Selective Histone Deacetylase Inhibitors Research Articles

Pharmacological activation of STAT1-GSDME pyroptotic circuitry reinforces epigenetic immunotherapy for hepatocellular carcinoma.

Genomic screening uncovered interferon-gamma (IFNγ) pathway defects in tumours refractory to immune checkpoint blockade (ICB). However, its non-mutational regulation and reversibility for therapeutic development remain less understood. We aimed to identify ICB resistance-associated druggable histone deacetylases (HDACs) and develop a readily translatable combination approach for patients with hepatocellular carcinoma (HCC). We correlated the prognostic outcomes of HCC patients from a pembrolizumab trial (NCT03419481) with tumourous cell expressions of all HDAC isoforms by single-cell RNA sequencing. We investigated the therapeutic efficacy and mechanism of action of selective HDAC inhibition in 4 ICB-resistant orthotopic and spontaneous models using immune profiling, single-cell multiomics and chromatin immunoprecipitation-sequencing and verified by genetic modulations and co-culture systems. HCC patients showing higher HDAC1/2/3 expressions exhibited deficient IFNγ signalling and poorer survival on ICB therapy. Transient treatment of a selective class-I HDAC inhibitor CXD101 resensitised HDAC1/2/3high tumours to ICB therapies, resulting in CD8+T cell-dependent antitumour and memory T cell responses. Mechanistically, CXD101 synergised with ICB to stimulate STAT1-driven antitumour immunity through enhanced chromatin accessibility and H3K27 hyperacetylation of IFNγ-responsive genes. Intratumoural recruitment of IFNγ+GZMB+cytotoxic lymphocytes further promoted cleavage of CXD101-induced Gasdermin E (GSDME) to trigger pyroptosis in a STAT1-dependent manner. Notably, deletion of GSDME mimicked STAT1 knockout in abolishing the antitumour efficacy and survival benefit of CXD101-ICB combination therapy by thwarting both pyroptotic and IFNγ responses. Our immunoepigenetic strategy harnesses IFNγ-mediated network to augment the cancer-immunity cycle, revealing a self-reinforcing STAT1-GSDME pyroptotic circuitry as the mechanistic basis for an ongoing phase-II trial to tackle ICB resistance (NCT05873244).

Kaempferol alleviates myocardial ischemia injury by reducing oxidative stress via the HDAC3-mediated Nrf2 signaling pathway

IntroductionKaempferol (KAE) is a flavonoid found in various plants. Recent studies showed that high dietary intake of KAE was associated with a lower risk of myocardial infarction; however, the cardioprotective mechanism of KAE remains unknown. ObjectivesTo determine the effect of KAE on cardiac injury in isoproterenol (ISO)-induced rats and cobalt chloride (CoCl2)-treated cardiomyocytes, and the underlying mechanisms. MethodsMale rats were pretreated with different doses of KAE for 14 days, and then injected with ISO to induce myocardial ischemia injury. We also established a model of myocardial cell injury using rat H9c2 cardiomyocytes stimulated with CoCl2. ResultsWe found that KAE pretreatment significantly alleviated myocardial injury and improved cardiac function in ISO-injected rats. In addition, KAE reduced oxidative stress in rats with myocardial ischemia by decreasing malondialdehyde concentration and increasing superoxide dismutase activity, and protection of the myocardial mitochondrial structure. KAE also attenuated CoCl2-induced injuryof H9c2 cardiomyocytes via suppression ofoxidative stress. With regard to the mechanism, we found that KAE down-regulated HDAC3 expression and up-regulated Nrf2 expression in ISO-induced rats and CoCl2-stimulated cardiomyocytes. Incubation of cardiomyocytes with HDAC3-selective inhibitor RGFP966 augmented the protective effect of KAE and reduced oxidative stress. By contrast, HDAC3 overexpression by adenovirus attenuated the effect of KAE on oxidative stress compared with KAE treatment group. HDAC3 also regulated Nrf2 expression in the cardiomyocytes with RGFP966 or an adenovirus overexpressing HDAC3; but Nrf2 inhibition reduced the effect of KAE on ROS generation in CoCl2-induced cardiomyocytes. Immunoprecipitation assay showed that HDAC3 interacted with Nrf2 in cardiomyocytes. Further studies found that KAE increased the acetylation level of Nrf2, while HDAC3 overexpression decreased the acetylation of Nrf2 compared with KAE treatment group. ConclusionOur data show that KAE ameliorates cardiac injury by reducing oxidative stress via the HDAC3-mediated Nrf2 signaling pathway in cardiomyocytes.

Arylcarboxamide Derivatives as Promising HDAC8 Inhibitors: An Overview in Light of Structure-activity Relationship and Binding Mode of Interaction Analysis

Abstract: HDAC8 is associated with several disease conditions as well as various cancers of several organs and hematological malignancies. To counter such pathophysiological and disease conditions, inhibition of HDAC8 may be a promising approach for anticancer drug development. In this article, a detail of arylcarboxamide-based potential HDAC8 inhibitors has been outlined. Considering their binding pattern of interactions along with the chemical features, effective and selective novel HDAC8 inhibitors can be designed further. Therefore, modification of these compounds provides greater possibilities for the development of novel HDAC8 inhibitors. Nevertheless, structural modification of such arylcarboxamide derivatives may be able to produce potent dual-inhibitory compounds along with HDAC8 inhibition. Thus, this article is quite useful for exploring and identifying several possibilities for arylcarboxamide-based HDAC8 inhibitors. Moreover, it can be concluded that further study of the arylcarboxamide-based HDAC8 inhibitors can be effectively used for the treatment of different cancerous and non-cancerous diseases.

Inhibition of HDAC6 mitigates high-fat diet-induced kidney inflammation and hypertension via reduced infiltration of macrophages

Obesity-mediated hypertension is a worldwide problem. Recent research has indicated that chronic inflammation is associated with the pathogenesis of obese hypertension. Activated immune cells infiltrate target organs, such as arteries, kidneys, and brain, causing end-organ damage and hypertension. Histone deacetylase 6 (HDAC6) regulates the inflammatory cell activity mediating the production of inflammatory cytokines and may play a role in the crosstalk between inflammation and hypertension. In this study, we investigated the roles of HDAC6 in high-fat diet (HFD)-induced kidney inflammation and hypertension. Nine-week-old male C57BL/6 mice were fed either a normal diet (ND) or HFD for 15 weeks. HFD-induced hypertension with increased HDAC6 activities in the kidney and bone marrow-derived macrophages (BMDM). When HFD group reached the hypertensive phase, each group of mice was intraperitoneally injected with vehicle or selective HDAC6 inhibitor Tubacin (1 mg/kg/day) for 14 days. Tubacin treatment lowered blood pressure (BP) of HFD-fed mice to the normal level with successful inhibition of HDAC6 activity. Immunohistochemical staining of F4/80, which is known as a macrophage marker, revealed that HFD promoted macrophage infiltration into the kidney. Consequently, pro-inflammatory factors TNFα and IL-6 gene expressions in the kidney were increased by HFD. Tubacin canceled HFD-induced macrophage infiltration and inflammation in the kidney. HDAC6 gene silencing and Tubacin treatment in Raw 264.7 cells also blocked the chemoattractant-stimulated cell migration in vitro. The results reveal the novel role of HDAC6 in BMDM migration, kidney inflammation, and high BP induced by HFD providing HDAC6 inhibitors as a therapeutic option for obesity-mediated hypertension.

Hydrazide-Based Class I Selective HDAC Inhibitors Completely Reverse Chemoresistance Synergistically in Platinum-Resistant Solid Cancer Cells.

In this work, we have synthesized a set of peptoid-based histone deacetylase inhibitors (HDACi) with a substituted hydrazide moiety as zinc-binding group. Subsequently, all compounds were evaluated in biochemical HDAC inhibition assays and for their antiproliferative activity against native and cisplatin-resistant cancer cell lines. The hydrazide derivatives with a propyl or butyl substituent (compounds 5 and 6) emerged as the most potent class I HDAC selective inhibitors (HDAC1-3). Further, compounds 5 and 6 outperformed entinostat in cytotoxicity assays and were able to reverse chemoresistance in cisplatin-resistant A2780 (ovarian) and Cal27 (head-neck) cancer cell lines. Moreover, the hydrazide derivatives 5 and 6 showed strong synergism with cisplatin (combination indices <0.2), again outperforming entinostat, and increased DNA damage, p21, and pro-apoptotic BIM expression, leading to caspase-mediated apoptosis and cell death. Thus, compounds 5 and 6 represent promising lead structures for developing new HDACi capable of reversing chemoresistance in cisplatin resistant cancer cells.

Discovery of organosulfur-based selective HDAC8 inhibitors with anti-neuroblastoma activity

Histone deacetylases (HDACs) are important epigenetic regulators of gene expression and various cellular processes, and are potential targets for anticancer therapy. In particular, HDAC8 is a promising therapeutic target for childhood neuroblastoma. To date, five HDAC inhibitors have been approved as anticancer drugs; however, all are non-selective HDAC inhibitors with various side effects. Furthermore, many promising HDAC inhibitors incorporate hydroxamic acid as a zinc binding group (ZBG), which may be associated with toxicity. Therefore, identification of isoform-selective HDAC inhibitors with novel ZBG is crucial. Here, a series of sulfur-based selective HDAC8 inhibitors featuring a novel ZBG were identified by modifying the early hit, ajoene, a component of garlic. Structure-activity relationship studies uncovered potent and selective HDAC8 inhibitors, and docking studies provided a structural rationale for HDAC8 inhibitory activity. One of the potent compounds, (Z)-1-phenyl-7-(4-methoxyphenyl)-2,3,7-trithiahepta-4-ene-7-oxide (15c), exhibited antiproliferative activity, with a GI50 of 2 µM, against neuroblastoma cell lines. 15c also showed significant in vivo efficacy in a neuroblastoma BE(2)-C xenograft model.

Nanostructured lipid carrier formulation for delivering poorly water-soluble ITF3756 HDAC inhibitor

Histone deacetylases (HDACs) are enzymes that play crucial roles in cellular processes by hydrolyzing acetyl-L-lysine side chains in core histones, thereby regulating gene expression and maintaining homeostasis. Histone deacetylase inhibitors (HDACi) have emerged as promising agents, particularly in cancer treatment, due to their ability to induce cytotoxic and pro-apoptotic effects. Selective HDAC6 inhibitors, such as ITF3756, have shown low off-target toxicity and promising pharmacological activities, but their poor water solubility limits their application in nanoparticulate drug delivery systems. Here, we optimized a nanostructured lipid carrier (NLC) formulation for delivering ITF3756 using the design of experiments (DOE) and response surface methodology (RSM). An interaction between the factor surfactant and formulation volume was observed, thus demonstrating that the surfactant concentration impacts the NLC size. It can be speculated that the higher the amount of the drug in the formulation, the lower the polydispersion index (PDI), thus resulting in more stable nanostructures. The optimized ITF3756-NLC demonstrated a size of 51.1 ± 0.3 nm, 8.85 ± 4.71 mV charge, and high entrapment efficiency (EE%), maintaining stability for 60 days. Moreover, ITF3756-NLC enhanced α-tubulin acetylation in melanoma, lung, and brain cancer cell lines, indicating retained or improved bioactivity. The ITF3756-NLC formulation offers a viable approach for enhancing the bioavailability and therapeutic efficacy of HDAC6 inhibitors, demonstrating potential for clinical applications in cancer immunotherapy.

HDAC6 Deletion Decreases Pristane-induced Inflammation.

Systemic lupus erythematosus is an autoimmune disease characterized by excessive inflammation and production of pathogenic Abs. Histone deacetylase 6 (HDAC6) is a class IIb histone deacetylase. It has been reported that selective HDAC6 inhibition decreases inflammation in lupus mouse models. In this study, sex- and age-matched wild-type (WT) and HDAC6-/- mice on the C57BL/6 background were administered 0.5 ml of pristane or PBS i.p. at 8-12 wk of age and were euthanized 10 d later. At sacrifice, body weight and spleen weight were measured, sera were collected, and splenocytes and peritoneal cells were harvested for flow cytometry. We found pristane administration increased the spleen weight with no difference between WT and HDAC6-/- mice. Pristane administration promoted the population of CD11b+Ly6C++ inflammatory monocytes and CD11b+Ly6G+ neutrophils. Peritoneal recruitment of these inflammatory monocytes and neutrophils was significantly decreased in HDAC6-/- mice compared with the WT mice. Flow cytometry results showed that the number of CD69+ T and B cells was increased in HDAC6-/- mice. Pristane administration also induced the IFN signature genes as determined by RT-qPCR. Furthermore, IFN signature genes were not affected in HDAC6-/- mice compared with the WT mice. In vitro studies in J774A.1 cells revealed that the selective HDAC6 inhibitor (ACY-738) increased acetylation of NF-κB while increasing Stat1 phosphorylation, which resulted in inducible NO synthase production in LPS/IFN-γ-stimulated cells. Taken together, these results demonstrate that although HDAC6 inhibition may inhibit some inflammatory pathways, others remain unaffected.

Natural Derivatives of Selective HDAC8 Inhibitors with Potent in Vivo Antitumor Efficacy against Breast Cancer.

HDAC8 is a therapeutic target with great promise for breast cancer. Here, we reported a novel compound corallorazine D from Nocardiopsis sp. XZB108, selectively inhibited HDAC8 (IC50 = 0.90 ± 0.014 μM), suggesting that it may be a promising nonhydroxamate HDAC8 inhibitor. Upon additional modifications of corallorazine D, a candidate compound 5k, demonstrated remarkable inhibitory potency against HDAC8 (IC50 = 0.12 ± 0.01 nM), 89-fold superior to PCI-34051. The selectivity of 5k was at least 439-fold, superior to corallorazine D, confirming the efficacy of our modifications. In an orthotopic mouse model of breast cancer, 5k displayed nearly 4-fold superior antitumor activity than SAHA. Furthermore, 5k triggered antitumor immunity by activating T cells. Treatment with 5k significantly increased the proportion of M1 macrophages and decreased the proportion of M2 macrophages (M1/M2 ratio = 2.67 ± 0.25). 5k represents a promising compound for further investigation as a potential treatment for breast cancer.

Chidamide plus R-GDP for relapsed/refractory diffuse large B-cell lymphoma in patients ineligible for autologous transplantation: A prospective, single-arm, phase II study.

In relapsed/refractory (R/R) diffuse large B-cell lymphoma (DLBCL), a negative prognosis is frequently linked to heightened epigenetic heterogeneity. Chidamide, a selective histone deacetylase inhibitor, shows promise as a targeted therapy for R/R DLBCL by targeting abnormal epigenetic changes associated with poor prognosis. A cohort of 27 ineligible patients with R/R DLBCL participated in an open - label, single - arm study. Chidamide was administered orally at a dose of 30 mg twice weekly for one week during the induction monotherapy phase. The subsequent combination therapy phase involved oral chidamide at a dose of 20 mg twice weekly for two weeks, followed by a one-week discontinuation period, in conjunction with intravenous R-GDP every 21 days. Among the cohort of 31 patients who underwent screening (median age: 67 years), 27 were ultimately included in the study, with 14 individuals successfully completing six cycles of C-R-GDP treatment. The overall best objective response rate was determined to be 79.1% (95% CI: 75.1%-83.3%), comprising a complete response rate of 45.8% (95% CI: 41.6%-49.9%) and a partial response rate of 33.3% (95% CI: 29.3%-37.4%). Within the subgroup of 14 patients who completed the full treatment regimen, the best objective response rate reached 100%, with 71.4% achieving complete response (n = 10) and 28.6% achieving partial response (n = 4). The median follow-up period for these patients was 17.0 months, ranging from 3.5 to 55 months. Progression-free survival was 5.9 months and overall survival was 48.3 months. Anemia was the most common adverse event, affecting all patients. Thrombocytopenia led to treatment interruption or dose reduction in 13 patients. Other common adverse events included hypocalcemia, hyponatremia, and hypokalemia. Three patients experienced grade 3 pneumonitis and one had grade 3 skin rash. Chidamide combined with R-GDP is a safe and effective treatment option for patients with R/R DLBCL who are not eligible for autologous stem cell transplantation.

Discovery of Potent Selective HDAC6 Inhibitors with 5-Phenyl-1H-indole Fragment: Virtual Screening, Rational Design, and Biological Evaluation.

Among the HDACs family, histone deacetylase 6 (HDAC6) has attracted extensive attention due to its unique structure and biological functions. Numerous studies have shown that compared with broad-spectrum HDACs inhibitors, selective HDAC6 inhibitors exert ideal efficacy in tumor treatment with insignificant toxic and side effects, demonstrating promising clinical application prospect. Herein, we carried out rational drug design by integrating a deep learning model, molecular docking, and molecular dynamics simulation technology to construct a virtual screening process. The designed derivatives with 5-phenyl-1H-indole fragment as Cap showed desirable cytotoxicity to the various tumor cell lines, all of which were within 15 μM (ranging from 0.35 to 14.87 μM), among which compound 5i had the best antiproliferative activities against HL-60 (IC50 = 0.35 ± 0.07 μM) and arrested HL-60 cells in the G0/G1 phase. In addition, 5i exhibited better isotype selective inhibitory activities due to the potent potency against HDAC6 (IC50 = 5.16 ± 0.25 nM) and the reduced inhibitory activities against HDAC1 (selective index ≈ 124), which was further verified by immunoblotting results. Moreover, the representative binding conformation of 5i on HDAC6 was revealed and the key residues contributing 5i's binding were also identified via decomposition free-energy analysis. The discovery of lead compound 5i also indicates that virtual screening is still a beneficial tool in drug discovery and can provide more molecular skeletons with research potential for drug design, which is worthy of widespread application.

Repurposing of known drugs from multiple libraries to identify novel and potential selective inhibitors of HDAC6 via in silico approach and molecular modeling

Histone deacetylase 6 (HDAC6, Class IIb) is a promising target for anticancer drugs. So far, few nonselective HDAC inhibitors have received regulatory approval as anticancer agents. However, they are associated with cell toxicity. Thus, isoform-selective inhibitors may be desirable. Here, we conducted structure-based virtual screening of multiple libraries containing a total of 2,250,135 compounds against HDAC6. The top hits with good docking scores and potential selectivity over HDAC10 (Class IIb) were submitted to 100 ns molecular dynamics simulation to monitor their dynamic behaviors and stability in the binding pockets of these enzymes. Furthermore, the drug-likeness and ADMET properties of these hits were estimated computationally. Four diverse compounds from different sources, including NCI and ZINC databases (BDH33926500, CID667061, Cromolyn, and ZINC000103531486), show potential selectivity for HDAC6.

Crucial Structural Understanding for Selective HDAC8 Inhibition: Common Pharmacophores, Molecular Docking, Molecular Dynamics, and Zinc Binder Analysis of selective HDAC8 inhibitors.

Overexpression of HDAC8 was observed in various cancers and inhibition of HDAC8 has emerged as a promising therapeutic approach in recent decades. This review aims to facilitate the discovery of novel selective HDAC8 inhibitors by analyzing the structural scaffolds of 66 known selective HDAC8 inhibitors, along with their IC50 values against HDAC8 and other HDACs. The inhibitors were clustered based on structural symmetry, and common pharmacophores for each cluster were identified using Phase. Molecular docking with all HDACs was performed to determine binding affinity and crucial interacting residues for HDAC8 inhibition. Representative inhibitors from each cluster were subjected to molecular dynamics simulation to analyze RMSD, RMSF, active site amino acid residues, and crucial interacting residues responsible for HDAC8 inhibition. The study reviewed the active site amino acid information, active site cavities of all HDACs, and the basic structure of Zn2+ binding groups. Common pharmacophores identified included AADHR_1, AADDR_1, ADDR_1, ADHHR_1, and AADRR_1. Molecular docking analysis revealed crucial interacting residues: HIS- 142, GLY-151, HIS-143, PHE-152, PHE-20 in the main pocket, and ARG-37, TYR-100, TYR-111, TYR-306 in the secondary pocket. The RMSD of protein and RMSF of active site amino acid residues for stable protein-ligand complexes were less than 2.4 Å and 1.0 Å, respectively, as identified from MD trajectories. The range of Molecular Mechanics Generalized Born Surface Area (MMGBSA) ΔG predicted from MD trajectories was between -15.8379 Å and -61.5017 Å kcal/mol. These findings may expedite the rapid discovery of selective HDAC8 inhibitors subject to experimental evaluation.

Dual-targeting class I HDAC inhibitor and ATM activator, SP-1-303, preferentially inhibits estrogen receptor positive breast cancer cell growth.

Dual-targeting chromatin regulation and DNA damage repair signaling presents a promising avenue for cancer therapy. Applying rational drug design, we synthesized a potent dual-targeting small molecule, SP-1-303. Here, we report SP-1-303 as a class I isoform selective histone deacetylase (HDAC) inhibitor and an activator of the ataxia-telangiectasia mutated protein (ATM). In vitro enzymatic assays demonstrated selective inhibition of HDAC1 and HDAC3. Cellular growth inhibition studies show that SP-1-303 differentially inhibits growth of estrogen receptor positive breast cancer (ER+ BC) cells with effective growth inhibition concentrations (EC50) for MCF-7 and T47D cells ranging from 0.32 to 0.34 μM, compared to 1.2-2.5 μM for triple negative breast cancer cells, and ~12 μM for normal breast epithelial cells. Western analysis reveals that SP-1-303 decreases estrogen receptor alpha (ER-α) expression and increases p53 protein expression, while inducing the phosphorylation of ATM and its substrates, BRCA1 and p53, in a time-dependent manner in ER+ BC cells. Pharmacokinetic evaluation demonstrates an area under the curve (AUC) of 5227.55 ng/ml × h with an elimination half-life of 1.26 h following intravenous administration in a rat model. Collectively, SP-1-303 emerges as a novel second generation class I (HDAC1 and HDAC3) selective HDAC inhibitor, and ATM activator, capable of modulating ER expression, and inhibiting growth of ER+ BC cells. Combined targeting of class I HDACs and ATM by SP-1-303 offers a promising therapeutic approach for treating ER+ breast cancers and supports further preclinical evaluation.

The efficacy and safety of chidamide in combination with etoposide and glucocorticoids for the treatment of hemophagocytic lymphohistiocytosis in adult patients: an open-label, single-center study.

Hemophagocytic lymphohistiocytosis (HLH) is a life-threatening condition characterized by hyperinflammation and organ failure, with a high mortality rate. Current first-line treatments for adult patients have limited efficacy and significant toxicity. The novel selective histone deacetylase inhibitor (HDACi), chidamide, has shown promise in preclinical studies for the potential treatment of HLH. An open-label, single-center study was conducted to evaluate the efficacy and safety of chidamide in combination with etoposide and glucocorticoids for the treatment of HLH in adult patients. Seventeen patients who fulfilled at least five of the eight HLH-2004 criteria were enrolled and treated with the combination therapy. The primary outcome was overall response rate (ORR), and secondary outcomes included survival, safety and tolerability, and changes in laboratory indicators. A total of 17 HLH patients who met the inclusion criteria were enrolled in this study, with a male to female ratio of 1.8:1. The age range at enrollment was 31 to 71 years old, with a median age of 52 years old. The ORR was 76.5% (13/17 patients), with a complete response (CR) rate of 17.6% (3/17 patients) and a partial response (PR) rate of 58.8% (10/17 patients). The median overall survival (OS) was not achieved, with OS at 6 months and 12 months being 81% and 65%, respectively. The median progression free survival (PFS) was not achieved, with PFS at 6 months and 12 months being 68% and 55%, respectively. Hematologic toxicities is the most common. Safety profile was favorable, with very few cases of grade 3/4 toxicities observed. The results showed that the levels of sCD25, platelets, aspartate aminotransferase, lactate dehydrogenase, and albumin in these patients were significantly improved 3 weeks after treatment. The addition of chidamide to etoposide and glucocorticoids may be a promising new treatment option for patients with HLH, with a high ORR, manageable safety profile, and significant improvement in laboratory indicators. Further research is needed to confirm these findings and determine the optimal dosing and duration of therapy.

Mocetinostat as a Novel Selective Histone Deacetylase Inhibitor in the Promotion of Apoptosis in glioblastoma Cell Line C6 and T98G

Abstract Background: Histone deacetylase (HDAC) enzymes play a crucial role in regulating gene expression and epigenetic alterations in cancer cells. Mocetinostat (MGCD0103) is a novel, isotype-selective HDAC inhibitor that targets Class I (HDAC1, 2, 3, and 8) and Class IV (HDAC11) enzymes. It has been approved for the use in phase II trials for Hodgkin’s lymphoma. Methods: In this study, the glioblastoma cell (GBM) lines T98G and C6 were treated with different concentrations of MGCD0103 (0.0, 0.5, 1.0, 1.5, 2.0, and 2.5 μM). Western blot analysis was used to evaluate protein expression and flow cytometry was employed to assess apoptosis. Results: The results demonstrated that MGCD0103 exerts multiple anti-cancer activities in GBMs. MGCD0103 modulated key signaling pathways, including inhibition of the Phosphatidylinositol 3- kinase (PI3K)/protein kinase B mechanism pathway and suppression of HDAC1 enzyme activity. High doses of MGCD0103 significantly induced apoptosis and suppressed cell proliferation by upregulating the pro-apoptotic protein Bcl-2-associated protein x and downregulating the anti-apoptotic proteins BH3 Interacting Domain Death Agonist and B-cell leukemia/lymphoma 2 protein. In addition, MGCD0103 treatment upregulated the expression of the tumor-suppressor gene and downregulated the E2F1 transcription factor. Furthermore, MGCD0103 facilitated cell differentiation by activating the glial fibrillary acidic protein Glial Fibrillary acidic protein (GFAP) as distinguish marker of astrocytes, and suppressing the undifferentiation markers Inhibitor of Deoxyribonucleic acid binding 2 and N-Myc proto-oncogene protein. Conclusion: This research suggests that MGCD0103 is a promising drug for inhibiting the proliferation, invasion, and migration of GBMs. The findings also provide new insights into the ability of MGCD0103 to induce differentiation in GBMs. Overall, these results indicate that MGCD0103 could be a potent therapeutic agent for the target of glioblastoma.

Discovery of a Highly Potent and Selective HDAC8 Degrader: Advancing the Functional Understanding and Therapeutic Potential of HDAC8.

HDAC8 plays crucial roles in biological processes, from gene regulation to cell motility, making it a highly desirable target for therapeutic intervention. HDAC8 also has deacetylase-independent activity which cannot be blocked by a conventional inhibitor. In this study, we report the discovery of YX862, a highly potent and selective hydrazide-based HDAC8-proteolysis targeting chimera (PROTAC) degrader. The selectivity is achieved through rational design of the warhead to spare HDAC3 activity from the previous HDAC3/8 dual degrader YX968. We demonstrate that the degradation of HDAC8 by YX862 increases acetylation levels of its nonhistone substrates such as SMC3 without significantly triggering histone PTM, supporting HDAC8's major role in nonhistone PTM regulation. YX862 exhibits promising on-target antiproliferative activity against DLBCL cells with higher potency than the HDAC8 selective inhibitor PCI-34051. As a selective HDAC8 degrader that avoids pan-HDAC inhibition, YX862 represents a valuable tool for exploring the biological and therapeutic potential of HDAC8.

Selective HDAC6 Inhibition Has the Potential for Anti-Cancer Effect in Renal Cell Carcinoma.

Despite significant advancements in systemic therapy for renal cell carcinoma (RCC), the prognosis for patients with metastatic RCC remains poor, as they are often incurable. Consequently, there is an urgent need for innovative therapeutic strategies to further enhance the efficacy of RCC treatment and improve patient outcomes. One such promising avenue lies in targeting histone deacetylase (HDAC) 6, a protein known to regulate numerous crucial biological processes implicated in cancer progression by modulating the acetylation status of various cytoplasmic proteins. To explore the therapeutic potential of HDAC6 inhibition in RCC, our study focused on investigating the effects of HDAC6 inhibitors on cultured RCC cells. Utilizing a panel of 12 small molecule selective HDAC6 inhibitors and employing genetic knockdown techniques, we examined the impact of HDAC6 inhibition on RCC cellular dynamics. Our findings revealed that HDAC6 inhibition exerted a profound effect on RCC cells, resulting in decreased cell viability and DNA replication. Importantly, this effect was attributed to the induction of apoptosis. Our study provides valuable insights into the mechanisms underlying the anticancer effects of selective HDAC6 inhibitors on RCC. A detailed understanding of the molecular mechanisms underlying the anticancer effects of HDAC6 inhibition is important to explore new therapeutic strategies for metastatic RCC.

Selective inhibition of HDAC6 by N-acylhydrazone derivative reduces the proliferation and induces senescence in carcinoma hepatocellular cells

Hepatocellular carcinoma (HCC) is a significant contributor to cancer-related deaths globally. Systemic therapy is the only treatment option for HCC at an advanced stage, with limited therapeutic response. In this study, we evaluated the antitumor potential of four N-acylhydrazone (NAH) derivatives, namely LASSBio-1909, 1911, 1935, and 1936, on HCC cell lines. We have previously demonstrated that the aforementioned NAH derivatives selectively inhibit histone deacetylase 6 (HDAC6) in lung cancer cells, but their effects on HCC cells have not been explored. Thus, the present study aimed to evaluate the effects of NAH derivatives on the proliferative behavior of HCC cells. LASSBio-1911 was the most cytotoxic compound against HCC cells, however its effects were minimal on normal cells. Our results showed that LASSBio-1911 inhibited HDAC6 in HCC cells leading to cell cycle arrest and decreased cell proliferation. There was also an increase in the frequency of cells in mitosis onset, which was associated with disturbing mitotic spindle formation. These events were accompanied by elevated levels of CDKN1A mRNA, accumulation of CCNB1 protein, and sustained ERK1 phosphorylation. Furthermore, LASSBio-1911 induced DNA damage, resulting in senescence and/or apoptosis. Our findings indicate that selective inhibition of HDAC6 may provide an effective therapeutic strategy for the treatment of advanced HCC, including tumor subtypes with integrated viral genome. Further, in vivo studies are required to validate the antitumor effect of LASSBio-1911 on liver cancer.

Design, synthesis and biological activity of oxyevodiamine-based histone deacetylase 6 inhibitors

Histone deacetylase 6 (HDAC6) was a potential target for Alzheimer’s disease (AD). In this study, a series of novel oxyevodiamine-based HDAC6 inhibitors with a variety of linker moieties were designed, synthesized and evaluated. Compound 12 with a benzyl linker was identified as a high potent and selective HDAC6 inhibitor. It inhibited HDAC6 with an IC50 value of 6.2 nM and was more than 200 fold selectivity over HDAC1. It also had lower cytotoxicity and higher anti-H2O2 activity in vitro comparing with other derivatives. Compound 12 might be a good lead as novel HDAC6 inhibitor for the treatment of AD.