Histone deacetylase inhibitors: multifunctional anticancer agents

Drug Discovery for Histone Deacetylase Inhibition: Past, Present and Future of Zinc-Binding Groups

Histone deacetylases (HDACs) are key regulators of gene expression, influencing chromatin remodeling and playing a crucial role in various physiological and pathological processes. Aberrant HDAC activity has been linked to cancer, neurodegenerative disorders, and inflammatory diseases, making these enzymes attractive therapeutic targets. HDAC inhibitors (HDACis) have gained significant attention, particularly those containing zinc-binding groups (ZBGs), which interact directly with the catalytic zinc ion in the enzyme's active site. The structural diversity of ZBGs profoundly impacts the potency, selectivity, and pharmacokinetics of HDACis. While hydroxamic acids remain the most widely used ZBGs, their limitations, such as metabolic instability and off-target effects, have driven the development of alternative scaffolds, including ortho-aminoanilides, mercaptoacetamides, alkylhydrazides, oxadiazoles, and more. This review explores the structural and mechanistic aspects of different ZBGs, their interactions with HDAC isoforms, and their influence on inhibitor selectivity. Advances in structure-based drug design have allowed the fine-tuning of HDACi pharmacophores, leading to more selective and efficacious compounds with improved drug-like properties. Understanding the nuances of ZBG interactions is essential for the rational design of next-generation HDACis, with potential applications in oncology, neuroprotection, and immunotherapy.

Mechanism and application of HDAC inhibitors in the treatment of hepatocellular carcinoma

Hepatoma is the sixth most malignant tumor in the world and the second leading cause of cancer death. Among the types of hepatoma, hepatocellular carcinoma (HCC) is the most important pathological type. For patients with early-stage HCC, the curative treatment is tumor resection. However, early diagnosis and treatment of HCC are difficult; the disease progresses rapidly, and the prognosis is poor. Due to the current limited treatment options for advanced HCC, the identification of new targeted agents is critical for the development of novel approaches to HCC treatment. Histone deacetylases (HDACs) is a protease that removes acetyl groups from histone lysine residues in proteins, and it plays an important role in the structural modification of chromosomes and the regulation of gene expression. Abnormally expressed HDACs can promote tumorigenesis by inducing biological processes such as cell proliferation, migration, and apoptosis inhibition. Since HDACs activity is upregulated in HCC, treatment regimens specifically inhibiting various HDACs have shown good efficacy. This article reviews the application of HDAC inhibitors in the treatment of HCC and explains their mechanisms of action. KEY MESSAGES: HDAC network and cellular effects of HDAC inhibitors. Role and mechanism of HDAC inhibitors in HCC. HDAC inhibitor combined with other ways to treat HCC. The side effects of HDACis in the treatment of HCC.

MIER2/PGC1A elicits sunitinib resistance via lipid metabolism in renal cell carcinoma

INTRODUCTION

Renal cell carcinoma (RCC) is one of the most common malignant tumors of the urinary system and accounts for more than 90 % of all renal tumors. Resistance to targeted therapy has emerged as a pivotal factor that contributes to the progressive deterioration of patients with advanced RCC. Metabolic reprogramming is a hallmark of tumorigenesis and progression, with an increasing body of evidence indicating that abnormal lipid metabolism plays a crucial role in the advancement of renal clear cell carcinoma.

OBJECTIVES

Clarify the precise mechanisms underlying abnormal lipid metabolism and drug resistance.

METHODS

Bioinformatics screening and analyses were performed to identify hub gene. qRT-PCR, western blot, chromatin immunoprecipitation (ChIP) assays, and other biological methods were used to explore and verify related pathways. Various cell line models and animal models were used to perform biological functional experiments.

RESULTS

In this study, we identified Mesoderm induction early response 2 (MIER2) as a novel biomarker for RCC, demonstrating its role in promoting malignancy and sunitinib resistance by influencing lipid metabolism in RCC. Mechanistically, MIER2 facilitated P53 deacetylation by binding to HDAC1. Acetylation modification augmented the DNA-binding stability and transcriptional function of P53, while deacetylation of P53 hindered the transcriptional process of PGC1A, leading to intracellular lipid accumulation in RCC. Furthermore, Trichostatin A (TSA), an inhibitor of HDAC1, was found to impede the MIER2/HDAC1/P53/PGC1A pathway, offering potential benefits for patients with sunitinib-resistant renal cell cancer.

CONCLUSION

Our findings highlight MIER2 as a key player in anchoring HDAC1 and inhibiting PGC1A expression through the deacetylation of P53, thereby inducing lipid accumulation in RCC and promoting drug resistance. Lipid-rich RCC cells compensate for energy production and sustain their own growth in a glycolysis-independent manner, evading the cytotoxic effects of targeted drugs and ultimately culminating in the development of drug resistance.

Thiazolidinedione derivatives: emerging role in cancer therapy

Cancer remains the leading cause of death worldwide, with the Globocan 2022 study reporting an estimated 9.7 million cancer deaths. Without the selectivity built for tumour cells, chemotherapeutic agents could be toxic to non-cancerous cells. Administration of such non-selective cytotoxic compounds causes severe side effects and could lead to death. Improved cancer treatments are required to overcome the limitations of the current cancer treatment. The potential of thiazolidinedione derivatives as anticancer drugs has recently drawn attention, despite their primary use as insulin sensitizers in the treatment of type 2 diabetes. The ability of thiazolidinedione derivatives to alter important molecular pathways implicated in carcinogenesis, such as cell proliferation, apoptosis, angiogenesis, Raf kinase, EGFR and HER-2 kinases, HDAC, COX-2 enzyme and metastasis, is highlighted in this review, which examines the growing relevance of these compounds in cancer treatment. Thiazolidinediones have anti-inflammatory, antioxidant, and antiproliferative properties in a variety of cancer types, including breast, colon, and prostate cancers, via activating the peroxisome proliferator-activated gamma receptor (PPARγ). In addition to examining the safety profile and difficulties in clinical translation, the paper looks at preclinical and clinical research that points to these medicines potential to improve the effectiveness of immunotherapy and chemotherapy. This review highlights the encouraging therapeutic possibilities and structure-activity relationship insight of TZDs for their anticancer activity and highlights the molecular level facets of the 'glitazone' pharmacophore for its anticancer activity.

HDAC and MEK inhibition synergistically suppresses HOXC6 and enhances PD-1 blockade efficacy in BRAFV600E-mutant microsatellite stable colorectal cancer

BACKGROUND

B-Raf proto-oncogene, serine/threonine kinase (BRAF)V600E-mutant microsatellite stable (MSS) colorectal cancer (CRC) constitutes a distinct CRC subgroup, traditionally perceived as minimally responsive to standard therapies. Recent clinical attempts, such as BRAF inhibitors (BRAFi) monotherapy and combining BRAFi with other inhibitors, have yielded unsatisfactory efficacy. This study aims to identify a novel therapeutic strategy for this challenging subgroup.

METHODS

We first performed a large-scale drug screening using patient-derived organoid models and cell lines to pinpoint potential therapies. Subsequently, we investigated the synergistic effects of identified effective inhibitors and probed their cooperative mechanisms. Concurrently, we explored the immune characteristics of BRAFV600E MSS CRC using RNA sequencing and multiplex immunohistochemistry. Finally, we established a CT26 BRAFV637E mouse cell line and validated the efficacy of combining these inhibitors and programmed death 1 (PD-1) blockades in immunocompetent mice.

RESULTS

Drug screening identified histone deacetylase (HDAC) inhibitor and mitogen-activated protein kinase kinase (MEK) inhibitor as significantly effective against BRAFV600E MSS CRC. Further research revealed that these two inhibitors have superior synergistic effects by comprehensively inhibiting the activation of the epidermal growth factor receptor, mitogen-activated protein kinase, and phosphoinositide 3-kinase-protein kinase B pathways and suppressing the key target homeobox C6 (HOXC6). HOXC6, overexpressed in BRAFV600E MSS CRC, regulates the MYC gene and contributes to treatment resistance, tumor growth, and metastasis. Moreover, the combination therapy demonstrated the ability to enhance antitumor immunity by synergistically upregulating the expression of immune activation-related genes, activating the cyclic guanosine monophosphate-adenosine monophosphate synthase/stimulator of interferon genes (cGAS/STING) pathway, and diminishing the tumor cells' DNA mismatch repair capacity. Notably, BRAFV600E MSS CRC was identified to exhibit a distinct immune microenvironment with increased PD-1+ cell infiltration and potential responsiveness to immunotherapy. Echoing the above findings, in vivo, HDAC and MEK inhibitors significantly improved PD-1 blockade efficacy, accompanied by increased CD8+ T-cell infiltration.

CONCLUSIONS

Our findings indicate that combining HDAC inhibitor, MEK inhibitor, and PD-1 blockade is a potential strategy for treating BRAFV600E-mutant MSS CRC, warranting further investigation in clinical settings.

Histone Deacetylase Inhibitors for Peripheral T-Cell Lymphomas

Histone deacetylase inhibitors (HDACis) are being recognized as a potentially effective treatment approach for peripheral T-cell lymphomas (PTCLs), a heterogeneous group of aggressive malignancies with an unfavorable prognosis. Recent evidence has shown that HDACis are effective in treating PTCL, especially in cases where the disease has relapsed or is resistant to conventional treatments. Several clinical trials have demonstrated that HDACis, such as romidepsin and belinostat, can elicit long-lasting positive outcomes in individuals with PTCLs, either when used alone or in conjunction with conventional chemotherapy. They exert their anti-tumor effects by regulating gene expression through the inhibition of histone deacetylases, which leads to cell cycle arrest, induction of programmed cell death, and,the transformation of cancerous T cells, as demonstrated by gene expression profile studies. Importantly, besides clinical trials, real-world evidence indicated that the utilization of HDACis presents a significant and beneficial treatment choice for PTCLs. However, although HDACis showed potential effectiveness, they could not cure most patients. Therefore, new combinations with conventional drugs as well as new targeted agents are under investigation.

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.

Pan-histone deacetylase inhibitor vorinostat suppresses osteoclastic bone resorption through modulation of RANKL-evoked signaling and ameliorates ovariectomy-induced bone loss

BACKGROUND

Estrogen deficiency-mediated hyperactive osteoclast represents the leading role during the onset of postmenopausal osteoporosis. The activation of a series of signaling cascades triggered by RANKL-RANK interaction is crucial mechanism underlying osteoclastogenesis. Vorinostat (SAHA) is a broad-spectrum pan-histone deacetylase inhibitor (HDACi) and its effect on osteoporosis remains elusive.

METHODS

The effects of SAHA on osteoclast maturation and bone resorptive activity were evaluated using in vitro osteoclastogenesis assay. To investigate the effect of SAHA on the osteoclast gene networks during osteoclast differentiation, we performed high-throughput transcriptome sequencing. Molecular docking and the assessment of RANKL-induced signaling cascades were conducted to confirm the underlying regulatory mechanism of SAHA on the action of RANKL-activated osteoclasts. Finally, we took advantage of a mouse model of estrogen-deficient osteoporosis to explore the clinical potential of SAHA.

RESULTS

We showed here that SAHA suppressed RANKL-induced osteoclast differentiation concentration-dependently and disrupted osteoclastic bone resorption in vitro. Mechanistically, SAHA specifically bound to the predicted binding site of RANKL and blunt the interaction between RANKL and RANK. Then, by interfering with downstream NF-κB and MAPK signaling pathway activation, SAHA negatively regulated the activity of NFATc1, thus resulting in a significant reduction of osteoclast-specific gene transcripts and functional osteoclast-related protein expression. Moreover, we found a significant anti-osteoporotic role of SAHA in ovariectomized mice, which was probably realized through the inhibition of osteoclast formation and hyperactivation.

CONCLUSION

These data reveal a high affinity between SAHA and RANKL, which results in blockade of RANKL-RANK interaction and thereby interferes with RANKL-induced signaling cascades and osteoclastic bone resorption, supporting a novel strategy for SAHA application as a promising therapeutic agent for osteoporosis.

Dysregulation of different modes of programmed cell death by epigenetic modifications and their role in cancer

Modifications of epigenetic factors affect our lives and can give important information regarding one's state of health. In cancer, epigenetic modifications play a crucial role, as they influence various programmed cell death types. The purpose of this review is to investigate how epigenetic modifications, such as DNA methylation, histone modifications, and non-coding RNAs, influence various cell death processes in suppressing or promoting cancer development. Autophagy and apoptosis are the most investigated programmed cell death modes, as based on the tumor stage these cell death types can either promote or prevent cancer evolution. Therefore, our discussion focuses on how epigenetic modifications affect autophagy and apoptosis, as well as their diagnostic and therapeutical potential in combination with available chemotherapeutics. Additionally, we summarize the available data regarding the role of epigenetic modifications on other programmed cell death modes, such as ferroptosis, necroptosis, and parthanatos in cancer and discuss current advancements.

The application of PROTAC in HDAC

Inducing protein degradation by proteolysis targeting chimera (PROTAC) has provided great opportunities for scientific research and industrial applications. Histone deacetylase (HDAC)-PROTAC has been widely developed since the first report of its ability to induce the degradation of SIRT2 in 2017. To date, ten of the eighteen HDACs (HDACs 1-8, HDAC10, and SIRT2) have been successfully targeted and degraded by HDAC-PROTACs. HDAC-PROTACs surpass traditional HDAC inhibitors in many aspects, such as higher selectivity, more potent antiproliferative activity, and the ability to disrupt the enzyme-independent functions of a multifunctional protein and overcome drug resistance. Rationally designing HDAC-PROTACs is a main challenge in development because slight variations in chemical structure can lead to drastic effects on the efficiency and selectivity of the degradation. In the future, HDAC-PROTACs can potentially be involved in clinical research with the support of the increased amount of in vivo data, pharmacokinetic evaluation, and pharmacological studies.

Repurposing Synthetic Congeners of a Natural Product Aurone Unveils a Lead Antitumor Agent Inhibiting Folded P-Loop Conformation of MET Receptor Tyrosine Kinase

A library of 24 congeners of the natural product sulfuretin were evaluated against nine panels representing nine cancer diseases. While sulfuretin elicited very weak activities at 10 µM concentration, congener 1t was identified as a potential compound triggering growth inhibition of diverse cell lines. Mechanistic studies in HCT116 colon cancer cells revealed that congener 1t dose-dependently increased levels of cleaved-caspases 8 and 9 and cleaved-PARP, while it concentration-dependently decreased levels of CDK4, CDK6, Cdc25A, and Cyclin D and E resulting in induction of cell cycle arrest and apoptosis in colon cancer HCT116 cells. Mechanistic study also presented MET receptor tyrosine kinase as the molecular target mediating the anticancer activity of compound 1t in HCT116 cells. In silico study predicted folded p-loop conformation as the form of MET receptor tyrosine kinase responsible for binding of compound 1t. Together, the current study presents compound 1t as an interesting anticancer lead for further development.

The HDAC inhibitor HFY-4A improves TUSC2 transcription to induce immunogenic cell death in breast cancer

We managed to explore the function of HFY-4A, a novel histone deacetylases (HDACs) inhibitor, on breast cancer as well as its potential mechanisms. MCF7 and T47D cells were treated with 0.8, 1.6 or 3.2 μM HFY-4A for 0-72 h, following of which CCK-8, colony formation, EdU staining, flow cytometry, Transwell, and wound healing assays were carried out. Western blot, immunohistochemistry, and ELISA were conducted for assaying the expression of immunogenic cell death (ICD)-related proteins. The interaction between HFY-4A, HDAC1, and tumor suppressor candidate 2 (TUSC2) was evaluated by chromatin immunoprecipitation assay. Further, the function of HFY-4A in breast cancer progression in vivo was evaluated using xenograft mouse models. HFY-4A inhibited the proliferation, migration, and invasion, and induced apoptosis of breast cancer cells in a dose-dependent manner. HFY-4A dose-dependently caused the ICD of breast cancer cells, as evidenced by the significant high levels of high-mobility group box 1 (HMGB1), calreticulin (CRT), heat shock protein 70 (HSP70), and HSP90. Interestingly, HFY-4A could facilitate TUSC2 transcription by promoting acetylation of histones on the TUSC2 promoter. The results of rescue assays revealed that HFY-4A repressed proliferation and mobility, but enhanced apoptosis and ICD through facilitating TUSC2 transcription in breast cancer. In breast cancer xenograft mouse models, HFY-4A was verified to inhibit tumor growth via upregulating TUSC2. HFY-4A could inhibit breast cancer cell proliferation and mobility, and enhanced apoptosis and ICD through facilitating TUSC2 transcription.

Histone deacetylase inhibitors inhibit lung adenocarcinoma metastasis via HDAC2/YY1 mediated downregulation of Cdh1

Metastasis is a leading cause of mortality in patients with lung adenocarcinoma. Histone deacetylases have emerged as promising targets for anti-tumor drugs, with histone deacetylase inhibitors (HDACi) being an active area of research. However, the precise mechanisms by which HDACi inhibits lung cancer metastasis remain incompletely understood. In this study, we employed a range of techniques, including qPCR, immunoblotting, co-immunoprecipitation, chromatin-immunoprecipitation, and cell migration assays, in conjunction with online database analysis, to investigate the role of HDACi and HDAC2/YY1 in the process of lung adenocarcinoma migration. The present study has demonstrated that both trichostatin A (TSA) and sodium butyrate (NaBu) significantly inhibit the invasion and migration of lung cancer cells via Histone deacetylase 2 (HDAC2). Overexpression of HDAC2 promotes lung cancer cell migration, whereas shHDAC2 effectively inhibits it. Further investigation revealed that HDAC2 interacts with YY1 and deacetylates Lysine 27 and Lysine9 of Histone 3, thereby inhibiting Cdh1 transcriptional activity and promoting cell migration. These findings have shed light on a novel functional mechanism of HDAC2/YY1 in lung adenocarcinoma cell migration.

Panobinostat inhibits breast cancer progression via Vps34-mediated exosomal pathway

Exosomes play crucial roles in intercellular communication, including tumor metastasis. Panobinostat (LBH589), a histone deacetylases (HDAC) inhibitor, is an emerging anti-tumor drug with promising efficacy in cancer therapy. This study was set out from recent evidence that exosome was a mechanism of intercellular drug transfer with significant pharmacological consequences. It enlightened us LBH589 might regulate tumor growth through exosomal secretion. Here we demonstrated LBH589 induced autophagy and facilitated secretory autophagy. Furthermore, LBH589 dose- and time-dependently stimulated exosomal release mediated by Vps34/Rab5C pathway, documented by the ablation of Vps34 and/or Rab5C in breast cancer cells. Additionally, the findings also presented LBH589 inhibited breast cancer progression via exosomes. Altogether, we revealed a novel mechanism of LBH589 in exosome-mediated anti-tumor effects in breast cancer. The schematic diagram of signaling pathways involved in the suppression of breast cancer progression by LBH589 via exosomes.

Enhanced antitumor activity of combined methotrexate and histone deacetylase inhibitor valproic acid on mammary cancer in vitro and in vivo

Histone deacetylase inhibitors (HDACIs) act as antiproliferative agents by promoting differentiation and inducing apoptosis. Valproic acid (VPA) is an HDACI that shows promising chemotherapeutic effect in several tumor cells. The present study aimed to investigate the inhibitory effect of VPA on the viability of mammary cancer cells and its enhancing effect with methotrexate (MTX) in vitro and in vivo. Treatment with VPA or MTX alone induced concentration-dependent cytotoxic effects in two breast cancer cell lines. VPA significantly increased the cytotoxicity of MTX 3 times against MCF7. VPA addition to MTX, however, did not produce any significant changes on MTX cytotoxicity against MDA-MB231. VPA (150 and 200 mg/kg) significantly inhibited the growth of IP and SC Ehrlich ascites carcinoma tumor mouse models and improved results were achieved for tumor inhibition when VPA was combined with MTX (1 and 2 mg/kg) in vivo. The antitumor activity was not associated with a significant increase in toxicity or mice mortality rate. All these findings suggest that the combination of MTX and VPA may have clinical and/or adjuvant therapeutic application in the treatment of mammary cancer.

Advances in the Design and Development of PROTAC-mediated HDAC degradation

Due to developments in modern chemistry, previously undruggable targets are becoming druggable thanks to selective degradation using the ubiquitin-proteasomal degradation system. PROteolysis TArgeting Chimeras (PROTACs) are heterobifunctional molecules designed specifically to degrade target proteins (protein of interest, POI). They are of significant interest to industry and academia as they are highly specific and can target previously undruggable target proteins from transcription factors to enzymes. More than 15 degraders are expected to be evaluated in clinical trials by the end of 2021. Herein, we describe recent advances in the design and development of PROTAC-mediated degradation of histone deacetylases (HDACs). PROTAC-mediated degradation of HDACs can offer some significant advantages over direct inhibition, such as the use of substoichiometric doses and the potential to disrupt enzyme-independent HDAC function. Herein, we discuss the potential implications of the degradation of HDACs with HDAC knockout studies and the selection of HDAC inhibitors and E3 ligase ligands for the design of the PROTACs. The potential utility of HDAC PROTACs in various disease pathologies from cancer to inflammation to neurodegeneration is driving the interest in this field.

Polycythemia Vera (PV): Update on Emerging Treatment Options

Polycythemia Vera (PV) is a chronic myeloproliferative neoplasm characterized by exuberant red cell production leading to a broad range of symptoms that compromise quality of life and productivity of patients. PV reduces survival expectation, primarily due to thrombotic events, transformation to blast phase and post-PV myelofibrosis or to development of second cancers, which are associates with poor prognosis. Current therapeutic first line recommendations based on risk adapted classification divided patients into two groups, according to age (< or >60 years) and presence of prior thrombotic events. Low-risk patients (age <60 years and no prior history of thrombosis) should be treated with aspirin (81-100 mg/d) and phlebotomy, to maintain hematocrit <45%. High-risk patients (age >60 years and/or prior history of thrombosis), in addition to aspirin and phlebotomies, should receive cytoreductive therapy in order to reduce thrombotic risk. Nowadays hydroxyurea still remains the cytoreductive agent of first choice, reserving Interferon to young patients or childbearing women. During the last years, ruxolitinib emerged as a new treatment in PV patients, as second line therapy: it appeared especially effective in patients with severe pruritus, symptomatic splenomegaly, or post-PV myelofibrosis symptoms. Currently, in PV treatment, several molecules have been tested or are under investigation. At present, the drug that has shown the most encouraging results is givinostat.

The Role of Histone Acetylation-/Methylation-Mediated Apoptotic Gene Regulation in Hepatocellular Carcinoma

Epigenetics, an inheritable phenomenon, which influences the expression of gene without altering the DNA sequence, offers a new perspective on the pathogenesis of hepatocellular carcinoma (HCC). Nonalcoholic steatohepatitis (NASH) is projected to account for a significant share of HCC incidence due to the growing prevalence of various metabolic disorders. One of the major molecular mechanisms involved in epigenetic regulation, post-translational histone modification seems to coordinate various aspects of NASH which will further progress to HCC. Mounting evidence suggests that the orchestrated events of cellular and nuclear changes during apoptosis can be regulated by histone modifications. This review focuses on the current advances in the study of acetylation-/methylation-mediated histone modification in apoptosis and the implication of these epigenetic regulations in HCC. The reversibility of epigenetic alterations and the agents that can target these alterations offers novel therapeutic approaches and strategies for drug development. Further molecular mechanistic studies are required to enhance information governing these epigenetic modulators, which will facilitate the design of more effective diagnosis and treatment options.

Multitarget Inhibition of Histone Deacetylase (HDAC) and Phosphatidylinositol-3-kinase (PI3K): Current and Future Prospects

The discovery of histone deacetylase (HDAC) inhibitors is a hot topic in the medicinal chemistry community regarding cancer research. This is related primarily to two factors: success in the clinic, e. g., the four FDA-approved HDAC inhibitors, and strong versatility to combine their pharmacophoric features to design new hybrid compounds with multitarget profiles. Thus, the selection of adequate pharmacophores to combine, i. e., combining targets that can result in a synergistic effect, is desirable, as it increases the probability of discovering a new useful therapeutic strategy. In this work, we highlight the design of multitarget HDAC/PI3K inhibitors. Although this approach is still in its early stages, many significant works have described the design and pharmacological evaluation of this new promising class of multitarget inhibitors, where compound CUDC-907, which is already in clinical trials, stands out. Therefore, the question emerges of whether there still space for the design and evaluation of new multitarget HDAC/PI3K inhibitors. When considering the selectivity profile of the described multitarget compounds, the answer appears to be in the affirmative, especially since the first examples of compounds with a certain selectivity profile only recently appeared in 2020.

New Perspectives on Polycythemia Vera: From Diagnosis to Therapy

Polycythemia vera (PV) is mainly characterized by elevated blood cell counts, thrombotic as well as hemorrhagic predisposition, a variety of symptoms, and cumulative risks of fibrotic progression and/or leukemic evolution over time. Major changes to its diagnostic criteria were made in the 2016 revision of the World Health Organization (WHO) classification, with both hemoglobin and hematocrit diagnostic thresholds lowered to 16.5 g/dL and 49% for men, and 16 g/dL and 48% for women, respectively. The main reason leading to these changes was represented by the recognition of a new entity, namely the so-called “masked PV”, as individuals suffering from this condition have a worse outcome, possibly owing to missed or delayed diagnoses and lower intensity of treatment. Thrombotic risk stratification is of crucial importance to evaluate patients’ prognosis at diagnosis. Currently, patients are stratified into a low-risk group, in the case of younger age (<60 years) and no previous thromboses, and a high-risk group, in the case of patients older than 60 years and/or with a previous thrombotic complication. Furthermore, even though they have not yet been formally included in a scoring system, generic cardiovascular risk factors, particularly hypertension, smoking, and leukocytosis, contribute to the thrombotic overall risk. In the absence of agents proven to modify its natural history and prevent progression, PV management has primarily been focused on minimizing the thrombotic risk, representing the main cause of morbidity and mortality. When cytoreduction is necessary, conventional therapies include hydroxyurea as a first-line treatment and ruxolitinib and interferon in resistant/intolerant cases. Each therapy, however, is burdened by specific drawbacks, underlying the need for improved strategies. Currently, the therapeutic landscape for PV is still expanding, and includes several molecules that are under investigation, like long-acting pegylated interferon alpha-2b, histone deacetylase inhibitors, and murine double minute 2 (MDM2) inhibitors.

Understanding the mechanistic insight of arsenic exposure and decoding the histone cipher

BACKGROUND

The study of heritable epigenetic changes in arsenic exposure has intensified over the last decade. Groundwater arsenic contamination causes a great threat to humans and, to date, no accurate measure has been formulated for remediation. The fascinating possibilities of epi-therapeutics identify the need for an in-depth mechanistic understanding of the epigenetic landscape.

OBJECTIVE

In this comprehensive review, we have set to analyze major studies pertaining to histone post-translational modifications in arsenic-mediated disease development and carcinogenesis during last ten years (2008-2018).

RESULTS

The role of the specific histone marks in arsenic toxicity has been detailed. A comprehensive list that includes major arsenic-induced histone modifications identified for the last 10 years has been documented and details of different states of arsenic, organisms, exposure type, study platform, and findings were provided. An arsenic signature panel was suggested to help in early prognosis. An attempt has been made to identify the grey areas of research.

PROSPECTS

Future prospective multi-target analyses of the inter-molecular crosstalk among different histone marks are needed to be explored further in order to understand the mechanism of arsenic toxicity and carcinogenicity and to confirm the suitability of these epi-marks as prognostic markers.

Romidepsin Induces G2/M Phase Arrest and Apoptosis in Cholangiocarcinoma Cells

Background:

Cholangiocarcinoma (CCA) is an extremely intractable malignancy since most patients are already in an advanced stage when firstly discovered. CCA needs more effective treatment, especially for advanced cases. Our study aimed to evaluate the effect of romidepsin on CCA cells in vitro and in vivo and explore the underlying mechanisms.

Methods:

The antitumor effect was determined by cell viability, cell cycle and apoptosis assays. A CCK-8 assay was performed to measure the cytotoxicity of romidepsin on CCA cells, and flow cytometry was used to evaluate the effects of romidepsin on the cell cycle and apoptosis. Moreover, the in vivo effects of romidepsin were measured in a CCA xenograft model.

Results:

Romidepsin could reduce the viability of CCA cells and induce G2/M cell cycle arrest and apoptosis, indicating that romidepsin has a significant antitumor effect on CCA cells in vitro. Mechanistically, the antitumor effect of romidepsin on the CCA cell lines was mediated by the induction of G2/M cell cycle arrest and promotion of cell apoptosis. The G2/M phase arrest of the CCA cells was associated with the downregulation of cyclinB and upregulation of the p-cdc2 protein, resulting in cell cycle arrest. The apoptosis of the CCA cells induced by romidepsin was attributed to the activation of caspase-3. Furthermore, romidepsin significantly inhibited the growth of the tumor volume of the CCLP-1 xenograft, indicating that romidepsin significantly inhibited the proliferation of CCA cells in vivo.

Conclusions:

Romidepsin suppressed the proliferation of CCA cells by inducing cell cycle arrest through cdc2/cyclinB and cell apoptosis by targeting caspase-3/PARP both in vitro and in vivo, indicating that romidepsin is a potential therapeutic agent for CCA.

Molecular Determinants of Cancer Therapy Resistance to HDAC Inhibitor-Induced Autophagy

Histone deacetylation inhibitors (HDACi) offer high potential for future cancer therapy as they can re-establish the expression of epigenetically silenced cell death programs. HDACi-induced autophagy offers the possibility to counteract the frequently present apoptosis-resistance as well as stress conditions of cancer cells. Opposed to the function of apoptosis and necrosis however, autophagy activated in cancer cells can engage in a tumor-suppressive or tumor-promoting manner depending on mostly unclarified factors. As a physiological adaption to apoptosis resistance in early phases of tumorigenesis, autophagy seems to resume a tumorsuppressive role that confines tumor necrosis and inflammation or even induces cell death in malignant cells. During later stages of tumor development, chemotherapeutic drug-induced autophagy seems to be reprogrammed by the cancer cell to prevent its elimination and support tumor progression. Consistently, HDACi-mediated activation of autophagy seems to exert a protective function that prevents the induction of apoptotic or necrotic cell death in cancer cells. Thus, resistance to HDACi-induced cell death is often encountered in various types of cancer as well. The current review highlights the different mechanisms of HDACi-elicited autophagy and corresponding possible molecular determinants of therapeutic resistance in cancer.

Targeting miRNAs by histone deacetylase inhibitors (HDACi): Rationalizing epigenetics-based therapies for breast cancer

MicroRNAs (miRNAs) belong to a group of short RNA molecules of ~22 nucleotides that play a significant role in the regulation of gene expression through post-transcriptional regulatory mechanisms. They can directly interact with their target mRNA molecules and induce target gene silencing. Many investigations over the past decade have revealed the involvement of different miRNAs in essential biological events. The expression of a considerable number of miRNAs is tightly regulated through epigenetic events such as histone modifications and DNA methylation. Notably, irregularities in these epigenetic events are associated with aberrant expression of miRNAs in a range of diseases including cancer. Impaired epigenetic events associated with aberrant expression of miRNAs can be pharmacologically modified using chromatin modifying drugs. Numerous pre-clinical and clinical data demonstrate that histone deacetylase inhibitors (HDACi) can re-establish the expression of aberrantly expressed miRNAs in a range of cancer types, rationalizing miRNAs as potential drug targets. This review highlights evidence from investigations assessing the effects of different classes of HDACi on miRNA expression in breast cancer (BC).

Suppressing Hedgehog signaling reverses drug resistance of refractory acute myeloid leukemia

Background

Hedgehog (Hh) signaling is involved in the pathogenesis of tumors. By performing gene chip analysis, we predicted that Hh signaling might regulate multiple downstream pathways in acute myeloid leukemia (AML).

Methods

In this study, the potential role of the Hh pathway in refractory AML, and the impact of Hh expression on clinical prognosis were examined. We also investigated the role of the Hh inhibitor NVP-LDE225 in reversing drug resistance of refractory primary AML cells in vitro and the roles of multiple drug-resistant HL60/Adriamycin-resistant cells in vitro and in vivo (in a xenograft mouse model). Finally, we explored the underlying mechanisms.

Results

Hh pathway was highly active in chemotherapy-resistant AML cells; by contrast, activation was less pronounced in chemosensitive cells and non-refractory primary cells. Strong activation of this pathway was associated with higher recurrence rates and poorer relapse-free and overall survival. NVP-LDE225 inhibited MRP1 protein expression, increased intracellular accumulation of Adriamycin, and reversed chemotherapeutic resistance. These effects were likely mediated through inhibition of the IGF-1R/Akt/MRP1 pathway. In the AML xenograft mouse model, NVP-LDE225 plus Adriamycin resulted in marked tumor regression.

Conclusion

These findings suggest that targeting the Hh pathway might be a therapeutic avenue for overcoming MDR resistance and preventing refractory AML.

MS-275 potentiates the effect of YM-155 in lung adenocarcinoma via survivin downregulation induced by miR-138 and miR-195

BACKGROUND

YM-155 has been proven to be an efficient antitumor suppressor in non-small cell lung cancer (NSCLC) cells. However, the suppressive effect of YM-155 on the expression of survivin is not sufficient and has a short half-life. MS-275, a histone deacetylase inhibitor, has significant antitumor capacity with a relatively long half-life. Our study explored whether MS-275 could enhance the inhibitory effect of YM-155 on LUAD proliferation.

METHODS

To investigate the synergistic effect of MS-275 and YM-155, we employed methyl thiazolyl tetrazolium and colony formation assays to access the inhibition effect of MS-275, YM-155, or a combination in A549 and HCC827 cell lines. We then detected the effect of MS-275 and YM-155 on the expression of survivin and pro-apoptotic proteins by Western blot and miR-138 or miR-195 expression by quantitative PCR. We also analyzed the methylation level of microRNAs (miRNAs) using methylation-sensitive quantitative PCR. Finally, we investigated the interaction between miRNAs and survivin by luciferase reporter assay.

RESULTS

MS-275 facilitated an inhibitory effect of YM-155 on lung adenocarcinoma cell proliferation. MS-275 can upregulate the level of acetylated H3, promote the degradation of DNA methyltransferases, and inhibit the methylation of miR-138 and miR-195 genes to elevate the expression of miR-138 and miR-195. Moreover, miR-138 and miR-195 showed a synergistic effect with YM-155 by directly binding to the 3 untranslated region of survivin to attenuate its expression.

CONCLUSION

For the first time, we report the synergistic effective of MS-275 and YM-155 and suggest a new direction for the future application of YM-155.

Marine anticancer drugs and their relevant targets: a treasure from the ocean

Marine organisms comprising animals and plants are wealthiest sources of bioactive compounds possessing various pharmacological properties specifically: free radical scavenging, antitumor, antimicrobial, analgesic, neuroprotective and immunomodulatory. Marine drugs provide an alternative source to meet the demand of effective, safe and low-cost drugs that are rising with the continuously growing world population. Cancer is one of the leading reasons of mortality in western nations in contrast to communicable diseases of developing nations. In spite of outstanding developments in cancer therapy in past three decades, there is still an insistent necessity for innovative drugs in the area of cancer biology, especially in the unexplored area of marine anticancer compounds. However, recent technological innovations in structure revelation, synthetic creation of new compounds and biological assays have made possible the isolation and clinical assessment of innumerable unique anticancer compounds from marine environment. This review provides an insight into the anticancer research so far conducted in the area of the marine natural products/synthetic derivatives, their possible molecular targets and the current challenges in the drug development. Graphical abstract.

Nerve-mediated expression of histone deacetylases regulates limb regeneration in axolotls

Axolotls have amazing abilities to regenerate their lost limbs. Nerve and wound epidermis have great impacts on this regeneration. Histone deacetylases (HDACs) have been shown to play roles in the regeneration of amphibian tails and limbs. In this study, a bi-phasic up-regulation of HDAC1 was noted before early differentiation stage of axolotl limb regeneration. Limb regeneration was delayed in larvae incubated with an HDAC inhibitor MS-275. Local injection of MS-275 or TSA, another HDAC inhibitor, into amputation sites of the juveniles did not interfere with wound healing but more profoundly inhibited local HDAC activities and blastema formation/limb regeneration. Elevation of HDAC1 expression was more apparent in wound epidermis than in mesenchyme. Prior denervation prohibited this elevation and limb regeneration. Supplementation of nerve factors BMP7, FGF2, and FGF8 in the stump ends after amputation on denervated limbs not only enabled HDAC1 up-regulation but also led to more extent of limb regeneration. In conclusion, nerve-mediated HDAC1 expression is required for blastema formation and limb regeneration.

Epigenetic Targeting of Autophagy via HDAC Inhibition in Tumor Cells: Role of p53

Tumor development and progression is the consequence of genetic as well as epigenetic alterations of the cell. As part of the epigenetic regulatory system, histone acetyltransferases (HATs) and deacetylases (HDACs) drive the modification of histone as well as non-histone proteins. Derailed acetylation-mediated gene expression in cancer due to a delicate imbalance in HDAC expression can be reversed by histone deacetylase inhibitors (HDACi). Histone deacetylase inhibitors have far-reaching anticancer activities that include the induction of cell cycle arrest, the inhibition of angiogenesis, immunomodulatory responses, the inhibition of stress responses, increased generation of oxidative stress, activation of apoptosis, autophagy eliciting cell death, and even the regulation of non-coding RNA expression in malignant tumor cells. However, it remains an ongoing issue how tumor cells determine to respond to HDACi treatment by preferentially undergoing apoptosis or autophagy. In this review, we summarize HDACi-mediated mechanisms of action, particularly with respect to the induction of cell death. There is a keen interest in assessing suitable molecular factors allowing a prognosis of HDACi-mediated treatment. Addressing the results of our recent study, we highlight the role of p53 as a molecular switch driving HDACi-mediated cellular responses towards one of both types of cell death. These findings underline the importance to determine the mutational status of p53 for an effective outcome in HDACi-mediated tumor therapy.

Computational QSAR model combined molecular descriptors and fingerprints to predict HDAC1 inhibitors

The dynamic balance between acetylation and deacetylation of histones plays a crucial role in the epigenetic regulation of gene expression. It is equilibrated by two families of enzymes: histone acetyltransferases and histone deacetylases (HDACs). HDACs repress transcription by regulating the conformation of the higher-order chromatin structure. HDAC inhibitors have recently become a class of chemical agents for potential treatment of the abnormal chromatin remodeling process involved in certain cancers. In this study, we constructed a large dataset to predict the activity value of HDAC1 inhibitors. Each compound was represented with seven fingerprints, and computational models were subsequently developed to predict HDAC1 inhibitors via five machine learning methods. These methods include naïve Bayes, κ-nearest neighbor, C4.5 decision tree, random forest, and support vector machine (SVM) algorithms. The best predicting model was CDK fingerprint with SVM, which exhibited an accuracy of 0.89. This model also performed best in five-fold cross-validation. Some representative substructure alerts responsible for HDAC1 inhibitors were identified by using MoSS in KNIME, which could facilitate the identification of HDAC1 inhibitors.

Effects of Class II-Selective Histone Deacetylase Inhibitor on Neuromuscular Function and Disease Progression in SOD1-ALS Mice

Emerging evidence indicates that transcriptome alterations due to epigenetic deregulation concur to ALS pathogenesis. Accordingly, pan-histone deacetylase (HDAC) inhibitors delay ALS development in mice, but these compounds failed when tested in ALS patients. Possibly, lack of selectivity toward specific classes of HDACs weakens the therapeutic effects of pan-HDAC inhibitors. Here, we tested the effects of the HDAC Class II selective inhibitor MC1568 on disease evolution, motor neuron survival as well as skeletal muscle function in SOD1G93A mice. We report that HDACs did not undergo expression changes during disease evolution in isolated motor neurons of adult mice. Conversely, increase in specific Class II HDACs (-4, -5 and -6) occurs in skeletal muscle of mice with severe neuromuscular impairment. Importantly, treatment with MC1568 causes early improvement of motor performances that vanishes at later stages of disease. Notably, motor improvement is not paralleled by reduced motor neuron degeneration but by increased skeletal muscle electrical potentials, reduced activation of mir206/FGFBP1-dependent muscle reinnervation signaling, and increased muscle expression of myogenic genes.

Sodium Valproate Inhibits Small Cell Lung Cancer Tumor Growth on the Chicken Embryo Chorioallantoic Membrane and Reduces the p53 and EZH2 Expression

The study aims to test the effect of different sodium valproate (NaVP) doses on small cell lung cancer NCI-H146 cells tumor in chicken embryo chorioallantoic membrane (CAM) model. Xenografts were investigated in the following groups: nontreated control and 5 groups treated with different NaVP doses (2, 3, 4, 6, and 8 mmol/L). Invasion of tumors into CAM in the nontreated group reached 76%. Tumors treated with 8 mmol/L NaVP doses significantly differed in tumor invasion frequency from the control and those treated with 2 mmol/L (P < .01). The calculated probability of 50% tumor noninvasion into CAM was when tumors were treated with 4 mmol/L of NaVP. Number of p53-positive cells in tumors was significantly reduced when treated with NaVP doses from 3 to 8 mmol/L as compared with control; number of EZH2-positive cells in control significantly differed from all NaVP-treated groups. No differences in p53- and EZH2-positive cell numbers were found among 4, 6, and 8 mmol/L NaVP-treated groups. Invaded tumors had an increased N-cadherin and reduced E-cadherin expression. The results indicate the increasing NaVP dose to be able to inhibit tumors progression. Expression of p53 and EZH2 may be promising target markers of therapeutic efficacy evaluation.

Histone deacetylase inhibitors alter the expression of molecular markers in breast cancer cells via microRNAs

Histone deacetylase inhibitors (HDACis) are able to suppress breast cancer cells in vitro and in vivo by altering the expression of estrogen receptor (ER), progesterone receptor (PR) or human epidermal growth factor receptor 2 (Her2/neu). Since HDACis can alter the expression of various microRNAs (miRNAs/miRs), the present study aimed to examine the role of miRNAs in the effects of HDACis on breast cancer cells. We first examined the mRNA expression of ER, PR, and Her2/neu using RT-PCR and the protein levels of ER, PR, and Her2/neu using western blot analysis in MDA-MB-231 and BT474 cells, after trichostatin A (TSA) or vorinostat (SAHA) treatment. We then conducted miRNA expression profiling using microarrays after BT474 cells were treated with TSA or SAHA. Finally, we examined the effects of synthetic miR-762 and miR-642a-3p inhibitors on SAHA-induced downregulation of Her2/neu and SAHA-induced apoptosis and PARP cleavage in BT474 cells. The results indicated that TSA and SAHA dose‑dependently enhanced the mRNA and protein expression levels of ER and PR in MDA‑MB‑231 and BT474 cells. In addition, the mRNA expression levels of Her2/neu were reduced in MDA‑MB‑231 cells, and the mRNA and protein expression levels of Her2/neu were reduced in BT474 cells in response to SAHA and TSA. Furthermore, treatment with TSA (0.2 µM) or SAHA (5.0 µM) induced a marked alteration in the expression of various miRNAs in BT474 cells. Notably, when cells were cotransfected with miR‑762 and miR‑642a‑3p inhibitors, SAHA‑induced downregulation of Her2/neu was inhibited, and SAHA‑induced apoptosis and poly (ADP‑ribose) polymerase cleavage were significantly reduced in BT474 cells. These results indicated that numerous HDACi‑induced miRNAs are required to downregulate Her2/neu levels and promote apoptosis of Her2‑overexpressing breast cancer cells.

Histone Deacetylase Inhibition Restores Expression of Hypoxia-Inducible Protein NDRG1 in Pancreatic Cancer

OBJECTIVES

N-myc downstream-regulated gene-1 (NDRG1) is a hypoxia-inducible and differentiation-related protein and candidate biomarker in pancreatic cancer. As NDRG1 expression is lost in high-grade tumors, the effects of the differentiating histone deacetylase inhibitor trichostatin A (TSA) were examined in human pancreatic cancer cell lines representing different tumor grades.

METHODS

PANC-1 (poorly differentiated) and Capan-1 (moderately to well-differentiated) cells were treated with TSA. Effects were assessed in vitro by microscopic analysis, colorimetric assays, cell counts, real-time polymerase chain reaction, and Western blotting.

RESULTS

Treatment of PANC-1 cells over 4 days with 0.5 μM TSA restored cellular differentiation, inhibited proliferation, and enhanced p21 protein expression. Trichostatin A upregulated NDRG1 mRNA and protein levels under normoxia from day 1 and by 6-fold by day 4 (P < 0.01 at all time points). After 24 hours under hypoxia, NDRG1 expression was further increased in differentiated cells (P < 0.01). Favorable changes were identified in the expression of other hypoxia-regulated genes.

CONCLUSIONS

Histone deacetylase inhibitors offer a potential novel epidrug approach for pancreatic cancer by reversing the undifferentiated phenotype and allowing patients to overcome resistance and better respond to conventional cytotoxic treatments.

Targeting triple negative breast cancer with histone deacetylase inhibitors

INTRODUCTION

Triple negative breast cancer (TNBC) is a heterogeneous disease characterized by poor outcomes, higher rates of relapse, lack of biomarkers for rational use of targeted treatments and insensitivity to current available treatments. Histone deacetylase inhibitors (HDACis) perform multiple cytotoxic actions and are emerging as promising multifunctional agents in TNBC. Areas covered: This review focuses on the challenges so far addressed in the targeted treatment of TNBC and explores the various mechanisms by which HDACis control cancer cell growth, tumor progression and metastases. Pivotal preclinical trials on HDACis like panobinostat, vorinostat, and entinostat show that these epigenetic agents exert an anti-proliferative effect on TNBC cells and control tumor growth by multiple mechanisms of action, including apoptosis and regulation of the epithelial to mesenchimal transition (EMT). Combination studies have reported the synergism of HDACis with other anticancer agents. Expert opinion: In recent years, treatment of TNBC has recorded a high number of failures in the development of targeted agents. HDACis alone or in combination strategies show promising activity in TNBC and could have implications for the future targeted treatment of TNBC patients. Future research should identify which agent synergizes better with HDACis and which patient will benefit more from these epigenetic agents.

Antiproliferative effects of TSA, PXD‑101 and MS‑275 in A2780 and MCF7 cells: Acetylated histone H4 and acetylated tubulin as markers for HDACi potency and selectivity

Inhibition of histone deacetylase enzymes (HDACs) has been well documented as an attractive target for the development of chemotherapeutic drugs. The present study investigated the effects of two prototype hydroxamic acid HDAC inhibitors, namely Trichostatin A (TSA) and Belinostat (PXD-101) and the benzamide Entinostat (MS-275) in A2780 ovarian carcinoma and MCF7 breast adenocarcinoma cells. The three HDACi inhibited the proliferation of A2780 and MCF7 cells at comparable levels, below the µM range. Enzyme inhibition assays in a cell-free system showed that TSA was the most potent inhibitor of total HDAC enzyme activity followed by PXD-101 and MS-275. Incubation of A2780 and MCF7 cells with the hydroxamates TSA and PXD-101 for 24 h resulted in a dramatic increase of acetylated tubulin induction (up to 30-fold for TSA). In contrast to acetylated tubulin, western blot analysis and flow cytometry indicated that the induction of acetylated histone H4 was considerably smaller. The benzamide MS-275 exhibited nearly a 2-fold induction of acetylated histone H4 and an even smaller induction of acetylated tubulin in A2780 and MCF7 cells. Taken together, these data suggest that although the three HDACi were equipotent in inhibiting proliferation of MCF7 and A2780 cells, only the benzamide MS-275 did not induce acetylated tubulin expression, a marker of class IIb HDACs.

Gold-chrysophanol nanoparticles suppress human prostate cancer progression through inactivating AKT expression and inducing apoptosis and ROS generation in vitro and in vivo

Controlled releasing of regulations remains the most convenient method to deliver various drugs. In the present study, we precipitated gold nanoparticles with chrysophanol. The gold-chrysophanol into poly (DL-lactide-co-glycolide) nanoparticles was loaded and the biological activity of chrysophanol nanoparticles on human LNCap prostate cancer cells, was tested to acquire the sustained releasing property. The circular dichroism spectroscopy indicated that chrysophanol nanoparticles effectively resulted in conformational alterations in DNA and regulated different proteins associated with cell cycle arrest. The reactive oxygen species (ROS), apoptosis, cell cycle, DNA damage, Cyto-c and caspase-3 activity were analyzed, and the expression levels of different anti- and pro-apoptotic were studied using immunoblotting analysis. The cytotoxicity assay suggested that chrysophanol nanoparticles preferentially killed prostate cancer cells in comparison to the normal cells. Chrysophanol nanoparticles reduced histone deacetylases (HDACs) to suppress cell proliferation and induce apoptosis by arresting the cell cycle in sub-G phase. In addition, the cell cycle-related proteins, including p27, CHK1, cyclin D1, CDK1, p-AMP-activated protein kinase (AMPK) and p-protein kinase B (AKT), were regulated by chrysophanol nanoparticles to prevent human prostate cancer cell progression. Chrysophanol nanoparticles induced apoptosis in LNCap cells by promoting p53/ROS crosstalk to prevent proliferation. Pharmacokinetic study in mice indicated that chrysophanol nanoparticle injection showed high bioavailability compared to the free chrysophanol. Also, in vivo study revealed that chrysophanol nanoparticles obviously reduced tumor volume and weight. In conclusion, the data above suggested that chrysophanol nanoparticles might be effective to prevent human prostate cancer progression.

An overview of benzo[b]thiophene-based medicinal chemistry

Among sulfur containing heterocycles, benzothiophene and its derivatives are at the focus as these candidates have structural similarities with active compounds to develop new potent lead molecules in drug design. Benzo[b]thiophene scaffold is one of the privileged structures in drug discovery as this core exhibits various biological activities allowing them to act as anti-microbial, anti-cancer, anti-inflammatory, anti-oxidant, anti-tubercular, anti-diabetic, anti-convulsant agents and many more. Further, numerous benzothiophene-based compounds as clinical drugs have been extensively used to treat various types of diseases with high therapeutic potency, which has led to their extensive developments. Due to the wide range of biological activities of benzothiophene, their structure activity relationships (SAR) have generated interest among medicinal chemists, and this has culminated in the discovery of several lead molecules against numerous diseases. The present review is endeavoring to highlight the progress in the various pharmacological activities of benzo[b]thiophene derivatives. It is hoped that this review will be helpful for new thoughts in the quest for rational designs of more active and less toxic benzothiophene-based medicinal drugs, as well as more effective diagnostic agents and pathologic probes. Also, SAR studies that highlight the chemical groups responsible for evoking the potential activities of benzothiophene derivatives are studied and compared.

Effect of Class II HDAC inhibition on glutamate transporter expression and survival in SOD1-ALS mice

Transcriptional deregulation emerges as a key pathogenetic mechanism in ALS pathogenesis, and non-class-specific histone deacetylase (HDACs) inhibitors proved of therapeutic efficacy in preclinical models of ALS. When tested in patients, however, these drugs failed, probably because of a lack of selectivity toward pathogenetic HDACs. Here, we studied the effects of MC1568, an inhibitor of Class-II HDACs which have been reported to contribute to ALS pathogenesis. We focused on transcriptional regulation of glutamate transporter EAAT2, whose reduced expression may contribute to motor neuron degeneration in ALS. We report that MC1568 highly increased EAAT2 transcripts in primary cultures of mouse glia, but these increases did not correlate with increased glutamate uptake capacity. Accordingly, we found that MC1568 augmented protein expression of EAAT2 together with its sumoylation, a post-translational modification typically altering protein function and localization. When tested in SOD1G93A mice, however, MC1568 fully restored the reduced spinal cord expression of EAAT2 and glutamate uptake up to control levels. A prolonged treatment with MC1568 (from onset to end stage) was unable to prolong survival of mice. Data reveal a key role of Class-II HDACs in expression and function of glutamate transporter, further corroborating preclinical and clinical evidence that the sole restoration of glutamate uptake is not of therapeutic relevance to ALS therapy.

The possible prognostic role of histone deacetylase and transforming growth factor β/Smad signaling in high grade gliomas treated by radio-chemotherapy: a preliminary immunohistochemical study

Glioblastoma (GBM) is the most common and aggressive tumor of the central nervous system. Unfortunately, patients affected by this disease have a very poor prognosis, due to high level of invasiveness and resistance to standard therapies. Although the molecular profile of GBM has been extensively investigated, the events responsible for its pathogenesis and progression remain largely unknown. Histone Deacetylases (HDAC) dependent epigenetic modifications and transforming growth factor (TGF)-β/Smad pathway seem to play an important role in GBM tumorigenesis, resistance to common therapies and poor clinical outcome. The aim of this study was to evaluate the involvement and the possible interaction between these two molecular cascades in the pathogenesis and prognosis of GBM. Immunohistochemistry (IHC) was performed on microdissected GBM samples, collected from 14 patients (6 men and 8 women) ranging in age from 43 to 74 years. The patients were previously divided, on the basis of their overall survival (OS), into two groups: short and long OS. Patients with poor prognosis showed hyperexpression of HDAC4 and HDAC6, an activation of the TGF-β/Smad pathway, with high levels of IL-13, SMAD2, PDGF and MMP3 expression, compared to the long survivors. The short OS group exhibits a decrease in SMAD7 expression and also low levels of p21 immunostaining, which represents a common target of the two pathways. The IHC data was confirmed by quantitative analysis and Immunoblotting. Our preliminary results suggest that both HDAC4 and HDAC6 together with the TGF-β/Smad pathway may be involved in progression of GBM and this cross talking could be a useful prognostic marker in this deadly disease.

The Impact of Environmental Factors in Influencing Epigenetics Related to Oxidative States in the Cardiovascular System

Oxidative states exert a significant influence on a wide range of biological and molecular processes and functions. When their balance is shifted towards enhanced amounts of free radicals, pathological phenomena can occur, as the generation of reactive oxygen species (ROS) in tissue microenvironment or in the systemic circulation can be detrimental. Epidemic chronic diseases of western societies, such as cardiovascular disease, obesity, and diabetes correlate with the imbalance of redox homeostasis. Current advances in our understanding of epigenetics have revealed a parallel scenario showing the influence of oxidative stress as a major regulator of epigenetic gene regulation via modification of DNA methylation, histones, and microRNAs. This has provided both the biological link and a potential molecular explanation between oxidative stress and cardiovascular/metabolic phenomena. Accordingly, in this review, we will provide current insights on the physiological and pathological impact of changes in oxidative states on cardiovascular disorders, by specifically focusing on the influence of epigenetic regulation. A special emphasis will highlight the effect on epigenetic regulation of human's current life habits, external and environmental factors, including food intake, tobacco, air pollution, and antioxidant-based approaches. Additionally, the strategy to quantify oxidative states in humans in order to determine which biological marker could best match a subject's profile will be discussed.

HDAC inhibitors show differential epigenetic regulation and cell survival strategies on p53 mutant colon cancer cells

Besides inactivating tumour suppressor activity in cells, mutations in p53 confer significant oncogenic functions and promote metastasis and resistance to anticancer therapy. A variety of therapies involving genetic and epigenetic signalling events regulate tumorogenesis and progression in such cases. Pharmacological interventions with HDAC inhibitors have shown promise in therapy. This work explores the changes in efficacy of the four HDAC inhibitors SAHA, MS-275, valproic acid and sodium butyrate on a panel of colon cancer cell lines - HCT116 (p53 wt), HCT116 p53-/-, HT29 and SW480 (with mutations in p53). Clonogenic assays, gene profiling and epigenetic expression done on these cells point to p53 dependent differential activity of the 4 HDAC inhibitors which also elevate methylation levels in p53 mutant cell lines. In silico modelling establishes the alterations in interactions that lead to such differential activity of valproic acid, one of the inhibitors considered for the work. Molecular Dynamic simulations carried out on the valproic acid complex ensure stability of the complex. This work establishes a p53 dependent epigenetic signalling mechanism triggered by HDAC inhibition expanding the scope of HDAC inhibitors in adjuvant therapy for p53 mutant tumours.

Inhibition of MDA-MB-231 breast cancer cell proliferation and tumor growth by apigenin through induction of G2/M arrest and histone H3 acetylation-mediated p21WAF1/CIP1 expression

Apigenin (4',5,7-trihydroxyflavone), a flavonoid commonly found in fruits and vegetables, has anticancer properties in various malignant cancer cells. However, the molecular basis of the anticancer effect remains to be elucidated. In this study, we investigated the cellular mechanisms underlying the induction of cell cycle arrest by apigenin. Our results showed that apigenin at the nonapoptotic induction concentration inhibited cell proliferation and induced cell cycle arrest at the G2/M phase in the MDA-MB-231 breast cancer cell line. Immunoblot analysis indicated that apigenin suppressed the expression of cyclin A, cyclin B, and cyclin-dependent kinase-1 (CDK1), which control the G2-to-M phase transition in the cell cycle. In addition, apigenin upregulated p21^WAF1/CIP1 and increased the interaction of p21^WAF1/CIP1 with proliferating cell nuclear antigen (PCNA), which inhibits cell cycle progression. Furthermore, apigenin significantly inhibited histone deacetylase (HDAC) activity and induced histone H3 acetylation. The subsequent chromatin immunoprecipitation (ChIP) assay indicated that apigenin increased acetylation of histone H3 in the p21^WAF1/CIP1 promoter region, resulting in the increase of p21^WAF1/CIP1 transcription. In a tumor xenograft model, apigenin effectively delayed tumor growth. In these apigenin-treated tumors, we also observed reductions in the levels of cyclin A and cyclin B and increases in the levels of p21^WAF1/CIP1 and acetylated histone H3. These findings demonstrate for the first time that apigenin can be used in breast cancer prevention and treatment through epigenetic regulation. © 2016 Wiley Periodicals, Inc. Environ Toxicol 32: 434-444, 2017.

Histone deacetylase inhibitor induces cell apoptosis and cycle arrest in lung cancer cells via mitochondrial injury and p53 up-acetylation

The reversibility of non-genotoxic phenotypic changes has been explored in order to develop novel preventive and therapeutic approaches for cancer. Quisinostat (JNJ-26481585), a novel second-generation histone deacetylase inhibitor (HDACi), has efficient therapeutic actions on non-small cell lung cancer (NSCLC) cell. The present study aims at investigating underlying molecular mechanisms involved in the therapeutic activity of quisinostat on NSCLC cells. We found that quisinostat significantly inhibited A549 cell proliferation in dose- and time-dependent manners. Up-acetylation of histones H3 and H4 and non-histone protein α-tubulin was induced by quisinostat treatment in a nanomolar concentration. We also demonstrated that quisinostat increased reactive oxygen species (ROS) production and destroyed mitochondrial membrane potential (ΔΨm), inducing mitochondria-mediated cell apoptosis. Furthermore, exposure of A549 cells to quisinostat significantly suppressed cell migration by inhibiting epithelial-mesenchymal transition (EMT) process. Bioinformatics analysis indicated that effects of quisinostat on NSCLC cells were associated with activated p53 signaling pathway. We found that quisinostat increased p53 acetylation at K382/K373 sites, upregulated the expression of p21^(Waf1/Cip1), and resulted in G1 phase arrest. Thus, our results suggest that the histone deacetylase can be a therapeutic target of NSCLC to discover and develop a new category of therapy for lung cancer.