Histone Deacetylase 6 Selective Inhibitor Research Articles

Discovery of novel inhibitors of histone deacetylase 6: Structure-based virtual screening, molecular dynamics simulation, enzyme inhibition and cell viability assays

Histone deacetylase 6 (HDAC6) contributes to cancer metastasis in several cancers, including triple-negative breast cancer (TNBC)—the most lethal form that lacks effective therapy. Although several efforts have been invested to develop selective HDAC6 inhibitors, none have been approved by the FDA. Toward this goal, existing computational studies used smaller compound libraries and shorter MD simulations. Here, we conducted a structure-based virtual screening of ZINC “Druglike” library containing 17,900,742 compounds using a Glide virtual screening protocol comprising various filters with increasing accuracy. The top 20 hits were subjected to molecular dynamics simulation, MM-GBSA binding energy calculations, and further ADMET prediction. Furthermore, enzyme inhibition assay and cell viability assay were performed on six available compounds from the identified hits. C4 (ZINC000077541942) with a good profile of predicted drug properties was found to inhibit HDAC6 (IC50: 4.7 ± 11.6 μM) with comparative affinity to that of the known HDAC6 selective inhibitor Tubacin (TA) in our experiments. C4 also demonstrated cytotoxic effects against triple-negative breast cancer (TNBC) cell line MDA-MB-231 with EC50 of 40.6 ± 12.7 μM comparable to that of TA (2–20 μM). Therefore, this compound, with pharmacophore features comprising a non-hydroxamic acid zinc-binding group, heteroaromatic linker, and cap group, is proposed as a novel HDAC6 inhibitor.

A novel HDAC6 inhibitor, CKD-504, is effective in treating preclinical models of huntington’s disease

Huntington's disease (HD) is a neurodegenerative disorder, of which pathogenesis is caused by a polyglutamine expansion in the amino-terminus of huntingtin gene that resulted in the aggregation of mutant HTT proteins. HD is characterized by progressive motor dysfunction, cognitive impairment and neuropsychiatric disturbances. Histone deacetylase 6 (HDAC6), a microtubule-associated deacetylase, has been shown to induce transport- and release-defect phenotypes in HD models, whilst treatment with HDAC6 inhibitors ameliorates the phenotypic effects of HD by increasing the levels of α-tubulin acetylation, as well as decreasing the accumulation of mutant huntingtin (mHTT) aggregates, suggesting HDAC6 inhibitor as a HD therapeutics. In this study, we employed in vitro neural stem cell (NSC) model and in vivo YAC128 transgenic (TG) mouse model of HD to test the effect of a novel HDAC6 selective inhibitor, CKD-504, developed by Chong Kun Dang (CKD Pharmaceutical Corp., Korea). We found that treatment of CKD-504 increased tubulin acetylation, microtubule stabilization, axonal transport, and the decrease of mutant huntingtin protein in vitro. From in vivo study, we observed CKD-504 improved the pathology of Huntington's disease: alleviated behavioral deficits, increased axonal transport and number of neurons, restored synaptic function in corticostriatal (CS) circuit, reduced mHTT accumulation, inflammation and tau hyperphosphorylation in YAC128 TG mouse model. These novel results highlight CKD-504 as a potential therapeutic strategy in HD. [BMB Reports 2023; 56(3): 178-183].

Pharmacological inhibition of HDAC6 improves muscle phenotypes in dystrophin-deficient mice by downregulating TGF-β via Smad3 acetylation

The absence of dystrophin in Duchenne muscular dystrophy disrupts the dystrophin-associated glycoprotein complex resulting in skeletal muscle fiber fragility and atrophy, associated with fibrosis as well as microtubule and neuromuscular junction disorganization. The specific, non-conventional cytoplasmic histone deacetylase 6 (HDAC6) was recently shown to regulate acetylcholine receptor distribution and muscle atrophy. Here, we report that administration of the HDAC6 selective inhibitor tubastatin A to the Duchenne muscular dystrophy, mdx mouse model increases muscle strength, improves microtubule, neuromuscular junction, and dystrophin-associated glycoprotein complex organization, and reduces muscle atrophy and fibrosis. Interestingly, we found that the beneficial effects of HDAC6 inhibition involve the downregulation of transforming growth factor beta signaling. By increasing Smad3 acetylation in the cytoplasm, HDAC6 inhibition reduces Smad2/3 phosphorylation, nuclear translocation, and transcriptional activity. These findings provide in vivo evidence that Smad3 is a new target of HDAC6 and implicate HDAC6 as a potential therapeutic target in Duchenne muscular dystrophy.

Design, synthesis, and biological evaluation of novel histone deacetylase 6 selective inhibitors

Histone deacetylase 6 (HDAC6) is distinguished from other HDACs by its ability to deacetylate α-tubulin and HSP90, and was reported to be related to a variety of human diseases, such as cancers, neurodegenerative diseases, and immunological disorders. The discovery of novel HDAC6 selective inhibitors is important directions of this research field. In this paper, on the basis of a Bcl-2/HDAC6 dual target inhibitor 7g reported by us previously, a novel type of HDAC6 inhibitors was obtained by removing the binding capability to Bcl-2 protein and the subsequent systematical optimization. Among them, compounds Ⅵ-9, Ⅵ-10 and Ⅵ-11 (IC50 = 3.2 ∼ 3.9 nM, SI = 20.6 ∼ 38.7) showed the best inhibitory activities against and excellent selectivity to HDAC6. These compounds displayed growth inhibitory selectivity to human multiple myeloma cell line over normal cell line, which indicated potential lower toxicity to normal cells and tissues.

Melatonin- and Ferulic Acid-Based HDAC6 Selective Inhibitors Exhibit Pronounced Immunomodulatory Effects In Vitro and Neuroprotective Effects in a Pharmacological Alzheimer's Disease Mouse Model.

The structures of melatonin and ferulic acid were merged into tertiary amide-based histone deacetylase 6 (HDAC6) inhibitors to develop multi-target-directed inhibitors for neurodegenerative diseases to incorporate antioxidant effects without losing affinity and selectivity at HDAC6. Structure-activity relationships led to compound 10b as a hybrid molecule showing pronounced and selective inhibition of HDAC6 (IC50 = 30.7 nM, > 25-fold selectivity over other subtypes). This compound shows comparable DPPH radical scavenging ability to ferulic acid, comparable ORAC value to melatonin and comparable Cu2+ chelating ability to EDTA. It also lacks neurotoxicity on HT-22 cells, exhibits a pronounced immunomodulatory effect, and is active in vivo showing significantly higher efficacy in an AD mouse model to prevent both Aβ25-35-induced spatial working and long-term memory dysfunction at lower dose (0.3 mg/kg) compared to positive control HDAC6 inhibitor ACY1215 and an equimolar mixture of the three entities ACY1215, melatonin and ferulic acid, suggesting potentially disease-modifying properties.

Preclinical Evaluation of an 18F-Labeled SW-100 Derivative for PET Imaging of Histone Deacetylase 6 in the Brain.

Histone deacetylase 6 (HDAC6), an enzyme involved in protein degradation, exhibits several unique properties, such as cytoplasmic localization and ubiquitin binding. HDAC6 has emerged as an interesting therapeutic target in the treatment of neurodegenerative disorders such as Alzheimer's and Parkinson's diseases. Techniques enabling noninvasive HDAC6 imaging in the brain could enhance understanding of its pathologic role, but development of brain-penetrating radioligands for HDACs imaging by positron emission tomography (PET) remains challenging. Here, we report the synthesis and evaluation of an 18F-labeled tetrahydroquinoline derivative, [18F]2, based on the HDAC6 selective inhibitor SW-100 as a brain HDAC6 imaging radioligand. [18F]2 was synthesized via copper-mediated radiofluorination from an arylboronic precursor, followed by removal of the catalyst by solid-phase extraction and then hydroxamic acid formation. [18F]2 demonstrated good penetration and moderate stability in the mouse brain. In mouse plasma, however, [18F]2 was rapidly metabolized to a corresponding carboxylic acid form. Blocking studies in mice with unlabeled compound 2 and HDAC6 selective inhibitors, including tubastatin A and ACY-775, demonstrated that the HDAC6 inhibitors displaced over 80% of [18F]2 taken up in the brain, indicating selective binding of [18F]2. These results suggest that [18F]2 is a potentially useful PET radioligand for brain HDAC6 imaging.

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.

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.

HDAC6 inhibition protects cardiomyocytes against doxorubicin-induced acute damage by improving α-tubulin acetylation

Doxorubicin (Dox) is an efficacious antineoplastic drug but is limited used for its cardiotoxicity. Histone Deacetylase 6 (HDAC6) has been indicated to participate in cardiomyopathies, however, its role in Dox-induced cardiac injury is largely unknown. In this study, we firstly aimed to determine the role of HDAC6 in Dox-induced cardiomyopathy. Immunoblotting revealed that Dox increased HDAC6 protein level and activity and decreased α-tubulin acetylation level in vitro and vivo. HDAC6 knockout (HDAC6−/−) mice showed obvious anti-Dox cardiotoxicity by conserved cardiac function monitored by echocardiography and the protection was reversed by Nocodazole, one drug lowering α-tubulin acetylation. Further mechanism investigation showed that improvement of mitochondria function and autophagy flux was partially inhibited by Nocodazole and Colchicine which lowers α-tubulin acetylation in neonatal rat cardiac myocytes. Aiming at transforming this research to clinical application, we then explored the effect of combined utilization of HDAC6 inhibitor and Dox on tumour and cardiac function. Results showed that Tubastatin A, one HDAC6 selective inhibitor, protected against Dox-induced acute cardiomyopathy without influencing the effect of Dox on inhibiting MDA-MB-231 subcutaneous tumour growth. These findings suggest a new treatment for cancer with Dox by combined utilization with HDAC6 selective inhibitors.

Histone Deacetylase 6-Selective Inhibitors and the Influence of Capping Groups on Hydroxamate-Zinc Denticity.

Four crystal structures are presented of histone deacetylase 6 (HDAC6) complexes with para-substituted phenylhydromaxamate inhibitors, including bulky peptoids. These structures provide insight regarding the design of capping groups that confer selectivity for binding to HDAC6, specifically with regard to interactions in a pocket formed by the L1 loop. Capping group interactions may also influence hydroxamate-Zn2+ coordination with monodentate or bidentate geometry.

Design, Synthesis and Biological Evaluation of a Phenyl Butyric Acid Derivative, N-(4-chlorophenyl)-4-phenylbutanamide: A HDAC6 Inhibitor with Anti-proliferative Activity on Cervix Cancer and Leukemia Cells.

The epigenetic regulation of genes in cancer could be targeted by inhibiting Histone deacetylase 6 (HDAC6), an enzyme involved in several types of cancer such as lymphoma, leukemia, ovarian cancer, etc. Through in silico methods, a set of Phenyl butyric acid derivatives with possible HDAC6 inhibitory activity were designed, rendering monophenylamides and biphenylamides using tubacin (HDAC6 selective inhibitor) as reference. The target compounds were submitted to theoretical ADMET analyses and their binding properties on different HDAC6 conformers were evaluated through docking calculations. These in silico studies allowed us to identify a compound named B-R2B. In order to have more information about the B-R2B binding recognition properties on HDAC6, the B-R2B-HDAC6 complex was submitted through 100 ns-long Molecular Dynamics (MD) simulation coupled to MMGBSA approach, revealing that B-R2B is located at the entrance of HDAC6 active pocket, blocking the passage of the substrate without reaching the HDAC6 binding site. Based on these results, B-R2B was synthesized, characterized and biologically tested. The HDAC6 fluorometric drug discovery kit Fluor-de-Lys (ENZO Life Sciences Inc.) was used to determine the HDAC6 human inhibitory activity (IC50 value) of B-R2B compound. In addition, B-R2B show IC50 values on cancer cell lines (HeLa; IC50 = 72.6 µM), acute myeloid leukemia (THP-1; IC50 = 16.5 µM), human mast leukemia (HMC; IC50 = 79.29 µM) and chronic myelogenous leukemia (Kasumi; IC50 = 101 µM). These results show that B-R2B is a HDAC6 inhibitor, specifically a non-competitive type in a similar way that tubacin does, according to MD simulations.

Cystathionine γ-lyase protects vascular endothelium: a role for inhibition of histone deacetylase 6.

Endothelial cystathionine γ-lyase (CSEγ) contributes to cardiovascular homeostasis, mainly through production of H2S. However, the molecular mechanisms that control CSEγ gene expression in the endothelium during cardiovascular diseases are unclear. The aim of the current study is to determine the role of specific histone deacetylases (HDACs) in the regulation of endothelial CSEγ. Reduced CSEγ mRNA expression and protein abundance were observed in human aortic endothelial cells (HAEC) exposed to oxidized LDL (OxLDL) and in aortas from atherogenic apolipoprotein E knockout (ApoE-/-) mice fed a high-fat diet compared with controls. Intact murine aortic rings exposed to OxLDL (50 μg/ml) for 24 h exhibited impaired endothelium-dependent vasorelaxation that was blocked by CSEγ overexpression or the H2S donor NaHS. CSEγ expression was upregulated by pan-HDAC inhibitors and by class II-specific HDAC inhibitors, but not by other class-specific inhibitors. The HDAC6 selective inhibitor tubacin and HDAC6-specific siRNA increased CSEγ expression and blocked OxLDL-mediated reductions in endothelial CSEγ expression and CSEγ promoter activity, indicating that HDAC6 is a specific regulator of CSEγ expression. Consistent with this finding, HDAC6 mRNA, protein expression, and activity were upregulated in OxLDL-exposed HAEC, but not in human aortic smooth muscle cells. HDAC6 protein levels in aortas from high-fat diet-fed ApoE-/- mice were comparable to those in controls, whereas HDAC6 activity was robustly upregulated. Together, our findings indicate that HDAC6 is upregulated by atherogenic stimuli via posttranslational modifications and is a critical regulator of CSEγ expression in vascular endothelium. Inhibition of HDAC6 activity may improve endothelial function and prevent or reverse the development of atherosclerosis.NEW & NOTEWORTHY Oxidative injury to endothelial cells by oxidized LDL reduced cystathionine γ-lyase (CSEγ) expression and H2S production, leading to endothelial dysfunction, which was prevented by histone deacetylase 6 (HDAC6) inhibition. Our data suggest HDAC6 as a novel therapeutic target to prevent the development of atherosclerosis.

Novel histone deacetylase 6 (HDAC6) selective inhibitors: a patent evaluation (WO2014181137)

ABSTRACTIntroduction: Histone deacetylases (HDACs) are known to deacetylate histones and other proteins, which makes HDAC inhibitors able to affect cell survival, cell signaling, transport, and gene expression. Those effects have been associated to the therapeutic success of HDAC inhibitors. Class I-selective or pan-HDAC inhibitors have been approved for cancer therapy by the US Food and Drug Administration (FDA). Moreover, HDAC6 selective inhibitors entered phase I and II clinical trials for treating multiple myeloma. The development of potent and selective HDAC inhibitors is a hot topic in current drug discovery.Areas covered: The invention described in this patent (WO2014181137) is related to hydroxamic acid derivatives with inhibitory activity towards HDACs, their synthetic process and pharmaceutical formulations, as well as a method for treating patients suffering from a list of selected tumoral, inflammatory, cardiac and chronic disorders.Expert opinion: The compounds disclosed within this patent are selective against HDAC6 and their structure is related to tubastatin A, a known HDAC6 selective inhibitor. They are newly synthesized diarylamines showing an improved selectivity profile compared to other diarylamines under clinical investigation.

Structural insights into HDAC6 tubulin deacetylation and its selective inhibition.

We report crystal structures of zebrafish histone deacetylase 6 (HDAC6) catalytic domains in tandem or as single domains in complex with the (R) and (S) enantiomers of trichostatin A (TSA) or with the HDAC6-specific inhibitor nexturastat A. The tandem domains formed, together with the inter-domain linker, an ellipsoid-shaped complex with pseudo-twofold symmetry. We identified important active site differences between both catalytic domains and revealed the binding mode of HDAC6 selective inhibitors. HDAC inhibition assays with (R)- and (S)-TSA showed that (R)-TSA was a broad-range inhibitor, whereas (S)-TSA had moderate selectivity for HDAC6. We identified a uniquely positioned α-helix and a flexible tryptophan residue in the loop joining α-helices H20 to H21 as critical for deacetylation of the physiologic substrate tubulin. Using single-molecule measurements and biochemical assays we demonstrated that HDAC6 catalytic domain 2 deacetylated α-tubulin lysine 40 in the lumen of microtubules, but that its preferred substrate was unpolymerized tubulin.

HDAC6 promotes cell proliferation and confers resistance to temozolomide in glioblastoma

Histone deacetylases are considered to be among the most promising targets in drug development for cancer therapy. Histone deacetylase 6 (HDAC6) is a unique cytoplasmic enzyme that regulates many biological processes involved in tumorigenesis through its deacetylase and ubiquitin-binding activities. Here, we report that HDAC6 is overexpressed in glioblastoma tissues and cell lines. Overexpression of HDAC6 promotes the proliferation and spheroid formation of glioblastoma cells. HDAC6 overexpression confers resistance to temozolomide (TMZ) mediated cell proliferation inhibition and apoptosis induction. Conversely, knockdown of HDAC6 inhibits cell proliferation, impairs spheroid formation and sensitizes glioblastoma cells to TMZ. The inhibition of HDAC6 deacetylase activity by selective inhibitors inhibits the proliferation of glioblastoma cells and induces apoptosis. HDAC6 selective inhibitors can sensitize glioblastoma cells to TMZ. Moreover, we showed that HDAC6 mediated EGFR stabilization might partly account for its oncogenic role in glioblastoma. TMZ resistant glioblastoma cells showed higher expression of HDAC6 and more activation of EGFR. HDAC6 inhibitors decrease EGFR protein levels and impair the activation of the EGFR pathway. Taken together, our results suggest that the inhibition of HDAC6 may be a promising strategy for the treatment of glioblastoma.

Development and Therapeutic Implications of Selective Histone Deacetylase 6 Inhibitors

This Perspective provides an in depth look at the numerous disease states in which histone deacetylase 6 (HDAC6) has been implicated. The physiological pathways, protein-protein interactions, and non-histone substrates relating to different pathological conditions are discussed with regard to HDAC6. Furthermore, the compounds and methods used to modulate HDAC6 activity are profiled. The latter half of this Perspective analyzes reported HDAC6 selective inhibitors in terms of structure, potency, and selectivity over the other HDAC isoforms with the intent of providing a comprehensive overview of the molecular tools available. Potential obstacles and future directions of HDAC6 research are also presented.

Abstract 5246: Histone deacetylase 6 (HDAC6) as a new modulator of the JAK/STAT pathway in melanoma.

Abstract There is a crescent interest to understand the cellular and molecular processes involved in the progression of melanoma. Such knowledge is crucial for the development of more efficacious treatments and improved diagnostics. Acetylation and deacetylation of proteins plays a crucial role in the control of important cellular pathways, such as transcriptional control, proliferation, apoptosis, immunogenicity, etc. Specifically, histone deacetylases (HDACs) have garnered significant interest due to the availability of drugs that selectively inhibits HDAC. We recently investigated the effect of HDAC6 selective inhibitor(s) (HDAC6i) in human melanoma cell lines (WM164, WM983A and SKMEL21) with regards to proliferation and cell cycle profile. Pharmacological inhibition of HDAC6 resulted in a delayed proliferation and G1 cell cycle arrest in all melanoma cell lines analyzed. In addition to the pharmacological inhibition of HDAC6, we explored the effect of HDAC6 knock-down using specific shRNA (HDAC6KD). In agreement with the previous data from pharmacological inhibition of HDAC6, the proliferation of HDAC6KD melanoma cells was diminished when compared to wild-type and non-target shRNA control cells. Likewise, we observed a similar G1 arrest in the cell cycle that was attained with the use of HDAC6 specific inhibitors. Our data has also implicated HDAC6 in the regulation of the STAT1 and STAT3 pathways in melanoma cells. After cytokine IL-6 and IFN-γ stimulation of melanoma cells we found significant changes in the phosphorylation and acetylation status of STAT3 and STAT1 proteins in KDHDAC6 cells and/or treated with HDAC6i. Supporting this data, we observed important changes in the expression of STAT1 and STAT3 target genes, including essential genes involved in cell cycle control and immune regulation. Moreover, we observed a delay in tumor growth in C57BL/6 mice challenged in vivo with B16 cells lacking HDAC6 when compared to wild type B16 cells. These studies provide critical insights into the molecular pathways and/or partners that are involved in the regulatory role of HDAC6 in cell proliferation survival and cytokine signaling of human melanoma cells. Collectively, our data has identified HDAC6 as an attractive therapeutic target in melanoma due to its ability to delay tumor growth and target the JAK/STAT pathways, known to be altered in several melanoma malignancies. Citation Format: Maritza Lienlaf, Patricio Perez-Villarroel, Jorge Canales, Tessa Knox, Fengdong Cheng, Danay Marante, David Woods, Karrune Woan, HongWei Wang, Ed Seto, Jeffrey S. Weber, Eduardo M. Sotomayor, Alejandro Villagra. Histone deacetylase 6 (HDAC6) as a new modulator of the JAK/STAT pathway in melanoma. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 5246. doi:10.1158/1538-7445.AM2013-5246