Histone Deacetylase Enzymes Research Articles

Development and Characterization of a Novel Carbon-11 Labeled Positron Emission Tomography Radiotracer for Neuroimaging of Sirtuin 1 with Benzoxazine-Based Compounds.

Sirtuins (SIRTs) comprise a group of histone deacetylase enzymes crucial for regulating metabolic pathways and contributing significantly to various disease mechanisms. Sirtuin 1 (SIRT1), among the seven known mammalian homologs, is extensively investigated and understood, playing a key role in neurodegenerative disorders and cancer. This study focuses on potential as a therapeutic target for conditions such as Parkinson's disease (PD), Huntington's disease (HD), and Alzheimer's disease (AD). Utilizing positron emission tomography (PET) as a noninvasive molecular imaging modality, we aimed to expedite the validation of a promising sirtuin 1 inhibitor for clinical trials. However, the absence of a validated sirtuin 1 PET radiotracer impedes clinical translation. We present the development of [11C]1, and 11C-labeled benzoxazine-based derivative, as a lead imaging probe. The radiosynthesis of [11C]1 resulted in a radiochemical yield of 31 ± 4%. Baseline studies demonstrated that [11C]1 exhibited excellent blood-brain barrier (BBB) penetration capability, with uniform accumulation throughout various brain regions. Self-blocking studies revealed that introducing an unlabeled compound 1, effectively blocking sirtuin 1, led to a substantial reduction in whole-brain uptake, emphasizing the in vivo specificity of [11C]1 for sirtuin 1. The development of [11C]1 provides a valuable tool for noninvasive imaging investigations in rodent models with aberrant sirtuin 1 expression. This novel radiotracer holds promise for advancing our understanding of sirtuin 1's role in disease mechanisms and may facilitate the validation of sirtuin 1 inhibitors in clinical trials.

Exploration of novel hydroxamate zinc binding group inhibitors against HDAC-1-3 enzymes by AI-based virtual screening: atomistic insights from steered molecular dynamics

Overexpression of histone deacetylase (HDAC) enzymes is linked to a wide variety of illnesses, including malignancies and neurological disorders, which makes HDAC inhibitors potentially therapeutic. However, most HDAC inhibitors lack subclass or isoform selectivity, which can be dangerous. Featuring both enhanced selectivity and toxicity profiles, slow-binding HDAC inhibitors offer promising treatment options for a variety of disorders. Diseases like cardiac, neurodegenerative disorders and diabetes are mainly associated with the HDAC1, HDAC2 and HDAC3 enzymes. The AI-based virtual screening tool PyRMD is implemented to identify the potential inhibitors from ∼2 million compounds. Based on the IC50 values, the top 10 compounds were selected for molecular docking. From the docking and ADMET study, the top-ranked three compounds were selected for molecular dynamics (MD) simulations. Further, to get more insights into the binding/unbinding mechanism of the ligand, we have employed the steered molecular dynamics (SMD) simulations. This study assists in developing Amber force field parameters for the HDAC1, HDAC2 and HDAC3 proteins and sheds light on the discovery of a potent drug. Our study suggests that hydroxamic acid derivative (i.e. referred to as Comp-1, CHEMBL600072) is the potential inhibitor for the series of HDAC-related diseases. Communicated by Ramaswamy H. Sarma

Effects of structurally distinct human HDAC6 and HDAC6/HDAC8 inhibitors against S. mansoni larval and adult worm stages.

Schistosomiasis is a major neglected parasitic disease that affects more than 240 million people worldwide caused by Platyhelminthes of the genus Schistosoma. The treatment of schistosomiasis relies on the long-term application of a single safe drug, praziquantel (PZQ). Unfortunately, PZQ is very effective on adult parasites and poorly on larval stage and immature juvenile worms; this can partially explain the re-infection in endemic areas where patients are likely to host parasites at different developmental stages concurrently. Moreover, the risk of development of drug resistance because of the widespread use of a single drug in a large population is nowadays a serious threat. Hence, research aimed at identifying novel drugs to be used alone or in combination with PZQ is needed. Schistosomes display morphologically distinct stages during their life cycle and epigenetic mechanisms are known to play important roles in parasite growth, survival, and development. Histone deacetylase (HDAC) enzymes, particularly HDAC8, are considered valuable for therapeutic intervention for the treatment of schistosomiasis. Herein, we report the phenotypic screening on both larvae and adult Schistosoma mansoni stages of structurally different HDAC inhibitors selected from the in-house Siena library. All molecules have previously shown inhibition profiles on human HDAC6 and/or HDAC8 enzymes. Among them we identified a quinolone-based HDAC inhibitor, NF2839, that impacts larval and adult parasites as well as egg viability and maturation in vitro. Importantly, this quinolone-based compound also increases histone and tubulin acetylation in S. mansoni parasites, thus representing a leading candidate for the development of new generation anti-Schistosoma chemotherapeutics.

Opportunities and Difficulties in the Repurposing of HDAC Inhibitors as Antiparasitic Agents

Ongoing therapy for human parasite infections has a few known drugs but with serious side effects and the problem of drug resistance, impelling us to discover novel drug candidates with newer mechanisms of action. Universally, this has boosted the research in the design and development of novel medicinal agents as antiparasitic drugs with a novel mode of action. Histone deacetylase inhibitors (HDACis) are used in a vast variety of diseases due to their anti-inflammatory properties. Drug repurposing strategies have already approved HDACis as cancer therapeutics and are now under investigation for many parasitic infections. Along with the expression of the gene, histone deacetylase (HDAC) enzymes also act as a slice of great multi-subunit complexes, targeting many non-histones, changing systemic and cellular levels signaling, and producing different cell-based specified effects. Zinc (Zn2+)- and nicotinamide adenine dinucleotide (NAD+)-dependent HDACs of parasites play pivotal roles in the alteration of gene expression of parasites. Some of them are already known to be responsible for the survival of several parasites under odd circumstances; thus, targeting them for therapeutic interventions will be novel for potential antiparasitic targets. This point of view outlines the knowledge of both class-I and class-II HDACis and sirtuin inhibitors that emerged to be the key players in the treatment of human parasitic disorders like Leishmaniasis, Schistosomiasis, Malaria, Trypanosomiasis, and Toxoplasmosis. This review also focuses on repurposing opportunities and challenges in HDAC inhibitors that are preceded by their clinical development as potent new antiparasitic drugs.

In Silico Prediction of Binding Affinities of Hybrid Molecules of Benzothiazole cross-linked with Hydroxamic acid by certain linkers

New hybrid molecules of Benzothiazole cross-linked with hydroxamic acid through an amino acid or aminoalkanoic acid are suggested. All the synthesized hybrid molecules (2A-E) were subjected to molecular docking to evaluate their binding affinities with histone deacetylase enzyme (HDAC8, PDB ID: 1T69) and recorded lower ΔG (-8.117, -6.322, -8.16, -7.939, - 9.46, respectively) than Vorinostat (suberoylanilide hydroxamic acid, SAHA), as the reference ligand, which recorded a much less value of -5.375, using the Maestro software (Schrödinger, version 2022-1). Moreover, compound 2E, which is Benzothiazole-p-amino benzoic acid-hydroxamate has recorded the lowest binding score (-9.460). This may indicate that this compound is the most active hybrid molecule. There were no violations from Lipinski’s rule and all the synthesized hybrid molecules comply with all parameters. SwissADME server was employed for the in silico molecular docking for prediction of the physicochemical and ADME properties of the investigated compounds. All hybrid molecules showed low possible passive oral absorption and no penetration into BBB. The hybrid molecules 2B and 2D may be considered as P-gp substrates. SAHA does not inhibit any of the CYP enzymes used in this study, while, the hybrid molecules 2B, 2D and 2E have shown possible inhibitory activities.

Calotropis procera: A double edged sword against glioblastoma, inhibiting glioblastoma cell line growth by targeting histone deacetylases (HDAC) and angiogenesis

Despite substantial investments in anti-glioblastoma (GBM) drug discovery over the last decade, progress is limited to preclinical stages, with clinical studies frequently encountering obstacles. Angiogenic and histone deacetylase inhibitors (HDACi) have shown profound results in pre-clinical studies. Investigating a multicomponent anti-cancer remedy that disrupts the tumor angiogenic blood vessels and simultaneously disrupts HDACs, while inducing minimal side effects, is critically needed. The crude extracts derived from medicinal plants serve as a renewable reservoir of anti-tumor drugs, exhibiting reduced toxicity compared to chemically synthesized formulations. Calotropis procera is a traditional medicinal plant, and its anticancer potential against many cancer cell lines has been reported, however its antiangiogenic and HDAC inhibitory action is largely unknown. The anticancer activity of methanol leaf extract of C. procera was tested in three types of human glioblastoma cell lines. Wild-type and transgenic zebrafish embryos were used to evaluate developmental toxicity and angiogenic activity. A human angiogenic antibody array was used to profile angiogenic proteins in the U251 GM cell line. A real-time reverse transcriptase polymerase chain reaction (RT PCR) assay was used to detect the differential expression of eleven HDAC genes in U251 cells treated with C. procera extract. The extract significantly reduced the proliferation of all three types of GBM cell lines and the cytotoxicity was found to be more pronounced in U251 GM cells, with an IC50 value of 2.63 ± 0.23 μg/ml, possibly by arresting the cell cycle at the G2/M transition. The extract did not exhibit toxic effects in zebrafish embryos, even at concentrations as high as 1000 μg/ml. The extract also inhibited angiogenic blood vessel formation in the transgenic zebrafish model in a dose-dependent manner. The results from the angiogenic antibody array have suggested novel angiogenesis targets that can be utilized to treat GBM. Real-time RT PCR analysis has shown that C. procrea extract caused an upregulation of HDAC5, 7, and 10, while the mRNA of HDAC1, 2, 3 and 8 (Class I HDACs), and HDAC4, 6, and 9 (Class II) were downregulated in U251 GM cells. The cytotoxicity of the C. procera extract on GBM cell lines could be due to its dual action by regulation of both tumor angiogenesis and histone deacetylases enzymes. Through this study, the C. procera leaf extract has been suggested as an effective remedy to treat GBM with minimal toxicity. In addition, various novel angiogenic and HDAC targets has been identified which could be helpful in designing better therapeutic strategies to manage glioblastoma multiforme in human patients.

Cereblon-recruiting proteolysis targeting chimeras (PROTACs) can determine the selective degradation of HDAC1 over HDAC3.

Histone deacetylase (HDAC) enzymes 1-3 exist in several corepressor complexes and are viable drug targets. To date, proteolysis targeting chimeras (PROTACs) designed to target HDAC1-3 typically exhibit the selective degradation of HDAC3. Herein, we report cereblon-recruiting PROTACs that degrade HDAC1 with selectivity over HDAC3.

Cinnamon extracts, trans-cinnamaldehyde and trans-cinnamic acid inhibit HDAC 1 activity.

Histone deacetylase (HDAC) enzymes play a key role in cell function and are implicated in several diseases such as inflammation, cancer, and neurodegeneration. Studies on natural products have revealed their potential and have led to increased research on natural HDAC inhibitors. Since the progression of these diseases is a prolonged process, dietary supplements and nutraceuticals consisting of plant extracts may be beneficial against HDAC related diseases. Beyond nutritional purposes, cinnamon (Cinnamomum cassia (L.) J. Presl), as a regularly consumed dietary additive due to its rich flavor, may present co-benefits during lifelong use. In this study, cinnamon extracts of differing polarities, trans-cinnamaldehyde and trans-cinnamic acid were evaluated for HDAC 1 inhibitory activity. The total phenol and flavonoid contents were quantified by spectrophotometry, while cinnamaldehyde and cinnamic acid analyses were performed using UPLC-DAD, ESI-MS/MS. Ethanol and dichloromethane extracts yielded the highest cinnamaldehyde and cinnamic acid contents of 389.17 mg per g extract and 11.85 mg per g extract, respectively. The essential oil (IC50: 51.11 μg ml-1) and 70% ethanol extract (IC50: 107.90 μg ml-1) showed the most potent HDAC 1 inhibitory activity. Individually, cinnamaldehyde and cinnamic acid were determined to have IC50 values of 7.58 μg ml-1 and 9.15 μg ml-1, respectively. As the 70% ethanol extract was able to yield remarkably lower cinnamaldehyde and cinnamic acid amounts, the potential of other moderately polar phenolic compounds for HDAC 1 inhibitory activity was revealed. The essential oil and 70% ethanol extracts of Cinnamomum cassia bark can be further evaluated in future studies for use in products against HDAC 1 related diseases.

Inhibition of PI3K-AKT-mTOR pathway and modulation of histone deacetylase enzymes reduce the growth of acute myeloid leukemia cells.

One of the most widespread forms of blood cancer is known as acute myeloid leukemia (AML) which has an incidence of 80% with poor prognosis. Although there are different treatment methods for AML in clinic, the heterogeneity and complexity of the disease show that new treatments are needed. The aim of this study is to investigate the anticancer effects of inhibition of PI3K and HDAC enzymes on CMK and MOLM-13 AML cells lines. We demonstrated that the combination of LY294002 with SAHA and Tubastatin A significantly decreased the cell viability of both cell lines. In contrast, the LY294002 and PCI-34051 combination did not show a significant difference compared to the single LY294002 administration. The combination treatment of LY294002 and HDAC inhibitors did not induce apoptosis significantly. However, LY294002 + SAHA and LY294002 + PCI-34051 resulted in G0/G1 and G2/M cell cycle arrest in CMK cells, respectively. On the other hand, compared to control cells, LY294002 + SAHA and LY294002 + PCI-34051 led to G0/G1 phase arrest in MOLM-13. Furthermore, the LY294002 + PCI-34051 combination elevated the expression rate of LC3BII/I, an autophagy marker, in CMK cells by 2.5-fold. Our study revealed that the combinations of PI3K inhibitor and HDAC inhibitors showed a synergistic effect and caused a reduction in cell viability and increased cell cycle arrest on MOLM-13 and CMK cell lines. In addition, the expression of LC3BII was elevated in the CMK cell line. In conclusion, although more mechanistic studies are required, a combinational inhibition of PI3K and HDAC could be a promising approach for AML.

Analyzing the fatty acid composition of goat milk and its HDAC inhibitory effects: A rational approach towards understanding the epigenetic impacts of goat milk

Goat milk is a rich source of fatty acids. This study intended to assess the inhibitory potential of goat milk and its extracted fatty acids on histone deacetylases (HDACs). Palmitic acid (C16:0) is the most prevalent saturated fatty acid in goat milk. Goat milk also contains a substantial amount of monounsaturated fatty acids, with oleic acid (C18:1) being the most abundant one. Additionally, the fatty acid profile of goat milk reveals the presence of polyunsaturated fatty acids, including linoleic acid (C18:2) and α-linolenic acid (C18:3n3). Interestingly, the fat extracted from goat milk showed a greater ability to inhibit HDAC enzymes in comparison to the whole milk. These findings, at least to the best of my knowledge, showed the HDAC inhibitory properties of goat milk for the first time, presenting new opportunities for the development of fatty acid-based epigenetic-targeted food products derived from goat milk.

Design, synthesis, and biological evaluation of HDAC6 inhibitors targeting L1 loop and serine 531 residue

Histone deacetylases (HDACs) are a group of enzymes that remove acetyl groups from histones, leading to the silencing of genes. Targeting specific isoforms of HDACs has emerged as a promising approach for cancer therapy, as it can overcome drawbacks associated with pan-HDAC inhibitors. HDAC6 is a unique HDAC isoform that deacetylates non-histone proteins and is primarily located in the cytoplasm. It also has two catalytic domains and a zinc-finger ubiquitin binding domain (Zf-UBD) unlike other HDACs. HDAC6 plays a critical role in various cellular processes, including cell motility, protein degradation, cell proliferation, and transcription. Hence, the deregulation of HDAC6 is associated with various malignancies. In this study, we report the design and synthesis of a series of HDAC6 inhibitors. We evaluated the synthesized compounds by HDAC enzyme assay and identified that compound 8g exhibited an IC50 value of 21 nM and 40-fold selective activity towards HDAC6. We also assessed the effect of compound 8g on various cell lines and determined its ability to increase protein acetylation levels by Western blotting. Furthermore, the increased acetylation of α-tubulin resulted in microtubule polymerization and changes in cell morphology. Our molecular docking study supported these findings by demonstrating that compound 8g binds well to the catalytic pocket via L1 loop of HDAC6 enzyme. Altogether, compound 8g represents a preferential HDAC6 inhibitor that could serve as a lead for the development of more potent and specific inhibitors.

Abstract LB_C11: Small-molecule bifunctional inhibitors of PARP1/2 and HDAC enzymes

Abstract Background: Poly(ADP-ribose) polymerase (PARP) plays a major role in DNA repair and PARP inhibitors (PARPi) have shown promise for the treatment of cancers with DNA damage repair defects, such as BRCA mutations. PARPi are currently approved for treatment of BRCA-mutated cancers and as a maintenance therapy for patients who have responded to platinum-based chemotherapy. To improve efficacy, overcome resistance, and expand the usage of PARPi to non-BRCA mutated disease, combination therapies with PARPi have emerged as an area of interest. Histone deacetylases (HDACs) play a major role in DNA repair and inhibition of HDACs has been shown to reduce tumor growth. PARPi combined with HDACi has shown enhanced efficacy in pre-clinical studies in various cancers, and a clinical trial of olaparib and vorinostat against metastatic breast cancer is ongoing. However, combination therapies can be limited clinically due to overlapping toxicities and differing pharmacokinetics. Here, we report the efficacy of a novel class of bifunctional small-molecule compounds (kt-3000) with both PARP1 and PARP2 inhibitory and HDAC inhibitory activities. Methods: PARP1 and PARP2 activity was measured using Trevigen Universal Colorimetric PARP Assay kit and BPS Bioscience PARP2 Colorimetric Assay kit respectively. HDAC activity was measured using HeLa nuclear extracts and a fluorogenic peptide-based biochemical assay. In vitro metabolism was determined by HPLC after incubation with human liver microsomes for up to 45 mins. Pharmacokinetic profiling was examined in mice up to 6 h after oral/intraperitoneal (IP) dosing. Results: kt-3000 compounds showed potent inhibition of PARP1 and PARP2 activity with IC50 values comparable to olaparib (low nM) and inhibition of HDACs with IC50 values in the low µM range. Metabolic and pharmacokinetic profiling suggest drug-like qualities in the class. Conclusion: kt-3000 molecules demonstrate potent inhibition of PARP1/2 and HDAC activities, with suitable pharmacokinetic properties for oral delivery. Further refinement and development of these bifunctional single-molecule inhibitors may offer a novel therapeutic opportunity for treatment of cancers with and without DNA damage repair defects. Citation Format: Sarah Truong, Louise Ramos, Beibei Zhai, Jay Joshi, Fariba Ghaidi, Mona Marzban, Hans Adomat, Charles Chen, John Langlands, Dennis Brown, Jeffrey Bacha, Colin Collins, Poul Sorensen, Wang Shen, Mads Daugaard. Small-molecule bifunctional inhibitors of PARP1/2 and HDAC enzymes [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2023 Oct 11-15; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2023;22(12 Suppl):Abstract nr LB_C11.

A histone deacetylase network regulates epigenetic reprogramming and viral silencing in HIV-infected cells

A long-lived latent reservoir of HIV-1-infected CD4 Tcells persists with antiretroviral therapy and prevents cure. We report that the emergence of latently infected primary CD4 Tcells requires the activity of histone deacetylase enzymes HDAC1/2 and HDAC3. Data from targeted HDAC molecules, an HDAC3-directed PROTAC, and CRISPR-Cas9 knockout experiments converge on a model where either HDAC1/2 or HDAC3 targeting can prevent latency, whereas all three enzymes must be targeted to achieve latency reversal. Furthermore, HDACi treatment targets features of memory Tcells that are linked to proviral latency and persistence. Latency prevention is associated with increased H3K9ac at the proviral LTR promoter region and decreased H3K9me3, suggesting that this epigenetic switch is a key proviral silencing mechanism that depends on HDAC activity. These findings support further mechanistic work on latency initiation and eventual clinical studies of HDAC inhibitors to interfere with latency initiation.

A randomized, double-blind, placebo-controlled study of histone deacetylase type 6 inhibition for the treatment of painful diabetic peripheral neuropathy.

Current treatments for painful diabetic peripheral neuropathy (DPN) are insufficiently effective for many individuals and do not treat nonpain signs and symptoms. The enzyme histone deacetylase type 6 (HDAC6) may play a role in the pathophysiology of painful DPN, and inhibition of HDAC6 has been proposed as a potential treatment. To assess the efficacy and safety of the novel HDAC6 inhibitor ricolinostat for the treatment of painful diabetic peripheral neuropathy. We conducted a 12-week randomized, double-blind, placebo-controlled phase 2 study of the efficacy of ricolinostat, a novel selective HDAC6 inhibitor, in 282 individuals with painful DPN. The primary outcome was the change in the patient-reported pain using a daily diary, and a key secondary outcome was severity of nonpain neuropathic signs using the Utah Early Neuropathy Scale (UENS) score. At the 12-week assessment, changes in average daily pain and UENS scores were not different between the ricolinostat and placebo groups. These results do not support the use of the HDAC6 inhibitor ricolinostat as a treatment for neuropathic pain in DPN for periods up to 12 weeks.

EXTH-28. ISOCITRATE DEHYDROGENASE MUTATIONS PREDICT SENSITIVITY TO HISTONE DEACETYLASE INHIBITION AND ENHANCED HISTONE ACETYLATION DYNAMICS ONLY IN THE CONTEXT OF GLIOMA

Abstract Isocitrate dehydrogenase 1/2 mutations (IDHmut) define a subtype of glioma with profound epigenetic dysregulation through genomic hypermethylation. IDHmut gliomas are incurable and fatal, demonstrating new treatments are needed. These mutations are common in other solid tumors, including chondrosarcoma (CS) and intrahepatic cholangiocarcinoma (ICC). Histone deacetylase (HDAC) enzymes compose a class of epigenetic drug targets utilized clinically to treat cancer, but their potential against IDHmut gliomas has not been extensively studied. We previously showed that IDHmut glioma cultures exhibit pronounced sensitivity to the effects mediated by the FDA-approved HDAC inhibitor (HDACi) panobinostat. Here, we integrate proliferation and cytoxicity data to show that this effect is unique to gliomas. In the context of histone H3 acetylation (H3KAc), panobinostat increased H3KAc, on average, by 7.6-fold and 30.5-fold in IDHwt and IDHmut glioma cultures, respectively (p< 0.001). This difference in HDACi-mediated H3KAc based on IDH status was not significant for CS and ICC. IDHmut gliomas are more sensitive two other FDA-approved HDACis: belinostat and vorinostat. RNA-Seq analysis showed that panobinostat more greatly affected gene expression in IDHmut glioma cells, particularly in the context of gene downregulation. Similarly, H3KAc ChIP-Seq showed a decrease in promoter histone acetylation moreso in IDHmut glioma cultures treated with panobinostat: there is an average loss of 1,236 and 14,759 H3KAc peaks at gene promoters in IDHwt and IDHmut cultures, respectively. This suggests that IDHmut gliomas exhibit enhanced histone acetylation dynamics in response to HDACi. Furthermore, using a PDX glioma model, we show that only mice engrafted with IDHmut glioma exhibit a significant survival increase in response to the HDACi belinostat: median survival was extended by 14 days in IDHmut glioma-bearing mice (p= 0.01), whereas belinostat extended median survival by 4 days in IDHwt glioma-bearing mice (p= 0.11). These results suggest that HDACi may be an effective in treating IDHmut gliomas.

Anti-Proliferative Properties of the Novel Hybrid Drug Met-ITC, Composed of the Native Drug Metformin with the Addition of an Isothiocyanate H2S Donor Moiety, in Different Cancer Cell Lines.

Metformin (Met) is the first-line therapy in type 2 diabetes mellitus but, in last few years, it has also been evaluated as anti-cancer agent. Several pathways, such as AMPK or PI3K/Akt/mTOR, are likely to be involved in the anti-cancer Met activity. In addition, hydrogen sulfide (H2S) and H2S donors have been described as anti-cancer agents affecting cell-cycle and inducing apoptosis. Among H2S donors, isothiocyanates are endowed with a further anti-cancer mechanism: the inhibition of the histone deacetylase enzymes. On this basis, a hybrid molecule (Met-ITC) obtained through the addition of an isothiocyanate moiety to the Met molecule was designed and its ability to release Met has been demonstrated. Met-ITC exhibited more efficacy and potency than Met in inhibiting cancer cells (AsPC-1, MIA PaCa-2, MCF-7) viability and it was less effective on non-tumorigenic cells (MCF 10-A). The ability of Met-ITC to release H2S has been recorded both in cell-free and in cancer cells assays. Finally, its ability to affect the cell cycle and to induce both early and late apoptosis has been demonstrated on the most sensitive cell line (MCF-7). These results confirmed that Met-ITC is a new hybrid molecule endowed with potential anti-cancer properties derived both from Met and H2S.

Expression of acetylated histones H3 and H4 and histone deacetylase enzymes HDAC1, HDAC2 and HDAC6 in simple mammary carcinomas of female dogs.

Histone deacetylation is an important mechanism involved in human breast cancer tumorigenesis and recent veterinary oncology studies also demonstrate a similar relationship in some canine neoplasms. The use of HDAC inhibitors in vitro and in vivo has demonstrated antitumor action on several strains of human and animal cancers. The present study aims to correlate the expression of H3K9Ac, H4K12Ac, HDAC1, HDAC2 and HDAC6 in simple mammary carcinomas in dogs with clinicopathological parameters and overall survival time. To this end, 61 samples of simple breast carcinomas were analyzed by the immunohistochemistry technique with subsequent validation of the antibodies by the Western Blot technique. The expressions obtained via a semi-quantitative way were categorized by assigning scores and classified into high or low expressions according to the given score, except for HDAC6, when the marking percentage was considered and subdivided into high and low expressions using the median value. For statistical analysis, the chi-square test or Fisher exact test were used as univariate analysis and correspondence analysis as a multivariate test, in addition to the Kaplan-Meier survival analysis. In the studied samples, the highest frequencies were determined for the high expression proteins H4K12Ac (88.5%), HDAC2 (65.6%) and HDAC6 (56.7%) and the low expression proteins H3K9Ac (73.8%) and HDAC1 (54.1%). An association between the low expression of HDAC1 and the presence of lymph node metastasis (p = 0.035) was indicated by univariate analysis while the high expression of HDAC1 was associated with favorable prognostic factors, such as the absence of lymph node metastasis and low mitotic index by multivariate analysis. Also, by multivariate analysis, the low expression of HDAC6 was correlated with the low expression of Ki67, smaller tumors, and better prognosis factors as well. Protein expression was not correlated with patients' overall survival time (p > 0.05). The high expressions of HDAC2 and HDAC6 in mammary carcinomas in female dogs may be useful information for research involving therapeutic targets with iHDACs since their inhibition favors hyperacetylation and transcription of tumor suppressor genes.

In-silico and in-vitro functional validation of imidazole derivatives as potential sirtuin inhibitor.

Epigenetic enzymes can interact with a wide range of genes that actively participate in the progression or repression of a diseased condition, as they are involved in maintaining cellular homeostasis. Sirtuins are a family of Class III epigenetic modifying enzymes that regulate cellular processes by removing acetyl groups from proteins. They rely on NAD+ as a coenzyme in contrast to classical histone deacetylases (HDACs) (Class I, II, and IV) that depend on Zn+ for their activation, linking their function to cellular energy levels. There are seven mammalian sirtuin isoforms (Sirt1-7), each located in different subcellular compartments. Sirtuins have emerged as a promising target, given that inhibitors of natural and synthetic sources are highly warranted. Imidazole derivatives are often investigated as sirtuin regulators due to their ability to interact with the binding site and modulate their activity. Imidazole bestows many possible substitutions on its ring and neighboring atoms to design and synthesize derivatives with specific target selectivity and improved pharmacokinetic properties, optimizing drug development. Ligand preparation, protein preparation, molecular docking, molecular dynamics, density function theory (DFT) analysis, and absorption, distribution, metabolism, and excretion (ADME) analysis were performed to understand the interacting potential and effective stability of the ligand with the protein. RT-PCR and Western blot analyses were performed to understand the impact of ligands on the gene and protein expression of Class III HDAC enzymes. We evaluated the sirtuin inhibition activity of our in-house compound comprised of imidazole derivatives by docking the molecules with the protein data bank. ADME properties of all the compounds used in the study were evaluated, and it was found that all fall within the favorable range of being a potential drug. The molecule with the highest docking score was analyzed using DFT, and the specific compound was used to treat the non-small cell lung cancer (NSCLC) cell lines A549 and NCI-H460. The gene and protein expression data support the in-silico finding that the compound Ethyl 2-[5-(4-chlorophenyl)-2-methyl-1-H-Imidazole-4-yl) acetate has an inhibitory effect on nuclear sirtuins. In conclusion, targeting sirtuins is an emerging strategy to combat carcinogenesis. In this study, we establish that Ethyl 2-[5-(4-chlorophenyl)-2-methyl-1-H-Imidazole-4-yl) acetate possesses a strong inhibitory effect on nuclear sirtuins in NSCLC cell lines.

Molecular Docking, ADMET Study, Synthesis, Characterization and Preliminary Antiproliferative Activity of Potential Histone Deacetylase Inhibitors with Isoxazole as New Zinc Binding Group

Histone acetylation is a highly interesting epigenetic target for drug therapy. Histone deacetylase enzymes (HDACs) are overexpressed in several diseases, including cancers. Most of the clinically used HDAC inhibitors involve hydroxamate group as a zinc-binding group (ZBG). Hydroxamates have a poor pharmacokinetic properties and high toxicity profile. Therefore, developing non-hydroximate HDAC inhibitors is a promising strategy for potency and selectivity enhancement. In this work, we designed new HDAC inhibitors with isoxazole moiety as ZBG using Ligand Designer from Glide (Schrodinger LLC). The cap group and the linker were optimized through trying various aliphatic and aromatic residues. The potential inhibition over HDAC8 for the optimally designed products was virtually evaluated using licensed Schrodinger modelling software. The results showed that the isoxazole has a potential bidentate interaction with HDAC8 active site zinc ion with acceptable fitness. ADMET/tox study performed to predict the pharmacokinetic properties for the final compounds. The final compounds showed a decent estimated drug-like properties. The intermediates and final compounds were successfully synthesized and purified using column chromatography. The chemical structure for intermediates and final compounds were characterized by IR and NMR spectroscopy.

Enhancing Therapeutic Efficacy: Harnessing the Synergy of Histone Deacetylase and BCL6 Inhibition in DLBCL

Background Diffuse large B-cell lymphoma (DLBCL) is characterized by its aggressive nature and resistance to standard chemotherapy, necessitating the development of new therapeutic approaches. Histone acetylation, a crucial epigenetic modification, is globally decreased in DLBCL. Chidamide, a histone deacetylase (HDACs) inhibitor, has shown promise in certain lymphomas but its effectiveness in DLBCL remains under investigation. Methods RNA-seq and gene enrichment analysis were performed to identify chidamide's impact on the biological processes in DLBCL. The key factor influencing chidamide sensitivity was determined through correlation analysis, utilizing gene expression levels from the Cancer Cell Line Encyclopedia and IC50 values of four HDAC inhibitors across multiple cancer cell lines sourced from the Genomics of Drug Sensitivity database. Histone acetylation levels, HAT and HDAC enzyme activity analysis, and co-immunoprecipitation were performed to investigate the underlying mechanism through which BCL6 influences chidamide sensitivity. A search among small molecule drugs in clinical investigation aimed to find drugs inhibiting BCL6 to enhance DLBCL sensitivity to chidamide. Synergy between HDAC and BCL6 inhibition was explored through synergistic effects, ubiquitination, and proteasomal degradation analysis. DLBCL mouse models were utilized to evaluate the therapeutic potential of combining chidamide and lenalidomide in vivo. Additionally, chidamide's effects on macrophage polarization were investigated through RNA-seq analysis of M1, M2, and chidamide-treated M2 macrophages. Results Chidamide exhibited potent suppression of DLBCL both in vitro and in vivo (Figure 1A), exerting a significant impact on diverse biological processes in DLBCL. BCL6 inhibited chidamide-induced histone acetylation by recruiting HDACs, leading to drug resistance in DLBCL cells. Lenalidomide could target BCL6 degradation through the ubiquitination pathway and restored the sensitivity of drug-resistant DLBCL to chidamide (Figure 1B). Additionally, chidamide had an impact on the tumor microenvironment. Chidamide inhibited the activity of M2-like tumor-associated macrophages and redirected the polarization of macrophages toward the M1 phenotype. Moreover, we conducted a single-arm multicenter clinical trial to evaluate the safety and efficacy of chidamide in combination with lenalidomide in DLBCL. Conclusions These findings highlighted HDACs as a viable therapeutic strategy for DLBCL, providing valuable insights into chidamide's global impact on the disease. Furthermore, BCL6 was a pivotal determinant of chidamide sensitivity and a reliable biomarker for treatment response. Integrating HDAC and BCL6 inhibition held potential for personalized and effective DLBCL treatments.