Histone deacetylases function as novel potential therapeutic targets for cancer

HDAC inhibitors: Promising agents for leukemia treatment

The essential role of epigenetic modification in the pathogenesis of a series of cancers have gradually been recognized. Histone deacetylase (HDACs), as well-known epigenetic modulators, are responsible for DNA repair, cell proliferation, differentiation, apoptosis and angiogenesis. Studies have shown that aberrant expression of HDACs is found in many cancer types. Thus, inhibition of HDACs has provided a promising therapeutic approach alternative for these patients. Since HDAC inhibitor (HDACi) vorinostat was first approved by the Food and Drug Administration (FDA) for treating cutaneous T-cell lymphoma (CTCL) in 2006, the combination of HDAC inhibitors with other molecules such as chemotherapeutic drugs has drawn much attention in current cancer treatment, especially in hematological malignancies therapy. Up to now, there have been more than twenty HDAC inhibitors investigated in clinic trials with five approvals being achieved. Indeed, Histone deacetylase inhibitors promote or enhance several different anticancer mechanisms and therefore are in evidence as potential antileukemia agents. In this review, we will focus on possible mechanisms by how HDAC inhibitors exert therapeutic benefit and their clinical utility in leukemia.

Epigenetic drugs as new emerging therapeutics: What is the scale's orientation of application and challenges?

Epigenetics is the study of heritable changes in gene expression or function without altering the DNA sequence. Important factors are part of epigenetic events, such as methylation, DNA histone rearrangements, nucleosome transposition, and non-coding RNAs. Dysregulated epigenetic mechanics are associated with various cancers' initiation, development, and metastasis. It is known that the occurrence and development of cancer can be controlled by regulating unexpected epigenetic events. Epi-drugs are used singly or in combination with chemotherapy and enhance antitumor activity, reduce drug resistance, and stimulate the host immune response. Despite these benefits, epigenetic therapy as a single therapy or in combination with other drugs leads to adverse effects. This review article introduces and compares the advantages, disadvantages, and side effects of using these drugs for the first time since their introduction. Also, this article describes the mechanism of action of various epigenetic drugs. Recommendations for future use of epigenetic drugs as cancer therapeutics are suggested as an overall conclusion.

Efficacy and safety of histone deacetylase inhibitors in peripheral T-cell lymphoma: a systematic review and meta-analysis on prospective clinical trials

Background

The overall survival of peripheral T-cell lymphoma (PTCL) is dismal. Histone deacetylase (HDAC) inhibitors have exhibited promising treatment outcomes for PTCL patients. Therefore, this work aims to systematically evaluate the treatment outcome and safety profile of HDAC inhibitor-based treatment for untreated and relapsed/refractory (R/R) PTCL patients.

Methods

The prospective clinical trials of HDAC inhibitors for the treatment of PTCL were searched on the Web of Science, PubMed, Embase, ClinicalTrials.gov, and Cochrane Library database. The pooled overall response rate, complete response (CR) rate, and partial response rate were measured. The risk of adverse events was evaluated. Moreover, the subgroup analysis was utilized to assess the efficacy among different HDAC inhibitors and efficacy in different PTCL subtypes.

Results

For untreated PTCL, 502 patients in seven studies were involved, and the pooled CR rate was 44% (95% CI, 39-48%). For R/R PTCL patients, there were 16 studies included, and the CR rate was 14% (95% CI, 11-16%). The HDAC inhibitor-based combination therapy exhibited better efficacy when compared with HDAC inhibitor monotherapy for R/R PTCL patients (P = 0.02). In addition, the pooled CR rate was 17% (95% CI, 13-22%), 10% (95% CI, 5-15%), and 10% (95% CI, 5-15%) in the romidepsin, belinostat, and chidamide monotherapy subgroups, respectively. In the R/R angioimmunoblastic T-cell lymphoma subgroup, the pooled ORR was 44% (95% CI, 35-53%), higher than other subtypes. A total of 18 studies were involved in the safety assessment of treatment-related adverse events. Thrombocytopenia and nausea were the most common hematological and non-hematological adverse events, respectively.

Conclusion

This meta-analysis demonstrated that HDAC inhibitors were effective treatment options for untreated and R/R PTCL patients. The combination of HDAC inhibitor and chemotherapy exhibited superior efficacy to HDAC inhibitor monotherapy in the R/R PTCL setting. Additionally, HDAC inhibitor-based therapy had higher efficacy in angioimmunoblastic T-cell lymphoma patients than that in other subtypes.

Oncogenic BRAF and p53 Interplay in Melanoma Cells and the Effects of the HDAC Inhibitor ITF2357 (Givinostat)

Oncogenic BRAF mutations have been widely described in melanomas and promote tumour progression and chemoresistance. We previously provided evidence that the HDAC inhibitor ITF2357 (Givinostat) targets oncogenic BRAF in SK-MEL-28 and A375 melanoma cells. Here, we show that oncogenic BRAF localises to the nucleus of these cells, and the compound decreases BRAF levels in both the nuclear and cytosolic compartments. Although mutations in the tumour suppressor p53 gene are not equally frequent in melanomas compared to BRAF, the functional impairment of the p53 pathway may also contribute to melanoma development and aggressiveness. To understand whether oncogenic BRAF and p53 may cooperate, a possible interplay was considered in the two cell lines displaying a different p53 status, being p53 mutated into an oncogenic form in SK-MEL-28 and wild-type in A375 cells. Immunoprecipitation revealed that BRAF seems to preferentially interact with oncogenic p53. Interestingly, ITF2357 not only reduced BRAF levels but also oncogenic p53 levels in SK-MEL-28 cells. ITF2357 also targeted BRAF in A375 cells but not wild-type p53, which increased, most likely favouring apoptosis. Silencing experiments confirmed that the response to ITF2357 in BRAF-mutated cells depends on p53 status, thus providing a rationale for melanoma-targeted therapy.

Knockdown of sirtuin6 positively regulates acetylation of DNMT1 to inhibit NOTCH signaling pathway in non-small cell lung cancer cell lines

BACKGROUND AND AIM

Sirtuin proteins (1-7) are nicotinamide adenine dinucleotide (NAD)-dependent deacetylases and ADP-ribosyl transferases (class III histone deacetylase enzymes (HDAC)) mainly involved in the removal of the acetyl group from histone proteins. SIRT6, one of the sirtuins, plays a major role in cancer progression in many types of cancer conditions. We recently reported that SIRT6 acts as an oncogene in NSCLC; thus, silencing of SIRT6 inhibits cell proliferation and induces apoptosis in NSCLC cell lines. NOTCH signaling has been reported to be involved in cell survival and regulates cell proliferation and differentiation. However, recent studies from different groups have converged on the notion that NOTCH1 may be an important oncogene in NSCLC. The abnormal expression of NOTCH signaling pathway members is a relatively frequent event in patients with NSCLC. SIRT6 and the NOTCH signaling pathway might play a critical role in tumorigenesis since they are highly expressed in NSCLC. This study has been performed to explore the exact mechanism by which SIRT6 inhibits cell proliferation and induces the apoptosis of NSCLC cell lines and its correlation with NOTCH signaling.

MAIN METHODS

In vitro experiments with human NSCLC cells have been performed. Immunocytochemistry study was used to analyze the expression of NOTCH1 and DNMT1 in A549 and NCI-H460 cell lines. RT-qPCR, Western Blot, Methylated DNA specific PCR, and Co-Immunoprecipitation were performed to explore the key events in the regulation of NOTCH signaling by silencing SIRT6 in NSCLC cell lines.

KEY FINDINGS

The findings of this study suggest that silencing of SIRT6 significantly promotes the acetylation status of DNMT1 and stabilizes it. Consequently, acetylated DNMT1 translocates into the nucleus and methylates the NOTCH1 promoter region, resulting in the hindering of NOTCH1-mediated NOTCH signaling.

Inhibition of histone deacetylase 6 destabilizes ERK phosphorylation and suppresses cancer proliferation via modulation of the tubulin acetylation-GRP78 interaction

BACKGROUND

The leading cause of cancer-related mortality worldwide is lung cancer, and its clinical outcome and prognosis are still unsatisfactory. The understanding of potential molecular targets is necessary for clinical implications in precision diagnostic and/or therapeutic purposes. Histone deacetylase 6 (HDAC6), a major deacetylase enzyme, is a promising target for cancer therapy; however, the molecular mechanism regulating cancer pathogenesis is largely unknown.

METHODS

The clinical relevance of HDAC6 expression levels and their correlation with the overall survival rate were analyzed based on the TCGA and GEO databases. HDAC6 expression in clinical samples obtained from lung cancer tissues and patient-derived primary lung cancer cells was evaluated using qRT-PCR and Western blot analysis. The potential regulatory mechanism of HDAC6 was identified by proteomic analysis and validated by immunoblotting, immunofluorescence, microtubule sedimentation, and immunoprecipitation-mass spectrometry (IP-MS) assays using a specific inhibitor of HDAC6, trichostatin A (TSA) and RNA interference to HDAC6 (siHDAC6). Lung cancer cell growth was assessed by an in vitro 2-dimensional (2D) cell proliferation assay and 3D tumor spheroid formation using patient-derived lung cancer cells.

RESULTS

HDAC6 was upregulated in lung cancer specimens and significantly correlated with poor prognosis. Inhibition of HDAC6 by TSA and siHDAC6 caused downregulation of phosphorylated extracellular signal-regulated kinase (p-ERK), which was dependent on the tubulin acetylation status. Tubulin acetylation induced by TSA and siHDAC6 mediated the dissociation of p-ERK on microtubules, causing p-ERK destabilization. The proteomic analysis demonstrated that the molecular chaperone glucose-regulated protein 78 (GRP78) was an important scaffolder required for p-ERK localization on microtubules, and this phenomenon was significantly inhibited by either TSA, siHDAC6, or siGRP78. In addition, suppression of HDAC6 strongly attenuated an in vitro 2D lung cancer cell growth and an in vitro 3D patient derived-lung cancer spheroid growth.

CONCLUSIONS

HDAC6 inhibition led to upregulate tubulin acetylation, causing GRP78-p-ERK dissociation from microtubules. As a result, p-ERK levels were decreased, and lung cancer cell growth was subsequently suppressed. This study reveals the intriguing role and molecular mechanism of HDAC6 as a tumor promoter, and its inhibition represents a promising approach for anticancer therapy.

Depsipeptides Targeting Tumor Cells: Milestones from In Vitro to Clinical Trials

Cancer is currently considered one of the most threatening diseases worldwide. Diet could be one of the factors that can be enhanced to comprehensively address a cancer patient's condition. Unfortunately, most molecules capable of targeting cancer cells are found in uncommon food sources. Among them, depsipeptides have emerged as one of the most reliable choices for cancer treatment. These cyclic amino acid oligomers, with one or more subunits replaced by a hydroxylated carboxylic acid resulting in one lactone bond in a core ring, have broadly proven their cancer-targeting efficacy, some even reaching clinical trials and being commercialized as "anticancer" drugs. This review aimed to describe these depsipeptides, their reported amino acid sequences, determined structure, and the specific mechanism by which they target tumor cells including apoptosis, oncosis, and elastase inhibition, among others. Furthermore, we have delved into state-of-the-art in vivo and clinical trials, current methods for purification and synthesis, and the recognized disadvantages of these molecules. The information collated in this review can help researchers decide whether these molecules should be incorporated into functional foods in the near future.

Transcription suppression is mediated by the HDAC1-Sin3 complex in Xenopus nucleoplasmic extract

Modification of histones provides a dynamic mechanism to regulate chromatin structure and access to DNA. Histone acetylation, in particular, plays a prominent role in controlling the interaction between DNA, histones, and other chromatin-associated proteins. Defects in histone acetylation patterns interfere with normal gene expression and underlie a wide range of human diseases. Here, we utilize Xenopus egg extracts to investigate how changes in histone acetylation influence transcription of a defined gene construct. We show that inhibition of histone deacetylase 1 and 2 (HDAC1/2) specifically counteracts transcription suppression by preventing chromatin compaction and deacetylation of histone residues H4K5 and H4K8. Acetylation of these sites supports binding of the chromatin reader and transcription regulator BRD4. We also identify HDAC1 as the primary driver of transcription suppression and show that this activity is mediated through the Sin3 histone deacetylase complex. These findings highlight functional differences between HDAC1 and HDAC2, which are often considered to be functionally redundant, and provide additional molecular context for their activity.

Anti-multiple myeloma potential of resynthesized belinostat derivatives: an experimental study on cytotoxic activity, drug combination, and docking studies

Multiple myeloma is a deadly cancer that is a complex and multifactorial disease. In the present study, 12 belinostat derivatives (four resynthesized and eight new), HDAC inhibitors, were resynthesized via either Knoevenagel condensation, or Wittig reaction, or Heck reaction. Then an evaluation of the antiproliferative activities against myeloma cells MOPC-315 was carried out. Amongst them, compound 7f was the most bioactive compound with an IC₅₀ of 0.090 ± 0.016 μM, being 3.5-fold more potent than the reference belinostat (IC₅₀ = 0.318 ± 0.049 μM). Furthermore, we also confirmed the inhibitory activity of 7f in a cellular model. Additionally, we found that the inhibitory activity of 7f against histone deacetylase 6 catalytic activity (HDAC6) is more potent than that of belinostat. Finally, we observed the strong synergistic interaction between the derivative 7f and the proteasome bortezomib inhibitor (CI = 0.26), while belinostat and bortezomib showed synergism with a CI value of 0.36. Taken together, the above results suggest that 7f is a promising HDAC inhibitor deserving further investigation.

Comprehensive Analysis of Histone Modifications in Hepatocellular Carcinoma Reveals Different Subtypes and Key Prognostic Models

Histone modification, an important epigenetic mechanism, is related to the carcinogenesis of hepatocellular carcinoma (HCC). In three datasets, we screened 88 epigenetic-dysregulated PCGs (epi-PCGs) , which were significantly associated with HCC survival and could cluster HCC into three molecular subtypes. These subtypes were associated with prognosis, immunomodulatory alterations, and response to different treatment strategies. Based on 88 epi-PCGs in the TCGA training set, a risk prediction model composed of 4 epi-PCGs was established. The model was closely related to the clinicopathological features and showed a strong predictive ability in different clinical subgroups. In addition, the risk prediction model was an independent prognostic factor for patients with HCC. The significance of epi-PCGs in HCC is revealed by our data analysis.

miR-589-5p Inhibits Cell Proliferation by Targeting Histone Deacetylase 3 in Triple Negative Breast Cancer

BACKGROUND

Histone deacetylase 3 (HDAC3) is a potential oncogene that is significantly up-regulated in patients with breast cancer. MicroRNAs (miRs) are a group of small non-coding and regulatory RNAs which have recently been proposed as promising molecules for breast cancer target therapy. In the current study, we investigated the impact of miR-589-5p/ HDAC3 axis on cancer cell development in triple negative breast cancer (TNBC) cells.

METHODS

In-silico analysis determined that miR-589-5p potentially targets HDAC3. We evaluated the HDAC3 and mir-589-5p expression levels in clinical samples and breast cancer cell lines including MDA-MB-231, MDA-MB-468, MCF-7 and MCF-10A. HDAC3 was knocked out to investigate its role on cancer cell progression. Anti-cancerous role of the miR-589-5p was assessed using an expression vector. We evaluated possible alteration in the cell cycle progression, cell viability and cell proliferation, after transient transfection.

RESULTS

HDAC3 was over-expressed in TNBC clinical samples and breast cancer cell lines compared to non-cancerous controls while miR-589-5p was down regulated in cancer cells. Suppression of HDAC3 decreased the cell viability, cell proliferation and colony formation. Similar results were observed after over-expression of the miR-589-5p. Dual-Luciferase reporter assay confirmed the direct targeting of HDAC3 by miR-589-5p.

CONCLUSION

Our results showed that miR-589-5p mediates its anti-proliferative effects on breast cancer cells via targeting HDAC3. These findings suggest that the miR-589-5p/ HDAC3 axis could be considered as a possible therapeutic strategy in TNBC.

Targeting Histone Deacetylases in Idiopathic Pulmonary Fibrosis: A Future Therapeutic Option

Idiopathic pulmonary fibrosis (IPF) is a progressive and fatal lung disease with limited therapeutic options, and there is a huge unmet need for new therapies. A growing body of evidence suggests that the histone deacetylase (HDAC) family of transcriptional corepressors has emerged as crucial mediators of IPF pathogenesis. HDACs deacetylate histones and result in chromatin condensation and epigenetic repression of gene transcription. HDACs also catalyse the deacetylation of many non-histone proteins, including transcription factors, thus also leading to changes in the transcriptome and cellular signalling. Increased HDAC expression is associated with cell proliferation, cell growth and anti-apoptosis and is, thus, a salient feature of many cancers. In IPF, induction and abnormal upregulation of Class I and Class II HDAC enzymes in myofibroblast foci, as well as aberrant bronchiolar epithelium, is an eminent observation, whereas type-II alveolar epithelial cells (AECII) of IPF lungs indicate a significant depletion of many HDACs. We thus suggest that the significant imbalance of HDAC activity in IPF lungs, with a “cancer-like” increase in fibroblastic and bronchial cells versus a lack in AECII, promotes and perpetuates fibrosis. This review focuses on the mechanisms by which Class I and Class II HDACs mediate fibrogenesis and on the mechanisms by which various HDAC inhibitors reverse the deregulated epigenetic responses in IPF, supporting HDAC inhibition as promising IPF therapy.

Lysine Acetylation/Deacetylation Modification of Immune-Related Molecules in Cancer Immunotherapy

As major post-translational modifications (PTMs), acetylation and deacetylation are significant factors in signal transmission and cellular metabolism, and are modulated by a dynamic process via two pivotal categories of enzymes, histone acetyltransferases (HATs) and histone deacetylases (HDACs). In previous studies, dysregulation of lysine acetylation and deacetylation has been reported to be associated with the genesis and development of malignancy. Scientists have recently explored acetylation/deacetylation patterns and prospective cancer therapy techniques, and the FDA has approved four HDAC inhibitors (HDACi) to be used in clinical treatment. In the present review, the most recent developments in the area of lysine acetylation/deacetylation alteration in cancer immunotherapy were investigated. Firstly, a brief explanation of the acetylation/deacetylation process and relevant indispensable enzymes that participate therein is provided. Subsequently, a multitude of specific immune-related molecules involved in the lysine acetylation/deacetylation process are listed in the context of cancer, in addition to several therapeutic strategies associated with lysine acetylation/deacetylation modification in cancer immunotherapy. Finally, a number of prospective research fields related to cancer immunotherapy concepts are offered with detailed analysis. Overall, the present review may provide a reference for researchers in the relevant field of study, with the aim of being instructive and meaningful to further research as well as the selection of potential targets and effective measures for future cancer immunotherapy strategies.

Role of ANO1 in tumors and tumor immunity

Dysregulation of gene amplification, cell-signaling-pathway transduction, epigenetic and transcriptional regulation, and protein interactions drives tumor-cell proliferation and invasion, while ion channels also play an important role in the generation and development of tumor cells. Overexpression of Ca²⁺-activated Cl- channel anoctamin 1 (ANO1) is shown in numerous cancer types and correlates with poor prognosis. However, the mechanisms involved in ANO1-mediated malignant cellular transformation and the role of ANO1 in tumor immunity remain unknown. In this review, we discuss recent studies to determine the role of ANO1 in tumorigenesis and provide novel insights into the role of ANO1 in the context of tumor immunity. Furthermore, we analyze the roles and potential mechanisms of ANO1 in different types of cancers, and provide novel notions for the role of ANO1 in the tumor microenvironment and for potential use of ANO1 in clinical applications. Our review shows that ANO1 is involved in tumor immunity and microenvironment, and may, therefore, be an effective biomarker and therapeutic drug target.

Suppression of histone deacetylase 1 by JSL-1 attenuates the progression and metastasis of cholangiocarcinoma via the TPX2/Snail axis

Histone deacetylases (HDACs) are entwined with the pathogenesis of various cancers and potentially serve as promising therapeutic targets. Herein, we intend to explore the potential role of HDAC1 inhibitor (JSL-1) in the tumorigenesis and metastasis of cholangiocarcinoma (CC) and to highlight the molecular basis of its function. As shown by bioinformatics analysis and immunohistochemical detection, high HDAC1 expression was witnessed in CC tissues relative to matched controls from patients with cholecystitis. The molecular network that HDAC1 silencing reduced the enrichment of HDAC1 and Snail on the TPX2 promoter was identified using immunoprecipitation and chromatin immunoprecipitation assays. Both short hairpin RNA (shRNA)-mediated knockdown of HDAC1 and JSL-1 treatment exhibited anti-proliferative, anti-migration and anti-invasion effects on CC cells through downregulation of TPX2. The in vivo xenograft model was developed in nude mice. Consistently, the anti-tumorigenic and anti-metastatic properties of shRNA against HDAC1 and HDAC1 inhibitor were validated in the in vivo settings. Taken together, our data supported the notion that HDAC1 inhibitor retards the initiation and development of CC via mediating the TPX2/Snail axis, highlighting the anti-tumor molecular network functioned in CC.

An activatable and tumor-targeting NIR fluorescent probe for imaging of histone deacetylase 6 in cancer cells and in vivo

An activatable and tumor-targeting near-infrared (NIR) fluorescent probe CyAc-RGD was synthesized for the imaging of histone deacetylase 6 (HDAC6). The probe exhibited higher sensitivity and specificity for HDAC6 detection in cancer cells. Moreover, CyAc-RGD demonstrated good tumor-targeting ability and realized HDAC6 imaging in vivo.

β-Carboline tethered cinnamoyl 2-aminobenzamides as class I selective HDAC inhibitors: Design, synthesis, biological activities and modelling studies

The effect of β-carboline motif as cap for HDAC inhibitors containing cinnamic acid as linker and benzamides as zinc binding group was examined in this study. A series of β-carboline-cinnamide conjugates have been synthesized and evaluated for their HDAC inhibitory activity and in vitro cytotoxicity against different human cancer cell lines. Almost all the compounds exhibited superior HDAC inhibitory activity than the standard drug Entinostat for in vitro enzymatic assay. Among the tested compounds, 7h displayed a noteworthy potency with an IC₅₀ value of 0.70 ± 0.15 µM against HCT-15 cell line when compared to the standard drug Entinostat (IC₅₀ of 3.87 ± 0.62 µM). The traditional apoptosis assays such as nuclear morphological alterations, AO/EB, DAPI, and Annexin-V/PI staining revealed the antiproliferative activity of 7h while depolarization of mitochondrial membrane potential by JC-1 was observed in dose-dependent manner. Cell cycle analysis also unveiled the typical accumulation of cells in G₂M phase and sub-G₁/S phase arrest. In addition, immunoblot analysis for compound 7h on HCT-15 indicated selective inhibition of the protein expression of class I HDAC 2 and 3 isoforms. Molecular docking analysis of compound 7h revealed that it can prominent binding with the active pocket of the HDAC 2. These finding suggest that the compound 7h can be a promising lead candidate for further investigation in the development of novel anti-cancer drug potentially inhibiting HDACs.

Pharmacotherapy for SARS-CoV-2 and Seizures for drug repurposing presumed on Mechanistic Targets

BACKGROUND

The currently circulating novel SARS-CoV-2 coronavirus disease (COVID-19) has brought the whole world to a standstill. Recent studies have deciphered the viral genome structure, epidemiology and are in the process of unveiling multiple mechanisms of pathogenesis. Apart from atypical pneumonia and lung disease manifestations, this disease has also been found to be associated with neurological symptoms, which include dizziness, headache, stroke, or seizures, among others. However, a possible direct or indirect association between SARS-CoV-2 and seizures is still not clear. In any manner, it may be of interest to analyze the drugs being used for viral infection in the background of epilepsy or vice versa.

OBJECTIVE

To identify the most credible drug candidate for COVID-19 in persons with epilepsy or COVID-19 patients experiencing seizures.

METHODS

A literature search for original and review articles was performed, and further, the Comparative Toxicogenomics Database was used to unearth the most credible drug candidate.

RESULTS

Our search based on common mechanistic targets affecting SARS-CoV-2 and seizures revealed ivermectin, dexamethasone, anakinra, and tocilizumab for protection against both COVID-19 and seizures. Amongst the antiseizure medications, we found valproic acid as the most probable pharmacotherapy for COVID-19 patients experiencing seizures.

CONCLUSION

These findings would hopefully provide the basis for initiating further studies on the pathogenesis and drug targeting strategies for this emerging infection accompanied with seizures or in people with epilepsy.

Histone Deacetylase Inhibitors and Papillary Thyroid Cancer

BACKGROUND/AIM

Papillary Thyroid Cancer (PTC) is the most common type of endocrine malignancy. Although PTC has an excellent prognosis, the recurrent or metastatic disease could affect patients' survival. Recent studies show that Histone Deacetylase Inhibitors (HDACIs) might be promising anticancer agents against PTC. The aim of this review is to evaluate the role of HDACIs as an additional modality in PTC treatment and to depict the latest trends of current research on this field.

MATERIALS AND METHODS

This literature review was performed using the MEDLINE database. The search strategy included terms: "thyroid cancer", "papillary", "HDAC", "histone", and "deacetylase".

RESULTS

Agents, such as Suberoyl Anilide Hydroxamic Acid, Trichostatin A, Valproic Acid, Sodium butyrate, Panobinostat, Belinostat, Romidepsin, CUDC907 and N-Hydroxy-7-(2-naphthylthio)-Hepanomide have shown promising anti-cancer effects on PTC cell lines but fail to trigger a major response in clinical trials.

CONCLUSION

HDACIs have no significant effect as monotherapy against PTC, but further research needs to be conducted in order to investigate their potential effect when used as an additional modality.

Ketogenic Diet in Cancer Prevention and Therapy: Molecular Targets and Therapeutic Opportunities

Although cancer is still one of the most significant global challenges facing public health, the world still lacks complementary approaches that would significantly enhance the efficacy of standard anticancer therapies. One of the essential strategies during cancer treatment is following a healthy diet program. The ketogenic diet (KD) has recently emerged as a metabolic therapy in cancer treatment, targeting cancer cell metabolism rather than a conventional dietary approach. The ketogenic diet (KD), a high-fat and very-low-carbohydrate with adequate amounts of protein, has shown antitumor effects by reducing energy supplies to cells. This low energy supply inhibits tumor growth, explaining the ketogenic diet's therapeutic mechanisms in cancer treatment. This review highlights the crucial mechanisms that explain the ketogenic diet's potential antitumor effects, which probably produces an unfavorable metabolic environment for cancer cells and can be used as a promising adjuvant in cancer therapy. Studies discussed in this review provide a solid background for researchers and physicians to design new combination therapies based on KD and conventional therapies.

Butyrate-containing structured lipids act on HDAC4, HDAC6, DNA damage and telomerase activity during promotion of experimental hepatocarcinogenesis

Hepatocellular carcinoma (HCC) presents with a high treatment resistance and poor prognosis. Early diagnosis and preventive approaches such as chemoprevention are essential for the HCC control. Therefore, we evaluated the chemopreventive effects of butyrate-containing structured lipids (STLs) administered during the promotion stage of hepatocarcinogenesis in rats submitted to the 'resistant hepatocyte' (RH) model. Administration of butyrate-containing STLs inhibited the incidence and mean number of visible hepatic nodules per rat and reduced the number and area of glutathione S-transferase placental form-positive (GST-P+) preneoplastic focal lesions in the livers. This was accompanied by the induction of apoptosis and an increased level of hepatic butyric acid. Treatment with butyrate-containing STLs resulted in increased histone H3 lysine 9 (H3K9) acetylation, reduction of total histone deacetylase (HDAC) activity, and lower levels of HDAC4 and HDAC6 proteins. The chemopreventive effect of butyrate-containing STLs was also associated with the increased nuclear compartmentalization of p53 protein and reduced expression of the Bcl-2 protein. In addition, rats treated with butyrate-containing STLs showed decreased DNA damage and telomerase activity in the livers. These results demonstrate that the suppressive activity of butyrate-containing STLs is associated with inhibition of elevated during hepatocarcinogenesis chromatin-modifying proteins HDAC4 and HDAC6, subcellular redistribution of the p53 protein, and decreased DNA damage and telomerase activity.

Romidepsin (FK228), A Histone Deacetylase Inhibitor and its Analogues in Cancer Chemotherapy

BACKGROUND

Human HDACs represent a group of enzymes able to modify histone and non-histone proteins, which interact with DNA to generate chromatin. The correlation between irregular covalent modification of histones and tumor development has been proved over the last decades. Therefore, HDAC inhibitors are considered as potential drugs in cancer treatment. Romidepsin (FK228), Belinostat (PXD-101), Vorinostat (SAHA), Panobinostat (LBH-589) and Chidamide were approved by FDA as novel antitumor agents.

OBJECTIVE

The aim of this review article is to highlight the structure-activity relationships of several FK228 analogues as HDAC inhibitors. In addition, the synergistic effects of a dual HDAC/PI3K inhibition by some derivatives have been investigated.

MATERIALS AND METHODS

PubMed, MEDLINE, CAPLUS, SciFinder Scholar database were considered by selecting articles which fulfilled the objectives of this review, dating from 2015 till present time.

RESULTS

HDAC inhibitors have a significant role in cancer pathogenesis and evolution. Class I HDAC isoforms are expressed in many tumor types, therefore, potent and selective Class I HDAC inhibitors are of great interest as candidate therapeutic agents with limited side effects. By structurebased optimization, several FK228 analogues [15 (FK-A5), 22, 23 and 26 (FK-A11)] were identified, provided with significant activity against Class I HDAC enzymes and dose dependent antitumor activity. Compound 26 was recognized as an interesting HDAC/PI3K dual inhibitor (IC₅₀ against p110α of 6.7 μM while for HDAC1 inhibitory activity IC₅₀ was 0.64 nM).

CONCLUSION

Romidepsin analogues HDAC inhibitors have been confirmed as useful anticancer agents. In addition, dual HDAC/PI3K inhibition showed by some of them exhibited synergistic effects in inducing apoptosis in human cancer cells. Further studies on FK228 analogues may positively contribute to the availability of potent agents in tumor treatment.

The clinical significance of histone deacetylase-8 in human breast cancer

Recent studies have shown that the histone deacetylase-8 (HDAC8), as one of the HDACs, regulates the expression and activity of various genes involved in cancer initiation and progression. The HDAC8 plays an epigenetic role to dysregulate expressions or to interact with transcription factors. Most researchers had focused on the HDAC 1-3 and 6, but today the HDAC8 isotype is a promising target in cancer therapy. Different studies, on breast cancer (BC) cells, have recently shown the HDAC8 overexpression and suggested its oncogenic potential. It seems that the HDAC8 could be a novel and promising target in breast cancer treatment. Some studies on BC demonstrated therapeutic properties of the inhibitors of HDAC8 such as suberoylanilide hydroxamic acid (SAHA), Trichostatin A, valproic acid, sodium butyrate, 1,3,4 oxadiazole with alanine hybrid [(R)-2-amino-N-((5-phenyl-1,3,4-oxadiazol-2-yl) methyl) propanamide (10b)], N-(2-Hydroxyphenyl)-2propylpentanamide (compound 2) and PCI-34051. In this review, we highlight the role and existing inhibitors of HDAC8 in BC pathogenesis and therapy.

Liver Cancer: Therapeutic Challenges and the Importance of Experimental Models

Liver cancer is one of the main causes of death related to cancer worldwide; its etiology is related with infections by C or B hepatitis virus, alcohol consumption, smoking, obesity, nonalcoholic fatty liver disease, diabetes, and iron overload, among other causes. Several kinds of primary liver cancer occur, but we will focus on hepatocellular carcinoma (HCC). Numerous cellular signaling pathways are implicated in hepatocarcinogenesis, including YAP-HIPPO, Wnt-β-catenin, and nuclear factor-κB (NF-κB); these in turn are considered novel therapeutic targets. In this review, the role of lipid metabolism regulated by peroxisome proliferator-activated receptor gamma (PPARγ) in the development of HCC will also be discussed. Moreover, recent evidence has been obtained regarding the participation of epigenetic changes such as acetylation and methylation of histones and DNA methylation in the development of HCC. In this review, we provide detailed and current information about these topics. Experimental models represent useful tools for studying the different stages of liver cancer and help to develop new pharmacologic treatments. Each model in vivo and in vitro has several characteristics and advantages to offer for the study of this disease. Finally, the main therapies approved for the treatment of HCC patients, first- and second-line therapies, are described in this review. We also describe a novel option, pirfenidone, which due to its pharmacological properties could be considered in the future as a therapeutic option for HCC treatment.

Studying Histone Deacetylase Inhibition and Apoptosis Induction of Psammaplin A Monomers with Modified Thiol Group

Psammaplin A (PsA) is a bromotyrosine disulfide dimer with histone deacetylase (HDAC) inhibition and acts through reduced monomer PsA-SH. We studied the connection of HDAC inhibition, cell growth inhibition, and apoptosis induction of PsA-SH by modifying the -SH group with deletion (6a) or replacement with hydroxamic acid (10b) or benzamide (12g). PsA-SH inhibits HDAC1/2/3 and 6a loses the HDAC inhibition ability. 10b inhibits HDAC1/2/3/6 while 12g shows selective inhibition of HDAC3. PsA-SH and 10b, but neither 6a nor 12g, induce apoptosis in human leukemia HL-60 cells associated with increased acetylation of Histone H3. PsA-SH and 10b inhibit growth of several solid tumor cell lines in vitro and Lewis lung cancer cell growth in vivo. PsA-SH is a simple scaffold for developing selective HDAC inhibitors and induces apoptosis through inhibiting HDAC1/2.

Apoptotic effects of valproic acid on miR-34a, miR-520h and HDAC1 gene in breast cancer

Identifying miRNAs involved in cancer and devising strategies to control their expression is a new therapeutic approach. Valproic acid (VPA) has attracted a lot of interest in cancer research. We evaluated the impact of VPA on the expression of miR-34a, miR-520h, and their target gene histone deacetylase 1 (HDAC1), as well as their relationship with apoptosis in breast cancer. First, through bioinformatics analyses, the possible target genes of miR-34a and miR-520h and their roles in apoptosis regulation were investigated. Then, miR-34a, miR-520h, and HDAC1 gene expression in tissues of breast cancer patients were determined using the qRT-PCR method. The anticancer impact of VPA on apoptosis and the expression levels of miR-34a, miR-520h, and HDAC1 gene were measured in MCF-7 and MDA-MB-231 cell lines. The bioinformatics analyses indicated that miR-34a and miR-520h might make a unique contribution in regulating the apoptosis pathway. The relative expression of miR-34a and miR-520h significantly decreased in cancer tissues, while the relative expression of HDAC1 increased. In the in vitro study, VPA led to apoptosis induction and increased lipid peroxidation products in breast cancer cells. Moreover, VPA increased the expression of miR- 34a and miR-520h and decreased HDAC1 expression in MCF-7 cells. In MDA-MB-231 cells, VPA decreased the expression of these miRNAs and increased the expression of HDAC1. It can be concluded that miR-34a and miR-520h are implicated in the apoptosis pathways, and thus, VPA can recruit as a possible option in breast cancer research due to its interference with epigenetic processes.

Histone Deacetylase Inhibitors as Multitarget-Directed Epi-Drugs in Blocking PI3K Oncogenic Signaling: A Polypharmacology Approach

Genetic mutations and aberrant epigenetic alterations are the triggers for carcinogenesis. The emergence of the drugs targeting epigenetic aberrations has provided a better outlook for cancer treatment. Histone deacetylases (HDACs) are epigenetic modifiers playing critical roles in numerous key biological functions. Inappropriate expression of HDACs and dysregulation of PI3K signaling pathway are common aberrations observed in human diseases, particularly in cancers. Histone deacetylase inhibitors (HDACIs) are a class of epigenetic small-molecular therapeutics exhibiting promising applications in the treatment of hematological and solid malignancies, and in non-neoplastic diseases. Although HDACIs as single agents exhibit synergy by inhibiting HDAC and the PI3K pathway, resistance to HDACIs is frequently encountered due to activation of compensatory survival pathway. Targeted simultaneous inhibition of both HDACs and PI3Ks with their respective inhibitors in combination displayed synergistic therapeutic efficacy and encouraged the development of a single HDAC-PI3K hybrid molecule via polypharmacology strategy. This review provides an overview of HDACs and the evolution of HDACs-based epigenetic therapeutic approaches targeting the PI3K pathway.

HMGB1: an important regulator of myeloid differentiation and acute myeloid leukemia as well as a promising therapeutic target

Abstract

High mobility group box 1 (HMGB1) is a non-histone nuclear protein which has been intensively studied in various physiological and pathological processes including leukemia. Here in this study, we further demonstrated that HMGB1 presents higher expression in the bone marrow mononuclear cells of acute myeloid leukemia (AML) patients compared with the normal controls and contributes to the AML pathogenesis and progression by inhibiting apoptosis, facilitating proliferation, and inducing myeloid differentiation blockade of AML cells. Mechanistic investigation revealed that transforming growth factor beta-induced (TGFBI) acts as a potential downstream target of HMGB1 and lentivirus-mediated knockdown of TGFBI expression impaired phorbol-12-myristate-13-acetate (PMA) and all-trans retinoic acid (ATRA)–induced myeloid differentiation of AML cell lines. On the other hand, chidamide, an orally histone deacetylase inhibitor, decreases HMGB1 expression significantly in AML cells with concomitant upregulation of TGFBI expression, and confers therapeutic effect on AML by inducing cell differentiation, apoptosis and inhibiting cell proliferation. In conclusion, our findings provide additional insights that HMGB1 is a promising therapeutic target of AML, and also present experimental evidence for the clinical application of chidamide as a novel agent in AML therapy by downregulating HMGB1 expression.

Key messages

HMGB1 induces cell proliferation and myeloid differentiation blockade and inhibits apoptosis of AML cells.

TGFBI acts as a potential target of HMGB1.

Chidamide, a selective HDAC inhibitor, confers promising therapeutic effect for AML via downregulating HMGB1 expression.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00109-020-01998-5.

Identification of key genes and important histone modifications in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the leading causes of cancer death in the world. It has been reported that HCC is closely related to the changes of histone modifications. However, finding histone modification patterns in key genes which related to HCC is still an important task. In our study, the patterns of 11 kinds of histone modifications in the promoter regions for the different types of genes were analyzed by hierarchical screening for hepatocyte (normal) cell line and HepG2 (tumor) cell line. The important histone modifications and their key modification regions in different types of genes were found. The results indicate that these important genes may play a pivotal role in the occurrence of HCC. By analyzing the differences of histone modifications and gene expression levels for these important genes between the two cell lines, we found that the signals of H3K4me3, H3K27ac, H3K9ac, and H3K4me2 in HCC are significantly stronger. The changed regions of important histone modifications in 17 key genes were also identified. For example, the H3K4me3 signals increased 150 times in regions (−1500, −500) bp and (0, 1000) bp of ARHGAP5 in tumor cell line than in normal cell line. Finally, a prognostic risk scoring model was constructed, and the effects of key genes on the prognosis of HCC were verified by the survival analysis. Our results may provide a more precise potential therapeutic targets for identifying key genes and histone modifications in HCC as new biomarkers.

Chidamide acts on the histone deacetylase-mediated miR-34a/Bcl-2 axis to regulate NB4 cell line proliferation and apoptosis

Acute promyelocytic leukemia (APL), a biologically and clinically distinct variant of acute myelogenous leukemia, is characterized by the fusion of the N-terminus of promyelocytic leukemia protein to the C terminus of retinoic acid receptor alpha, mostly due to chromosomal translocation t(15;17). Chidamide, a synthetic analogue of MS-275 identified from a group of benzamide-type compounds, has been found to have efficient anticancer activity in basic and clinical research studies. However, the concrete role and underlying mechanism of Chidamide in the treatment of APL has not been well characterized. Our data demonstrate that Chidamide inhibited the expression of histone deacetylase (HDAC) to induce apoptosis and suppress proliferation in NB4 cells. Mechanistically, Chidamide increases the expression of miR-34a by suppressing HDAC. Furthermore, B-cell lymphoma-2 (Bcl-2) is a direct target of miR-34a, the expression of which is regulated by miR-34a. Functionally, Chidamide inhibits cell proliferation and promotes apoptosis through miR-34a/Bcl-2. Chidamide exerts its anticancer effect via the HDAC-mediated miR-34a/Bcl-2 axis, providing potential targets for APL therapy.

2-O-Methylmagnolol, a Magnolol Derivative, Suppresses Hepatocellular Carcinoma Progression via Inhibiting Class I Histone Deacetylase Expression

Magnolia officinalis is widely used in Southeast Asian countries for the treatment of fever, headache, diarrhea, and stroke. Magnolol is a phenolic compound extracted from M. officinalis, with proven antibacterial, antioxidant, anti-inflammatory, and anticancer activities. In this study, we modified magnolol to synthesize a methoxylated derivative, 2-O-methylmagnolol (MM1), and investigated the use of MM1, and magnolol in the treatment of liver cancer. We found that both magnolol and MM1 exhibited inhibitory effects on the growth, migration, and invasion of hepatocellular carcinoma (HCC) cell lines and halted the cell cycle at the G1 phase. MM1 also demonstrated a substantially better tumor-suppressive effect than magnolol. Further analysis suggested that by inhibiting class I histone deacetylase expression in HCC cell lines, magnolol and MM1 induced p21 expression and p53 activation, thereby causing cell cycle arrest and inhibiting HCC cell growth, migration, and invasion. Subsequently, we verified the significant tumor-suppressive effects of magnolol and MM1 in an animal model. Collectively, these findings demonstrate the anti-HCC activities of magnolol and MM1 and their potential for clinical use.

PAICS contributes to gastric carcinogenesis and participates in DNA damage response by interacting with histone deacetylase 1/2

Phosphoribosylaminoimidazole carboxylase, phosphoribosylaminoimidazole succinocarboxamide synthetase (PAICS), an essential enzyme involved in de novo purine biosynthesis, is connected with formation of various tumors. However, the specific biological roles and related mechanisms of PAICS in gastric cancer (GC) remain unclear. In the present study, we identified for the first time that PAICS was significantly upregulated in GC and high expression of PAICS was correlated with poor prognosis of patients with GC. In addition, knockdown of PAICS significantly induced cell apoptosis, and inhibited GC cell growth both in vitro and in vivo. Mechanistic studies first found that PAICS was engaged in DNA damage response, and knockdown of PAICS in GC cell lines induced DNA damage and impaired DNA damage repair efficiency. Further explorations revealed that PAICS interacted with histone deacetylase HDAC1 and HDAC2, and PAICS deficiency decreased the expression of DAD51 and inhibited its recruitment to DNA damage sites by impairing HDAC1/2 deacetylase activity, eventually preventing DNA damage repair. Consistently, PAICS deficiency enhanced the sensitivity of GC cells to DNA damage agent, cisplatin (CDDP), both in vitro and in vivo. Altogether, our findings demonstrate that PAICS plays an oncogenic role in GC, which act as a novel diagnosis and prognostic biomarker for patients with GC.

Synthesis and Biological Evaluation of HDAC Inhibitors With a Novel Zinc Binding Group

Vorinostat (SAHA) with great therapeutic potential has been approved by the FDA for the treatment of cutaneous T-cell lymphoma as the first HDACs inhibitor, but the drawbacks associated with hydroxamic acid group (poor stability, easy metabolism, weak binding ability to class IIa isozymes, and poor selectivity) have been exposed during the continuous clinical application. Based on the pharmacophore of HDAC inhibitors, two series of compounds with novel zinc binding group (ZBG) were designed and synthesized, and the antitumor bioactivities were evaluated in four human cancer cell lines (A549, Hela, HepG2, and MCF-7). Among the synthesized compounds, compounds a6, a9, a10, b8, and b9 exhibited promising inhibitory activities against the selected tumor cell lines, especially compounds a9 and b8 on Hela's cytostatic activity (a9: IC₅₀ = 11.15 ± 3.24 μM; b8: IC₅₀ = 13.68 ± 1.31 μM). The enzyme inhibition assay against Hela extracts and HDAC1&6 subtypes showed that compound a9 had a certain broad-spectrum inhibitory activity, while compound b8 had selective inhibitory activity against HDAC6, which was consistent with Western blot results. In addition, the inhibitory mechanism of compounds a9 and b8 in HDAC1&6 were both compared through computational approaches, and the binding interactions between the compounds and the enzymes target were analyzed from the perspective of energy profile and conformation. In summary, the compounds with novel ZBG exhibited certain antitumor activities, providing valuable hints for the discovery of novel HDAC inhibitors.

Hydroxygenkwanin Inhibits Class I HDAC Expression and Synergistically Enhances the Antitumor Activity of Sorafenib in Liver Cancer Cells

Abnormal histone deacetylase (HDAC) expression is closely related to cancer development and progression. Many HDAC inhibitors have been widely used in cancer treatment; however, severe side effects often limit their clinical application. In this study, we attempted to identify natural compounds with HDAC inhibitory activity and low physiological toxicity and explored their feasibility and mechanisms of action in liver cancer treatment. A yeast screening system was used to identify natural compounds with HDAC inhibitory activity. Further, western blotting was used to verify inhibitory effects on HDAC in human liver cancer cell lines. Cell functional analysis was used to explore the effects and mechanisms and the in vitro results were verified in BALB/c nude mice. We found that hydroxygenkwanin (HGK), an extract from Daphne genkwa, inhibited class I HDAC expression, and thereby induced expression of tumor suppressor p21 and promoted acetylation and activation of p53 and p65. This resulted in the inhibition of growth, migration, and invasion of liver cancer cells and promoted cell apoptosis. Animal models revealed that HGK inhibited tumor growth in a synergistic manner with sorafenib. HGK inhibited class I HDAC expression and had low physiological toxicity. It has great potential as an adjuvant for liver cancer treatment and may be used in combination with anticancer drugs like sorafenib to improve therapeutic efficacy.

Zinc Dependent Histone Deacetylase Inhibitors in Cancer Therapeutics: Recent Update

BACKGROUND

Histone deacetylases (HDAC) are an important class of enzymes that play a pivotal role in epigenetic regulation of gene expression that modifies the terminal of core histones leading to remodelling of chromatin topology and thereby controlling gene expression. HDAC inhibitors (HDACi) counter this action and can result in hyperacetylation of histones, thereby inducing an array of cellular consequences such as activation of apoptotic pathways, generation of reactive oxygen species (ROS), cell cycle arrest and autophagy. Hence, there is a growing interest in the potential clinical use of HDAC inhibitors as a new class of targeted cancer therapeutics. Methodology and Result: Several research articles spanning between 2016 and 2017 were reviewed in this article and presently offer critical insights into the important strategies such as structure-based rational drug design, multi-parameter lead optimization methodologies, relevant SAR studies and biology of various class of HDAC inhibitors, such as hydroxamic acids, benzamides, cyclic peptides, aliphatic acids, summarising the clinical trials and results of various combination drug therapy till date.

CONCLUSION

This review will provide a platform to the synthetic chemists and biologists to cater the needs of both molecular targeted therapy and combination drug therapy to design and synthesize safe and selective HDAC inhibitors in cancer therapeutics.

HDAC Overexpression in a NUT Midline Carcinoma of the Parotid Gland with Exceptional Survival: A Case Report

NUT midline carcinoma (NMC) is a recently described entity with a predilection for young individuals, characterised by a rearrangement of NUT, most commonly with BRD4. It usually involves midline structures, with a minority of cases presenting outside the midline axis. Given its dismal prognosis, new molecularly targeted therapies (eg, HDAC inhibitors) are gaining ground, but the HDAC expression pattern remains unknown. We describe the exceptional evolution of a NMC arising in the parotid gland. A 34-year-old male presented with a rapidly growing 35 mm left-parotid mass. Parotidectomy and lymphadenectomy were performed. The tumour invaded the surrounding soft tissue and lay adjacent to the surgical margin. No lymph node metastases were identified. Histology revealed blue nests of undifferentiated cells merging with foci of necrosis and occasional abrupt foci of keratinising squamous epithelium. FISH analysis confirmed a rearrangement of NUT, but not of BRD4. A diagnosis of NMC was rendered. Currently, after adjuvant chemoradiotherapy and 47 months after diagnosis, the patient is alive and well. The tumour was found to have increased immunoexpression of HDAC2, 4 and 6 and phospho-HDAC4/5/7. This case emphasises the importance of considering NMC in the differential diagnosis of poorly differentiated carcinomas of the head and neck region in young adults, even away from midline structures. As molecular targets hold the promise of successful therapy for the vast majority of NMC patients, the knowledge of their HDAC expression patterns will probably be relevant.

Identification of lysine acetylome in cervical cancer by label-free quantitative proteomics

BACKGROUND

Lysine acetylation is a post-translational modification that regulates a diversity of biological processes, including cancer development.

METHODS

Here, we performed the quantitative acetylproteomic analysis of three primary cervical cancer tissues and corresponding adjacent normal tissues by using the label-free proteomics approach.

RESULTS

We identified a total of 928 lysine acetylation sites from 1547 proteins, in which 495 lysine acetylation sites corresponding to 296 proteins were quantified. Further, 41 differentially expressed lysine acetylation sites corresponding to 30 proteins were obtained in cervical cancer tissues compared with adjacent normal tissues (Fold change > 2 and P < 0.05), of which 1 was downregulated, 40 were upregulated. Moreover, 75 lysine acetylation sites corresponding to 58 proteins were specifically detected in cancer tissues or normal adjacent tissues. Motif-X analysis showed that kxxxkxxxk, GkL, AxxEk, kLxE, and kkxxxk are the most enriched motifs with over four-fold increases when compared with the background matches. KEGG analysis showed that proteins identified from differently and specifically expressed peptides may influence key pathways, such as Notch signaling pathway, viral carcinogenesis, RNA transport, and Jak-STAT, which play an important role in tumor progression. Furthermore, the acetylated levels of CREBBP and S100A9 in cervical cancer tissues were confirmed by immunoprecipitation (IP) and Western blot analysis.

CONCLUSIONS

Taken together, our data provide novel insights into the role of protein lysine acetylation in cervical carcinogenesis.

Recent advances in class IIa histone deacetylases research

Epigenetic control plays an important role in gene regulation through chemical modifications of DNA and post-translational modifications of histones. An essential post-translational modification is the histone acetylation/deacetylation-process which is regulated by histone acetyltransferases (HATs) and histone deacetylases (HDACs). The mammalian zinc dependent HDAC family is subdivided into three classes: class I (HDACs 1-3, 8), class II (IIa: HDACs 4, 5, 7, 9; IIb: HDACs 6, 10) and class IV (HDAC 11). In this review, recent studies on the biological role and regulation of class IIa HDACs as well as their contribution in neurodegenerative diseases, immune disorders and cancer will be presented. Furthermore, the development, synthesis, and future perspectives of selective class IIa inhibitors will be highlighted.

HDAC inhibitors induce proline dehydrogenase (POX) transcription and anti-apoptotic autophagy in triple negative breast cancer

Triple-negative breast cancer (TNBC) is the most aggressive subtype of breast cancer with poor clinical outcomes and without effective targeted therapies. Numerous studies have suggested that HDAC inhibitors (TSA/SAHA) may be effective in TNBCs. Proline oxidase, also known as proline dehydrogenase (POX/PRODH), is a key enzyme in the proline metabolism pathway and plays a vital role in tumorigenesis. In this study, we found that HDAC inhibitors (TSA/SAHA) significantly increased POX expression and autophagy through activating AMPK. Depletion of POX decreased autophagy and increased apoptosis induced by HDAC inhibitors in TNBC cells. These results suggest that POX contributes to cell survival under chemotherapeutic stresses and might serve as a potential target for treatment of TNBC.

H3K18Ac as a Marker of Cancer Progression and Potential Target of Anti-Cancer Therapy

Acetylation and deacetylation are posttranslational modifications (PTMs) which affect the regulation of chromatin structure and its remodeling. Acetylation of histone 3 at lysine placed on position 18 (H3K18Ac) plays an important role in driving progression of many types of cancer, including breast, colon, lung, hepatocellular, pancreatic, prostate, and thyroid cancer. The aim of this review is to analyze and discuss the newest findings regarding the role of H3K18Ac and acetylation of other histones in carcinogenesis. We summarize the level of H3K18Ac in different cancer cell lines and analyze its association with patients’ outcomes, including overall survival (OS), progression-free survival (PFS), and disease-free survival (DFS). Finally, we describe future perspectives of cancer therapeutic strategies based on H3K18 modifications.

Apoptosis Induction byHistone Deacetylase Inhibitors in Cancer Cells: Role of Ku70

Histone deacetylases (HDACs) are a group of enzymes that regulate gene transcription by controlling deacetylation of histones and non-histone proteins. Overexpression of HDACs is found in some types of tumors and predicts poor prognosis. Five HDAC inhibitors are approved for the treatment of cutaneous T-cell lymphoma, peripheral T-cell lymphoma, and multiple myeloma. Treatment with HDAC inhibitors regulates gene expression with increased acetylated histones with unconfirmed connection with therapy. Apoptosis is a key mechanism by which HDAC inhibitors selectively kill cancer cells, probably due to acetylation of non-histone proteins. Ku70 is a protein that repairs DNA breaks and stabilizes anti-apoptotic protein c-FLIP and proapoptotic protein Bax, which is regulated by acetylation. HDAC inhibitors induce Ku70 acetylation with repressed c-FLIP and activated Bax in cancer cells. Current studies indicate that Ku70 is a potential target of HDAC inhibitors and plays an important role during the induction of apoptosis.

Identification and Characterization of AES-135, a Hydroxamic Acid-Based HDAC Inhibitor That Prolongs Survival in an Orthotopic Mouse Model of Pancreatic Cancer

Pancreatic ductal adenocarcinoma (PDAC) is an aggressive, incurable cancer with a 20% 1 year survival rate. While standard-of-care therapy can prolong life in a small fraction of cases, PDAC is inherently resistant to current treatments, and novel therapies are urgently required. Histone deacetylase (HDAC) inhibitors are effective in killing pancreatic cancer cells in in vitro PDAC studies, and although there are a few clinical studies investigating combination therapy including HDAC inhibitors, no HDAC drug or combination therapy with an HDAC drug has been approved for the treatment of PDAC. We developed an inhibitor of HDACs, AES-135, that exhibits nanomolar inhibitory activity against HDAC3, HDAC6, and HDAC11 in biochemical assays. In a three-dimensional coculture model, AES-135 kills low-passage patient-derived tumor spheroids selectively over surrounding cancer-associated fibroblasts and has excellent pharmacokinetic properties in vivo. In an orthotopic murine model of pancreatic cancer, AES-135 prolongs survival significantly, therefore representing a candidate for further preclinical testing.

Histone Deacetylases (HDACs) Guided Novel Therapies for T-cell lymphomas

T-cell lymphomas are a heterogeneous group of cancers with different pathogenesis and poor prognosis. Histone deacetylases (HDACs) are epigenetic modifiers that modulate many key biological processes. In recent years, HDACs have been fully investigated for their roles and potential as drug targets in T-cell lymphomas. In this review, we have deciphered the modes of action of HDACs, HDAC inhibitors as single agents, and HDACs guided combination therapies in T-cell lymphomas. The overview of HDACs on the stage of T-cell lymphomas, and HDACs guided therapies both as single agents and combination regimens endow great opportunities for the cure of T-cell lymphomas.

Histone Deacetylase Inhibitors and Phenotypical Transformation of Cancer Cells

Histone deacetylase inhibitors (HDIs) are a group of potent epigenetic drugs which have been investigated for their therapeutic potential in various clinical disorders, including hematological malignancies and solid tumors. Currently, several HDIs are already in clinical use and many more are on clinical trials. HDIs have shown efficacy to inhibit initiation and progression of cancer cells. Nevertheless, both pro-invasive and anti-invasive activities of HDIs have been reported, questioning their impact in carcinogenesis. The aim of this review is to compile and discuss the most recent findings on the effect of HDIs on the epithelial-mesenchymal transition (EMT) process in human cancers. We have summarized the impact of HDIs on epithelial (E-cadherin, β-catenin) and mesenchymal (N-cadherin, vimentin) markers, EMT activators (TWIST, SNAIL, SLUG, SMAD, ZEB), as well as morphology, migration and invasion potential of cancer cells. We further discuss the use of HDIs as monotherapy or in combination with existing or novel anti-neoplastic drugs in relation to changes in EMT.