Histone Deacetylase Inhibitor Research Articles

Entinostat, a class I selective histone deacetylase inhibitor, plus exemestane for Chinese patients with hormone receptor-positive advanced breast cancer: An overall survival update and long-term safety from the randomised, double-blind, placebo-controlled, phase 3 trial.

1050 Background: Entinostat, a synthetic benzamide derivative HDAC inhibitor, selectively targets Class I HDAC enzymes. In a randomized, double-blind, phase 3 trial, entinostat with exemestane demonstrated a statistically significant progression-free survival (PFS) benefit compared to placebo, with a median PFS of 6.32 months versus 3.72 months (HR 0.76, 95% CI 0.58-0.98, p=0.046; Binghe Xu, et al. Acta Pharm Sin B. 2023). This analysis focus on the results of overall survival (OS) and long-term safety. Methods: Patients eligible for this study had HR+/HER2– advanced breast cancer (ABC) with disease relapse or progression following at least one prior endocrine therapy (ET). They were randomly assigned in a 2:1 ratio to receive either entinostat (5mg, weekly) or placebo in combination with exemestane until disease progression or unacceptable toxicity. The primary endpoint of the study was PFS. Secondary endpoints included OS, objective response rate, clinical benefit rate and safety. Median OS was estimated using the Kaplan-Meier method and the HR and its 95% CI were calculated using the multivariate Cox proportional hazard regression model. Results: A total of 354 patients were randomized to receive either entinostat (n=235) or placebo (n=119). As of the data cutoff date (July 31, 2023), 196 (55.4%) OS events had occurred, with a median follow-up of 31.83 months. There were 127 (54.0%) deaths in the entinostat arm compared to 69 (58.0%) deaths in the placebo arm. The entinostat demonstrated improved OS compared to placebo, with a median OS of 38.39 months versus 29.18 months (HR 0.837, 95% CI 0.624-1.124, p=0.237) in the full analysis set (FAS). The results of the per-protocol analysis set (PPS) were consistent with those of the FAS, showing a median OS of 39.01 months versus 33.98 months (HR 0.796, 95% CI 0.588-1.079, p=0.142). Notably, 179 (76.2%) patients in the entinostat arm and 100 (84%) patients in the placebo arm received new anti-cancer regimens, including CDK4/6 inhibitors (14.5% vs 24.4%), chemotherapy (54.9% vs 63.9%), endocrine therapy (40.4% vs 42.9%), and herbal medicines (9.8% vs 3.4%). After adjusting for the imbalance in the use of CDK4/6 inhibitors and chemotherapy between the treatment arms, the HR for overall survival was 0.78 (95% CI 0.58-1.05, p=0.097). The updated safety results were generally consistent with the previous analysis. Conclusions: The combination of entinostat with exemestane has provided clinically meaningful OS benefit in addition to the previously observed PFS benefit over exemestane alone in patients with pre-treated, ET-resistant ABC. These findings further support entinostat as an effective and safe treatment option for the specific patient population. Clinical trial information: NCT03538171 .

Advances in non-Hydroxamate based Histone Deacetylase Inhibitors as Anticancer Agents

Advances in non-Hydroxamate based Histone Deacetylase Inhibitors as Anticancer Agents

Short Chain Fatty Acid Sodium Butyrate Increases miR-21, miR-143 and miR-145 Expression in Human Colorectal Cancer HCT-116 Cell Line.

Sodium butyrate (NaBu) is a short-chain fatty acid; it is one of the histone deacetylase inhibitors, which can alter both genetic and epigenetic expressions. The present study aimed to elucidate the effect of Na-Bu on the expression of miR-21, miR-143, and miR-145 in human colorectal cancer HCT-116 cell lines. This study was done in Tehran Medical Sciences, Islamic Azad University, Tehran, Iran. HCT-116 cell line was treated with diverse concentrations of NaBu (6.25 mM to 200 mM) at 24, 48, and 72 h. MTT assay was used for assessing the cytotoxicity. Quantitative Real-Time-PCR was performed to investigate the gene expression of miR-21, miR-143, and miR-145. IC50 values were evaluated by MTT assay. IC50 for HCT-116 was 50 mM, 12.5 mM, and 6.25 mM for 24, 48, and 72 h of incubation, respectively. According to the Real-Time-PCR results, 50 mM NaBu after 24 h caused a significant up-regulation in the expression of the miR-21, miR-143, and miR-145 (P<0.05). In 48 h, incubation, 12.5 mM NaBu caused a significant up-regulation in the expression of the miR-21, miR-143, and miR-145 (P<0.05). In treated cells with 6.25 mM NaBu after 72 h of incubation caused a significant up-regulation in the expression of the miR-21, miR-143, and miR-145 compared with untreated cells (P<0.05). The upregulation of miR-21, miR-143, and miR-145 expression are mediated by transcriptional regulation and the activation of this miR promoter is modulated by histone acetylation. The employment of NaBu may represent a promising approach for improving HDACi drug-based therapies for colon cancers.

Histone deacetylase inhibition mitigates fibrosis-drivendisease progression in recessive dystrophicepidermolysis bullosa.

Recessive dystrophic epidermolysis bullosa (RDEB) is a blistering disease caused by mutations in the gene encoding type VII collagen (C7). RDEB is associated with fibrosis, which is responsible for severe complications. The phenotypic variability observed in siblings with RDEB suggests that epigenetic modifications contribute to disease severity. Identifying epigenetic changes may help to uncover molecular mechanisms underlying RDEB pathogenesis and new therapeutic targets. To investigate histone acetylation in RDEB skin and to explore histone deacetylase inhibitors (HDACi) as therapeutic molecules capable of counteracting fibrosis and disease progression in RDEB mice. Acetylated histone levels were detected in human skin by immunofluorescence and in RDEB fibroblasts by enzyme-linked immunosorbent assay (ELISA). The effects of givinostat and valproic acid (VPA) on RDEB fibroblast fibrotic behaviour were assessed by a collagen-gel contraction assay, Western blot and immunocytofluorescence for α-smooth muscle actin, and ELISA for released transforming growth factor (TGF)-β1. RNA sequencing was performed in HDACi- and vehicle-treated RDEB fibroblasts. VPA was systemically administered to RDEB mice and effects on overt phenotype were monitored. Fibrosis was investigated in the skin using histological and immunofluorescence analyses. Eye and tongue defects were examined microscopically. Mass spectrometry proteomics was performed on skin protein extracts from VPA-treated RDEB and control mice. Histone acetylation decreases in RDEB skin and primary fibroblasts. RDEB fibroblasts treated with HDACi lowered fibrotic traits, including contractility, TGF-β1 release and proliferation. VPA administration to RDEB mice mitigated severe manifestations affecting the eyes and paws. These effects were associated with fibrosis inhibition. Proteomic analysis of mouse skin revealed that VPA almost normalized protein sets involved in protein synthesis and immune response, processes linked to the increased susceptibility to cancer and bacterial infections seen in people with RDEB. Dysregulated histone acetylation contributes to RDEB pathogenesis by facilitating the progression of fibrosis. Repurposing of HDACi could be considered for disease-modifying treatments in RDEB.

FK228 suppress the growth of human malignant pleural mesothelioma tumor independent to epithelioid or non-epithelioid histology

Human malignant pleural mesothelioma (hMPM) is an aggressive, rare disease with a poor prognosis. Histologically, MPM is categorized into epithelioid, biphasic, and sarcomatoid subtypes, with the epithelioid subtype generally displaying a better response to treatment. Conversely, effective therapies for the non-epithelioid subtypes are limited. This study aimed to investigate the potential role of FK228, a histone deacetylase inhibitor, in the suppression of hMPM tumor growth. We conducted a comprehensive analysis of the histological and molecular characteristics of two MPM cell lines, CRL-5820 (epithelioid) and CRL-5946 (non-epithelioid). CRL-5946 cells and non-epithelioid patient-derived xenografted mice exhibited heightened growth rates compared to those with epithelioid MPM. Both CRL-5946 cells and non-epithelioid mice displayed a poor response to cisplatin. However, FK228 markedly inhibited the growth of both epithelioid and non-epithelioid tumor cells in vitro and in vivo. Cell cycle analysis revealed FK228-induced G1/S and mitotic arrest in MPM cells. Caspase inhibitor experiments demonstrated that FK228-triggered apoptosis occurred via a caspase-dependent pathway in CRL-5946 but not in CRL-5820 cells. Additionally, a cytokine array analysis showed that FK228 reduced the release of growth factors, including platelet-derived and vascular endothelial growth factors, specifically in CRL-5946 cells. These results indicate that FK228 exhibits therapeutic potential in MPM by inducing cytotoxicity and modulating the tumor microenvironment, potentially benefiting both epithelioid and non-epithelioid subtypes.

Entinostat in patients with relapsed or refractory abdominal neuroendocrine tumors.

Gastroenteropancreatic neuroendocrine tumors (GEP-NETs) are rare neoplasms with an increasing annual incidence and prevalence. Many are metastatic at presentation or recur following surgical resection and require systemic therapy, for which somatostatin analogs such as octreotide or lanreotide comprise typical first-line therapies. Nonetheless, treatment options remain limited. Epigenetic processes such as histone modifications have been implicated in malignant transformation and progression. In this study, we evaluated the anti-proliferative effects of a histone deacetylase (HDAC) inhibitor, entinostat, which was computationally predicted to show anti-cancer activity, as confirmed in in vitro and in vivo models of GEP-NETs. This was a phase II study to evaluate the efficacy and safety of entinostat in patients with relapsed or refractory abdominal NETs. The primary objective was to estimate the objective response rate to entinostat. Additionally, with each patient as his/her own control we estimated the rates of tumor growth prior to enrollment on study and while receiving entinostat. Patients received 5 mg entinostat weekly until disease progression or intolerable toxicity. The dose could be changed to 10 mg biweekly for patients who did not experience grade ≥ 2 treatment-related adverse events (AEs) in cycle 1, but was primarily administered at the starting 5 mg weekly dose. The study enrolled only 5 patients due to early termination by the drug sponsor. The first patient that enrolled had advanced disease and died within days of enrollment before follow-up imaging due to a grade 5 AE unrelated to study treatment and was considered non-evaluable. Best RECIST response for the remaining 4 patients was stable disease (SD) with time on study of 154+, 243, 574, and 741 days. With each patient as his/her own control, rates of tumor growth on entinostat were markedly reduced with rates 17%, 20%, 33%, and 68% of the rates prior to enrollment on study. Toxicities possibly or definitely related to entinostat included grade 2/3 neutrophil count decrease [2/4 (50%)/ 2/4 (50%)], grade 3 hypophosphatemia [1/4, (25%)], grade 1/2 fatigue [1/4 (25%)/ 2/4 (50%)], and other self-limiting grade 1/2 AEs. In the treatment of relapsed or refractory abdominal NETs, entinostat 5 mg weekly led to prolonged SD and reduced the rate of tumor growth by 32% to 83% with an acceptable safety profile (ClinicalTrials.gov Identifier: NCT03211988).

Inhibition of HDAC activity directly reprograms murine embryonic stem cells to trophoblast stem cells

Embryonic stem cells (ESCs) can differentiate into all cell types of the embryonic germ layers. ESCs can also generate totipotent 2C-like cells and trophectodermal cells. However, these latter transitions occur at low frequency due to epigenetic barriers, the nature of which is not fully understood. Here, we show that treating mouse ESCs with sodium butyrate (NaB) increases the population of 2C-like cells and enables direct reprogramming of ESCs into trophoblast stem cells (TSCs) without a transition through a 2C-like state. Mechanistically, NaB inhibits histone deacetylase activities in the LSD1-HDAC1/2 corepressor complex. This increases acetylation levels in the regulatory regions of both 2C- and TSC-specific genes, promoting their expression. In addition, NaB-treated cells acquire the capacity to generate blastocyst-like structures that can develop beyond the implantation stage invitro and form deciduae invivo. These results identify how epigenetics restrict the totipotent and trophectoderm fate in mouse ESCs.

CGAS-STING-TBK1 Signaling Promotes Valproic Acid-Responsive Human Cytomegalovirus Immediate-Early Transcription during Infection of Incompletely Differentiated Myeloid Cells.

Repression of human cytomegalovirus (HCMV) immediate-early (IE) gene expression is a key regulatory step in the establishment and maintenance of latent reservoirs. Viral IE transcription and protein accumulation can be elevated during latency by treatment with histone deacetylase inhibitors such as valproic acid (VPA), rendering infected cells visible to adaptive immune responses. However, the latency-associated viral protein UL138 inhibits the ability of VPA to enhance IE gene expression during infection of incompletely differentiated myeloid cells that support latency. UL138 also limits the accumulation of IFNβ transcripts by inhibiting the cGAS-STING-TBK1 DNA-sensing pathway. Here, we show that, in the absence of UL138, the cGAS-STING-TBK1 pathway promotes both IFNβ accumulation and VPA-responsive IE gene expression in incompletely differentiated myeloid cells. Inactivation of this pathway by either genetic or pharmacological inhibition phenocopied UL138 expression and reduced VPA-responsive IE transcript and protein accumulation. This work reveals a link between cytoplasmic pathogen sensing and epigenetic control of viral lytic phase transcription and suggests that manipulation of pattern recognition receptor signaling pathways could aid in the refinement of MIEP regulatory strategies to target latent viral reservoirs.

In-Cell Testing of Zinc-Dependent Histone Deacetylase Inhibitors in the Presence of Class-Selective Fluorogenic Substrates: Potential and Limitations of the Method.

The development of anticancer drugs based on zinc-dependent histone deacetylase inhibitors (HDACi) has acquired great practical significance over the past decade. The most important HDACi characteristics are selectivity and strength of inhibition since they determine the mechanisms of therapeutic action. For in-cell testing of the selectivity of de novo-synthesized HDACi, Western blot analysis of the level of acetylation of bona fide protein substrates of HDACs of each class is usually used. However, the high labor intensity of this method prevents its widespread use in inhibitor screening. We developed an in-cell high-throughput screening method based on the use of three subtype-selective fluorogenic substrates of the general structure Boc-Lys(Acyl)-AMC, which in many cases makes it possible to determine the selectivity of HDACi at the class level. However, we found that the additional inhibitory activity of HDACi against metallo-β-lactamase domain-containing protein 2 (MBLAC2) leads to testing errors.

Selective inhibition of Histone deacetylases reverses vascular remodeling and improves right ventricle function in pulmonary hypertension

Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Longfonds and CVON Background Pulmonary arterial hypertension (PAH) is a progressive fatal disease characterized by abnormal remodeling of pulmonary vessels, leading to increased vascular resistance and ultimately right ventricle (RV) failure. Disturbed BMPR2/TGFβ signaling is a driver of disease progression. Inhibition of Histone deacetylases (HDACs) using small molecule inhibitors attenuated vascular remodeling, however, they worsened RV function in animal models of PAH. Objectives The aim of this study is to validate if the selective HDAC inhibitor Quisinostat reverses pulmonary vascular remodeling and improves RV function. Methods and results We found that protein levels of HDAC1 are increased in the lungs of PAH patients. Treating microvascular endothelial cells (MVECs) and smooth muscle cells of PAH patients with Quisinostat significantly decreased TGF-β signaling and strongly decreased cell proliferation and the levels of inflammatory cytokines. In the MCT-shunt and Sugen Hypoxia rat models of severe angioproliferative PAH, Quisinostat reversed abnormal vascular remodeling and improved RV function. Furthermore, Quisinostat could be combined safely with the contemporary PAH standard of care. Finally, Quisinostat improved the RV function in rats with RV pressure load induced by pulmonary artery banding, and no systemic or cardiotoxic effects were observed. Conclusions Our data demonstrate that selective inhibition of HDACs reverses pulmonary vascular remodeling and improves RV function. These data support the establishment of a clinical trial with Quisinostat in patients with PAH.

Silk fibroin promotes H3K9me3 expression and chromatin reorganization to regulate endothelial cell proliferation.

Silk fibroin (SF), which is extensively utilized in tissue engineering and vascular grafts for enhancing vascular regeneration, has not been thoroughly investigated for its epigenetic effects on endothelial cells (EC). This study employed RNA sequencing analysis to evaluate the activation of histone modification regulatory genes in EC treated with SF. Subsequent investigations revealed elevated H3K9me3 levels in SF-treated EC, as evidenced by immunofluorescence and western blot analysis. The study utilized H2B-eGFP endothelial cells to demonstrate that SF treatment results in the accumulation of H2B-marked chromatin in the nuclear inner cavities of EC. Inhibition of H3K9me3 levels by a histone deacetylase inhibitor TSA decreased cell proliferation. Furthermore, the activation of the MAPK signaling pathway using chromium picolinate decreased the proliferative activity and H3K9me3 level in SF-treated EC. SF also appeared to enhance cell growth and proliferation by modulating the H3K9me3 level and reorganizing chromatin, particularly after oxidative stress induced by H2O2 treatment. In summary, these findings indicate that SF promotes EC proliferation by increasing the H3K9me3 level even under stress conditions.

Molecular heterogeneity of BCL2/MYC double expressor lymphoma underlies sensitivity to histone deacetylase inhibitor.

Molecular heterogeneity of BCL2/MYC double expressor lymphoma underlies sensitivity to histone deacetylase inhibitor.

Mechanistic and Structural Insights on Difluoromethyl-1,3,4-oxadiazole Inhibitors of HDAC6.

Histone deacetylase 6 (HDAC6) is increasingly recognized for its potential in targeted disease therapy. This study delves into the mechanistic and structural nuances of HDAC6 inhibition by difluoromethyl-1,3,4-oxadiazole (DFMO) derivatives, a class of non-hydroxamic inhibitors with remarkable selectivity and potency. Employing a combination of nuclear magnetic resonance (NMR) spectroscopy and liquid chromatography-mass spectrometry (LC-MS) kinetic experiments, comprehensive enzymatic characterizations, and X-ray crystallography, we dissect the intricate details of the DFMO-HDAC6 interaction dynamics. More specifically, we find that the chemical structure of a DMFO and the binding mode of its difluoroacetylhydrazide derivative are crucial in determining the predominant hydrolysis mechanism. Our findings provide additional insights into two different mechanisms of DFMO hydrolysis, thus contributing to a better understanding of the HDAC6 inhibition by oxadiazoles in disease modulation and therapeutic intervention.

HDAC6-mediated deacetylation of FLOT2 maintains stability and tumorigenic function of FLOT2 in nasopharyngeal carcinoma.

Flotillin-2 (FLOT2) is a prototypical oncogenic and a potential target for cancer therapy. However, strategies for targeting FLOT2 remain undefined. Post-translational modifications are crucial for regulating protein stability, function, and localization. Understanding the mechanisms and roles of post-translational modifications is key to developing targeted therapies. This study aims to investigate the regulation and function of lysine acetylation of FLOT2 in nasopharyngeal carcinoma, providing new insights for targeting FLOT2 in cancer intervention. The PhosphoSitePlus database was used to analyze the lysine acetylation sites of FLOT2, and a lysine acetylation site mutation of FLOT2 [FLOT2 (K211R)] was constructed. Nasopharyngeal carcinoma cells were treated with histone deacetylase (HDAC) inhibitor trichostatin A (TSA) and Sirt family deacetylase inhibitor nicotinamide (NAM). TSA-treated human embryonic kidney (HEK)-293T were transfected with FLOT2 mutant plasmids. Co-immunoprecipitation (Co-IP) was used to detect total acetylation levels of FLOT2 and the effects of specific lysine (K) site mutations on FLOT2 acetylation. Western blotting was used to detect FLOT2/FLAG-FLOT2 protein expression in TSA-treated nasopharyngeal carcinoma cells transfected with FLOT mutant plasmids, and real-time reverse transcription PCR (real-time RT-PCR) was used to detect FLOT2 mRNA expression. Nasopharyngeal carcinoma cells were treated with TSA combined with MG132 or chloroquine (CQ) to analyze FLOT2 protein expression. Cycloheximide (CHX) was used to treat HEK-293T cells transfected with FLAG-FLOT2 (WT) or FLAG-FLOT2(K211R) plasmids to assess protein degradation rates. The BioGrid database was used to identify potential interactions between FLOT2 and HDAC6, which were validated by Co-IP. HEK-293T cells were co-transfected with FLAG-FLOT2 (WT)/FLAG-FLOT2 (K211R) and Vector/HDAC6 plasmids, and grouped into FLAG-FLOT2 (WT)+Vector, FLAG-FLOT2 (WT)+HDAC6, FLAG-FLOT2 (K211R)+Vector, and FLAG-FLOT2 (K211R)+HDAC6 to analyze the impact of K211R mutation on total lysine acetylation levels. In 6-0B cells, overexpression of FLOT2 (WT) and FLOT2 (K211R) was performed, and the biological functions of FLOT2 acetylation site mutants were assessed using cell counting kit-8 (CCK-8), colony formation, and Transwell invasion assays. The PhosphoSitePlus database indicated that FLOT2 has an acetylation modification at the K211 site. Co-IP confirmed significant acetylation of FLOT2, with TSA significantly increasing overall FLOT2 acetylation levels, while NAM had no effect. Mutation at the K211 site significantly reduced overall FLOT2 acetylation, unaffected by TSA. TSA decreased FLOT2 protein expression in nasopharyngeal carcinoma cells without affecting FLOT2 mRNA levels or FLOT2 (K211R) protein expression in transfected cells. The degradation rate of FLOT2 (K211R) protein was significantly slower than that of FLOT2 (WT). The proteasome inhibitor MG132 prevented TSA-induced FLOT2 degradation, while the lysosome inhibitor CQ did not. BioGrid data suggested a potential interaction between FLOT2 and HDAC6, confirmed by Co-IP. Knockdown of HDAC6 in nasopharyngeal carcinoma cells significantly increased FLOT2 acetylation; co-transfection of HDAC6 and FLAG-FLOT2 (WT) significantly decreased total lysine acetylation levels, whereas co-transfection of HDAC6 and FLAG-FLOT2 (K211R) had no effect. Knockdown of HDAC6 significantly reduced FLOT2 protein levels without affecting mRNA levels. MG132 prevented HDAC6-knockdown-induced FLOT2 degradation. Knockdown of HDAC6 significantly accelerated FLOT2 degradation. Nasopharyngeal carcinoma cells transfected with FLOT2 (K211R) showed significantly higher proliferation and invasion than those transfected with FLOT2 (WT). The K211 site of FLOT2 undergoes acetylation modification, and HDAC6 mediates deacetylation at this site, inhibiting proteasomal degradation of FLOT2 and maintaining its stability and tumor-promoting function in nasopharyngeal carcinoma.

Inhibition of histone deacetylases class I improves adipogenic differentiation of human periodontal ligament cells.

Periodontal ligament stem cells (PDLSCs) show plasticity towards the adipogenic lineage; however, little has been done on the participation of epigenetic mechanisms. Histone acetylation is a dynamic process, though balanced by histone acetyltransferases (HATs) and histone deacetylases (HDACs) activities. This process can be halted by HDACs inhibitors, such as trichostatin A (TSA) and valproic acid (VPA). This study aimed to determine the role of HDACs class I in adipogenic differentiation of PDL cells. PDLSCs were treated with TSA at concentrations of 100, 200, and 250 nM, or VPA at 1, 4 and 8 mM. Cell viability was assessed using MTT assays. Gene expression of pluripotency markers (NANOG, OCT4, SOX2), HAT genes (p300, GCN5), and HDACs genes (HDAC1-3) was analyzed by RT-qPCR. Adipogenic differentiation was evaluated via oil red O staining, and acetylation of histone H3 lysine 9 (H3K9ac) was examined by Western blot. VPA treatment resulted in a 60% reduction in cell proliferation, compared to a 50% when using TSA. Cell viability was not affected by either inhibitor. Furthermore, both TSA and VPA induced adipogenic differentiation, through an increase in the deposition of lipid droplets and in GCN5 and p300 expression were observed. Western blot analysis showed that TSA increased H3K9ac levels on adipogenic differentiation of PDLSCs. These findings highlight the potential of HDAC inhibitors as a tool for modulating H3K9 acetylation status and thus influencing adipogenic differentiation of PDLCs.

Sulfur(VI) Fluoride Exchange Chemistry in Solid-Phase Synthesis of Compound Arrays: Discovery of Histone Deacetylase Inhibitors.

Multistep synthesis performed on solid support is a powerful means to generate small-molecule libraries for the discovery of chemical probes to dissect biological mechanisms as well as for drug discovery. Therefore, expansion of the collection of robust chemical transformations amenable to solid-phase synthesis is desirable for achieving chemically diverse libraries for biological testing. Here, we show that sulfur(VI) fluoride exchange (SuFEx) chemistry, exemplified by pairing phenols with aryl fluorosulfates, can be used for the solid-phase synthesis of biologically active compounds. As a case study, we designed and synthesized a library of 84 hydroxamic acid-containing small molecules, providing a rich source of inhibitors with diverse selectivity profiles across the human histone deacetylase enzyme family. Among other discoveries, we identified a scaffold that furnished inhibitors of HDAC11 with exquisite selectivity in vitro and a selective inhibitor of HDAC6 that was shown to affect the acetylation of α-tubulin over histone sites H3K18, H3K27, as well as SMC3 in cultured cells. Our results encourage the further use of SuFEx chemistry for the synthesis of diverse small-molecule libraries and provide insight for future design of selective HDAC inhibitors.

Antidepressant effect and mechanism of TMP269 on stress-induced depressive-like behavior in mice

TMP269, a class IIA histone deacetylase inhibitor with selectivity, that has a protective effect on the central nervous system, yet its specific mechanism of action remains ambiguous. Although major depressive disorder (MDD) is highly prevalent, its pathophysiology is poorly understood. Recent evidence suggests that histone deacetylase 5 plays a key role in the pathological process of depression and the fact that preclinical studies have shown HDAC5 to be a potential antidepressant target, the search for natural drugs or small molecule compounds that can target HDAC5 may be a potential therapeutic strategy for the treatment of depression. In addition, we examined the role of the Brain-derived neurotrophic factor (BDNF), an important neurotrophic factor for neuronal survival and growth, as a potential downstream target of HDAC5. We found downward revision of HDAC5 levels in the hippocampus ameliorated depressive-like behavior in LH (Learned helplessness) mice. Furthermore, injection of HDAC5 overexpressing adenoviral vectors in the hippocampal dentate gyrus of wild-type mice produced a somewhat depressive-like phenotype. Pharmacological, immunofluorescence and biochemical experiments showed that TMP269 could produce antidepressant effects by inhibiting mouse hippocampal HDAC5 and thus modulating its downstream BDNF. Over all, TMP269 mitigated LH-induced depressive-like behaviors and abnormalities in synapse formation and neurogenesis within the hippocampus. These findings suggest potential beneficial effects of TMP269 on depression.

Design, synthesis and antiproliferative activity of raloxifene/histone deacetylase inhibitor hybrids in breast cancer

Antiestrogen/histone deacetylase inhibitor (HDACi) hybrids were designed by merging structures of raloxifene with suberoylanilide hydroxamic acid, incorporating the HDACi unit into the phenolic ring of the antiestrogen. These hybrids were synthesized with a range of HDACi chain lengths and assessed for bifunctionality. Four hybrids, 21 (YW471), 22 (YW490), 27(YW486), and 28 (YW487) showed good potency both as antiestrogens in a BRET assay and in a fluorometric HDACi assay. The antiproliferative activity of the hybrids was demonstrated in both ER+ MCF7 and ER– MDA-MB-231 breast cancer cell lines.

HDAC activity is dispensable for repression of cell-cycle genes by DREAM and E2F:RB complexes

Histone deacetylases (HDACs) play a crucial role in transcriptional regulation and are implicated in various diseases, including cancer. They are involved in histone tail deacetylation and canonically linked to transcriptional repression. Previous studies suggested that HDAC recruitment to cell-cycle gene promoters via the retinoblastoma (RB) protein or the DREAM complex through SIN3B is essential for G1/S and G2/M gene repression during cell-cycle arrest and exit. Here we investigate the interplay among DREAM, RB, SIN3 proteins, and HDACs in the context of cell-cycle gene repression. Knockout of SIN3B does not globally derepress cell-cycle genes in non-proliferating HCT116 and C2C12 cells. Loss of SIN3A/B moderately upregulates several cell-cycle genes in HCT116 cells but does so independently of DREAM/RB. HDAC inhibition does not induce general upregulation of RB/DREAM target genes in arrested transformed or non-transformed cells. Our findings suggest that E2F:RB and DREAM complexes can repress cell-cycle genes without relying on HDAC activity.

Role of histone deacetylases and sirtuins in the ischaemic stroke: a protocol for a systematic review and meta-analysis of animal studies

BackgroundStroke is a major cause of global mortality and disability. Currently, the treatment of acute ischaemic stroke through reperfusion has posed several challenges, raising the need for complementary options to...