Small Molecule Histone Deacetylase Inhibitors Research Articles

Design, synthesis, and histone deacetylase inhibition study of novel 4-(2-aminoethyl) phenol derivatives.

Histone deacetylases (HDACs) have been identified as promising targets for anticancer treatment. The study demonstrates virtual screening, molecular docking, and synthesis of 4-(2-aminoethyl) phenol derivatives as HDAC inhibitors. The virtual screening and molecular docking analysis led to the identification of 10 representative compounds, which were evaluated based on their drug-like properties. The results demonstrated that these compounds effectively interacted with the active site pocket of HDAC 3 through π-stacking, Zn2+ coordination, hydrogen bonding, and hydrophobic interactions with catalytic residues. Furthermore, a series of 4-(2-aminoethyl) phenol derivatives were synthesized, and their HDAC inhibitory activity was evaluated. Compounds 18 and 20 showed significant HDAC inhibitory activity of 64.94 ± 1.17% and 52.45 ± 1.45%, respectively, compared to the solvent control. The promising results of this study encourage further research on 4-(2-aminoethyl) phenol derivatives and may provide significant insight into the design of novel small molecule HDAC inhibitors to fight against target-specific malignancies of chronic obstructive pulmonary disease and nonsmall cell lung cancer in the future.

NOXA Accentuates Apoptosis Induction by a Novel Histone Deacetylase Inhibitor.

Epigenetic modifiers of the histone deacetylase (HDAC) family are often dysregulated in cancer cells. Experiments with small molecule HDAC inhibitors (HDACi) have proven that HDACs are a vulnerability of transformed cells. We evaluated a novel hydroxamic acid-based HDACi (KH16; termed yanostat) in human pancreatic ductal adenocarcinoma (PDAC) cells, short- and long-term cultured colorectal cancer (CRC) cells, and retinal pigment epithelial cells. We show that KH16 induces cell cycle arrest and apoptosis, both time and dose dependently in PDAC and CRC cells. This is associated with altered expression of BCL2 family members controlling intrinsic apoptosis. Recent data illustrate that PDAC cells frequently have an altered expression of the pro-apoptotic BH3-only protein NOXA and that HDACi induce an accumulation of NOXA. Using PDAC cells with a deletion of NOXA by CRISPR-Cas9, we found that a lack of NOXA delayed apoptosis induction by KH16. These results suggest that KH16 is a new chemotype of hydroxamic acid HDACi with superior activity against solid tumor-derived cells. Thus, KH16 is a scaffold for future research on compounds with nanomolar activity against HDACs.

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

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

Selective Inhibition of Class II HDAC Isoforms 4 and 5 Provides a Promising Therapeutic Intervention for MLL-Rearranged Acute Lymphoblastic Leukemia in Infants

▪MLL-rearranged acute lymphoblastic leukemia (ALL) is characterized by deregulation of the epigenome and shows susceptibility towards epigenetic perturbators such as histone deacetylase (HDAC) inhibitors. Hence, HDACs represent attractive drug targets and a variety of small molecule HDAC inhibitors have been developed and evaluated for the treatment of hematological malignancies. However, most broad-spectrum inhibitors, which simultaneously target the majority of human HDAC isoforms, often induce toxicity, especially in combination with other therapeutic agents. Therefore, selective inhibition of only one or two HDAC isoforms may represent a better alternative, provided that disease-specific dependency on specific HDACs has been identified.We examined the effects of shRNA-mediated knock-down of the class II HDACs (i.e. HDAC4, HDAC5, HDAC6, HDAC7 and HDAC9) in the MLL-rearranged ALL cell lines SEM and ALL-PO. Except for HDAC9, loss of expression (both on the mRNA and protein level) of all HDACs led to strong reductions in viable cells (0.70 to 0.19-fold; p=0.02-0.0016) in both models due to apoptosis, cell cycle arrest, or a combination thereof.Next, we evaluated the in vitro efficacy of a variety of class II HDAC-specific inhibitors on a panel of MLL-rearranged ALL (n=5) using 4-day viability MTT assays. This revealed that the selective HDAC4/5 inhibitor LMK-235 was able to recapitulate the loss-of-function phenotype of HDAC4 and HDAC5. Dose response curves showed complete growth inhibition in MLL-rearranged ALL cell lines (n=5), as well as in primary MLL-rearranged infant ALL patient samples (n=4), with IC 50 values of ~100 nM and 40-100 nM, respectively. Importantly, at these concentrations, LMK-235 hardly affected whole bone marrow samples derived from healthy individuals (n=2), for which IC 50 values were ~1 µM.To further explore the potential of class II HDAC inhibitor-based therapeutic strategies, we performed a combinatorial drug screen to identify compounds that synergize with LMK-235. For this, a compound library (comprising >200 unique agents) was screened in the absence and presence of varying concentrations of LMK235 in the MLL-rearranged cell line models SEM and ALL-PO. This, and subsequent validation experiments in additional cell line models, revealed that Venetoclax (BCL2 inhibitor), Trametinib (MEK/ERK inhibitor), Ponatinib (multi-tyrosine kinase inhibitor) and Omipalisib (a PI3K/mTOR inhibitor) strongly synergized with LMK-235. Average ZIP synergy scores ranged from 10-30, with peak ZIP scores up to 40. Importantly, synergistic effects were consistent over all concentration combinations tested. The addition of 50-100 nM LMK-235 strongly reduced IC 50 values for Omipalisib, Ponatinib and Venetoclax (0.27-fold p=0.003, 0.11-fold p=0.0005, 0.75-fold p=0.0004, respectively) in both models.In preparation to assess the in vivo efficacy of LMK-235 in patient-derived xenograft (PDX) mouse models of MLL-rearranged infant ALL, pharmacokinetic/pharmacodynamic (PK/PD) analysis was performed in immunodeficient NSG mice (n=5). For this, mice were treated with 20 mg/kg of LMK-235, daily administered via intraperitoneal injections for a total of 29 days. While none of the mice showed signs of toxicity or weight loss, LMK-235 plasma levels were stably maintained at concentrations that are highly effective against MLL-rearranged ALL cells in vitro.Taken together, these data demonstrate that various class II HDAC isoforms are targetable vulnerabilities in MLL-rearranged ALL and that pharmaceutical inhibition of HDAC4/5 by LMK-235 represents an attractive therapeutic option. Moreover, high levels of synergy observed between this HDAC inhibitor and various agents belonging to drug classes already reported to be effective against MLL-rearranged ALL, warrants pre-clinical evaluation in vivo. Currently, the assessment of the in vivo efficacy of LMK-235 monotherapy in MLL-rearranged infant ALL PDX models is in progress, after which promising synergistic HDAC inhibitor-based drug combinations will be evaluated. To determine the additional therapeutic value, the efficacy of LMK-235 and promising synergistic combinations will be evaluated in the background of conventional combination chemotherapy, where PDX models will receive a mouse-adapted version of induction therapy currently applied for treatment of MLL-rearranged infant ALL patients. DisclosuresNo relevant conflicts of interest to declare.

Small-molecule HDAC and Akt inhibitors suppress tumor growth and enhance immunotherapy in multiple myeloma

BackgroundMultiple myeloma (MM) is an incurable disease. The acquisition of resistance to drugs, including immunomodulatory drugs (IMiDs), has a negative effect on its prognosis. Cereblon (CRBN) is a key mediator of the bioactivities of IMiDs such as lenalidomide. Moreover, genetic alteration of CRBN is frequently detected in IMiD-resistant patients and is considered to contribute to IMiD resistance. Thus, overcoming resistance to drugs, including IMiDs, is expected to improve clinical outcomes. Here, we examined potential mechanisms of a histone deacetylase (HDAC) inhibitor and Akt inhibitor in relapsed/refractory MM patients.MethodsWe established lenalidomide-resistant cells by knocking down CRBN with RNAi-mediated downregulation or knocking out CRBN using CRISPR-Cas9 in MM cells. Additionally, we derived multi-drug (bortezomib, doxorubicin, or dexamethasone)-resistant cell lines and primary cells from relapsed/refractory MM patients. The effects of HDAC and Akt inhibitors on these drug-resistant MM cells were then observed with a particular focus on whether HDAC inhibitors enhance immunotherapy efficacy. We also investigated the effect of lenalidomide on CRBN-deficient cells.ResultsThe HDAC inhibitor suppressed the growth of drug-resistant MM cell lines and enhanced the antibody-dependent cellular cytotoxicity (ADCC) of therapeutic antibodies by upregulating natural killer group 2D (NKG2D) ligands in MM cells. CRBN-deficient cells showed lenalidomide-induced upregulation of phosphorylated glycogen synthase kinase-3 (p-GSK-3) and c-Myc phosphorylation. Moreover, HDAC and Akt inhibitors downregulated c-Myc by blocking GSK-3 phosphorylation. HDAC and Akt inhibitors also exhibited synergistic cytotoxic and c-Myc-suppressive effects. The dual HDAC and PI3K inhibitor, CUDC-907, exhibited cytotoxic and immunotherapy-enhancing effects in MM cells, including multi-drug-resistant lines and primary cells from lenalidomide-resistant patients.ConclusionsThe combination of an HDAC and an Akt inhibitor represents a promising approach for the treatment of relapsed/refractory MM.

Small-molecule inhibitors of histone deacetylase improve CRISPR-based adenine base editing.

CRISPR-based base editors (BEs) are widely used to induce nucleotide substitutions in living cells and organisms without causing the damaging DNA double-strand breaks and DNA donor templates. Cytosine BEs that induce C:G to T:A conversion and adenine BEs that induce A:T to G:C conversion have been developed. Various attempts have been made to increase the efficiency of both BEs; however, their activities need to be improved for further applications. Here, we describe a fluorescent reporter-based drug screening platform to identify novel chemicals with the goal of improving adenine base editing efficiency. The reporter system revealed that histone deacetylase inhibitors, particularly romidepsin, enhanced base editing efficiencies by up to 4.9-fold by increasing the expression levels of proteins and target accessibility. The results support the use of romidepsin as a viable option to improve base editing efficiency in biomedical research and therapeutic genome engineering.

A Comparative Study of Target Engagement Assays for HDAC1 Inhibitor Profiling.

Histone deacetylases (HDACs) are epigenetic modulators linked to diseases including cancer and neurodegeneration. Given their therapeutic potential, highly sensitive biochemical and cell-based profiling technologies have been developed to discover small-molecule HDAC inhibitors. Ultimately, the therapeutic action of these inhibitors is dependent on a physical engagement with their intended targets in cellular and tissue environments. Confirming target engagement in the cellular environment is particularly relevant for HDACs since they function as part of cell type-specific multiprotein complexes. Here we implemented two recently developed high-throughput target engagement technologies, NanoBRET and SplitLuc CETSA, to profile 349 compounds in the Epigenetic-Focused collection for HDAC1 binding. We found that the two HDAC1 target engagement assays correlated well with each other and with orthogonal activity-based assays, in particular those carried out in cellular environments rather than with isolated HDAC proteins. The assays detected a majority of the previously described HDAC1 inhibitors in the collection and, importantly, triaged HDAC inhibitors known to target other HDACs.

Crafting Carbazole-Based Vorinostat and Tubastatin-A-like Histone Deacetylase (HDAC) Inhibitors with Potent in Vitro and in Vivo Neuroactive Functions.

Small-molecule inhibitors of HDACs (HDACi) induce hyperacetylation of histone and nonhistone proteins and have emerged as potential therapeutic agents in most animal models tested. The established HDACi vorinostat and tubastatin-A alleviate neurodegenerative and behavioral conditions in animal models of neuropsychiatric disorders restoring the neurotrophic milieu. In spite of the neuroactive pharmacological role of HDACi (vorinostat and tubastatin-A), they are limited by efficacy and toxicity. Considering these limitations and concern, we have designed novel compounds 3–11 as potential HDACi based on the strategic crafting of the key pharmacophoric elements of vorinostat and tubastatin-A into architecting a single molecule. The molecules 3–11 were synthesized through a multistep reaction sequence starting from carbazole and were fully characterized by NMR and mass spectral analysis. The novel molecules 3–11 showed remarkable pan HDAC inhibition and the potential to increase the levels of acetyl H3 and acetyl tubulin. In addition, few novel HDAC inhibitors 4–8, 10, and 11 exhibited significant neurite outgrowth-promoting activity with no observable cytotoxic effects, and interestingly, compound 5 has shown comparably more neurite growth than the parent compounds vorinostat and tubastatin-A. Also, compound 5 was evaluated for possible mood-elevating effects in a chronic unpredictable stress model of Zebrafish. It showed potent anxiolytic and antidepressant-like effects in the novel tank test and social interaction test, respectively. Furthermore, the potent in vitro and in vivo neuroactive compound 5 has shown selectivity for class II over class I HDACs. Our results suggest that the novel carbazole-based HDAC inhibitors, crafted with vorinostat and tubastatin-A pharmacophoric moieties, have potent neurite outgrowth activity and potential to be developed as therapeutics to treat depression and related psychiatric disorders.

Peptide-Based 2-Aminophenylamide Probes for Targeting Endogenous Class I Histone Deacetylase Complexes.

Lysine deacetylases or histone deacetylases (HDACs) remove acetylation markers from numerous cellular proteins, thereby regulating their function and activity. Recently established peptide probes containing the HDAC‐trapping amino acid α‐aminosuberic acid ω‐hydroxamate (AsuHd) have been used to investigate the compositions of HDAC complexes in a site‐specific manner. Here we report the new HDAC‐trapping amino acid 2‐amino‐8‐[(2‐aminophenyl)amino]‐8‐oxooctanoic acid (AsuApa) and the utility of AsuApa‐containing probes for HDAC complex profiling on a proteome‐wide scale. Unlike AsuHd‐containing probes, AsuApa enriched only HDACs 1, 2, and 3 efficiently and was the most potent probe tested for capturing the last of these. These findings indicate that the inherent specificity of reported small‐molecule pimelic diphenylamide HDAC inhibitors is preserved in AsuApa and that this HDAC‐trapping amino acid represents a potent tool for investigating class I HDAC complexes.

Abstract 4725: Efficacy of a new small-molecule inhibitor of histone deacetylase 6 (HDAC6) in preclinical models of B-cell lymphoma and acute myeloid leukemia

Abstract Histone deacetylase 6 (HDAC6) is a protein modifier that is an increasingly attractive pharmacological target. Interestingly, the observation that the HDAC6 knock-out mouse is not lethal, in contrast to those undergoing complete loss of class I, II and III HDACs, suggests that specific HDAC6 inhibitors may be better tolerated than pan-HDAC inhibitors or drugs that target the other HDAC classes. In this regard, the compound ACY-1215 (Rocilinostat), the described selective HDAC6 inhibitor, is undergoing clinical trials for the treatment of multiple myeloma. Taking into account the previous information about HDAC6 inhibitor structures, the structural differences between HDAC6 and other HDAC isoforms and also the structural information of other developed HDAC inhibitors, we have previously designed and synthesized a new potential HDAC6 selective inhibitor, QTX125 with growth inhibitory effects in mantle cell lymphoma (MCL) cell lines, mouse models and ex vivo treatment of primary samples obtained from patients with MCL. Herein, we have extended these findings to show that the newly identified HDAC6 inhibitor QTX125 is also able to inhibit the growth of preclinical models of other B-cell lymphomas such as follicular lymphoma and Burkitt’s cell lymphoma, but also of acute acute myeloid leukemia. In addition beyond a-tubulin, a well known HDAC6 target, we have developed a pharmacological and proteomic screening to identify other proteins modified by HDAC6 that can contribute to the described lymphoma and leukemia phenotypes. Citation Format: Lorea Villanueva, Montserrat Perez-Salvia, Eneko Aldaba, Yosu Vara, Myriam Fabre, Cristina Ferrer, Carme Masdeu, Aizpea Zubia, Eider San Sebastian, Dorleta Otaegui, Pere Llinàs-Arias, Margalida Rosselló-Tortella, María Berdasco, Fernando Setien, Catia Moutinho, Alberto Villanueva, Eva González-Barca, Josep Muncunill, José Tomás Navarro, Miguel Ángel Piris, Fernando Cossio, Manel Esteller. Efficacy of a new small-molecule inhibitor of histone deacetylase 6 (HDAC6) in preclinical models of B-cell lymphoma and acute myeloid leukemia [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 4725.

The nonepigenetic role for small molecule histone deacetylase inhibitors in the regulation of cardiac function.

Eight million US adults are projected to suffer from heart failure (HF) by 2030. Of concern, 5-year mortality rates following HF diagnosis approximate 40%. Small molecule histone deacetylase (HDAC) inhibitors have demonstrated efficacy for the treatment and reversal of HF. Historically, HDACs were studied as regulators of nucleosomal histones, in which lysine deacetylation on histone tails changed DNA-histone protein electrostatic interactions, leading to chromatin condensation and changes in gene expression. However, recent proteomics studies have demonstrated that approximately 4500 proteins can be acetylated in various tissues; the function of most of these remains unknown. This Review will focus on the nonepigenetic role for lysine acetylation in the heart, with a focus on nonepigenetic actions for HDAC inhibitors on cardiac function.

Efficacy of a New Small-Molecule Inhibitor of Histone Deacetylase 6 (HDAC6) in Preclinical Models of B-Cell Lymphoma and Acute Myeloid Leukemia

Histone deacetylase 6 (HDAC6) is a protein modifier that is an increasingly attractive pharmacological target. Interestingly, the observation that the HDAC6 knock-out mouse is not lethal, in contrast to those undergoing complete loss of class I, II and III HDACs, suggests that specific HDAC6 inhibitors may be better tolerated than pan-HDAC inhibitors or drugs that target the other HDAC classes. In this regard, the compound ACY-1215 (Rocilinostat), the described selective HDAC6 inhibitors, is undergoing clinical trials for the treatment of multiple myeloma. Taking into account the previous information about HDAC6 inhibitor structures, the structural differences between HDAC6 and other HDAC isoforms and also the structural information of other developed HDAC inhibitors, we have previously designed and synthesized a new potential HDAC6 selective inhibitor, QTX125 with growth inhibitory effects in mantle cell lymphoma (MCL) cell lines, mouse models and ex vivo treatment of primary samples obtained from patients with MCL. Herein, we have extended these findings to show that the newly identified HDAC6 inhibitor QTX125 is also able to inhibit the growth of preclinical models of other B-cell lymphomas such as follicular lymphoma and Burkitt's cell lymphoma, but also of acute acute myeloid leukemia. In addition beyond a-tubulin, a well known HDAC6 target, we have developed a pharmacological and proteomic screening to identify other proteins modified by HDAC6 that can contribute to the described lymphoma and leukemia phenotypes. DisclosuresEneko:Quimatryx: Employment. Yosu:Quimatryx: Employment. Myriam:Oncomatryx: Employment. Cristina:Oncomatryx: Employment. González-Barca:Roche: Speakers Bureau; Celtrion: Consultancy; Gilead: Consultancy; janssen: Consultancy, Speakers Bureau. Fernando:Quimatryx: Consultancy.

Epigenetic regulation of cardiac fibroblast senescence by class I histone deacetylases and ING2

Fibrosis is estimated to contribute to 45% of deaths in the western world. A key cellular mediator of fibrosis is the activated myofibroblast, which is characterized by the secretion of extracellular matrix (ECM) proteins. Myofibroblasts are thought to initially have a positive mechanical influence following an injury. However, long-term activation of these cells can lead to excessive ECM accumulation, culminating in fibrosis and organ failure. Cellular senescence is an irreversible form of cell cycle arrest, associated with a senescence-associated secretory phenotype (SASP), which is characterized by production of ECM-degrading enzymes such as matrix metalloproteases. Thus, it has been proposed that induction of the SASP might be a promising strategy for the resolution of organ fibrosis. In this context, histone deacetylase (HDAC) inhibitors might be candidate therapies for senescence modulation, as this class of enzymes is intensely involved in the control of cellular proliferation. Here, adult rat ventricular fibroblasts stimulated with TGF-β were used as a cell-based model of myofibroblast activation, and a panel of isoform-selective HDAC inhibitors was tested. Inhibitors of class I HDACs (especially HDAC1 and HDAC2), but not class IIa or IIb HDACs, potently stimulated cardiac fibroblast senescence, as assessed by upregulation of p16 and p21 gene expression, enhanced b-galactosidase activity, and induction of the classical SASP pathway. The mechanism of stimulation of senescence by class I HDAC inhibitors appears to involve ING2, a methyl-histone reader protein and phosphoinositide receptor. These findings define a chromatin signaling program for cardiac fibroblast senescence that could be could targeted with ‘epigenetic therapies’ such as small molecule HDAC inhibitors to treat fibrosis of the heart.

Abstract 3982: Dual inhibition of HDAC and PI3 kinase signaling pathways with CUDC-907 in treatment of p53-driven medulloblastoma

Abstract Comprehensive studies of the medulloblastoma (MB) genome, epigenome and transcriptome have placed MB in four molecular subgroups: WNT, SHH, and two non-WNT/non-SHH: Group 3 and Group 4. Furthermore, studies suggest that p53-mutated SHH MBs frequently harbor genetic anomalies involving MYCN and GLI2 amplifications, which confer poor prognosis and resistance to treatments. The phosphatidylinositol-3-kinase (PI3K)/AKT/mammalian target of rapamycin (mTOR) intracellular signaling pathway that regulates cell growth, survival and invasion, is commonly deregulated in MB. Therefore, the PI3K/Akt/mTOR pathway may be a suitable target for therapeutic intervention. Moreover, Histone deacetylases (HDAC) regulate cancer initiation and progression, and studies have shown that small molecule inhibitors of HDAC can effectively limit MB proliferation. We aim to determine the status of tumor suppressor gene p53 in defining metastatic potential in SHH-MB and to establish the therapeutic efficacy of targeting these pathways in p53-driven MB cells with a dual agent or individual agents. Immunohistochemistry and FISH were used to determine the status of mutant p53 and MYC amplification or iso-p53, respectively, in MB tumors (n=41). p53-mutant MB cell line was used to investigate the signaling pathway that regulates proliferation, migration, and drug resistance using inhibitors of HDAC (LBH-589) and PI3K/mTOR (BKM-120/rapamycin) or CUDC-907 (dual inhibitor of HDACs and the PI3K/AKT). Results demonstrated that: 1) GAB-1 was highly expressed in the Shh group (82%) and KV1 expression was evenly distributed in all subtypes; 2) loss of p53 and overexpression of MYC varied in each subtype, but did not correlate with metastasis; 3) combined treatment with LBH-589 and BKM-120 or single treatment with CUDC-907 reduced cell proliferation, migration and S-phase entry; 4) MB cells were resistant to BKM -120, while LBH-589 or CUDC-907 caused apoptosis; 5) tumor formation was suppressed by BKM-120 given with mTOR inhibitors; 6) AKT and 4E-BP1 dephosphorylated following treatments with BKM-120 or CUDC-907. In conclusion, despite current clinical limitations, dual HDAC and PI3K inhibitors may benefit the understanding of aberrant signaling pathways in genetically driven MB, and may provide basis for future targeted therapies. Citation Format: Jennifer S. Ronecker, Julia Pazniokas, Anubhav G. Amin, Raphael Salles Scortegagna de Medeiros, Sidnei Epelman, Chirag Ghandi, Nelci Zanon, Meic H. Schmidt, Meena Jhanwar-Uniyal. Dual inhibition of HDAC and PI3 kinase signaling pathways with CUDC-907 in treatment of p53-driven medulloblastoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3982.

M344 promotes nonamyloidogenic amyloid precursor protein processing while normalizing Alzheimer’s disease genes and improving memory

Alzheimer's disease (AD) comprises multifactorial ailments for which current therapeutic strategies remain insufficient to broadly address the underlying pathophysiology. Epigenetic gene regulation relies upon multifactorial processes that regulate multiple gene and protein pathways, including those involved in AD. We therefore took an epigenetic approach where a single drug would simultaneously affect the expression of a number of defined AD-related targets. We show that the small-molecule histone deacetylase inhibitor M344 reduces beta-amyloid (Aβ), reduces tau Ser396 phosphorylation, and decreases both β-secretase (BACE) and APOEε4 gene expression. M344 increases the expression of AD-relevant genes: BDNF, α-secretase (ADAM10), MINT2, FE65, REST, SIRT1, BIN1, and ABCA7, among others. M344 increases sAPPα and CTFα APP metabolite production, both cleavage products of ADAM10, concordant with increased ADAM10 gene expression. M344 also increases levels of immature APP, supporting an effect on APP trafficking, concurrent with the observed increase in MINT2 and FE65, both shown to increase immature APP in the early secretory pathway. Chronic i.p. treatment of the triple transgenic (APPsw/PS1M146V/TauP301L) mice with M344, at doses as low as 3 mg/kg, significantly prevented cognitive decline evaluated by Y-maze spontaneous alternation, novel object recognition, and Barnes maze spatial memory tests. M344 displays short brain exposure, indicating that brief pulses of daily drug treatment may be sufficient for long-term efficacy. Together, these data show that M344 normalizes several disparate pathogenic pathways related to AD. M344 therefore serves as an example of how a multitargeting compound could be used to address the polygenic nature of multifactorial diseases.

Class I HDACs control a JIP1-dependent pathway for kinesin-microtubule binding in cardiomyocytes

Class I histone deacetylase (HDAC) inhibitors block hypertrophy and fibrosis of the heart by suppressing pathological signaling and gene expression programs in cardiac myocytes and fibroblasts. The impact of HDAC inhibition in unstressed cardiac cells remains poorly understood. Here, we demonstrate that treatment of cultured cardiomyocytes with small molecule HDAC inhibitors leads to dramatic induction of c-Jun amino-terminal kinase (JNK)-interacting protein-1 (JIP1) mRNA and protein expression. In contrast to prior findings, elevated levels of endogenous JIP1 in cardiomyocytes failed to significantly alter JNK signaling or cardiomyocyte hypertrophy. Instead, HDAC inhibitor-mediated induction of JIP1 was required to stimulate expression of the kinesin heavy chain family member, KIF5A. We provide evidence for an HDAC-dependent regulatory circuit that promotes formation of JIP1:KIF5A:microtubule complexes that regulate intracellular transport of cargo such as autophagosomes. These findings define a novel role for class I HDACs in the control of the JIP1/kinesin axis in cardiomyocytes, and suggest that HDAC inhibitors could be used to alter microtubule transport in the heart.

HDAC1-3 inhibitor MS-275 enhances IL10 expression in RAW264.7 macrophages and reduces cigarette smoke-induced airway inflammation in mice

Chronic obstructive pulmonary disease (COPD) constitutes a major health burden. Studying underlying molecular mechanisms could lead to new therapeutic targets. Macrophages are orchestrators of COPD, by releasing pro-inflammatory cytokines. This process relies on transcription factors such as NF-κB, among others. NF-κB is regulated by lysine acetylation; a post-translational modification installed by histone acetyltransferases and removed by histone deacetylases (HDACs). We hypothesized that small molecule HDAC inhibitors (HDACi) targeting class I HDACs members that can regulate NF-κB could attenuate inflammatory responses in COPD via modulation of the NF-κB signaling output. MS-275 is an isoform-selective inhibitor of HDAC1-3. In precision-cut lung slices and RAW264.7 macrophages, MS-275 upregulated the expression of both pro- and anti-inflammatory genes, implying mixed effects. Interestingly, anti-inflammatory IL10 expression was upregulated in these model systems. In the macrophages, this was associated with increased NF-κB activity, acetylation, nuclear translocation, and binding to the IL10 promoter. Importantly, in an in vivo model of cigarette smoke-exposed C57Bl/6 mice, MS-275 robustly attenuated inflammatory expression of KC and neutrophil influx in the lungs. This study highlights for the first time the potential of isoform-selective HDACi for the treatment of inflammatory lung diseases like COPD.

Roles of HDACs in the Responses of Innate Immune Cells and as Targets in Inflammatory Diseases.

Histone deacetylases (HDACs) are an emerging class of molecules involved in the epigenetic regulation of innate immune responses through Toll-like receptor (TLR) and interferon (IFN) signaling pathways. HDACs are also key drivers of inflammatory diseases via epigenetic regulation through chromatin DNA and histone modification by methylation and acetylation, among other mechanisms, which control innate immune cell gene expression. Importantly, these epigenetic changes are reversible, and HDACs may also be targeted by small-molecule HDAC inhibitors, which have been used in clinical settings for cancer therapy. Here, we highlight HDACs as strong therapeutic molecules and explore HDAC-induced mechanisms regulating innate immune responses and inflammatory cytokine control, with the goal of developing personalized medicine for the treatment of human diseases, including inflammatory diseases and immune disorders. Currently, this novel class of immunomodulatory therapeutics is being evaluated in the laboratory, in preclinical models, and in the clinic.

An HDAC6 Inhibitor Confers Protection and Selectively Inhibits B-Cell Infiltration in DSS-Induced Colitis in Mice.

Small molecule histone deacetylase (HDAC) inhibitors with anti-inflammatory activity may be candidates for targeting intestinal inflammatory pathways in inflammatory bowel disease (IBD). This study investigated whether treatment with a potent HDAC6 inhibitor, BML-281, could protect against colonic inflammation and prevent inflammatory cell infiltration into the colon to drive disease pathology in a mouse model of acute dextran sodium sulfate (DSS) colitis. Control and acute DSS-colitis mice were treated with BML-281 (1 mg/kg per day s.c. and 10 mg/kg per day s.c.) for 8 days. Changes in disease pathology, colonic structure, function, alterations in inflammatory milieu, together with colonic inflammatory cell flux, were assessed by weight loss and disease activity index in vivo and by flow cytometry, gene expression, and histology ex vivo. Anti-inflammatory responses of BML-281 on human polymorphonuclear leukocytes were assessed in vitro. Administration of BML-281 to DSS-treated mice attenuated colitis, weight loss, and disease pathology, including changes in colon structure and function, by eliciting broad-spectrum anti-inflammatory effects and preventing infiltration and activation of key immune cells in the lamina propria of the intestinal epithelium. Among different immune cells, BML-281 particularly suppressed the infiltration of CD19+ B-cells into the inflamed colonic lamina propria. This study supports the targeting of HDAC6 as an anti-inflammatory strategy for treating colon inflammation progressing to IBD. Some HDAC inhibitors are used in the clinic to treat cancer, and the results here for BML-281 highlight the potential for HDAC6 inhibitors to be used in a clinical setting for preventing and treating colonic inflammation and IBD in humans.

The multifaceted influence of histone deacetylases on DNA damage signalling and DNA repair.

Histone/protein deacetylases play multiple roles in regulating gene expression and protein activation and stability. Their deregulation during cancer initiation and progression cause resistance to therapy. Here, we review the role of histone deacetylases (HDACs) and the NAD+ dependent sirtuins (SIRTs) in the DNA damage response (DDR). These lysine deacetylases contribute to DNA repair by base excision repair (BER), nucleotide excision repair (NER), mismatch repair (MMR), non-homologous end joining (NHEJ), homologous recombination (HR) and interstrand crosslink (ICL) repair. Furthermore, we discuss possible mechanisms whereby these histone/protein deacetylases facilitate the switch between DNA double-strand break (DSB) repair pathways, how SIRTs play a central role in the crosstalk between DNA repair and cell death pathways due to their dependence on NAD+, and the influence of small molecule HDAC inhibitors (HDACi) on cancer cell resistance to genotoxin based therapies. Throughout the review, we endeavor to identify the specific HDAC targeted by HDACi leading to therapy sensitization.