from several limitations, such as dose-dependent toxicity and poor pharmacokinetic properties. Consequently, there is no clinically approved NAMPT inhibitor. Hence, research on discovering more effective and less toxic dual-targeted NAMPT inhibitors with desirable pharmacokinetic properties has drawn attention recently. This review summarizes the previously reported dual-targeted NAMPT inhibitors, focusing on their design strategies and advantages over the single-targeted therapies.

A real-world pharmacovigilance study investigating the toxicities of histone deacetylase inhibitors

Histone deacetylase (HDAC) inhibitors are emerging as promising treatments for hematological malignancies, with potential applications extending to solid tumors in the future. Given their wide-ranging biological effects, there is a pressing need for a thorough understanding of the toxicities linked to HDAC inhibition. In this study, a pharmacovigilance analysis was conducted using the FDA Adverse Event Reporting System database. Suspected adverse events linked to HDAC inhibitors were detected through various statistical methodologies, including reporting odds ratio, proportional reporting ratio, information component, and Empirical Bayes Geometric Mean. Our study findings have illuminated that, among the total reported cases examined, gastrointestinal disorders accounted for 13% patients of the cohort, while lymphatic system disorders comprised 8% cases of the cohort, all of which manifested as adverse events induced by HDAC inhibitors. Importantly, the usage of HDAC inhibitors was found to be associated with incidents of atrial fibrillation, heart failure, respiratory failure, hepatic dysfunction, and acute kidney injury. Romidepsin and belinostat demonstrated more pronounced signals of adverse events compared to panobinostat and vorinostat, emphasizing the need for vigilant monitoring of adverse events in this particular population. Furthermore, atrial fibrillation (clinical priority score of 7 points) emerged as the paramount medical event warranting utmost clinical attention. Eventually, multiple adverse events were observe to emerge within the initial and second months following the initiation of treatment. Vigilant monitoring and supportive care strategies are critical in addressing the toxicities associated with HDAC inhibitors, particularly those concerning cardiotoxicity, respiratory toxicity, renal toxicity, and hepatotoxicity.

Epigenetic-based differentiation therapy for Acute Myeloid Leukemia

Despite the development of novel therapies for acute myeloid leukemia, outcomes remain poor for most patients, and therapeutic improvements are an urgent unmet need. Although treatment regimens promoting differentiation have succeeded in the treatment of acute promyelocytic leukemia, their role in other acute myeloid leukemia subtypes needs to be explored. Here we identify and characterize two lysine deacetylase inhibitors, CM-444 and CM-1758, exhibiting the capacity to promote myeloid differentiation in all acute myeloid leukemia subtypes at low non-cytotoxic doses, unlike other commercial histone deacetylase inhibitors. Analyzing the acetylome after CM-444 and CM-1758 treatment reveals modulation of non-histone proteins involved in the enhancer-promoter chromatin regulatory complex, including bromodomain proteins. This acetylation is essential for enhancing the expression of key transcription factors directly involved in the differentiation therapy induced by CM-444/CM-1758 in acute myeloid leukemia. In summary, these compounds may represent effective differentiation-based therapeutic agents across acute myeloid leukemia subtypes with a potential mechanism for the treatment of acute myeloid leukemia.

Romidepsin exhibits anti-esophageal squamous cell carcinoma activity through the DDIT4-mTORC1 pathway

Esophageal squamous cell carcinoma (ESCC) is one of the most common human malignancies worldwide and is associated with high morbidity and mortality. Current treatment options are limited, highlighting the need for development of novel effective agents. Here, a high-throughput drug screening (HTS) was performed using ESCC cell lines in both two- and three-dimensional culture systems to screen compounds that have anti-ESCC activity. Our screen identified romidepsin, a histone deactylase inhibitor, as a potential anti-ESCC agent. Romidepsin treatment decreased cell viability, induced apoptosis and cell cycle arrest in ESCC cell lines, and these findings were confirmed in ESCC cell line-derived xenografted (CDX) mouse models. Mechanically, romidepsin induced transcriptional upregulation of DNA damage-inducible transcript 4 (DDIT4) gene by histone hyperacetylation at its promoter region, leading to the inhibition of mammalian target of rapamycin complex 1 (mTORC1) pathway. Furthermore, romidepsin exhibited better efficacy and safety compared to the conventional therapeutic drugs in ESCC patient-derived xenografted (PDX) mouse models. These data indicate that romidepsin may be a novel option for anti-ESCC therapy.

Exploring the role of histone deacetylase and histone deacetylase inhibitors in the context of multiple myeloma: mechanisms, therapeutic implications, and future perspectives

Histone deacetylase inhibitors (HDACis) are a significant category of pharmaceuticals that have developed in the past two decades to treat multiple myeloma. Four drugs in this category have received approval from the U.S. Food and Drug Administration (FDA) for use: Panobinonstat (though canceled by the FDA in 2022), Vorinostat, Belinostat and Romidepsin. The efficacy of this group of drugs is attributed to the disruption of many processes involved in tumor growth through the inhibition of histone deacetylase, and this mode of action leads to significant anti-multiple myeloma (MM) activity. In MM, inhibition of histone deacetylase has many downstream consequences, including suppression of NF-κB signaling and HSP90, upregulation of cell cycle regulators (p21, p53), and downregulation of antiapoptotic proteins including Bcl-2. Furthermore, HDACis have a variety of direct and indirect oxidative effects on cellular DNA. HDAC inhibitors enhance normal immune function, thereby decreasing the proliferation of malignant plasma cells and promoting autophagy. The various biological effects of inhibiting histone deacetylase have a combined or additional impact when used alongside other chemotherapeutic and targeted drugs for multiple myeloma. This helps to decrease resistance to treatment. Combination treatment regimens that include HDACis have become an essential part of the therapy for multiple myeloma. These regimens incorporate drugs from other important classes of anti-myeloma agents, such as immunomodulatory drugs (IMiDs), conventional chemotherapy, monoclonal antibodies, and proteasome inhibitors. This review provides a comprehensive evaluation of the clinical efficacy and safety data pertaining to the currently approved histone deacetylase inhibitors, as well as an explanation of the crucial function of histone deacetylase in multiple myeloma and the characteristics of the different histone deacetylase inhibitors. Moreover, it provides a concise overview of the most recent developments in the use of histone deacetylase inhibitors for treating multiple myeloma, as well as potential future uses in treatment.

HDAC inhibitors as pharmacological treatment for Duchenne muscular dystrophy: a discovery journey from bench to patients

Earlier evidence that targeting the balance between histone acetyltransferases (HATs) and deacetylases (HDACs), through exposure to HDAC inhibitors (HDACis), could enhance skeletal myogenesis, prompted interest in using HDACis to promote muscle regeneration. Further identification of constitutive HDAC activation in dystrophin-deficient muscles, caused by dysregulated nitric oxide (NO) signaling, provided the rationale for HDACi-based therapeutic interventions for Duchenne muscular dystrophy (DMD). In this review, we describe the molecular, preclinical, and clinical evidence supporting the efficacy of HDACis in countering disease progression by targeting pathogenic networks of gene expression in multiple muscle-resident cell types of patients with DMD. Given that givinostat is paving the way for HDACi-based interventions in DMD, next-generation HDACis with optimized therapeutic profiles and efficacy could be also explored for synergistic combinations with other therapeutic strategies.

Epigenetic Mechanisms Histone Deacetylase-Dependent Regulate the Glioblastoma Angiogenic Matrisome and Disrupt Endothelial Cell Behavior In Vitro

Glioblastoma (GBM) is the most aggressive brain tumor and different efforts have been employed in the search for new drugs and therapeutic protocols for GBM. Epitranscriptomics has shed light on new druggable Epigenetic therapies specifically designed to modulate GBM biology and behavior such as Histone Deacetylase inhibitors (iHDAC). Although the effects of iHDAC on GBM have been largely explored, there is a lack of information on the underlaying mechanisms HDAC-dependent that modulate the repertoire of GBM secreted molecules focusing on the set of Extracellular Matrix (ECM) associated proteins, the Matrisome, that may impact the surrounding tumor microenvironment. To acquire a better comprehension of the impacts of HDAC activity on the GBM Matrisome, we studied the alterations on the Matrisome-associated ECM regulators, Core Matrisome ECM glycoproteins, ECM-affiliated proteins and Proteoglycans upon HDAC inhibition in vitro as well as their relationship with glioma pathophysiological/clinical features and angiogenesis. For this, U87MG GBM cells were treated for with iHDAC or vehicle (control) and the whole secretome was processed by Mass Spectrometry NANOLC-MS/MS. In silico analyses revealed that proteins associated to the Angiogenic Matrisome (AngioMatrix), including Decorin, ADAM10, ADAM12 and ADAM15 were differentially regulated in iHDAC versus control secretome. Interestingly, genes coding for the Matrisome proteins differentially regulated were found mutated in patients and were correlated to glioma pathophysiological/clinical features. In vitro functional assays, using HBMEC endothelial cells exposed to the secretome of control or iHDAC treated GBM cells, coupled to 2D and 3D GBM cell culture system, showed impaired migratory capacity of endothelial cells and disrupted tubulogenesis in a Fibronectin and VEGF independent fashion. Collectively, our study provides understanding of epigenetic mechanisms HDAC-dependent to key Matrisomal proteins that may contribute to identify new druggable Epigenetic therapies or gliomagenesis biomarkers with relevant implications to improve therapeutic protocols for this malignancy.

Development of Potent Dual BET/HDAC Inhibitors via Pharmacophore Merging and Structure-Guided Optimization

Bromodomain and extra-terminal domain (BET) proteins and histone deacetylases (HDACs) are prime targets in cancer therapy. Recent research has particularly focused on the development of dual BET/HDAC inhibitors for hard-to-treat tumors, such as pancreatic cancer. Here, we developed a new series of potent dual BET/HDAC inhibitors by choosing starting scaffolds that enabled us to optimally merge the two functionalities into a single compound. Systematic structure-guided modification of both warheads then led to optimized binders that were superior in potency to both parent compounds, with the best molecules of this series binding to both BRD4 bromodomains as well as HDAC1/2 with EC50 values in the 100 nM range in cellular NanoBRET target engagement assays. For one of our lead molecules, we could also show the selective inhibition of HDAC1/2 over all other zinc-dependent HDACs. Importantly, this on-target activity translated into promising efficacy in pancreatic cancer and NUT midline carcinoma cells. Our lead molecules effectively blocked histone H3 deacetylation in pancreatic cancer cells and upregulated the tumor suppressor HEXIM1 and proapoptotic p57, both markers of BET inhibition. In addition, they have the potential to downregulate the oncogenic drivers of NUT midline carcinoma, as demonstrated for MYC and TP63 mRNA levels. Overall, this study expands the portfolio of available dual BET/class I HDAC inhibitors for future translational studies in different cancer models.

Risk of atrial fibrillation in patients with multiple myeloma: what is known and directions for future study

BACKGROUND

Multiple myeloma (MM) is a prevalent hematological tumor, and recent clinical data have highlighted the significance of atrial fibrillation (AF) as a crucial complication affecting the prognosis of MM. This review aims to consolidate findings from published clinical studies, focusing on the epidemiological characteristics of AF in MM patients and the associated risks arising from MM treatments such as autologous hematopoietic stem cell transplantation, proteasome inhibitors, and immunomodulatory agents.

MAIN BODY

While existing data partially demonstrate a strong correlation between MM and AF, further clinical studies are necessary to comprehensively investigate their association. These studies should encompass various aspects, including the risk of AF resulting from MM treatment, the impact of AF-induced embolic events and heart failure on MM prognosis, as well as the influence of AF management methods like catheter ablation or left atrial appendage closure on MM prognosis.

CONCLUSIONS

The supplementation of future data will provide more precise guidance for managing MM patients. By incorporating information regarding AF risk associated with MM treatment and examining the effects of AF management strategies on MM prognosis, healthcare professionals can enhance their decision-making process when caring for individuals with MM.

Associations between HIFs and tumor immune checkpoints: mechanism and therapy

Hypoxia, which activates a variety of signaling pathways to enhance tumor cell growth and metabolism, is among the primary features of tumor cells. Hypoxia-inducible factors (HIFs) have a substantial impact on a variety of facets of tumor biology, such as epithelial-mesenchymal transition, metabolic reprogramming, angiogenesis, and improved radiation resistance. HIFs induce hypoxia-adaptive responses in tumor cells. Many academics have presented preclinical and clinical research targeting HIFs in tumor therapy, highlighting the potential applicability of targeted HIFs. In recent years, the discovery of numerous pharmacological drugs targeting the regulatory mechanisms of HIFs has garnered substantial attention. Additionally, HIF inhibitors have attained positive results when used in conjunction with traditional oncology radiation and/or chemotherapy, as well as with the very promising addition of tumor immunotherapy. Immune checkpoint inhibitors (CPIs), which are employed in a range of cancer treatments over the past decades, are essential in tumor immunotherapy. Nevertheless, the use of immunotherapy has been severely hampered by tumor resistance and treatment-related toxicity. According to research, HIF inhibitors paired with CPIs may be game changers for multiple malignancies, decreasing malignant cell plasticity and cancer therapy resistance, among other things, and opening up substantial new pathways for immunotherapy drug development. The structure, activation mechanisms, and pharmacological sites of action of the HIF family are briefly reviewed in this work. This review further explores the interactions between HIF inhibitors and other tumor immunotherapy components and covers the potential clinical use of HIF inhibitors in combination with CPIs.

Discovery of potent pyrrolo-pyrimidine and purine HDAC inhibitors for the treatment of advanced prostate cancer

The development of drugs for the treatment of advanced prostate cancer (PCA) remains a challenging task. In this study we have designed, synthesized and tested twenty-nine novel HDAC inhibitors based on three different zinc binding groups (trifluoromethyloxadiazole, hydroxamic acid, and 2-mercaptoacetamide). These warheads were conveniently tethered to variously substituted phenyl linkers and decorated with differently substituted pyrrolo-pyrimidine and purine cap groups. Remarkably, most of the compounds showed nanomolar inhibitory activity against HDAC6. To provide structural insights into the Structure-Activity Relationships (SAR) of the investigated compounds, docking of representative inhibitors and molecular dynamics of HDAC6-inhibitor complexes were performed. Compounds of the trifluoromethyloxadiazole and hydroxamic acid series exhibited promising anti-proliferative activities, HDAC6 targeting in PCA cells, and in vitro tumor selectivity. Representative compounds of the two series were tested for solubility, cell permeability and metabolic stability, demonstrating favorable in vitro drug-like properties. The more interesting compounds were subjected to migration assays, which revealed that compound 13 and, to a lesser extent, compound 15 inhibited the invasive behaviour of androgen-sensitive and -insensitive advanced prostate cancer cells. Compound 13 was profiled against all HDACs and found to inhibit all members of class II HDACs (except for HDAC10) and to be selective with respect to class I and class IV HDACs. Overall, compound 13 combines potent inhibitory activity and class II selectivity with favorable drug-like properties, an excellent anti-proliferative activity and marked anti-migration properties on PCA cells, making it an excellent lead candidate for further optimization.

Establishment and characterization of a novel cell line (SCCOHT-CH-1) and PDX models derived from Chinese patients of small cell ovarian carcinoma of the hypercalcemic type

Small cell carcinoma of the ovary hypercalcemic type (SCCOHT) is a rare and aggressive malignancy that poses a significant clinical challenge due to its grim prognosis. Unfortunately, only three SCCOHT cell lines are currently available for scientific research. In this study, we have successfully established a novel SCCOHT cell line from a recurrent lesion of a SCCOHT patient, named SCCOHT-CH-1. We comprehensively characterized the novel cell line by employing techniques such as morphological observation, CCK-8 assay, Transwell assay, clone formation assay, short tandem repeat sequence (STR) analysis, karyotype analysis, immunohistochemical staining, western blot assay, and xenograft tumor formation assay. SCCOHT-CH-1 cells were small circular and had a unique STR profile. The population-doubling time of SCCOHT-CH-1 was 33.02 h. The cell line showed potential migratory and invasive ability. Compared with another SCCOHT cell line COV434, SCCOHT-CH-1 exhibited higher expression of AKT, VIM, and CCND1. At the same time, SCCOHT-CH-1 has the ability of tumorigenesis in vivo. We also successfully constructed three patient-derived xenograft (PDX) models of SCCOHT, which were pathologically diagnosed to be consistent with the primary tumor, accompanied by loss of SAMRCA4 protein expression. The establishment of SCCOHT-CH-1 cell line and PDX models from Chinese people represent a pivotal step toward unraveling the molecular mechanism of SCCOHT and fostering the development of targeted interventions to tackle this challenging malignancy.

Discovery of (S)-N1-(thiazol-2-yl) pyrrolidine-1,2-dicarboxamide derivatives targeting PI3Ka/HDAC6 for the treatment of cancer

Recently, PI3K and HDAC have been considered as promising targets for the cancer therapy. A couple of pan-PI3K/HDAC dual inhibitors have been developed as a new class of anticancer agents. Herein, we discovered a new series of (S)-N1-(thiazol-2-yl) pyrrolidine-1,2-dicarboxamide derivatives targeting PI3Kα/HDAC6. All the derivatives exerted dual-target inhibitory activities. Particularly, in the enzymatic selectivity assay, compound 21j was identified as a subtype-selective PI3Kα/HDAC6 dual inhibitor (IC50 = 2.9 and 26 nM against PI3Kα and HDAC6, respectively), which displayed high potency against L-363 cell line with IC50 value of 0.17 μM. In addition, 21j significantly inhibited phosphorylation of pAkt(Ser473) and induced accumulation of acetylated α-tubulin while having a negligible effect on the levels of acetylated Histone H3 and H4 at nanomolar level. Attributed to its favorable in vitro performance, 21j has the potential to alleviate the adverse effects resulted from pan-PI3K inhibition and pan-HDAC inhibition. It is valuable for further functional investigation as an anti-cancer agent.

Selective HDAC3 Inhibitors with Potent In Vivo Antitumor Efficacy against Triple-Negative Breast Cancer

HDAC3 modulation shows promise for breast cancer, including triple-negative cases. Novel pyrazino-hydrazide-based HDAC3 inhibitors were designed and synthesized. Lead compound 4i exhibited potent HDAC3 inhibition (IC50 = 14 nM) with at least 121-fold selectivity. It demonstrated strong cytotoxicity against triple-negative breast cancer cells (IC50: 0.55 μM for 4T1, 0.74 μM for MDA-MB-231) with least normal cell toxicity. Metabolically stable 4i displayed a superior pharmacokinetic profile. A dose-dependent therapeutic efficacy of 4i was observed in a tumor-bearing mouse model. The biomarker analysis with tumor tissues displayed enhanced acetylation on Ac-H3K9, Ac-H3K27, and Ac-H4K12 compared to Ac-tubulin and Ac-SMC3 indicating HDAC3 selectivity of 4i in vivo. The immunoblotting study with tumor tissue showed upregulation of apoptotic proteins caspase-3, caspase-7, and cytochrome c and the downregulation of proliferation markers Bcl-2, CD44, EGFR, and Ki-67. Compound 4i represents a promising candidate for targeted breast cancer therapy, particularly for cases with triple-negative breast cancer.

Mocetinostat activates Krüppel-like factor 4 and protects against tissue destruction and inflammation in osteoarthritis

Osteoarthritis (OA) is the most common joint disorder, and disease-modifying OA drugs (DMOADs) represent a major need in OA management. Krüppel-like factor 4 (KLF4) is a central transcription factor upregulating regenerative and protective functions in joint tissues. This study was aimed to identify small molecules activating KLF4 expression and to determine functions and mechanisms of the hit compounds. High-throughput screening (HTS) with 11,948 clinical-stage compounds was performed using a reporter cell line detecting endogenous KLF4 activation. Eighteen compounds were identified through the HTS and confirmed in a secondary screen. After testing in SW1353 chondrosarcoma cells and human chondrocytes, mocetinostat - a class I selective histone deacetylase (HDAC) inhibitor - had the best profile of biological activities. Mocetinostat upregulated cartilage signature genes in human chondrocytes, meniscal cells, and BM-derived mesenchymal stem cells, and it downregulated hypertrophic, inflammatory, and catabolic genes in those cells and synoviocytes. I.p. administration of mocetinostat into mice reduced severity of OA-associated changes and improved pain behaviors. Global gene expression and proteomics analyses revealed that regenerative and protective effects of mocetinostat were dependent on peroxisome proliferator-activated receptor γ coactivator 1-α. These findings show therapeutic and protective activities of mocetinostat against OA, qualifying it as a candidate to be used as a DMOAD.

A Bifunctional PARP-HDAC Inhibitor with Activity in Ewing Sarcoma

PURPOSE

Histone deacetylase (HDAC) inhibition has been shown to induce pharmacologic "BRCAness" in cancer cells with proficient DNA repair activity. This provides a rationale for exploring combination treatments with HDAC and PARP inhibition in cancer types that are insensitive to single-agent PARP inhibitors (PARPi). Here, we report the concept and characterization of a novel bifunctional PARPi (kt-3283) with dual activity toward PARP1/2 and HDAC enzymes in Ewing sarcoma cells.

EXPERIMENTAL DESIGN

Inhibition of PARP1/2 and HDAC was measured using PARP1/2, HDAC activity, and PAR formation assays. Cytotoxicity was assessed by IncuCyte live cell imaging, CellTiter-Glo, and spheroid assays. Cell-cycle profiles were determined using propidium iodide staining and flow cytometry. DNA damage was examined by γH2AX expression and comet assay. Inhibition of metastatic potential by kt-3283 was evaluated via ex vivo pulmonary metastasis assay (PuMA).

RESULTS

Compared with FDA-approved PARP (olaparib) and HDAC (vorinostat) inhibitors, kt-3283 displayed enhanced cytotoxicity in Ewing sarcoma models. The kt-3283-induced cytotoxicity was associated with strong S and G2-M cell-cycle arrest in nanomolar concentration range and elevated DNA damage as assessed by γH2AX tracking and comet assays. In three-dimensional spheroid models of Ewing sarcoma, kt-3283 showed efficacy in lower concentrations than olaparib and vorinostat, and kt-3283 inhibited colonization of Ewing sarcoma cells in the ex vivo PuMA model.

CONCLUSIONS

Our data demonstrate the preclinical justification for studying the benefit of dual PARP and HDAC inhibition in the treatment of Ewing sarcoma in a clinical trial and provides proof-of-concept for a bifunctional single-molecule therapeutic strategy.

Panobinostat-loaded folate targeted liposomes as a promising drug delivery system for treatment of canine B-cell lymphoma

Introduction

Cancer is a major public health problem with over 19 million cases reported in 2020. Similarly to humans, dogs are also largely affected by cancer, with non-Hodgkin's lymphoma (NHL) among the most common cancers in both species. Comparative medicine has the potential to accelerate the development of new therapeutic options in oncology by leveraging commonalities between diseases affecting both humans and animals. Within this context, in the present study, we investigated the potential of panobinostat (Pan)-loaded folate-targeted PEGylated liposomes (FA-PEG-Pan-Lip) for the treatment of canine B-cell lymphoma, while contributing to new perspectives in comparative oncology.

Methods and results

Two formulations were developed, namely: PEG-Pan-Lip and FA-PEG-Pan-Lip. Firstly, folate receptor expression in the CLBL-1 canine B-cell lymphoma cell line was assessed. After confirming receptor expression, both Pan-loaded formulations (PEG-Pan-Lip, FA-PEG-Pan-Lip) demonstrated dose-dependent inhibitory effects on CLBL-1 cell proliferation. The FA-PEG-Pan-Lip formulation (IC50 = 10.9 ± 0.03 nM) showed higher cytotoxicity than the non-targeted PEG-Pan-Lip formulation (IC50 = 12.9 ± 0.03 nM) and the free panobinostat (Pan) compound (IC50 = 18.32±0.03 nM). Moreover, mechanistically, both Pan-containing formulations induced acetylation of H3 histone and apoptosis. Flow cytometry and immunofluorescence analysis of intracellular uptake of rhodamine-labeled liposome formulations in CLBL-1 cells confirmed cellular internalization of PEG-Lip and FA-PEG-Lip formulations and higher uptake profile for the latter. Biodistribution studies of both radiolabeled formulations in CD1 and SCID mice revealed a rapid clearance from the major organs and a 1.6-fold enhancement of tumor uptake at 24 h for 111In-FA-PEG-Pan-Lip (2.2 ± 0.1 %ID/g of tumor) compared to 111In-PEG-Pan-Lip formulation (1.2±0.2 %ID/g of tumor).

Discussion

In summary, our results provide new data validating Pan-loaded folate liposomes as a promising targeted drug delivery system for the treatment of canine B-cell lymphoma and open innovative perspectives for comparative oncology.

Immunomodulatory effects of inulin and its intestinal metabolites

"Dietary fiber" (DF) refers to a type of carbohydrate that cannot be digested fully. DF is not an essential nutrient, but it plays an important part in enhancing digestive capacity and maintaining intestinal health. Therefore, DF supplementation in the daily diet is highly recommended. Inulin is a soluble DF, and commonly added to foods. Recently, several studies have found that dietary supplementation of inulin can improve metabolic function and regulate intestinal immunity. Inulin is fermented in the colon by the gut microbiota and a series of metabolites is generated. Among these metabolites, short-chain fatty acids provide energy to intestinal epithelial cells and participate in regulating the differentiation of immune cells. Inulin and its intestinal metabolites contribute to host immunity. This review summarizes the effect of inulin and its metabolites on intestinal immunity, and the underlying mechanisms of inulin in preventing diseases such as type 2 diabetes mellitus, inflammatory bowel disease, chronic kidney disease, and certain cancer types.

Anticancer Study of a Novel Pan-HDAC Inhibitor MPT0G236 in Colorectal Cancer Cells

Colorectal cancer (CRC) is one of the most commonly diagnosed malignancies and a leading cause of cancer worldwide. Histone deacetylases (HDACs), which regulate cell proliferation and survival, are associated with the development and progression of cancer. Moreover, HDAC inhibitors are promising therapeutic targets, with five HDAC inhibitors approved for cancer treatment to date. However, their safety profile necessitates the exploration of well-tolerated HDAC inhibitors that can be used in cancer therapeutic strategies. In this study, the pan-HDAC inhibitor MPT0G236 reduced the viability and inhibited the proliferation of human colorectal cancer cells, and normal human umbilical vein endothelial cells (HUVECs) showed reduced sensitivity. These findings indicated that MPT0G236 specifically targeted malignant tumor cells. Notably, MPT0G236 significantly inhibited the activities of HDAC1, HDAC2, and HDAC3, Class I HDACs, as well as HDAC6, a Class IIb HDAC, at low nanomolar concentrations. Additionally, it promoted the accumulation of acetyl-α-tubulin and acetyl-histone H3 in HCT-116 and HT-29 cells in a concentration-dependent manner. Furthermore, MPT0G236 treatment induced G2/M cell cycle arrest in CRC cells by initially regulating the levels of cell-cycle-related proteins, such as p-MPM2; specifically reducing p-cdc2 (Y15), cyclin B1, and cdc25C levels; and subsequently inducing apoptosis through the caspase-dependent pathways and PARP activation. Our findings demonstrate that MPT0G236 exhibits significant anticancer activity in human colorectal cancer cells.

Investigating the Synergistic Potential of Low-Dose HDAC3 Inhibition and Radiotherapy in Alzheimer's Disease Models

We have previously shown that histone deacetylase (HDAC) inhibition and cranial radiotherapy (RT) independently improve molecular and behavioral Alzheimer's disease (AD)-like phenotypes. In the present study, we investigate the synergistic potential of using both RT and HDACi as a low-dose combination therapy (LDCT) to maximize disease modification (reduce neuroinflammation and amyloidogenic APP processing, increase neurotrophic gene expression) while minimizing the potential for treatment-associated side effects.LDCT consisted of daily administration of the HDAC3 inhibitor RGFP966 and/or bi-weekly cranial x-irradiation. Amyloid-beta precursor protein (APP) processing and innate immune response to LDCT were assessed in vitro and in vivo using human and murine cell models and 3xTg-AD mice. After 2 months of LDCT in mice, behavioral analyses as well as expression and modification of key AD-related targets (Aβ, tau, Csf1r, Bdnf, etc.) were assessed in the hippocampus (HIP) and prefrontal cortex (PFC).LDCT induced a tolerant, anti-inflammatory innate immune response in microglia and increased non-amyloidogenic APP processing in vitro. Both RT and LDCT improved the rate of learning and spatial memory in the Barnes maze test. LDCT induced a unique anti-AD HIP gene expression profile that included upregulation of neurotrophic genes and downregulation of inflammation-related genes. RT lowered HIP Aβ42/40 ratio and Bace1 protein, while LDCT lowered PFC p-tau181 and HIP Bace1 levels.Our study supports the rationale for combining complementary therapeutic approaches at low doses to target multifactorial AD pathology synergistically. Namely, LDCT with RGFP966 and cranial RT shows disease-modifying potential against a wide range of AD-related hallmarks.

Discovery of (S)-N-(2-Amino-4-fluorophenyl)-4-(1-(3-(4-((dimethylamino)methyl)phenyl)-6-oxopyridazin-1(6H)-yl)ethyl)benzamide as Potent Class I Selective HDAC Inhibitor for Oral Anticancer Drug Candidate

A novel series of benzamide derivatives were successively designed and synthesized prepared from the pyridazinone scaffold. Among them, (S)-17b, demonstrated potent inhibitory activity in vitro toward human class I HDAC isoforms and human myelodysplastic syndrome (SKM-1) cell line. Also, (S)-17b strongly increased the intracellular level of acetyl-histone H3 and P21 simultaneously and effectively induced G1 cell cycle arrest and apoptosis. Through oral dosing in SKM-1 xenograft models, (S)-17b exhibited excellent in vivo antitumor activity. In addition, compound (S)-17b showed better antitumor efficacy on mouse models with intact immune system than those with thymus deficiencies. Furthermore, this compound displayed a favorable pharmacokinetic profile in ICR mice and SD rat, respectively, minimal metabolic property differences among hepatocytes from five species, and a low inhibition upon the human ether-a-go-go (hERG) channel with an IC₅₀ value of 34.6 μΜ. This novel compound (S)-17b may serve as a new drug candidate for further investigation.

Dual targeted 2-Benzylideneindanone pendant hydroxamic acid group exhibits selective HDAC6 inhibition along with tubulin stabilization effect

Abnormal epigenetics has been recognised as an early event in tumour progression and aberrant acetylation of lysine in particular has been understood in tumorigenesis. Therefore, it has become an attractive target for anticancer drug development. However, HDAC inhibitors have limited success due to toxicity and drug resistance concerns. Present study deals with design and synthesis of bivalent indanone based HDAC6 and antitubulin ligands as anticancer agents. Two of the analogues 9 and 21 exhibited potent antiproliferative activities (IC₅₀, 0.36-3.27 µM) and high potency against HDAC 6 enzyme. Compound 21 showed high selectivity against HDAC 6 while 9 exhibited low selectivity. Both the compounds also showed microtubule stabilization effects and moderate anti-inflammatory effect. Dual targeted anticancer agents with concomitant anti-inflammatory effects will be more attractive clinical candidates in future.

Histone deacetylase inhibitors as a potential new treatment for psoriatic disease and other inflammatory conditions

Collectively known as psoriatic disease, psoriasis and psoriatic arthritis (PsA) are immune-mediated inflammatory diseases in which patients present with cutaneous and musculoskeletal inflammation. Affecting roughly 2-3% of the world's total population, there remains unmet therapeutic needs in both psoriasis and PsA despite the availability of current immunomodulatory treatments. As a result, patients with psoriatic disease often experience reduced quality of life. Recently, a class of small molecules, commonly investigated as anti-cancer agents, called histone deacetylase (HDAC) inhibitors, have been proposed as a new promising anti-inflammatory treatment for immune- and inflammatory-related diseases. In inflammatory diseases, current evidence is derived from studies on diseases like rheumatoid arthritis (RA) and systematic lupus erythematosus (SLE), and while there are some reports studying psoriasis, data on PsA patients are not yet available. In this review, we provide a brief overview of psoriatic disease, psoriasis, and PsA, as well as HDACs, and discuss the rationale behind the potential use of HDAC inhibitors in the management of persistent inflammation to suggest its possible use in psoriatic disease.

Histone Deacetylases: Molecular Mechanisms and Therapeutic Implications for Muscular Dystrophies

Histone deacetylases (HDACs) are enzymes that regulate the deacetylation of numerous histone and non-histone proteins, thereby affecting a wide range of cellular processes. Deregulation of HDAC expression or activity is often associated with several pathologies, suggesting potential for targeting these enzymes for therapeutic purposes. For example, HDAC expression and activity are higher in dystrophic skeletal muscles. General pharmacological blockade of HDACs, by means of pan-HDAC inhibitors (HDACi), ameliorates both muscle histological abnormalities and function in preclinical studies. A phase II clinical trial of the pan-HDACi givinostat revealed partial histological improvement and functional recovery of Duchenne Muscular Dystrophy (DMD) muscles; results of an ongoing phase III clinical trial that is assessing the long-term safety and efficacy of givinostat in DMD patients are pending. Here we review the current knowledge about the HDAC functions in distinct cell types in skeletal muscle, identified by genetic and -omic approaches. We describe the signaling events that are affected by HDACs and contribute to muscular dystrophy pathogenesis by altering muscle regeneration and/or repair processes. Reviewing recent insights into HDAC cellular functions in dystrophic muscles provides new perspectives for the development of more effective therapeutic approaches based on drugs that target these critical enzymes.

Evaluation of Small-Molecule HDAC Inhibitors Through In Vitro and In Cellulo Approaches

The aberrant activity of histone deacetylases (HDACs) across a broad range of cancers and other disease indications has led to the development of small-molecule inhibitors that target one or more members of the HDAC protein family. Emerging HDAC inhibitors that show promise in drug discovery programs must be assessed across a range of in vitro assays to establish an inhibitor profile for potency and cellular selectivity towards target HDAC(s) as well as preliminary absorption, distribution, metabolism, and excretion (ADME) features. Here we provide an overview of methods to determine a subset of pivotal in vitro drug-like parameters for HDAC inhibitors (HDACi). We initially describe protocols for parallel artificial membrane permeability assays (PAMPA) to evaluate the passive permeability of small molecules across lipid membranes. Subsequently, we elaborate on cytotoxicity assays using CellTiter-Blue to determine HDACi-induced cell death in healthy/diseased cellular models. We next focus on assessing the target engagement of inhibitors with the appropriate HDAC isoforms in a cellular environment via Western blotting of acetylated HDAC substrates. Finally, we provide detailed guidelines on how to assess the metabolic stability of HDACi through whole blood stability assays. Collectively, these assays provide an overview of the permeability, selectivity, and stability of the HDAC inhibitor under development.

CDK regulators—Cell cycle progression or apoptosis—Scenarios in normal cells and cancerous cells

Serine/threonine kinases called cyclin-dependent kinases (CDKs) interact with cyclins and CDK inhibitors (CKIs) to control the catalytic activity. CDKs are essential controllers of RNA transcription and cell cycle advancement. The ubiquitous overactivity of the cell cycle CDKs is caused by a number of genetic and epigenetic processes in human cancer, and their suppression can result in both cell cycle arrest and apoptosis. This review focused on CDKs, describing their kinase activity, their role in phosphorylation inhibition, and CDK inhibitory proteins (CIP/KIP, INK 4, RPIC). We next compared the role of different CDKs, mainly p21, p27, p57, p16, p15, p18, and p19, in the cell cycle and apoptosis in cancer cells with respect to normal cells. The current work also draws attention to the use of CDKIs as therapeutics, overcoming the pharmacokinetic barriers of pan-CDK inhibitors, analyze new chemical classes that are effective at attacking the CDKs that control the cell cycle (cdk4/6 or cdk2). It also discusses CDKI's drawbacks and its combination therapy against cancer patients. These findings collectively demonstrate the complexity of cancer cell cycles and the need for targeted therapeutic intervention. In order to slow the progression of the disease or enhance clinical outcomes, new medicines may be discovered by researching the relationship between cell death and cell proliferation.

Structural and Functional Changes in Aging Kidneys

The renal condition is one of the crucial predictors of longevity; therefore, early diagnosis of any dysfunction plays an important role. Kidneys are highly susceptible to the aging process. Unfavorable conditions may lead to a significant disturbance of the body's homeostasis. Apart from physiological changes, there are some conditions such as hypertension, diabetes or obesity which contribute to the acceleration of the aging process. A determination of macroscopic and microscopic changes is essential for assessing the progression of aging. With age, we observe a decrease in the volume of renal parenchyma and an increase in adipose tissue in the renal sinuses. Senescence may also be manifested by the roughness of the kidney surface or simple renal cysts. The main microscopic changes are a thickening of the glomerular basement membrane, nephrosclerosis, an accumulation of extracellular matrix, and mesangial widening. The principal aspect of stopping unfavorable changes is to maintain health. Studies have shown many useful ways to mitigate renal aging. This review is focused especially on medications such as renin-angiotensin-aldosterone system blockers or resveratrol, but even eating habits and lifestyle.

A chronicle review of new techniques that facilitate the understanding and development of optimal individualized therapeutic strategies for chordoma

Chordoma is a rare malignant bone tumor that mainly occurs in the sacrum and the clivus/skull base. Surgical resection is the treatment of choice for chordoma, but the local recurrence rate is high with unsatisfactory prognosis. Compared with other common tumors, there is not much research and individualized treatment for chordoma, partly due to the rarity of the disease and the lack of appropriate disease models, which delay the discovery of therapeutic strategies. Recent advances in modern techniques have enabled gaining a better understanding of a number of rare diseases, including chordoma. Since the beginning of the 21st century, various chordoma cell lines and animal models have been reported, which have partially revealed the intrinsic mechanisms of tumor initiation and progression with the use of next-generation sequencing (NGS) techniques. In this study, we performed a systematic overview of the chordoma models and related sequencing studies in a chronological manner, from the first patient-derived chordoma cell line (U-CH1) to diverse preclinical models such as the patient-derived organoid-based xenograft (PDX) and patient-derived organoid (PDO) models. The use of modern sequencing techniques has discovered mutations and expression signatures that are considered potential treatment targets, such as the expression of Brachyury and overactivated receptor tyrosine kinases (RTKs). Moreover, computational and bioinformatics techniques have made drug repositioning/repurposing and individualized high-throughput drug screening available. These advantages facilitate the research and development of comprehensive and personalized treatment strategies for indicated patients and will dramatically improve their prognoses in the near feature.

Modified Suberoylanilide Hydroxamic Acid Reduced Drug-Associated Immune Cell Death and Organ Damage under Lipopolysaccharide Inflammatory Challenge

Histone deacetylase inhibitors (HDACi) induce potent anti-inflammatory responses when used to treat inflammatory diseases. Suberoylanilide hydroxamic acid (SAHA), a pan-HDACi, decreases pro-inflammatory cytokine levels and attenuates cytokine storm in sepsis; however, its toxicity profile toward immune cells has limited its use as a sepsis therapeutic. Here, we developed a modification to SAHA by para-hydroxymethylating the capping group to generate SAHA-OH. We discovered that SAHA-OH provides a favorable improvement to the toxicity profile compared to SAHA. SAHA-OH significantly reduced primary macrophage apoptosis and splenic B cell death as well as mitigated organ damage using a lipopolysaccharide (LPS)-induced endotoxemia mouse model. Furthermore, SAHA-OH retained anti-inflammatory responses similar to SAHA as measured by reductions in LPS-induced proinflammatory cytokine secretions in vitro and in vivo. These effects were attributed to a decreased selectivity of HDAC1, 2, 3, 8 and an increased selectivity for HDAC6 for SAHA-OH as determined by IC50 values. Our results support the potential for SAHA-OH to modulate acute proinflammatory responses while mitigating SAHA-associated drug toxicity for use in the treatment of inflammation-associated diseases and conditions.

High Efficacy and Drug Synergy of HDAC6-Selective Inhibitor NN-429 in Natural Killer (NK)/T-Cell Lymphoma

NK/T-cell lymphoma (NKTCL) and γδ T-cell non-Hodgkin lymphomas (γδ T-NHL) are highly aggressive lymphomas that lack rationally designed therapies and rely on repurposed chemotherapeutics from other hematological cancers. Histone deacetylases (HDACs) have been targeted in a range of malignancies, including T-cell lymphomas. This study represents exploratory findings of HDAC6 inhibition in NKTCL and γδ T-NHL through a second-generation inhibitor NN-429. With nanomolar in vitro HDAC6 potency and high in vitro and in cellulo selectivity for HDAC6, NN-429 also exhibited long residence time and improved pharmacokinetic properties in contrast to older generation inhibitors. Following unique selective cytotoxicity towards γδ T-NHL and NKTCL, NN-429 demonstrated a synergistic relationship with the clinical agent etoposide and potential synergies with doxorubicin, cytarabine, and SNS-032 in these disease models, opening an avenue for combination treatment strategies.

Therapeutic approaches to Epstein-Barr virus cancers

Epstein-Barr virus (EBV) establishes a lifelong latent infection that can be a causal agent for a diverse spectrum of cancers and autoimmune disease. A complex and dynamic viral lifecycle evades eradication by the host immune system and confounds antiviral therapeutic strategies. To date, there are no clinically approved vaccines or therapies that selectively target EBV as the underlying cause of EBV-associated disease. Here, we review the challenges and recent advances in the development of EBV-specific therapeutics for treatment of EBV-associated cancers.

Current trends in development of HDAC-based chemotherapeutics

BACKGROUND

Histone deacetylases (HDACs) are one of the essential epigenetic targets in cancer treatment. These enzymes play key roles in post-translation modification (PTM) and gene expression, and consequently, their inhibitors are about to find their place in pharmacotherapy. Most of the currently approved HDAC inhibitors (HDACIs) are wide-spectrum with poor clinical outcomes and numerous side effects. Therefore, new generations of HDAC-based chemotherapeutics with better clinical outcomes are emerging, e.g., isoform-selective inhibitors, multitargeted HDACIs, as well as HDAC degraders.

AIM

The review intended to introduce drug design approaches which were used for designing novel agents which can be beneficial in the process of finding new and more effective HDACI-based therapeutics.

METHODS

PubMed and other databases were searched for literature regarding the structure-function of HDAC isoforms, and strategies used to design HDAC inhibitors. Also, all clinical trials available from the ClinicalTrials site for years 2021-2022 were investigated.

KEY FINDINGS

It is expected that the future of drug discovery projects in HDAC field will concentrate mostly on issues such as isoform-selectivity, multitargeted HDAC inhibitors and HDAC degraders. Deeper knowledge of the 3D structure of HDACs complexed with inhibitors and extensive delineation of biological roles of HDACs are needed for efficient investigations leading to the discovery of novel potent inhibitors.

SIGNIFICANCE

Histone deacetylases (HDACs) are one of the important epigenetic targets in cancer treatment drug discovery. Comprehending the structure of HDAC isoforms along with applied drug design strategies can inspire new ideas.

Characterizing HDAC Pathway Copy Number Variation in Pan-Cancer

Background: Histone deacetylase (HDAC) plays a crucial role in regulating the expression and activity of a variety of genes associated with tumor progression and immunotherapeutic processes. The aim of this study was to characterize HDAC pathway copy number variation (CNV) in pan-cancer. Methods: A total of 10,678 tumor samples involving 33 types of tumors from The Cancer Genome Atlas (TCGA) were included in the study. Results: HDAC pathway CNV and CNV gain were identified as prognostic risk factors for pan-cancer species. The differences of tumor characteristics including tumor mutational burden, tumor neoantigen burden, high-microsatellite instability, and microsatellite stable between HDAC pathway CNV altered-type group and wild-type group varied among the various cancer species. In some cancer types, HDAC pathway CNV alteration was positively correlated with loss of heterozygosity, CNV burden, ploidy, and homologous recombination defect score markers, while it was significantly negatively correlated with immune score and stroma score. There were significant differences in immune characteristics such as major histocompatibility complex class I (MHC-I), MHC-II, chemokines, cytolytic-activity, and IFN-γ between the two groups. Immune cycle characteristics varied from one cancer type to another. Conclusion: This study reveals a tumor and immune profile of HDAC pathway CNV as well as its unlimited potential in immune prognosis.

Leveraging modeling and simulation to optimize the therapeutic window for epigenetic modifier drugs

Dysregulated epigenetic processes can lead to altered gene expression and give rise to malignant transformation and tumorigenesis. Epigenetic drugs aim to revert the phenotype of cancer cells to normally functioning cells, and are developed and applied to treat both hematological and solid cancers. Despite this promising therapeutic avenue, the successful development of epigenetic modulators has been challenging. We argue that besides identifying the right responder patient population, the selection of an optimized dosing regimen is equally important. For the majority of epigenetic modulators, hematological adverse effects such as thrombocytopenia, anemia or neutropenia are frequently observed and may limit their therapeutic potential. Therefore, one of the key challenges is to identify a dosing regimen that maximizes drug efficacy and minimizes toxicity. This requires a good understanding of the quantitative relationship between the administered dose, the drug exposure and the magnitude and duration of drug response related to safety and efficacy. With case examples, we highlight how modeling and simulation has been successfully applied to address those questions. As an outlook, we suggest the combination of efficacy and safety prediction models that capture the quantitative, mechanistic relationships governing the balance between their safety and efficacy dynamics. A stepwise approach for its implementation is presented. Utilizing in silico explorations, the impact of dosing regimen on the therapeutic window can be explored. This will serve as a basis to select the most promising dosing regimen that maximizes efficacy while minimizing adverse effects and to increase the probability of success for the given epigenetic drug.

Isoform selective versus non-selective histone deacetylase inhibitors in HIV latency reversal

HIV remains incurable due to the persistence of a latent viral reservoir found in HIV infected cells, primarily resting memory CD4+ T cells. Depletion of this reservoir may be the only way to end this deadly epidemic. In latency, the integrated proviral DNA of HIV is transcriptionally silenced partly due to the activity of histone deacetylases (HDACs). One strategy proposed to overcome this challenge, is the use of HDAC inhibitors as latency reversal agents to induce viral expression (shock) under the cover of antiretroviral therapy (ART). It is hoped that this will lead to elimination of the reservoir by immunologic and viral cytopathic (kill). However, there are 18 isoforms of HDACs leading to varying selectivity for HDAC inhibitors. Here we review HDAC inhibitors with emphasis on their selectivity for HIV latency reversal.