HDAC6: a key regulator of cytoskeleton, cell migration and cell-cell interactions

Distribution, metabolism, and excretion of [14C] purinostat mesylate, a novel selective HDAC I/IIb inhibitor, in rats analyzed by high-performance liquid chromatography coupled with LTQ orbitrap mass spectrometry/radioactivity monitoring

Purinostat Mesylate (PM) is a novel and highly efficient selective histone deacetylase (HDAC) I/IIb inhibitor for hematologic tumor treatment that was granted Investigational New Drug (IND) approval for clinical investigation by the National Medical Products Administration and is currently in phase IIb clinical trials for relapsed/refractory diffuse large B-cell lymphoma. In this paper, the excretion, distribution, and metabolism properties of this IND were researched by High-Performance Liquid Chromatography coupled with LTQ Orbitrap Mass Spectrometry/Radioactivity Monitoring (HPLC-LTQ-Orbitrap-MS/RAM) and liquid scintillation counting. Following a single intravenous dose of [14C] PM to rats, a total of 98.49 % of the dose was recovered from intact rats within 0-168 h post-dose, with 14.16 % in urine and 83.15 % in feces, most of which was recovered within the first 24 h post-dose. For bile duct cannulated rats, a total of 95.54 % of the dose was recovered, with 62.37 % in bile, 23.37 % in urine and 8.58 % in feces within 0-72 h post-dose, suggesting that [14C] PM was excreted mainly into feces via biliary excretion. [14C] PM was distributed widely and eliminated rapidly throughout the body, with the lung, liver, kidney and intestine as the main organs. Interestingly, slow elimination was observed in the spleen, which could benefit the functional restoration of the spleen in hematological tumors. In terms of metabolism, [14C] PM underwent an extensive metabolic transformation in rats. Fourteen metabolites were tentatively identified, with major phase I metabolic pathways encompassing reduction, N-dealkylation, and oxidative deamination. Concomitantly, the primary phase II metabolic routes involved acetylation and glucuronic acid conjugation. This study was the first comprehensive PM pharmacokinetic study utilizing [14C] isotope labeling technology.

Unlocking the potential of novel tetrahydro-β-carboline-based HDAC6 inhibitors for colorectal cancer therapy: Design, synthesis and biological evaluation

Altered histone deacetylase 6 (HDAC6) expression and function have been linked to cancer progression, positioning it as a promising therapeutic target for cancer treatment. Herein, we introduce HDAC6 inhibitors based on the tetrahydro-β-carboline scaffold, with compound 18d exhibiting the strongest HDAC6 inhibitory potency, achieving an IC50 of 1.3 nM. Compound 18d exhibited significant growth inhibitory activity against an NCI panel of 60 human cancer cell lines with a minimal cytotoxic effect on non-tumor cells. In vitro mechanistic investigations were conducted in HCT-116 colorectal cancer cells where the capability of 18d to enhance the acetylation of α-tubulin (HDAC6 substrate) rather than nuclear H3 histone (HDAC1 substrate) confirmed selective inhibition of HDAC6 subtype. Additionally, compound 18d was observed to suppress the S phase and promote accumulation in the apoptotic sub-G1 phase, potentially through increasing cleaved caspase 3 and reducing Bcl-2 levels in HCT-116 cells. A wound healing assay also elicited the ability of 18d to hinder cell migration. Notably, 18d could suppress the phosphorylation of extracellular signal-regulated kinase (ERK)1/2, a crucial signaling pathway implicated in cancer cell proliferation, migration and apoptosis. Moreover, downregulation of the critical immune checkpoint protein programmed death-ligand 1 (PD-L1) revealed a potential role of 18d in augmenting immune response towards tumor cells. In summary, these findings highlight 18d's dual role in direct tumor growth suppression and immune system sensitization, highlighting a broader cancer therapeutic potential beyond conventional HDAC inhibition.

The diphenylpyrimidine derivative as a novel HDAC6 inhibitor alleviates atopic dermatitis through anti-inflammatory effects facilitated via TLR4/MAPK, STAT3 and NF-κB pathways

Atopic dermatitis (AD) is a systemic immune disease that primarily affects infants and children, characterized by recurring severe pruritus and chronic eczema. Studies have demonstrated that histone deacetylase 6 inhibitors (HDAC6is) can exhibit anti-inflammatory activities by regulating the acetylation level of target proteins. Building on these findings, our research focused on a synthetic diphenylpyrimidine derivative, specifically 15b, which we identified as a potent HDAC6i and an effective anti-inflammatory agent. This designation was determined by its safety profile, HDAC6 inhibitory activity, selectivity, and its anti-inflammatory effects in lipopolysaccharide (LPS)-stimulated RAW264.7 cells. In 2,4-dinitrochlorobenzene (DNCB)-induced AD mice, daily intraperitoneal injections of 15b significantly alleviated symptoms such as skin edema, dryness, crusting, and peeling, and reduced the frequency of scratching. Moreover, 15b mitigated ear swelling, addressed the increase in epidermal thickness, and reduced mast cell infiltration. Further mechanistic studies revealed that 15b selectively inhibited HDAC6, enhanced the acetylation of α-tubulin and heat shock protein 90 (HSP90) in RAW264.7 cells and BALB/c mice back skin tissue, and attenuated the activation of TLR4/MAPK, STAT3, NF-κB pathways. Consequently, both inflammatory cytokines (IL-4 and IFN-γ) and proteins (iNOS and COX-2) were dose-dependently decreased. These findings suggest that the HDAC6 inhibitor 15b can serve as a potential anti-inflammatory agent for the treatment of AD.

Histone deacetylase 6 inhibition attenuates pathological cardiac hypertrophy by promoting autophagy through MAP1LC3B ubiquitination

Cardiac hypertrophy is an adaptive response of the heart to pathological stimuli that may lead to cardiac dysfunction and heart failure. Histone deacetylase 6 (HDAC6) participates in the progression of multiple cardiovascular diseases, including chronic hypertension, ischemic stroke, and acute cardiac injury. A delicate balance of autophagy regulates heart homeostasis, whereas dysregulated autophagy is involved in myocardial hypertrophy. However, whether HDAC6 participates in pathological cardiac hypertrophy by regulating autophagy remains unclear. In this paper, we report for the first time that HDAC6 is involved in isoproterenol (ISO)-induced pathological cardiac hypertrophy by interacting with and ubiquitinating MAP1LC3B. First, the expression level of HDAC6 was found to be increased in cardiac hypertrophy models induced by ISO. HDAC6 overexpression promoted the expression of hypertrophic genes and enhanced cell surface area. Conversely, HDAC6 inhibition attenuated ISO-induced hypertrophic responses. Mechanistically, HDAC6 promoted hypertrophic responses by negatively regulating autophagy. Furthermore, HDAC6 interacted with MAP1LC3B and mediated its monoubiquitination, thereby contributing to reduced MAP1LC3B levels and impaired autophagy. Inhibition of HDAC6 activity in mice abrogated the hypertrophic effects of ISO by restoring MAP1LC3B expression. In summary, our data demonstrate that HDAC6 participates in ISO-induced cardiac hypertrophy by limiting the availability of MAP1LC3B and suppressing autophagy. © 2025 The Pathological Society of Great Britain and Ireland.

HDAC6 is involved in diabetic nephropathy by regulating TGFβ/Smads and NF-κB signaling pathways

Histone deacetylase 6 (HDAC6), a cytoplasmic member of the histone deacetylase family, plays an incompletely understood role in diabetic nephropathy (DN). While the TGF-β/Smads and NF-κB signaling pathways are established mediators of renal fibrosis and inflammation respectively, the potential regulatory effect of HDAC6 on these pathways in DN remains to be elucidated. Notably, Smad7 has been documented as a negative regulator of both TGF-β/Smads and NF-κB signaling pathways. This study utilized high glucose to establish a diabetic cell model and employed a high-fat diet combined with STZ injection to create a diabetic animal model to explore HDAC6's role in DN and its potential mechanism. Our research indicates that HDAC6 is upregulated in DN, and inhibiting HDAC6 activity with ACY1215 or downregulating HDAC6 expression with siRNA can suppress the TGF-β/Smads and NF-κB signaling pathways, thereby reducing renal fibrosis and inflammation. Moreover, further studies have shown that lentivirus-mediated overexpression of HDAC6 results in increased expression of FN and p-Smad2/3, decreased expression of Smad7 compared to their respective controls. ACY1215, an HDAC6 inhibitor, could alleviate DN by suppression of both the TGF-β/Smads and NF-κB signaling pathways. To sum up, this study reveals that HDAC6 is involved in the pathogenesis and progression of DN. Mechanistically, HDAC6 may participate in DN by regulating the TGF-β/Smads and NF-κB signaling pathways through Smad7.

The advances in acetylation modification in senescence and aging-related diseases

Aging is a process in which organisms or cells undergo a decline in their functions. Epigenetic modification changes have been recognized as a senescence hallmark in both natural aging and stimulation-induced senescence. An acetylation modification is a dynamic process, which plays a crucial role in the senescence process through DNA stability, metabolism, and signaling pathways. We summarized the role and regulatory pathways of acetylation modifications in senescence. Various cell fate-determining proteins regulate multiple cellular processes through acetylation modifications. These processes interact and coordinate with each other, forming an integrated regulatory network framework that collectively drives cellular senescence via multiple systemic mechanisms. Based on these findings, we proposed the "acetylation-network regulation-cellular senescence" model, to elaborate how acetylation contributes to senescence. We believe this insight could provide new directions and intervention strategies for senescence and aging-related diseases.

HDAC6 inhibition upregulates endothelial SOD3 expression via Sp1 acetylation and attenuates angiotensin II-induced hypertension

Extracellular superoxide dismutase (SOD3) plays an important role in maintaining vascular redox homeostasis by eliminating superoxides. The angiotensin II (AngII) peptide mediates vasoconstriction in part via reactive oxygen species (ROS) but has pathologic effects when elevated in adults. Histone deacetylase 6 (HDAC6) modulates the acetylation of non-histone substrates and is associated with hypertensive disorders. Here, we investigated the potential regulation of SOD3 by HDAC6 in human aortic endothelial cells (HAECs) and its implications for AngII-induced oxidative stress and hypertension. HDAC6 inhibition (via the specific inhibitor tubastatin A (TubA), gene knockdown, or a deacetylase activity-deficient mutant) significantly increased SOD3 protein and mRNA expression but did not affect SOD1 or SOD2 protein levels. Conversely, AngII downregulated SOD3 levels and increased ROS and superoxide levels; these effects were antagonized by TubA. We confirmed that the transcription factor Sp1 mediates TubA-induced as well as basal SOD3 expression. Notably, TubA strongly augmented Sp1 acetylation at lysine 703, which activated Sp1 binding to the proximal SOD3 promoter region and, consequently, SOD3 expression. Alternatively, AngII decreased Sp1 acetylation, and TubA-mediated SOD3 induction was reduced upon overexpression of an acetylation-resistant Sp1 mutant (K703R) compared to that by the wild-type protein. Consistent with these findings, aortic SOD3 expression was significantly higher in HDAC6-deficient mice than in wild-type mice. Moreover, AngII infusion-mediated blood pressure elevation was reduced in HDAC6-deficient mice compared with that in wild-type mice. Collectively, our results suggest that HDAC6 inhibition leads to SOD3 upregulation by enhancing Sp1 acetylation in HAECs, thereby mitigating AngII-induced oxidative stress and hypertension.

Histone Deacetylase Inhibitors Promote the Anticancer Activity of Cisplatin: Mechanisms and Potential

Cisplatin is a widely used DNA-targeting anticancer drug. Histone deacetylase inhibitors (HDACi) cause histone hyperacetylation, changing chromatin structure and accessibility of genomic DNA by the genotoxic drug. As a consequence, HDACi could promote cisplatin cytotoxicity. Hence, the underlying mechanisms by which HDACi alter the action pathways of cisplatin to promote its anticancer activity have attracted increasing attention during the past decades. It has been commonly accepted that HDACi elevate the acetylation level of histones to release genomic DNA to cisplatin attack, increasing the level of cisplatin-induced DNA lesions to promote cisplatin cytotoxicity. However, how the HDACi-enhanced cisplatin lesion on DNA impacts the downstream biological processes, and whether the promotion of HDACi to cisplatin activity is attributed to their inherent anticancer activity or to their induced elevation of histone acetylation, have been in debate. Several studies showed that HDACi-enhanced DNA lesion could promote cisplatin-induced apoptosis, cell cycle arrest, and reactive oxygen species (ROS) generation, subsequently promoting cisplatin efficiency. In contrast, HDACi-induced elimination of ROS and inhibition of ferroptosis were thought to be the main ways by which HDACi protect kidneys from acute injury caused by cisplatin. Based on our recent research, we herein review and discuss the advances in research on the mechanisms of HDACi-induced enhancement in cisplatin cytotoxicity. Given that histone acetyltransferase (HAT) inhibitors also show an effect enhancing cisplatin cytotoxicity, we will discuss the diverse roles of histone acetylation in cancer therapy in addition to the synergistic anticancer effect and potential of HDACi with genotoxic drugs and radiotherapy.

HDAC6 inhibition through WT161 synergizes with temozolomide, induces apoptosis, reduces cell motility, and decreases β-catenin levels in glioblastoma cells

Glioblastoma multiforme (GBM) accounts for 70% of all primary malignancies of the central nervous system. Current treatment strategies involve surgery followed by chemotherapy with temozolomide (TMZ); however, the median survival after treatment is approximately 15 months. Many GBM cases develop resistance to TMZ, resulting in a poor prognosis for patients, which underscores the urgent need for novel therapeutic approaches. One promising avenue is the inhibition of histone deacetylase 6 (HDAC6), an enzyme that deacetylates α-tubulin and is increasingly recognized as a potential pharmacological target in cancer. In GBM specifically, HDAC6 overexpression has been linked to poor prognosis and chemoresistance. In this study, we demonstrate that HDAC6 protein levels are elevated in GBM and evaluate the effects of the novel selective HDAC6 inhibitor, WT161, on U251, U87, and T98G cells to assess its potential to revert the malignant phenotype. Our results show a significant increase in acetylated α-tubulin levels, suppression of cell growth, cell cycle arrest at the G2/M phase, and decreased clonogenicity of 2D-cultured GBM cells. Additionally, WT161 acted synergistically with TMZ, induced apoptosis and enhanced TMZ-induced apoptosis. Notably, HDAC6 inhibition resulted in reduced cell migration and invasion, associated with decreased β-catenin levels. When cultured in 3D conditions, WT161-treated T98G spheroids were sensitized to TMZ and exhibited reduced migration. Finally, HDAC6 inhibition altered the metabolome, particularly affecting metabolites associated with lipid peroxidation. In conclusion, our data reveal, for the first time, the efficacy of the selective HDAC6 inhibitor WT161 in a preclinical GBM setting.

Identification of autophagy-related immune targets for enhancing immunotherapy in pancreatic cancer aggressiveness

BACKGROUND

Pancreatic cancer (PC) presents significant challenges in oncology, with metastasis critically affecting patient outcomes. Autophagy-related genes (ARGs)'s involvement in influencing immune activity and metastasis in PC remains inadequately understood.

AIM

This study seeks to identify and validate five ARGs that could serve as immune targets, enhancing enhancing Pancreatic cancer metastasis (PCM)'s prognostic models and informing immunotherapy strategies.

METHODS

ARGs that were diffentially expressed were screened, followed by Cox regression and LASSO analyses to pinpoint five genes linked to overall survival (OS). A prognostic model was developed and validated using ROC curves. Functional analyses, including GO and KEGG, were performed to elucidate ARG mechanisms. Immune infiltration and TFs/microRNA/mRNA networks were assessed to understand ARG-immune cell interactions. Experimental validation employed real-time PCR, IHC, and Western blotting, supported by TCGA data. Functional assays explored RHEB's role in PC, particularly its interaction with LC3.

RESULTS

Five ARGs (CASP1, RHEB, CHMP2B, MYC, and HDAC6) were identified, contributing to a robust prognostic model where low-risk individuals showed significantly longer OS. The model demonstrated high AUC scores, indicating strong prognostic capability. CD8 T cells and Treg cells' elevated levels were observed in metastatic subjects. RHEB knockdown suppressed cancer cell proliferation and invasion, with a negative correlation between RHEB and LC3, suggesting a role in autophagy-mediated modulation of PC metastasis.

CONCLUSION

This study introduces a novel prognostic model incorporating five ARGs, highlighting their potential as immune targets for cancer immunotherapy. The negative correlation between RHEB and LC3 suggests a therapeutic pathway for PCM intervention, laying the groundwork for more effective anti-cancer strategies. These findings advance the identification of novel immune targets and signaling pathways, aligning with precision medicine goals in cancer treatment.

Inhibition of HDAC6 elicits anticancer effects on head and neck cancer cells through Sp1/SOD3/MKP1 signaling axis to downregulate ERK phosphorylation

Oxidative stress caused by reactive oxygen species (ROS) and superoxides is linked to various cancer-related biological events. Extracellular superoxide dismutase (SOD3), an antioxidant enzyme that removes superoxides, contributes to redox homeostasis and has the potential to regulate tumorigenesis. Histone deacetylase 6 (HDAC6), a major HDAC isoform responsible for mediating the deacetylation of non-histone protein substrates, also plays a role in cancer progression. In this study, we examined the potential effects of HDAC6 inhibition on SOD3 expression in head and neck cancer (HNC) cells and its impact on cell proliferation, which remains unaddressed. We found that functional inactivation of HDAC6, through the use of chemical inhibitors such as tubastatin A (TubA), gene knockdown, or overexpression of an inactive mutant, strongly upregulated protein and mRNA levels of SOD3 in HNC cell lines FaDu and Detroit562. Mechanistically, TubA induced acetylation of the transcription factor Sp1 at Lys703, which consequently enhanced its binding to the SOD3 proximal promoter region and increased SOD3 expression. An acetylation-defective Sp1 mutant (K703R) was much less effective in inducing SOD3 expression compared to wild-type Sp1. TubA reduced intracellular ROS and superoxide levels, and this antioxidative effect was attenuated in SOD3 knockdown cells. Similar to the changes in ROS levels, HDAC6 inhibition as well as SOD3 overexpression suppressed cell proliferation and the stimulatory phosphorylation of extracellular signal-regulated kinase 1/2 (ERK1/2), whereas SOD3 knockdown produced opposite effects in both resting and TubA-treated conditions. In addition, SOD3 overexpression prevented ROS-induced ERK1/2 phosphorylation and enhanced the protein stability of mitogen-activated protein kinase phosphatase 1 (MKP1), thereby counteracting ERK1/2 phosphorylation. We further showed that SOD3-mediated ERK1/2 dephosphorylation was moderated in MKP1 knockdown cells. Collectively, these results suggest that HDAC6 inhibition elicits anticancer effects on HNC cells by promoting Sp1 acetylation-dependent SOD3 upregulation, leading to MKP1 stabilization and subsequent ERK1/2 inactivation.

Regulation of HDAC6 Catalytic Activity in Cancer: The Role of Post-Translational Modifications and Protein-Protein Interactions

Histone deacetylase 6 (HDAC6) is a large multidomain protein that deacetylates lysine residues on cytoplasmic proteins, influencing numerous cellular processes. Both the catalytic and noncatalytic functions of HDAC6 have been implicated in cancer development and progression. Over a decade of research on catalytic domain inhibitors has shown that these drugs are well tolerated, exhibit anticancer activity, and can alleviate chemotherapy-induced peripheral neuropathies. However, their effectiveness in treating solid tumours remains uncertain. HDAC6 activity is regulated by protein-protein interactions and post-translational modifications, which may allosterically influence its catalytic domains. As a result, effective inhibition of HDAC6 in cancer using small molecule inhibitors requires a more sophisticated understanding of its role within tumour cells, including whether its expression correlates with deacetylase activity. A comprehensive understanding of cancer-specific HDAC6 expression, functional activity, and activation states will be critical for refining the use of HDAC6 inhibitors in cancer therapy.

HDAC6 Facilitates PRV and VSV Infection by Inhibiting Type I Interferon Production

HDAC6 modulates viral infection through diverse mechanisms. Here, we investigated the role of HDAC6 in influencing viral infection in pig cells with the aim of exploiting the potential antiviral gene targets in pigs. Using gene knockout and overexpression strategies, we found that HDAC6 knockout greatly reduced PRV and VSV infectivity, whereas HDAC6 overexpression increased their infectivity in PK15 cells. Mechanistic studies identified HDAC6 as a DNA damage inhibitor in PK15 cells. HDAC6 overexpression attenuated DNA damage levels, which can further reduce type I IFN production to promote viral infection. Conversely, HDAC6 deficiency can limit viral infection by increasing DNA damage-mediated type I IFN production. This work demonstrates that HDAC6 affects the infection process of multiple viruses by modulating type I IFN production, highlighting a regulatory role of HDAC6 linking host immune response and viral infection levels in pig cells.

Molecular Imaging Reveals Antineuroinflammatory Effects of HDAC6 Inhibition in Stroke Models

Ischemic stroke is a devastating disease that causes neuronal death, neuroinflammation, and other cerebral damage. However, effective therapeutic strategies for ischemic stroke are still lacking. Histone deacetylase 6 (HDAC6) has been implicated in the pathogenesis of ischemic stroke, and the pharmacological inhibition of HDAC6 has shown promising neuroprotective effects. In this study, we utilized positron emission tomography (PET) imaging with the HDAC6-specific radioligand [18F]PB118 to investigate the dynamic changes of HDAC6 expression in the brain after ischemic injury. The results revealed a significant decline in [18F]PB118 uptake in the ipsilateral hemisphere on the first day after ischemia, followed by a gradual increase on days 4 and 7. To evaluate the therapeutic potential of HDAC6 inhibitors, we developed a novel brain-permeable and potent HDAC6 inhibitor, PB131, and assessed its neuroprotective effects in an ischemic stroke mouse model. PET imaging studies demonstrated that PB131 treatment alleviated the decline in [18F]PB118 uptake and reduced the infarct size in middle cerebral artery occlusion mice. Furthermore, PET imaging with the TSPO-specific radioligand [18F]FEPPA revealed that PB131 significantly suppressed neuroinflammation in the ischemic brain. These findings provide insights into the dynamic changes of HDAC6 in ischemic stroke and the potential of HDAC6 inhibitors as novel therapeutic agents for this condition.

Phase separation of phospho-HDAC6 drives aberrant chromatin architecture in triple-negative breast cancer

How dysregulated liquid-liquid phase separation (LLPS) contributes to the oncogenesis of female triple-negative breast cancer (TNBC) remains unknown. Here we demonstrate that phosphorylated histone deacetylase 6 (phospho-HDAC6) forms LLPS condensates in the nuclei of TNBC cells that are essential for establishing aberrant chromatin architecture. The disordered N-terminal domain and phosphorylated residue of HDAC6 facilitate effective LLPS, whereas nuclear export regions exert a negative dominant effect. Through phase-separation-based screening, we identified Nexturastat A as a specific disruptor of phospho-HDAC6 condensates, which effectively suppresses tumor growth. Mechanistically, importin-β interacts with phospho-HDAC6, promoting its translocation to the nucleus, where 14-3-3θ mediates the condensate formation. Disruption of phospho-HDAC6 LLPS re-established chromatin compartments and topologically associating domain boundaries, leading to disturbed chromatin loops. The phospho-HDAC6-induced aberrant chromatin architecture affects chromatin accessibility, histone acetylation, RNA polymerase II elongation and transcriptional profiles in TNBC. This study demonstrates phospho-HDAC6 LLPS as an emerging mechanism underlying the dysregulation of chromatin architecture in TNBC.

Nuclear podosomes regulates cellular migration in Tau and Alzheimer's disease

The neuronal cytoskeleton has remained a less explored area of research in establishing neuroprotection. HDAC6 has been studied with respect to many neurodegenerative diseases, especially AD. It exhibits the ability to interact with various cytoskeletal proteins and to promote migration in cells. Podosomes are actin microstructures that help cells to migrate in the extracellular environment. The aim of this review is to bring into focus the significance of studies on the involvement of podosomes in Alzheimer's disease. We have suggested that Histone Deacetylase 6 plays a vital role in AD, through its interactions with the various signalling processes in the cell, most importantly the cytoskeletal remodelling machinery within the podosomes.

ROS-responsive thioketal nanoparticles delivering system for targeted ulcerative colitis therapy with potent HDAC6 inhibitor, tubastatin A

Ulcerative colitis (UC) is a common gastrointestinal problem characterized by the mucosal injury primarily affecting the large intestine. Currently available therapies are not satisfactory as evidenced by high relapse rate and adverse effects. In this study we aimed to develop an effective drug delivery system using reactive oxygen species (ROS)-responsive thioketal nanoparticles (TKNP), to deliver tubastatin A, a potent HDAC6 inhibitor, to the inflamed colon in mice with ulcerative colitis (UC). TKNPs were synthesized by step-growth polymerization from an acetal exchange reaction while TUBA-TKNP was prepared using the single emulsion solvent evaporation technique. Our developed nanoparticle showed release of tubastatin A only in presence of ROS which is found to be highly present at the site of inflamed colon. Oral administration of TUBA-TKNP resulted in the higher accumulation of tubastatin A at the inflamed colon site and decreased the inflammation as evidenced by reduced infiltration of immune cells and decreased level of pro-inflammatory cytokines in TUBA-TKNP treated mice. In summary, our results show the successful localization of tubastatin A at the site of colon inflammation through TUBA-TKNP delivery, as well as resolution of clinical features of UC in mice.

Small molecules targeting HDAC6 for cancer treatment: Current progress and novel strategies

Histone deacetylase 6 (HDAC6) plays a crucial role in the initiation and progression of various cancers, as its overexpression is linked to tumor growth, invasion, migration, survival, apoptosis, and angiogenesis. Therefore, HDAC6 has emerged as an attractive target for anticancer drug discovery in the past decade. However, the development of conventional HDAC6 inhibitors has been hampered by their limited clinical efficacy, acquired resistance, and inability to inhibit non-enzymatic functions of HDAC6. To overcome these challenges, new strategies, such as dual-acting inhibitors, targeted protein degradation (TPD) technologies (including PROTACs, HyT), are essential to enhance the anticancer activity of HDAC6 inhibitors. In this review, we focus on the recent advances in the design and development of HDAC6 modulators, including isoform-selective HDAC6 inhibitors, HDAC6-based dual-target inhibitors, and targeted protein degraders (PROTACs, HyT), from the perspectives of rational design, pharmacodynamics, pharmacokinetics, and clinical status. Finally, we discuss the challenges and future directions for HDAC6-based drug discovery for cancer therapy.

HDAC6 inhibition disrupts HDAC6-P300 interaction reshaping the cancer chromatin landscape

BACKGROUND

Histone deacetylases (HDACs) are crucial regulators of gene expression, DNA synthesis, and cellular processes, making them essential targets in cancer research. HDAC6, specifically, influences protein stability and chromatin dynamics. Despite HDAC6's potential therapeutic value, its exact role in gene regulation and chromatin remodeling needs further clarification. This study examines how HDAC6 inactivation influences lysine acetyltransferase P300 stabilization and subsequent effects on chromatin structure and function in cancer cells.

METHODS AND RESULTS

We employed the HDAC6 inhibitor ITF3756, siRNA, or CRISPR/Cas9 gene editing to inactivate HDAC6 in different epigenomic backgrounds. Constantly, this inactivation led to significant changes in chromatin accessibility, particularly increased acetylation of histone H3 lysines 9, 14, and 27 (ATAC-seq and H3K27Ac ChIP-seq analysis). Transcriptomics, proteomics, and gene ontology analysis revealed gene changes in cell proliferation, adhesion, migration, and apoptosis. Significantly, HDAC6 inactivation altered P300 ubiquitination, stabilizing P300 and leading to downregulating genes critical for cancer cell survival.

CONCLUSIONS

Our study highlights the substantial impact of HDAC6 inactivation on the chromatin landscape of cancer cells and suggests a role for P300 in contributing to the anticancer effects. The stabilization of P300 with HDAC6 inhibition proposes a potential shift in therapeutic focus from HDAC6 itself to its interaction with P300. This finding opens new avenues for developing targeted cancer therapies, improving our understanding of epigenetic mechanisms in cancer cells.

MFN2 coordinates mitochondria motility with α-tubulin acetylation and this regulation is disrupted in CMT2A

Mitofusin-2 (MFN2), a large GTPase residing in the mitochondrial outer membrane and mutated in Charcot-Marie-Tooth type 2 disease (CMT2A), is a regulator of mitochondrial fusion and tethering with the ER. The role of MFN2 in mitochondrial transport has however remained elusive. Like MFN2, acetylated microtubules play key roles in mitochondria dynamics. Nevertheless, it is unknown if the α-tubulin acetylation cycle functionally interacts with MFN2. Here, we show that mitochondrial contacts with microtubules are sites of α-tubulin acetylation, which occurs through MFN2-mediated recruitment of α-tubulin acetyltransferase 1 (ATAT1). This activity is critical for MFN2-dependent regulation of mitochondria transport, and axonal degeneration caused by CMT2A MFN2 associated R94W and T105M mutations may depend on the inability to release ATAT1 at sites of mitochondrial contacts with microtubules. Our findings reveal a function for mitochondria in α-tubulin acetylation and suggest that disruption of this activity plays a role in the onset of MFN2-dependent CMT2A.

HDAC6 inhibitor promotes reactive oxygen species-meditated clearance of Staphylococcus aureus in macrophage

Staphylococcus aureus (S. aureus) pneumonia has become an increasingly important public health problem. Recent evidence suggests that epigenetic modifications are critical in the host immune defence against pathogen infection. In this study, we found that S. aureus infection induces the expression of histone deacetylase 6 (HDAC6) in a dose-dependent manner. Furthermore, by using a S. aureus pneumonia mouse model, we showed that the HDAC6 inhibitor, tubastatin A, demonstrates a protective effect in S. aureus pneumonia, decreasing the mortality and destruction of lung architecture, reducing the bacterial burden in the lungs and inhibiting inflammatory responses. Mechanistic studies in primary bone marrow-derived macrophages demonstrated that the HDAC6 inhibitors, tubastatin A and tubacin, reduced the intracellular bacterial load by promoting bacterial clearance rather than regulating phagocytosis. Finally, N-acetyl-L- cysteine, a widely used reactive oxygen species (ROS) scavenger, antagonized ROS production and significantly inhibited tubastatin A-induced S. aureus clearance. These findings demonstrate that HDAC6 inhibitors promote the bactericidal activity of macrophages by inducing ROS, an important host factor for S. aureus clearance and production. Our study identified HDAC6 as a suitable epigenetic modification target for preventing S. aureus infection, and tubastatin A as a useful compound in treating S. aureus pneumonia.

Hippocampal HDAC6 promotes POCD by regulating NLRP3-induced microglia pyroptosis via HSP90/HSP70 in aged mice

BACKGROUND

Postoperative Cognitive Dysfunction (POCD) has attracted increased attention, but its precise mechanism remains to be explored. This study aimed to figure out whether HDAC6 could regulate NLRP3-induced pyroptosis by modulating the functions of HSP70 and HSP90 in microglia to participate in postoperative cognitive dysfunction in aged mice.

METHODS

Animal models of postoperative cognitive dysfunction in aged mice were established by splenectomy under sevoflurane anesthesia. Morris water maze was used to examine the cognitive function and motor ability. Sixteen-months-old C57BL/6 male mice were randomly divided into six groups: control group (C group), sham surgery group (SA group), splenectomy group (S group), splenectomy + HDAC6 inhibitor ACY-1215 group (ACY group), splenectomy + HDAC6 inhibitor ACY-1215 + HSP70 inhibitor Apoptozole group (AP group), splenectomy + solvent control group (SC group). The serum and hippocampus of mice were taken after mice were executed. The protein levels of HDAC6, HSP90, HSP70, NLRP3, GSDMD-N, cleaved-Caspase-1 (P20), IL-1β were detected by western blotting. Serum IL-1β, IL-6 and S100β were measured using ELISA assay, and cell localization of HDAC6 was detected by immunofluorescence. In vitro experiments, BV2 cells were used to validate whether this mechanism worked in microglia. The protein levels of HDAC6, HSP90, HSP70, NLRP3, GSDMD-N, P20, IL-1β were detected by western blotting and the content of IL-1β in the supernatant was measured using ELISA assay. The degree of acetylation of HSP90, the interaction of HSP70, HSP90 and NLRP3 were analyzed by coimmunoprecipitation assay.

RESULTS

Splenectomy under sevoflurane anesthesia in aged mice could prolong the escape latency, reduce the number of crossing platforms, increase the expression of HDAC6 and activate the NLRP3 inflammasome to induce pyroptosis in hippocampus microglia. Using ACY-1215 could reduce the activation of NLRP3 inflammasome, the pyroptosis of microglia and the degree of spatial memory impairment. Apoptozole could inhibit the binding of HSP70 to NLRP3, reduce the degradation of NLRP3 and reverse the protective effect of HDAC6 inhibitors. The results acquired in vitro experiments closely resembled those in vivo, LPS stimulation led to the pyroptosis of BV2 microglia cells and the release of IL-1β due to the activation of the NLRP3 inflammasome, ACY-1215 showed the anti-inflammatory effect and Apoptozole exerted the opposite effect.

CONCLUSIONS

Our findings suggest that hippocampal HDAC6 promotes POCD by regulating NLRP3-induced microglia pyroptosis via HSP90/HSP70 in aged mice.

Mechanistic Sequence of Histone Deacetylase Inhibitors and Radiation Treatment: An Overview

Histone deacetylases inhibitors (HDACis) have shown promising therapeutic outcomes in haematological malignancies such as leukaemia, multiple myeloma, and lymphoma, with disappointing results in solid tumours when used as monotherapy. As a result, combination therapies either with radiation or other deoxyribonucleic acid (DNA) damaging agents have been suggested as ideal strategy to improve their efficacy in solid tumours. Numerous in vitro and in vivo studies have demonstrated that HDACis can sensitise malignant cells to both electromagnetic and particle types of radiation by inhibiting DNA damage repair. Although the radiosensitising ability of HDACis has been reported as early as the 1990s, the mechanisms of radiosensitisation are yet to be fully understood. This review brings forth the various protocols used to sequence the administration of radiation and HDACi treatments in the different studies. The possible contribution of these various protocols to the ambiguity that surrounds the mechanisms of radiosensitisation is also highlighted.

Novel Potential Therapeutic Targets in Autosomal Dominant Polycystic Kidney Disease from the Perspective of Cell Polarity and Fibrosis

Autosomal dominant polycystic kidney disease (ADPKD), a congenital genetic disorder, is a notable contributor to the prevalence of chronic kidney disease worldwide. Despite the absence of a complete cure, ongoing research aims for early diagnosis and treatment. Although agents such as tolvaptan and mTOR inhibitors have been utilized, their effectiveness in managing the disease during its initial phase has certain limitations. This review aimed to explore new targets for the early diagnosis and treatment of ADPKD, considering ongoing developments. We particularly focus on cell polarity, which is a key factor that influences the process and pace of cyst formation. In addition, we aimed to identify agents or treatments that can prevent or impede the progression of renal fibrosis, ultimately slowing its trajectory toward end-stage renal disease. Recent advances in slowing ADPKD progression have been examined, and potential therapeutic approaches targeting multiple pathways have been introduced. This comprehensive review discusses innovative strategies to address the challenges of ADPKD and provides valuable insights into potential avenues for its prevention and treatment.

Molecular hybridization: a powerful tool for multitarget drug discovery

INTRODUCTION

The current drug discovery paradigm of 'one drug, multiple targets' has gained attention from both the academic medicinal chemistry community and the pharmaceutical industry. This is in response to the urgent need for effective agents to treat multifactorial chronic diseases. The molecular hybridization strategy is a useful tool that has been widely explored, particularly in the last two decades, for the design of multi-target drugs.

AREAS COVERED

This review examines the current state of molecular hybridization in guiding the discovery of multitarget small molecules. The article discusses the design strategies and target selection for a multitarget polypharmacology approach to treat various diseases, including cancer, Alzheimer's disease, cardiac arrhythmia, endometriosis, and inflammatory diseases.

EXPERT OPINION

Although the examples discussed highlight the importance of molecular hybridization for the discovery of multitarget bioactive compounds, it is notorious that the literature has focused on specific classes of targets. This may be due to a deep understanding of the pharmacophore features required for target binding, making targets such as histone deacetylases and cholinesterases frequent starting points. However, it is important to encourage the scientific community to explore diverse combinations of targets using the molecular hybridization strategy.

The ZIKV NS5 Protein Aberrantly Alters the Tubulin Cytoskeleton, Induces the Accumulation of Autophagic p62 and Affects IFN Production: HDAC6 Has Emerged as an Anti-NS5/ZIKV Factor

Zika virus (ZIKV) infection and pathogenesis are linked to the disruption of neurogenesis, congenital Zika syndrome and microcephaly by affecting neural progenitor cells. Nonstructural protein 5 (NS5) is the largest product encoded by ZIKV-RNA and is important for replication and immune evasion. Here, we studied the potential effects of NS5 on microtubules (MTs) and autophagy flux, together with the interplay of NS5 with histone deacetylase 6 (HDAC6). Fluorescence microscopy, biochemical cell-fractionation combined with the use of HDAC6 mutants, chemical inhibitors and RNA interference indicated that NS5 accumulates in nuclear structures and strongly promotes the acetylation of MTs that aberrantly reorganize in nested structures. Similarly, NS5 accumulates the p62 protein, an autophagic-flux marker. Therefore, NS5 alters events that are under the control of the autophagic tubulin-deacetylase HDAC6. HDAC6 appears to degrade NS5 by autophagy in a deacetylase- and BUZ domain-dependent manner and to control the cytoplasmic expression of NS5. Moreover, NS5 inhibits RNA-mediated RIG-I interferon (IFN) production, resulting in greater activity when autophagy is inhibited (i.e., effect correlated with NS5 stability). Therefore, it is conceivable that NS5 contributes to cell toxicity and pathogenesis, evading the IFN-immune response by overcoming HDAC6 functions. HDAC6 has emerged as an anti-ZIKV factor by targeting NS5.

HDAC6 Enhances Endoglin Expression through Deacetylation of Transcription Factor SP1, Potentiating BMP9-Induced Angiogenesis

Histone deacetylase 6 (HDAC6) plays a crucial role in the acetylation of non-histone proteins and is notably implicated in angiogenesis, though its underlying mechanisms were previously not fully understood. This study conducted transcriptomic and proteomic analyses on vascular endothelial cells with HDAC6 knockdown, identifying endoglin (ENG) as a key downstream protein regulated by HDAC6. This protein is vital for maintaining vascular integrity and plays a complex role in angiogenesis, particularly in its interaction with bone morphogenetic protein 9 (BMP9). In experiments using human umbilical vein endothelial cells (HUVECs), the pro-angiogenic effects of BMP9 were observed, which diminished following the knockdown of HDAC6 and ENG. Western blot analysis revealed that BMP9 treatment increased SMAD1/5/9 phosphorylation, a process hindered by HDAC6 knockdown, correlating with reduced ENG expression. Mechanistically, our study indicates that HDAC6 modulates ENG transcription by influencing promoter activity, leading to increased acetylation of transcription factor SP1 and consequently altering its transcriptional activity. Additionally, the study delves into the structural role of HDAC6, particularly its CD2 domain, in regulating SP1 acetylation and subsequently ENG expression. In conclusion, the present study underscores the critical function of HDAC6 in modulating SP1 acetylation and ENG expression, thereby significantly affecting BMP9-mediated angiogenesis. This finding highlights the potential of HDAC6 as a therapeutic target in angiogenesis-related processes.

Emerging therapeutic strategies in cancer therapy by HDAC inhibition as the chemotherapeutic potent and epigenetic regulator

In developing new cancer medications, attention has been focused on novel epigenetic medicines called histone deacetylase (HDAC) inhibitors. Our understanding of cancer behavior is being advanced by research on epigenetics, which also supplies new targets for improving the effectiveness of cancer therapy. Most recently published patents emphasize HDAC selective drugs and multitarget HDAC inhibitors. Though significant progress has been made in emerging HDAC selective antagonists, it is urgently necessary to find new HDAC blockers with novel zinc-binding analogues to avoid the undesirable pharmacological characteristics of hydroxamic acid. HDAC antagonists have lately been explored as a novel approach to treating various diseases, including cancer. The complicated terrain of HDAC inhibitor development is summarized in this article, starting with a discussion of the many HDAC isotypes and their involvement in cancer biology, followed by a discussion of the mechanisms of action of HDAC inhibitors, their current level of development, effect of miRNA, and their combination with immunotherapeutic.

Cleavage of HDAC6 to dampen its antiviral activity by nsp5 is a common strategy of swine enteric coronaviruses

HDAC6, a structurally and functionally unique member of the histone deacetylase (HDAC) family, is an important host factor that restricts viral infection. The broad-spectrum antiviral activity of HDAC6 makes it a potent antiviral agent. Previously, we found that HDAC6 functions to antagonize porcine deltacoronavirus (PDCoV), an emerging enteropathogenic coronavirus with zoonotic potential. However, the final outcome is typically a productive infection that materializes as cells succumb to viral infection, indicating that the virus has evolved sophisticated mechanisms to combat the antiviral effect of HDAC6. Here, we demonstrate that PDCoV nonstructural protein 5 (nsp5) can cleave HDAC6 at glutamine 519 (Q519), and cleavage of HDAC6 was also detected in the context of PDCoV infection. More importantly, the anti-PDCoV activity of HDAC6 was damaged by nsp5 cleavage. Mechanistically, the cleaved HDAC6 fragments (amino acids 1-519 and 520-1159) lost the ability to degrade PDCoV nsp8 due to their impaired deacetylase activity. Furthermore, nsp5-mediated cleavage impaired the ability of HDAC6 to activate RIG-I-mediated interferon responses. We also tested three other swine enteric coronaviruses (transmissible gastroenteritis virus, porcine epidemic diarrhea virus, and swine acute diarrhea syndrome-coronavirus) and found that all these coronaviruses have adopted similar mechanisms to cleave HDAC6 in both an overexpression system and virus-infected cells, suggesting that cleavage of HDAC6 is a common strategy utilized by swine enteric coronaviruses to antagonize the host's antiviral capacity. Together, these data illustrate how swine enteric coronaviruses antagonize the antiviral function of HDAC6 to maintain their infection, providing new insights to the interaction between virus and host.IMPORTANCEViral infections and host defenses are in constant opposition. Once viruses combat or evade host restriction, productive infection is achieved. HDAC6 is a broad-spectrum antiviral protein that has been demonstrated to inhibit many viruses, including porcine deltacoronavirus (PDCoV). However, whether HDAC6 is reciprocally targeted and disabled by viruses remains unclear. In this study, we used PDCoV as a model and found that HDAC6 is targeted and cleaved by nsp5, a viral 3C-like protease. The cleaved HDAC6 loses its deacetylase activity as well as its ability to degrade viral proteins and activate interferon responses. Furthermore, this cleavage mechanism is shared among other swine enteric coronaviruses. These findings shed light on the intricate interplay between viruses and HDAC6, highlighting the strategies employed by viruses to evade host antiviral defenses.

Targeting glycogen synthase kinase-3β for Alzheimer's disease: Recent advances and future Prospects

Senile plaques induced by β-amyloid (Aβ) abnormal aggregation and neurofibrillary tangles (NFT) caused by tau hyperphosphorylation are important pathological manifestations of Alzheimer's disease (AD). Glycogen synthase kinase-3 (GSK-3) is a conserved kinase; one member GSK-3β is highly expressed in the AD brain and involved in the formation of NFT. Hence, pharmacologically inhibiting GSK-3β activity and expression is a good approach to treat AD. As summarized in this article, multiple GSK-3β inhibitors has been comprehensively summarized over recent five years. However, only lithium carbonate and Tideglusib have been studied in clinical trials of AD. Besides ATP-competitive and non-ATP-competitive inhibitors, peptide inhibitors, allosteric inhibitors and other types of inhibitors have gradually attracted more interest. Moreover, considering the close relationship between GSK-3β and other targets involved in cholinergic hypothesis, Aβ aggregation hypothesis, tau hyperphosphorylation hypothesis, oxidative stress hypothesis, neuro-inflammation hypothesis, etc., diverse multifunctional molecules and multi-target directed ligands (MTDLs) have also been disclosed. We hope that these recent advances and critical perspectives will facilitate the discovery of safe and effective GSK-3β inhibitors for AD treatment.

Paxillin/HDAC6 regulates microtubule acetylation to promote directional migration of keratinocytes driven by electric fields

Endogenous electric fields (EFs) have been demonstrated to facilitate wound healing by directing the migration of epidermal cells. Despite the identification of numerous molecules and signaling pathways that are crucial for the directional migration of keratinocytes under EFs, the underlying molecular mechanisms remain undefined. Previous studies have indicated that microtubule (MT) acetylation is linked to cell migration, while Paxillin exerts a significant influence on cell motility. Therefore, we postulated that Paxillin could enhance EF-induced directional migration of keratinocytes by modulating MT acetylation. In the present study, we observed that EFs (200 mV/mm) induced migration of human immortalized epidermal cells (HaCaT) towards the anode, while upregulating Paxillin, downregulating HDAC6, and increasing the level of microtubule acetylation. Our findings suggested that Paxillin plays a pivotal role in inhibiting HDAC6-mediated microtubule acetylation during directional migration under EF regulation. Conversely, downregulation of Paxillin decreased microtubule acetylation and electrotaxis of epidermal cells by promoting HDAC6 expression, and this effect could be reversed by the addition of tubacin, an HDAC6-specific inhibitor. Furthermore, we observed that EFs also mediated the polarization of Paxillin and acetylated α-tubulin, which is critical for directional migration. In conclusion, our study revealed that MT acetylation in EF-guided keratinocyte migration is regulated by the Paxillin/HDAC6 signaling pathway, providing a novel theoretical foundation for the molecular mechanism of EF-guided directional migration of keratinocytes.

Zinc-Dependent Histone Deacetylases in Lung Endothelial Pathobiology

A monolayer of endothelial cells (ECs) lines the lumen of blood vessels and, as such, provides a semi-selective barrier between the blood and the interstitial space. Compromise of the lung EC barrier due to inflammatory or toxic events may result in pulmonary edema, which is a cardinal feature of acute lung injury (ALI) and its more severe form, acute respiratory distress syndrome (ARDS). The EC functions are controlled, at least in part, via epigenetic mechanisms mediated by histone deacetylases (HDACs). Zinc-dependent HDACs represent the largest group of HDACs and are activated by Zn2+. Members of this HDAC group are involved in epigenetic regulation primarily by modifying the structure of chromatin upon removal of acetyl groups from histones. In addition, they can deacetylate many non-histone histone proteins, including those located in extranuclear compartments. Recently, the therapeutic potential of inhibiting zinc-dependent HDACs for EC barrier preservation has gained momentum. However, the role of specific HDAC subtypes in EC barrier regulation remains largely unknown. This review aims to provide an update on the role of zinc-dependent HDACs in endothelial dysfunction and its related diseases. We will broadly focus on biological contributions, signaling pathways and transcriptional roles of HDACs in endothelial pathobiology associated mainly with lung diseases, and we will discuss the potential of their inhibitors for lung injury prevention.

Histone deacetylase inhibitors VPA and WT161 ameliorate the pathological features and cognitive impairments of the APP/PS1 Alzheimer's disease mouse model by regulating the expression of APP secretases

BACKGROUND

Alzheimer's disease (AD) is a degenerative neurological disorder. Recent studies have indicated that histone deacetylases (HDACs) are among the most prominent epigenetic therapy targets and that HDAC inhibitors have therapeutic effects on AD. Here, we identified sodium valproate (VPA), a pan-HDAC inhibitor, and WT161, a novel HDAC6 selective inhibitor, as potential therapeutic agents for AD. Underlying molecular mechanisms were investigated.

METHODS

A cellular model, N2a-APPswe, was established via lentiviral infection, and the APPswe/PSEN1dE9 transgenic mouse model was employed in the study. LC-MS/MS was applied to quantify the concentration of WT161 in the mouse brain. Western blotting, immunohistochemical staining, thioflavin-S staining and ELISA were applied to detect protein expression in cells, tissues, or serum. RNA interference was utilized to knockdown the expression of specific genes in cells. The cognitive function of mice was assessed via the nest-building test, novel object recognition test and Morris water maze test.

RESULTS

Previous studies have focused mainly on the impact of HDAC inhibitors on histone deacetylase activity. Our study discovered that VPA and WT161 can downregulate the expression of multiple HDACs, such as HDAC1 and HDAC6, in both AD cell and mouse models. Moreover, they also affect the expression of APP and APP secretases (BACE1, PSEN1, ADAM10). RNA interference and subsequent vitamin C induction further confirmed that the expression of APP and APP secretases is indeed regulated by HDAC1 and HDAC6, with the JNK pathway being the intermediate link in this regulatory process. Through the above pathways, VPA and WT161 effectively reduced Aβ deposition in both AD cell and mouse models and significantly improved cognitive function in AD mice.

CONCLUSIONS

In general, we have discovered that the HDAC6-JNK-APP secretases cascade is an important pathway for VPA and WT161 to exert their therapeutic effects on AD. Investigations into the safety and efficacy of VPA and WT161 were also conducted, providing essential preclinical evidence for assessing these two epigenetic drugs for the treatment of AD.

Role of Histone Deacetylase 6 and Histone Deacetylase 6 Inhibition in Colorectal Cancer

Histone deacetylase 6 (HDAC6), by deacetylation of multiple substrates and association with interacting proteins, regulates many physiological processes that are involved in cancer development and invasiveness such as cell proliferation, apoptosis, motility, epithelial to mesenchymal transition, and angiogenesis. Due to its ability to remove misfolded proteins, induce autophagy, and regulate unfolded protein response, HDAC6 plays a protective role in responses to stress and enables tumor cell survival. The scope of this review is to discuss the roles of HDCA6 and its implications for the therapy of colorectal cancer (CRC). As HDAC6 is overexpressed in CRC, correlates with poor disease prognosis, and is not essential for normal mammalian development, it represents a good therapeutic target. Selective inhibition of HDAC6 impairs growth and progression without inducing major adverse events in experimental animals. In CRC, HDAC6 inhibitors have shown the potential to reduce tumor progression and enhance the therapeutic effect of other drugs. As HDAC6 is involved in the regulation of immune responses, HDAC6 inhibitors have shown the potential to improve antitumor immunity by increasing the immunogenicity of tumor cells, augmenting immune cell activity, and alleviating immunosuppression in the tumor microenvironment. Therefore, HDAC6 inhibitors may represent promising candidates to improve the effect of and overcome resistance to immunotherapy.

Autophagy regulation and protein kinase activity of PIK3C3 controls sertoli cell polarity through its negative regulation on SCIN (scinderin)

Sertoli cells are highly polarized testicular cells that provide a nurturing environment for germ cell development and maturation during spermatogenesis. The class III phosphatidylinositol 3-kinase (PtdIns3K) plays core roles in macroautophagy in various cell types; however, its role in Sertoli cells remains unclear. Here, we generated a mouse line in which the gene encoding the catalytic subunit, Pik3c3, was specifically deleted in Sertoli cells (cKO) and found that after one round of normal spermatogenesis, the cKO mice quickly became infertile and showed disruption of Sertoli cell polarity and impaired spermiogenesis. Subsequent proteomics and phosphoproteomics analyses enriched the F-actin cytoskeleton network involved in the disorganized Sertoli-cell structure in cKO testis which we identified a significant increase of the F-actin negative regulator SCIN (scinderin) and the reduced phosphorylation of HDAC6, an α-tubulin deacetylase. Our results further demonstrated that the accumulation of SCIN in cKO Sertoli cells caused the disorder and disassembly of the F-actin cytoskeleton, which was related to the failure of SCIN degradation through the autophagy-lysosome pathway. Additionally, we found that the phosphorylation of HDAC6 at site S59 by PIK3C3 was essential for its degradation through the ubiquitin-proteasome pathway. As a result, the HDAC6 that accumulated in cKO Sertoli cells deacetylated SCIN at site K189 and led to a disorganized F-actin cytoskeleton. Taken together, our findings elucidate a new mechanism for PIK3C3 in maintaining the polarity of Sertoli cells, in which both its autophagy regulation or protein kinase activities are required for the stabilization of the actin cytoskeleton.Abbreviations: ACTB: actin, beta; AR: androgen receptor; ATG14: autophagy related 14; BafA1: bafilomycin A1; BECN1: beclin 1, autophagy related; BTB: blood-testis barrier; CASP3: caspase 3; CDC42: cell division cycle 42; CDH2: cadherin 2; CHX: cycloheximide; CTNNA1: catenin (cadherin associated protein), alpha 1; CYP11A1: cytochrome P450, family 11, subfamily A, polypeptide 1; EBSS: Earle's balanced salt solution; ES: ectoplasmic specialization; FITC: fluorescein isothiocyanate; GAPDH: glyceraldehyde-3-phosphate dehydrogenase; GCNA: germ cell nuclear acidic protein; GJA1: gap junction protein, alpha 1; H2AX: H2A.X variant histone; HDAC6: histone deacetylase 6; KIT: KIT proto-oncogene, receptor tyrosine kinase; LAMP1: lysosomal associated membrane protein 1; MAP3K5: mitogen-activated protein kinase kinase kinase 5; MAP1LC3B: microtubule associated protein 1 light chain 3 beta; OCLN: occludin; PIK3C3: phosphatidylinositol 3-kinase catalytic subunit type 3; PIK3R4: phosphoinositide-3-kinase regulatory subunit 4; PNA: arachis hypogaea lectin; RAC1: Rac family small GTPase 1; SCIN: scinderin; SQSTM1/p62: sequestosome 1; SSC: spermatogonia stem cell; STK11: serine/threonine kinase 11; TJP1: tight junction protein 1; TubA: tubastatin A; TUBB3: tubulin beta 3 class III; TUNEL: TdT-mediated dUTP nick-end labeling; UB: ubiquitin; UVRAG: UV radiation resistance associated gene; VIM: vimentin; WT1: WT1 transcription factor; ZBTB16: zinc finger and BTB domain containing 16.

Knockdown of HDAC6 alleviates ventricular remodeling in experimental dilated cardiomyopathy via inhibition of NLRP3 inflammasome activation and promotion of cardiomyocyte autophagy

Histone deacetylases (HDACs) has been implicated in cardiac diseases, while the role of HDAC6 in dilated cardiomyopathy (DCM) remains obscure. The in silico analyses predicted potential association of HDAC6 with autophagy-related genes and DCM. Thus, we evaluated the functional relevance of HDAC6 in DCM in vivo and in vitro. We developed a rat model in vivo and a cell model in vitro by doxorubicin (DOX) induction to simulate DCM. HDAC6 expression was determined in myocardial tissues of DCM rats. DCM rats exhibited elevated HDAC6 mRNA and protein expression as compared to sham-operated rats. We knocked HDAC6 down and/or overexpressed NLRP3 in vivo and in vitro to characterize their roles in cardiomyocyte autophagy. It was established that shRNA-mediated HDAC6 silencing augmented cardiomyocyte autophagy and suppressed NLRP3 inflammasome activation, thus ameliorating cardiac injury in myocardial tissues of DCM rats. Besides, in DOX-injured cardiomyocytes, HDAC6 silencing also diminished NLRP3 inflammasome activation and cell apoptosis but enhanced cell autophagy, whereas ectopic NLRP3 expression negated the effects of HDAC6 silencing. Since HDAC6 knockdown correlates with enhanced cardiomyocyte autophagy and suppressed NLRP3 inflammasome activation through an interplay with NLRP3, it is expected to be a potential biomarker and therapeutic target for DCM. 1. HDAC6 was up-regulated in DCM rats. 2. HDAC6 knockdown promoted cardiomyocyte autophagy to relieve cardiac dysfunction. 3. HDAC6 knockdown inhibited NLRP3 inflammasome and promoted cardiomyocyte autophagy. 4. Silencing HDAC6 promoted autophagy and repressed apoptosis in cardiomyocytes. 5. This study provides novel therapeutic targets for DCM.

Involvement of Ataxin-3 (ATXN3) in the malignant progression of pancreatic cancer via deubiquitinating HDAC6

BACKGROUND

Pancreatic cancer is a common digestive system cancer and one of the most lethal malignancies worldwide. Ataxin-3 (ATXN3) protein is a deubiquitinating enzyme implicated in the occurrence of diverse human cancers. The potential role of ATXN3 in pancreatic cancer still remains unclear.

METHODS

ATXN3 was screened from differentially-upregulated genes of GSE71989, GSE27890 and GSE40098 datasets. The mRNA and protein levels of ATXN3 was evaluated in pancreatic cancer samples and cell lines. Through the gain- and loss-of-function experiments, the effects of ATXN3 on cell proliferation, migration and invasion were evaluated using cell counting kit-8 (CCK-8), 5-ethynyl-2'-deoxyuridine (EdU) staining, wound healing and Transwell assays. Subsequently, the interaction between ATXN3 and HDAC6 was confirmed using double immunofluorescence staining, co-immunoprecipitation (co-IP) and proximity ligation assay (PLA). The underlying mechanism of ATXN3 was determined by knockdown of HDAC6 in ATXN3-upregulated pancreatic cancer cells. The function of ATXN3 in vivo was verified through xenograft assay.

RESULTS

High expression of ATXN3 was found in pancreatic cancer tissues. Increased ATXN3 expression dramatically promoted cell proliferation, migration, and invasion. The malignant phenotypes were suppressed in ATXN3-silenced pancreatic cancer cells. ATXN3 was proved to interact with HDAC6 and regulate its degradation through deubiquitination. Downregulation of HDAC6 inhibited ATXN3-induced development of pancreatic cancer cells through regulating the expression of PCNA, vimentin and E-cadherin. ATXN3 facilitated tumor growth of pancreatic cancer and increased HDAC6 expression in vivo.

CONCLUSIONS

This study confirmed that ATXN3 facilitated malignant phenotypes of pancreatic cancer via reducing the ubiquitination of HDAC6.

Recent development of selective inhibitors targeting the HDAC6 as anti-cancer drugs: Structure, function and design

HDAC6, a member of the histone deacetylase family, mainly is a cytosolic protein and regulates cell growth by acting on non-histone substrates, such as α -tubulin, cortactin, heat shock protein HSP90, programmed death 1 (PD-1) and programmed death ligand 1 (PD-L1), that are closely related to the proliferation, invasion, immune escape and angiogenesis of cancer tissues. The approved drugs targeting the HDACs are all pan-inhibitors and have many side effects due to their lack of selectivity. Therefore, development of selective inhibitors of HDAC6 has attracted much attention in the field of cancer therapy. In this review, we will summarize the relationship between HDAC6 and cancer, and discuss the design strategies of HDAC6 inhibitors for cancer treatment in recent years.

HIV Infection: Shaping the Complex, Dynamic, and Interconnected Network of the Cytoskeleton

HIV-1 has evolved a plethora of strategies to overcome the cytoskeletal barrier (i.e., actin and intermediate filaments (AFs and IFs) and microtubules (MTs)) to achieve the viral cycle. HIV-1 modifies cytoskeletal organization and dynamics by acting on associated adaptors and molecular motors to productively fuse, enter, and infect cells and then traffic to the cell surface, where virions assemble and are released to spread infection. The HIV-1 envelope (Env) initiates the cycle by binding to and signaling through its main cell surface receptors (CD4/CCR5/CXCR4) to shape the cytoskeleton for fusion pore formation, which permits viral core entry. Then, the HIV-1 capsid is transported to the nucleus associated with cytoskeleton tracks under the control of specific adaptors/molecular motors, as well as HIV-1 accessory proteins. Furthermore, HIV-1 drives the late stages of the viral cycle by regulating cytoskeleton dynamics to assure viral Pr55Gag expression and transport to the cell surface, where it assembles and buds to mature infectious virions. In this review, we therefore analyze how HIV-1 generates a cell-permissive state to infection by regulating the cytoskeleton and associated factors. Likewise, we discuss the relevance of this knowledge to understand HIV-1 infection and pathogenesis in patients and to develop therapeutic strategies to battle HIV-1.

HDAC6 inhibition: a significant potential regulator and therapeutic option to translate into clinical practice in renal transplantation

Histone deacetylase 6 (HDAC6), an almost exclusively cytoplasmic enzyme, plays an essential role in many biological processes and exerts its deacetylation-dependent/independent effects on a variety of target molecules, which has contributed to the flourishing growth of relatively isoform-specific enzyme inhibitors. Renal transplantation (RT) is one of the alternatively preferred treatments and the most cost-effective treatment approaches for the great majority of patients with end-stage renal disease (ESRD). HDAC6 expression and activity have recently been shown to be increased in kidney disease in a number of studies. To date, a substantial amount of validated studies has identified HDAC6 as a pivotal modulator of innate and adaptive immunity, and HDAC6 inhibitors (HDAC6i) are being developed and investigated for use in arrays of immune-related diseases, making HDAC6i a promising therapeutic candidate for the management of a variety of renal diseases. Based on accumulating evidence, HDAC6i markedly open up new avenues for therapeutic intervention to protect against oxidative stress-induced damage, tip the balance in favor of the generation of tolerance-related immune cells, and attenuate fibrosis by inhibiting multiple activations of cell profibrotic signaling pathways. Taken together, we have a point of view that targeting HDAC6 may be a novel approach for the therapeutic strategy of RT-related complications, including consequences of ischemia-reperfusion injury, induction of immune tolerance in transplantation, equilibrium of rejection, and improvement of chronic renal graft interstitial fibrosis after transplantation in patients. Herein, we will elaborate on the unique function of HDAC6, which focuses on therapeutical mechanism of action related to immunological events with a general account of the tantalizing potential to the clinic.

HDAC6 Deficiency Has Moderate Effects on Behaviors and Parkinson's Disease Pathology in Mice

Histone deacetylase 6 (HDAC6) is involved in the regulation of protein aggregation and neuroinflammation, but its role in Parkinson's disease (PD) remains controversial. In this study, Hdac6^-/- mice were generated by CRISPR-Cas9 technology for exploring the effect of HDAC6 on the pathological progression of PD. We found that male Hdac6^-/- mice exhibit hyperactivity and certain anxiety. In the acute 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced PD mice, though motor injury was slightly alleviated by HDAC6 deficiency, dopamine (DA) depletion in the striatum, the decrease in the number of DA neurons in the substantia nigra (SN) and the reduction in DA neuronal terminals were not affected. In addition, activation of glial cells and the expression of α-synuclein, as well as the levels of apoptosis-related proteins in the nigrostriatal pathway, were not changed in MPTP-injected wild-type and Hdac6^-/- mice. Therefore, HDAC6 deficiency leads to moderate alterations of behaviors and Parkinson's disease pathology in mice.

HDAC6 Degrades nsp8 of Porcine Deltacoronavirus through Deacetylation and Ubiquitination to Inhibit Viral Replication

Porcine deltacoronavirus (PDCoV) is an emerging swine enteropathogenic coronavirus that has the potential to infect humans. Histone deacetylase 6 (HDAC6) is a unique type IIb cytoplasmic deacetylase with both deacetylase activity and ubiquitin E3 ligase activity, which mediates a variety of cellular processes by deacetylating histone and nonhistone substrates. In this study, we found that ectopic expression of HDAC6 significantly inhibited PDCoV replication, while the reverse effects could be observed after treatment with an HDAC6-specific inhibitor (tubacin) or knockdown of HDAC6 expression by specific small interfering RNA. Furthermore, we demonstrated that HDAC6 interacted with viral nonstructural protein 8 (nsp8) in the context of PDCoV infection, resulting in its proteasomal degradation, which was dependent on the deacetylation activity of HDAC6. We further identified the key amino acid residues lysine 46 (K46) and K58 of nsp8 as acetylation and ubiquitination sites, respectively, which were required for HDAC6-mediated degradation. Through a PDCoV reverse genetics system, we confirmed that recombinant PDCoV with a mutation at either K46 or K58 exhibited resistance to the antiviral activity of HDAC6, thereby exhibiting higher replication compared with wild-type PDCoV. Collectively, these findings contribute to a better understanding of the function of HDAC6 in regulating PDCoV infection and provide new strategies for the development of anti-PDCoV drugs. IMPORTANCE As an emerging enteropathogenic coronavirus with zoonotic potential, porcine deltacoronavirus (PDCoV) has sparked tremendous attention. Histone deacetylase 6 (HDAC6) is a critical deacetylase with both deacetylase activity and ubiquitin E3 ligase activity and is extensively involved in many important physiological processes. However, little is known about the role of HDAC6 in the infection and pathogenesis of coronaviruses. Our present study demonstrates that HDAC6 targets PDCoV-encoded nonstructural protein 8 (nsp8) for proteasomal degradation through the deacetylation at the lysine 46 (K46) and the ubiquitination at K58, suppressing viral replication. Recombinant PDCoV with a mutation at K46 and/or K58 of nsp8 displayed resistance to the antiviral activity of HDAC6. Our work provides significant insights into the role of HDAC6 in regulating PDCoV infection, opening avenues for the development of novel anti-PDCoV drugs.

The Epigenetics of Migraine

Migraine is a complex neurological disorder and a major cause of disability. A wide range of different drug classes such as triptans, antidepressants, anticonvulsants, analgesics, and beta-blockers are used in acute and preventive migraine therapy. Despite a considerable progress in the development of novel and targeted therapeutic interventions during recent years, e.g., drugs that inhibit the calcitonin gene-related peptide (CGRP) pathway, therapy success rates are still unsatisfactory. The diversity of drug classes used in migraine therapy partly reflects the limited perception of migraine pathophysiology. Genetics seems to explain only to a minor extent the susceptibility and pathophysiological aspects of migraine. While the role of genetics in migraine has been extensively studied in the past, the interest in studying the role of gene regulatory mechanisms in migraine pathophysiology is recently evolving. A better understanding of the causes and consequences of migraine-associated epigenetic changes could help to better understand migraine risk, pathogenesis, development, course, diagnosis, and prognosis. Additionally, it could be a promising avenue to discover new therapeutic targets for migraine treatment and monitoring. In this review, we summarize the state of the art regarding epigenetic findings in relation to migraine pathogenesis and potential therapeutic targets, with a focus on DNA methylation, histone acetylation, and microRNA-dependent regulation. Several genes and their methylation patterns such as CALCA (migraine symptoms and age of migraine onset), RAMP1, NPTX2, and SH2D5 (migraine chronification) and microRNA molecules such as miR-34a-5p and miR-382-5p (treatment response) seem especially worthy of further study regarding their role in migraine pathogenesis, course, and therapy. Additionally, changes in genes including COMT, GIT2, ZNF234, and SOCS1 have been linked to migraine progression to medication overuse headache (MOH), and several microRNA molecules such as let-7a-5p, let-7b-5p, let-7f-5p, miR-155, miR-126, let-7g, hsa-miR-34a-5p, hsa-miR-375, miR-181a, let-7b, miR-22, and miR-155-5p have been implicated with migraine pathophysiology. Epigenetic changes could be a potential tool for a better understanding of migraine pathophysiology and the identification of new therapeutic possibilities. However, further studies with larger sample sizes are needed to verify these early findings and to be able to establish epigenetic targets as disease predictors or therapeutic targets.

TDP-43 Controls HIV-1 Viral Production and Virus Infectiveness

The transactive response DNA-binding protein (TARDBP/TDP-43) is known to stabilize the anti-HIV-1 factor, histone deacetylase 6 (HDAC6). TDP-43 has been reported to determine cell permissivity to HIV-1 fusion and infection acting on tubulin-deacetylase HDAC6. Here, we studied the functional involvement of TDP-43 in the late stages of the HIV-1 viral cycle. The overexpression of TDP-43, in virus-producing cells, stabilized HDAC6 (i.e., mRNA and protein) and triggered the autophagic clearance of HIV-1 Pr55^Gag and Vif proteins. These events inhibited viral particle production and impaired virion infectiveness, observing a reduction in the amount of Pr55^Gag and Vif proteins incorporated into virions. A nuclear localization signal (NLS)-TDP-43 mutant was not able to control HIV-1 viral production and infection. Likewise, specific TDP-43-knockdown reduced HDAC6 expression (i.e., mRNA and protein) and increased the expression level of HIV-1 Vif and Pr55^Gag proteins and α-tubulin acetylation. Thus, TDP-43 silencing favored virion production and enhanced virus infectious capacity, thereby increasing the amount of Vif and Pr55^Gag proteins incorporated into virions. Noteworthy, there was a direct relationship between the content of Vif and Pr55^Gag proteins in virions and their infection capacity. Therefore, for TDP-43, the TDP-43/HDAC6 axis could be considered a key factor to control HIV-1 viral production and virus infectiveness.

Curriculum vitae of HDAC6 in solid tumors

Histone deacetylase 6 (HDAC6) is the only member of the HDAC family that resides primarily in the cytoplasm with two catalytic domains and a ubiquitin-binding domain. HDAC6 is highly expressed in various solid tumors and participates in a wide range of biological activities, including hormone receptors, the p53 signaling pathway, and the kinase cascade signaling pathway due to its unique structural foundation and abundant substrate types. Additionally, HDAC6 can function as an oncogenic factor in solid tumors, boosting tumor cell proliferation, invasion and metastasis, drug resistance, stemness, and lowering tumor cell immunogenicity, so assisting in carcinogenesis. Pan-HDAC inhibitors for cancer prevention are associated with potential cardiotoxicity in clinical investigations. It's interesting that HDAC6 silencing didn't cause any significant harm to normal cells. Currently, the use of HDAC6 specific inhibitors, individually or in combination, is among the most promising therapies in solid tumors. This review's objective is to give a general overview of the structure, biological functions, and mechanism of HDAC6 in solid tumor cells and in the immunological milieu and discuss the preclinical and clinical trials of selective HDAC6 inhibitors. These endeavors highlight that targeting HDAC6 could effectively kill tumor cells and enhance patients' immunity during solid tumor therapy.

Advances in the Mechanistic Study of the Control of Oxidative Stress Injury by Modulating HDAC6 Activity

Oxidative stress is defined as an injury resulting from a disturbance in the dynamic equilibrium of the redox environment due to the overproduction of active/radical oxygen exceeding the antioxidative ability of the body. This is a key step in the development of various diseases. Oxidative stress is modulated by different factors and events, including the modification of histones, which are the cores of nucleosomes. Histone modification includes acetylation and deacetylation of certain amino acid residues; this process is catalyzed by different enzymes. Histone deacetylase 6 (HDAC6) is a unique deacetylating protease that also catalyzes the deacetylation of different nonhistone substrates to regulate various physiologic processes. The intimate relationship between HDAC6 and oxidative stress has been demonstrated by different studies. The present paper aims to summarize the data obtained from a mechanistic study of HDAC6 and oxidative stress to guide further investigations on mechanistic characterization and drug development.

Response to microplastic exposure: An exploration into the sea urchin immune cell proteome

It is now known that the Mediterranean Sea currently is one of the major hotspot for microplastics (MPs; < 5 mm) pollution and that the risks will be even more pronounced in the coming years. Thus, the in-depth study of the mechanisms underlying the MPs toxicity in key Mediterranean organisms, subjected to high anthropic pressures, has become a categorical imperative to pursue. Here, we explore for the first time the sea urchins immune cells profile combined to their proteome upon in vivo exposure (72 h) to different concentrations of polystyrene-microbeads (micro-PS) starting from relevant environmental concentrations (10, 50, 10³, 10⁴ MP/L). Every 24 h, immunological parameters were monitored. After 72 h, the abundance of MPs was examined in various organs and coelomocytes were collected for proteomic analysis based on a shotgun label free proteomic approach. While sea urchins treated with the lowest concentration tested (10 and 50 micro-PS/L) did not show the presence of micro-PS in any tissue, in the specimens exposed to the highest concentration (10³ and 10⁴ micro-PS) there was an internalisation of 9.75 ± 2.75 and 113.75 ± 34.5 MP/g, respectively. Proteomic analyses revealed that MPs exposure altered coelomocytes protein profile not only compared to the control group but also among the different micro-PS concentrations and these variations are micro-PS concentration dependent. The proteins exclusively expressed in the coelomocytes of specimens exposed to MPs are mainly metabolite interconversion enzymes, involved in cellular processes, indicating a severe alteration of the cellular metabolic pathways. Overall, these findings provide new insights on the mode of action of MPs in the sea urchin immune cells both at the molecular and cellular level.

Histone deacetylase inhibitors as a potential new treatment for psoriatic disease and other inflammatory conditions

Collectively known as psoriatic disease, psoriasis and psoriatic arthritis (PsA) are immune-mediated inflammatory diseases in which patients present with cutaneous and musculoskeletal inflammation. Affecting roughly 2-3% of the world's total population, there remains unmet therapeutic needs in both psoriasis and PsA despite the availability of current immunomodulatory treatments. As a result, patients with psoriatic disease often experience reduced quality of life. Recently, a class of small molecules, commonly investigated as anti-cancer agents, called histone deacetylase (HDAC) inhibitors, have been proposed as a new promising anti-inflammatory treatment for immune- and inflammatory-related diseases. In inflammatory diseases, current evidence is derived from studies on diseases like rheumatoid arthritis (RA) and systematic lupus erythematosus (SLE), and while there are some reports studying psoriasis, data on PsA patients are not yet available. In this review, we provide a brief overview of psoriatic disease, psoriasis, and PsA, as well as HDACs, and discuss the rationale behind the potential use of HDAC inhibitors in the management of persistent inflammation to suggest its possible use in psoriatic disease.

Epigenetic Abnormalities in Chondrosarcoma

In recent years, our understanding of the epigenetic mechanisms involved in tumor pathology has improved greatly. DNA and histone modifications, such as methylation, demethylation, acetylation, and deacetylation, can lead to the up-regulation of oncogenic genes, as well as the suppression of tumor suppressor genes. Gene expression can also be modified on a post-transcriptional level by microRNAs that contribute to carcinogenesis. The role of these modifications has been already described in many tumors, e.g., colorectal, breast, and prostate cancers. These mechanisms have also begun to be investigated in less common tumors, such as sarcomas. Chondrosarcoma (CS) is a rare type of tumor that belongs to sarcomas and is the second most common malignant bone tumor after osteosarcoma. Due to unknown pathogenesis and resistance to chemo- and radiotherapies of these tumors, there is a need to develop new potential therapies against CS. In this review, we summarize current knowledge on the influence of epigenetic alterations in the pathogenesis of CS by discussing potential candidates for future therapies. We also emphasize ongoing clinical trials that use drugs targeting epigenetic modifications in CS treatment.

New chimeric HDAC inhibitors for the treatment of colorectal cancer

Colorectal cancer is the third most common cause of cancer-associated deaths due to a high recurrence rate and an increasing occurrence of resistance to established therapies. This highlights the importance of developing new chemotherapeutic agents. The current study focuses on cancer-specific targets such as apoptosis-inhibiting survivin, which distinguishes cancer cells from healthy tissue. A combination of pharmacophores of established anticancer agents to afford chimeric pleiotropic chemotherapeutic agents was tested on this cancer entity. We analysed the effects of the dual mode anticancer agents, animthioxam, brimbam, troxbam, and troxham, as well as their structural congeners suberoylanilide hydroxamic acid and combretastatin A-4 on human cancer cell lines. Their cytotoxicity was determined using the MTT assay, further techniques for detecting apoptotic events, cell cycle analyses, clonogenic and wound healing assays, immunostaining, histone deacetylase (HDAC) activity measurements, and Western blot analysis for the detection of survivin expression in HCT116 colon cancer cells. Molecular docking studies were conducted to assess potential molecular targets of the test compounds. The test compounds were found selectively cytotoxic toward cancer cells by inducing apoptosis. The metastatic potential was effectively reduced by disruption of the microtubular cytoskeleton. The test compounds were also proven to be general HDAC inhibitors and to lead to reduced survivin expression.