HDAC Inhibitors Research Articles

Immunoliposomes for Neuroblastoma: Review of the Past Experience and Design of a Novel Nanoparticle.

High-risk/refractory neuro-blastoma (NBL) treatments include anti-GD2-monoclonal antibodies (mAbs). Several immunoliposomes (ILs) covered with anti-GD2-mAbs (GD2-ILs) have been tested pre-clinically. We aimed to review literature on GD2-IL for characteristics of nanoparticles/payloads, conjugation of mAb/fragments and preclinical data, as well as to explore the feasibility of a recently proposed GD2-IL loaded with the antimetabolite oxamate. Initial PubMed search was generalized for immunoliposomes in cancer. Further search was focused on papers for GD2-IL [keywords: "Immunoliposomes and cancer (or neuroblastoma)"]. There were 811 results on "immunoliposomes"; >50% were on "immunoliposomes, cancer" (n=439, June 2024). Seventeen items resulted from "immunoliposomes, neuroblastoma" (one was "publishers' correction"). Sixteen GD2-IL references were reviewed (1993-current). The mean±SD GD2-ILs size was 124.8±31 nm (range=86-171). Six papers described GD2-ILs with DNA-damaging agents [doxorubicin (n=4), etoposide (n=1), irinotecan+HDAC inhibitor (n=1)]. Other payloads included: fenretinide (n=4 papers), C-myb antisense (n=2), survivin inhibitor (n=1), tyrosine kinase inhibitor (n=1), IL15 (n=1), and oxamate (n=1). These 9 drug-loads included both hydrophilic and hydrophobic molecules. Except for IL15 and C-myb antisense with high molecular weights (MWs), and oxamate with low MW, the remaining compounds had comparable MWs (496±100 g/mol, range=349-588.6). The overall encapsulation efficiency was 66.2±25.6%. There were 17-30 mAb molecules attached to an IL with PEGylation. Experiments with GD2-positive/GD2-negative cells demonstrated selective efficacy/tropism of GD2-ILs. Mouse models confirmed efficacy, GD2-specific tumor accumulation, decreased toxicity, and improved pharmacokinetic-pharmacodynamics. PEGylated anti-GD2-IL may allow NBL tropism. A size of approximately 100 nm could allow vascular permeability and packaging of oxamate in amounts needed for profound/selective lactate dehydrogenase-A inhibition. Thus, oxamate-loaded GD2-ILs may allow exploring the great translational potential of Warburg effect inhibition in GD2-positive cancers.

Combinatorial PARP and HDAC inhibition synergistically promotes cell death and overcomes cisplatin treatment tolerance in cervical cancer cell lines

Combinatorial PARP and HDAC inhibition synergistically promotes cell death and overcomes cisplatin treatment tolerance in cervical cancer cell lines

Slow-Binding and Covalent HDAC Inhibition: A New Paradigm?

Slow-Binding and Covalent HDAC Inhibition: A New Paradigm?

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.

Panobinostat Synergizes with Chemotherapeutic Agents and Improves Efficacy of Standard-of-Care Chemotherapy Combinations in Ewing Sarcoma Cells

Background: The survival rate of patients with Ewing sarcoma (EWS) has seen very little improvement over the past several decades and remains dismal for those with recurrent or metastatic disease. HDAC2, ALK, JAK1, and CDK4 were identified as potential targets using RNA sequencing performed on EWS patient tumors with the bioinformatic analysis of gene expression. Methods/Results: The pan-HDAC inhibitor Panobinostat was cytotoxic to all the Ewing sarcoma cell lines tested. Mechanistically, Panobinostat decreases the expression of proteins involved in the cell cycle, including Cyclin D1 and phospho-Rb, and DNA damage repair, including CHK1. Further, Panobinostat induces a G1 cell cycle arrest. The combination of Panobinostat with Doxorubicin or Etoposide, both of which are used as standard of care in upfront treatment, leads to a synergistic effect in EWS cells. The combination of Panobinostat and Doxorubicin induces an accumulation of DNA damage, a decrease in the expression of DNA damage repair proteins CHK1 and CHK2, and an increase in caspase 3 cleavage. The addition of Panobinostat to standard-of-care chemotherapy combinations significantly reduces cell viability compared to that of chemotherapy alone. Conclusions: Overall, our data indicate that HDAC2 is overexpressed in many EWS tumor samples and HDAC inhibition is effective in targeting EWS cells, alone and in combination with standard-of-care chemotherapy agents. This work suggests that the addition of an HDAC inhibitor to upfront treatment may improve response.

Combining ERAP1 silencing and entinostat therapy to overcome resistance to cancer immunotherapy in neuroblastoma

BackgroundCheckpoint immunotherapy unleashes tumor control by T cells, but it is undermined in non-immunogenic tumors, e.g. with low MHC class I expression and low neoantigen burden, such as neuroblastoma (NB). Endoplasmic reticulum aminopeptidase 1 (ERAP1) is an enzyme that trims peptides before loading on MHC class I molecules. Inhibition of ERAP1 results in the generation of new antigens able of inducing potent anti-tumor immune responses. Here, we identify a novel non-toxic combinatorial strategy based on genetic inhibition of ERAP1 and administration of the HDAC inhibitor (HDACi) entinostat that increase the immunogenicity of NB, making it responsive to PD-1 therapy.MethodsCRISPR/Cas9-mediated gene editing was used to knockout (KO) the ERAP1 gene in 9464D NB cells derived from spontaneous tumors of TH-MYCN transgenic mice. The expression of MHC class I and PD-L1 was evaluated by flow cytometry (FC). The immunopeptidome of these cells was studied by mass spectrometry. Cocultures of splenocytes derived from 9464D bearing mice and tumor cells allowed the assessment of the effect of ERAP1 inhibition on the secretion of inflammatory cytokines and activation and migration of immune cells towards ERAP1 KO cells by FC. Tumor cell killing was evaluated by Caspase 3/7 assay and flow cytometry analysis. The effect of ERAP1 inhibition on the immune content of tumors was analyzed by FC, immunohistochemistry and multiple immunofluorescence.ResultsWe found that inhibition of ERAP1 makes 9464D cells more susceptible to immune cell-mediated killing by increasing both the recall and activation of CD4+ and CD8+ T cells and NK cells. Treatment with entinostat induces the expression of MHC class I and PD-L1 molecules in 9464D both in vitro and in vivo. This results in pronounced changes in the immunopeptidome induced by ERAP1 inhibition, but also restrains the growth of ERAP1 KO tumors in vivo by remodelling the tumor-infiltrating T-cell compartment. Interestingly, the absence of ERAP1 in combination with entinostat and PD-1 blockade overcomes resistance to PD-1 immunotherapy and increases host survival.ConclusionsThese findings demonstrate that ERAP1 inhibition combined with HDACi entinostat treatment and PD-1 blockade remodels the immune landscape of a non-immunogenic tumor such as NB, making it responsive to checkpoint immunotherapy.

Xylanase enhances gut microbiota-derived butyrate to exert immune-protective effects in a histone deacetylase-dependent manner

BackgroundCommensal bacteria in the intestine release enzymes to degrade and ferment dietary components, producing beneficial metabolites. However, the regulatory effects of microbial-derived enzymes on the intestinal microbiota composition and the influence on host health remain elusive. Xylanase can degrade xylan into oligosaccharides, showing wide application in feed industry.ResultsTo validate the immune-protective effects of xylanase, Nile tilapia was used as the model and fed with xylanase. The results showed that dietary xylanase improved the survival rate of Nile tilapia when they were challenged with Aeromonas hydrophila. The transcriptome analysis showed significant enrichment of genes related to interleukin-17d (il-17d) signaling pathway in the xylanase treatment group. High-throughput sequencing revealed that dietary xylanase altered the composition of the intestinal microbiota and directly promoted the proliferation of Allobaculum stercoricanis which could produce butyrate in vitro. Consequently, dietary xylanase supplementation increased the butyrate level in fish gut. Further experiment verified that butyrate supplementation enhanced the expression of il-17d and regenerating islet-derived 3 gamma (reg3g) in the gut. The knockdown experiment of il-17d confirmed that il-17d is necessary for butyrate to protect Nile tilapia from pathogen resistance. Flow cytometry analysis indicated that butyrate increased the abundance of IL-17D+ intestinal epithelial cells in fish. Mechanistically, butyrate functions as an HDAC3 inhibitor, enhancing il-17d expression and playing a crucial role in pathogen resistance.ConclusionDietary xylanase significantly altered the composition of intestinal microbiota and increased the content of butyrate in the intestine. Butyrate activated the transcription of il-17d in intestinal epithelial cells by inhibiting histone deacetylase 3, thereby protecting the Nile tilapia from pathogen infection. This study elucidated how microbial-derived xylanase regulates host immune function, providing a theoretical basis for the development and application of functional enzymes.7BVRPuQYn3eQdwFeU5j8vPVideo

Histone deacetylase inhibition disrupts the molecular signature of the glioblastoma secretome related to extracellular vesicle-associated proteins and targets RAB7a and RAB14 in vitro

Glioblastoma (GBM) is the most aggressive brain tumor with a poor prognosis. While Histone Deacetylase inhibitors have shown promising results in inhibiting cancer cell invasion and promoting apoptosis, their effects on GBM secretion, specifically focusing on extracellular vesicles (EVs) secretion, remain largely unexplored. Using label-free NANOLC-MS/MS methodology, we identified significant changes in the abundance of membrane traffic regulatory proteins in the secretome of U87MG cells after the treatment with the HDAC inhibitor Trichostatin A (TSA). In silico analysis showed that TSA treatment disrupted the secretion pattern of EVs-associated proteins and cellular signaling pathways, both qualitatively and quantitatively. Notably, RAB14/RAB7a interaction was only observed in the secretome of cells treated with TSA. In vitro assays revealed that TSA treatment of glioma cells increased EVs secretion and intracellular protein levels of RAB7a and RAB14 without affecting gene expression, suggesting a role of these two EVs-associated proteins in grade IV glioma cells. Additionally, an integrative approach using clinical data highlighted a correlation between DNA mutations affecting vesicle traffic coding-genes and clinical and phenotypic outcomes in glioma patients. These findings provide insights into the interplay between epigenetics and GBM intracellular trafficking, potentially leading to improved strategies for targeting and modifying the complex signaling network established between GBM cells and the tumor cell microenvironment.

Genetic and Molecular Heterogeneity of Synovial Sarcoma and Associated Challenges in Therapy.

Synovial sarcoma (SS) is one of the most common types of pediatric soft tissue sarcoma (STS) being far less frequent in adults. This STS type is characterized by one specific chromosomal translocation SS18-SSX and the associated changes in signaling. However, other genetic and epigenetic abnormalities in SS do not necessarily include SS18-SSX-related events, but abnormalities are more sporadic and do not correlate well with the prognosis and response to therapy. Currently, targeted therapy for synovial sarcoma includes a limited range of drugs, and surgical resection is the mainstay treatment for localized cancer with adjuvant or neoadjuvant chemotherapy and radiotherapy. Understanding the molecular characteristics of synovial sarcoma subtypes is becoming increasingly important for detecting new potential targets and developing innovative therapies. Novel approaches to treating synovial sarcoma include immune-based therapies (such as TCR-T cell therapy to NY-ESO-1, MAGE4, PRAME or using immune checkpoint inhibitors), epigenetic modifiers (HDAC inhibitors, EZH2 inhibitors, BRD disruptors), as well as novel or repurposed receptor tyrosine kinase inhibitors. In the presented review, we aimed to summarize the genetic and epigenetic landscape of SS as well as to find out the potential niches for the development of novel diagnostics and therapies.

Identification of targetable epigenetic vulnerabilities in uveal melanoma.

Uveal melanoma (UM) is the most prevalent primary intraocular malignancy in adults, which preferentially metastasizes to the liver in approximately half of all cases. Metastatic UM is notoriously resistant to therapy and is almost uniformly fatal. UM metastasis is most strongly associated with mutational inactivation of the BAP1 tumor suppressor gene. Given the role of BAP1 in epigenetic regulation as the ubiquitin hydrolase subunit of the polycomb repressive deubiquitinase (PR-DUB) complex, we conducted high-throughput drug screening using a well-characterized epigenetic compound library to identify new therapeutic vulnerabilities. We identified several promising new lead compounds, in particular the extra-terminal domain protein (BET) inhibitor mivebresib (ABBV-075). Mivebresib significantly improved survival rates in a metastatic uveal melanoma xenograft mouse model and entirely prevented detectable metastases to the bones, spinal cord, and brain. RNA sequencing revealed a notable overlap between the genes and pathways affected by HDAC and BET inhibition, including the reversal of gene signatures linked to high metastatic risk and upregulation of genes associated with a neuronal phenotype. Together, we found that UM cells are particularly vulnerable to class I HDAC and BET inhibition, and highlight the BET inhibitor mivebresib as a promising candidate for further clinical evaluation.

Effect and mechanism of novel HDAC inhibitor ZDLT-1 in colorectal cancer by regulating apoptosis and inflammation

BackgroundHistone deacetylase (HDAC) is a potential target for Colorectal Cancer (CRC) molecular target therapy, dehydroharmine derivative ZDLT-1 was designed to inhibit CRC cell proliferation by inhibiting HDAC target. This study aimed to explore the effect of ZDLT-1 could induce apoptosis in CRC in vitro and in vivo, and determine the mechanism of ZDLT-1. MethodsFirst, MTT assay, colony formation, wound healing, Transwell assay, Hoechst33342 staining and Annexin V-FITC/PI double staining assay were used to investigate the in vitro effect of ZDLT-1. Second, the toxicity and the anti-tumor effect of ZDLT-1 by subcutaneous tumorigenesis assay were used to determine the in vivo effect of ZDLT-1. In terms of mechanism, we evaluated the effect of ZDLT-1 on HDAC downstream proteins such as HIF-1α, NF-κB, Cleaved-Caspase-3/9, GSDMD and acetylated histone by immunofluorescence and Western blot assessments. ResultsThis study confirmed that ZDLT-1 had anti-tumor activity by inhibiting cell proliferation in vitro and solid tumor growth in vivo. Furthermore, ZDLT-1 can inhibit CRC cell invasion, migration and apoptosis in vitro. Moreover, ZDLT-1 can promote the expression of apoptosis proteins in HIF-1α/Caspase-3/Caspase-9 pathway and inhibit the expression of tumor-related immune proteins mainly in NF-κB/GSDMD/GSDME pathway. ConclusionZDLT-1 as HDAC inhibitor could suppresses CRC cell growth in vivo and in vitro by triggering HIF-1α/Caspase-3/Caspase-9 pathway in promoting apoptosis, and triggering NF-κB/GSDMD/GSDME pathway in inhibiting tumor inflammation. Our results propose dehydroharmine derivative ZDLT-1 as a promising therapeutic small molecular agent for CRC.

LMK235 ameliorates inflammation and fibrosis after myocardial infarction by inhibiting LSD1-related pathway

Background: Histone deacetylase 4 (HDAC4) and histone deacetylase 5 (HDAC5) are two isoforms of class IIa HDACs, and LMK235 is an HDAC inhibitor with higher selectivity for HDAC4/5. This study aimed to explore the expression and subcellular localization of HDAC4/5 and determine the mechanisms underlying the impact of LMK235 on ventricular remodelling post-MI. Methods: The MI model was established by left anterior descending branch (LAD) ligation, and LMK235 or vehicle was intraperitoneally injected daily for 21 days. Cardiac function was determined by echocardiography. Inflammation was evaluated by HE staining and measuring inflammatory cytokine expression, and fibrosis was evaluated by Masson staining and measuring fibrotic biomarker expression. Results: We found that LMK235 ameliorated cardiac dysfunction post-MI by suppressing inflammation and fibrosis, and LMK235 inhibited upregulation of lysine-specific demethylase 1 (LSD1) expression post-MI. In macrophages, LMK235 attenuated lipopolysaccharide (LPS) - induced inflammatory cytokine expression and inhibited LSD1 expression, while overexpression of LSD1 abrogated the anti-inflammatory effect of LMK235. In cardiac fibroblasts, LMK235 attenuated transforming growth factor-β1 (TGF-β1) - induced fibrotic biomarker expression and inhibited LSD1 expression, while overexpression of LSD1 abrogated the antifibrotic effect of LMK235. Conclusion: LMK235 attenuates chronic inflammation and fibrosis post-MI, leading to improved cardiac function. The anti-inflammatory effect of LMK235 may result from inhibition of the LSD1-NF-κB pathway in macrophages. The antifibrotic effect of LMK235 may result from inhibition of the LSD1-Smad2/3 pathway in cardiac fibroblasts.

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.

Unlocking Apoptotic Pathways: Overcoming Tumor Resistance in CAR-T-Cell Therapy.

Chimeric antigen receptor (CAR)-T-cell therapy has transformed cancer treatment, leading to remarkable clinical outcomes. However, resistance continues to be a major obstacle, significantly limiting its efficacy in numerous patients. This review critically examines the challenges associated with CAR-T-cell therapy, with a particular focus on the role of apoptotic pathways in overcoming resistance. We explore various strategies to sensitize tumor cells to CAR-T-cell-mediated apoptosis, including the use of combination therapies with BH3 mimetics, Mcl-1 inhibitors, IAP inhibitors, and HDAC inhibitors. These agents inhibit anti-apoptotic proteins and activate intrinsic mitochondrial pathways, enhancing the susceptibility of tumor cells to apoptosis. Moreover, targeting the extrinsic pathway can increase the expression of death receptors on tumor cells, further promoting their apoptosis. The review also discusses the development of novel CAR constructs that enhance anti-apoptotic protein expression, such as Bcl-2, which may counteract CAR-T cell exhaustion and improve antitumor efficacy. We assess the impact of the tumor microenvironment (TME) on CAR-T cell function and propose dual-targeting CAR-T cells to simultaneously address both myeloid-derived suppressor cells (MDSCs) and tumor cells. Furthermore, we explore the potential of combining agents like PPAR inhibitors to activate the cGAS-STING pathway, thereby improving CAR-T cell infiltration into the tumor. This review highlights that enhancing tumor cell sensitivity to apoptosis and increasing CAR-T cell cytotoxicity through apoptotic pathways could significantly improve therapeutic outcomes. Targeting apoptotic proteins, particularly those involved in the intrinsic mitochondrial pathway, constitutes a novel approach to overcoming resistance. The insights presented herein lay a robust foundation for future research and clinical applications aimed at optimizing CAR-T cell therapies.

405 (PB393): A combination of AURK inhibitor and HDAC inhibitor can restrain Anaplastic Thyroid Cancer aggressiveness: a drug repurposing story

405 (PB393): A combination of AURK inhibitor and HDAC inhibitor can restrain Anaplastic Thyroid Cancer aggressiveness: a drug repurposing story

310 (PB298): Synergistic Anti-Tumor Effects of the Novel HDAC Inhibitor, ABT-301, with Immune Checkpoint Inhibitors in Colorectal Cancer Through Regulation of Immune Response and Anti-Angiogenesis

310 (PB298): Synergistic Anti-Tumor Effects of the Novel HDAC Inhibitor, ABT-301, with Immune Checkpoint Inhibitors in Colorectal Cancer Through Regulation of Immune Response and Anti-Angiogenesis

Silencing GNAS enhances HDAC3i efficacy in CREBBP wild type B cell lymphoma.

The genetic era has opened the opportunity of using personalized therapeutic approaches, in part based on targeting genes with somatic mutations. For example, lymphomas harboring the highly recurrent CREBBP mutation show dependency on HDAC3, thus selective inhibition of HDAC3 reversed the epigenetic effects of CREBBP mutation, halted lymphoma growth, and induced MHC class II expression, enabling the T-cells to recognize and kill lymphoma cells. However, CREBBP wild type (WT) cells are less sensitive to this approach. In this issue of Leukemia, He et al. have executed a genome-wide CRISPR screening that identified GNAS as a target to maximize the therapeutic activity of HDAC3 inhibition in CREBBP WT lymphoma.

Harmonizing QSAR Machine Learning‐Based Models and Docking Approaches for Identifying Novel Histone Deacetylase 2 Inhibitors

AbstractMachine learning (ML) algorithms have gained widespread application in constructing computational models for predicting the bioactivity and physicochemical properties of numerous compounds, notably HDAC inhibitors. In this work, 2801 unique compounds with confirmed bioassays on HDAC2 were collected and employed to train ML models to virtually screening and possibly design potential inhibitors for HDAC2. A meticulous 3‐step procedure was first proposed to ensure the hits are within the application domain of the screening models. Through virtual screening of 91 million compounds, 59 structures were suggested by the four highest predictability models as potential HDAC2 inhibitors. The bioactivity of these compounds is further confirmed through a validated docking protocol, wherein 57 out of the 59 active hits proposed by the four models exhibited superior affinity with HDAC2 compared to vorinostat, with docking scores ranging from −10.74 to −7.06 kcal/mol. Lead optimization strategies were then implemented on the top‐performing compound from the molecular docking scores, CID 122648337, enhancing its binding affinity and interactions within the HDAC2 active site. This optimization led to the creation of two novel lead compounds, demonstrating higher affinity to HDAC2 than the initial hits. The stability of lead compounds in the active site was confirmed via MD simulations.

Design, Synthesis, and Biological Evaluation of HDAC Inhibitors Containing Natural Product-Inspired N-Linked 2-Acetylpyrrole Cap.

Drawing inspiration from the structural resemblance between a natural product N-(3-carboxypropyl)-2-acetylpyrrole and phenylbutyric acid, a pioneer HDAC inhibitor evaluated in clinical trials, we embarked on the design and synthesis of a novel array of HDAC inhibitors containing an N-linked 2-acetylpyrrole cap by utilizing the pharmacophore fusion strategy. Among them, compound 20 exhibited potential inhibitory activity on HDAC1, and demonstrated notable potency against RPMI-8226 cells with an IC50 value of 2.89 ± 0.43 μM, which was better than chidamide (IC50 = 10.23 ± 1.02 μM). Western blot analysis and Annexin V-FTIC/propidium iodide (PI) staining showed that 20 could enhance the acetylation of histone H3, as well as remarkably induce apoptosis of RPMI-8226 cancer cells. The docking study highlighted the presence of a hydrogen bond between the carbonyl oxygen of the 2-acetylpyrrole cap group and Phe198 of the HDAC1 enzyme in 20, emphasizing the crucial role of introducing this natural product-inspired cap group. Molecular dynamics simulations showed that the docked complex had good conformational stability. The ADME parameters calculation showed that 20 possesses remarkable theoretical drug-likeness properties. Taken together, these results suggested that 20 is worthy of further exploration as a potential HDAC-targeted anticancer drug candidate.

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.