Histone deacetylases, transcriptional control, and cancer

Histone deacetylase inhibitors: targeting epigenetic regulation in the treatment of acute leukemia

Acute leukemia (AL) is a rare yet perilous malignancy. Currently, the primary treatment for AL involves combination chemotherapy as the cornerstone of comprehensive measures, alongside hematopoietic stem cell transplantation as a radical approach. However, despite these interventions, mortality rates remain high, particularly among refractory/recurrent patients or elderly individuals with a poor prognosis. Acetylation, a form of epigenetic regulation, has emerged as a promising therapeutic avenue for treating AL. Recent studies have highlighted the potential of acetylation regulation as a novel treatment pathway. Histone deacetylase inhibitors (HDACis) play a pivotal role in modulating the differentiation and development of tumor cells through diverse pathways, simultaneously impacting the maturation and function of lymphocytes. HDACis demonstrate promise in enhancing survival rates and achieving a complete response in both acute myeloid leukemia and acute T-lymphoblastic leukemia patients. This article provides a comprehensive review of the advancements in HDACi therapy for AL, shedding light on its potential implications for clinical practice.

Discovering novel derivatives of STAT3 and HDAC inhibitors with anti-tumor activity

In modern cancer therapy, blockage of more than one target is a standard approach, and there are already many dual-target drugs that can achieve multiple inhibition through a single molecule. Herein, we designed and synthesized a series of novel derivatives with signal transducer and activator of transcription 3 (STAT3) and histone deacetylase (HDAC) inhibitory activity through strategy of combining pharmacophore based on the STAT3 inhibitor E28 and HDAC inhibitor MS-275. Among them, compound 24 (IC50 = 8.22 ± 0.27 μM) showed better anti-tumor activity than the clinical Class I HDAC inhibitor MS-275 (IC50 = 14.65 ± 0.24 μM) in MCF-7 breast cancer cells. Furthermore, the dual inhibition to HDAC and STAT3 of compound 24 was validated by western blot analysis. The study provides new tool compounds for further exploration of STAT3-HDAC pathway inhibitor achieved with a single molecule.

A Pilot Study of the Combination of Entinostat with Capecitabine in Advanced Breast Cancer

Background

Breast cancer has an unacceptably high recurrence rate when any residual disease is found following neoadjuvant treatment of high-risk disease. Based on clinical data suggesting an adjuvant role for epigenetic modifying agents in breast cancer and preclinical data suggesting synergistic activity of entinostat combined with capecitabine, we conducted a phase I, open-label study of these agents in metastatic breast cancer (MBC). Both agents have published doses for use in combination therapy, but the agents had not previously been combined with each other in a human trial.

Methods

A multisite phase I dose escalation study was performed at two academic centers. Patients with pretreated, HER2-negative MBC, and measurable disease were enrolled. Dual dose escalation was performed via a Bayesian partial order continual assessment method. Dose levels ranged from entinostat 3 mg to 5 mg and capecitabine 800 mg/m2 to 1000 mg/m2.

Results

Thirteen patients with MBC and a median of 4 lines of prior therapy were enrolled across four dose level combinations. The most common toxicities were neutropenia, thrombocytopenia, and palmar-plantar dysesthesia, which were expected toxicities. No new safety signals were observed. One dose-limiting toxicity was observed, which did not exceed a prespecified toxicity rate of 25%. The median treatment duration was 2.37 months. No partial nor complete responses were observed. The study was halted early prior to entering an expansion phase, due to drug supply limitations.

Conclusion

The tested dosing combinations of entinostat and capecitabine are likely safe in heavily pretreated metastatic breast cancer. This study's clinical investigation of entinostat in breast cancer was halted, but drug development of this agent continues outside the US. There remains a need for postoperative adjuvant drug therapy for the subpopulation of breast cancer patients with high-risk residual cancer after curative therapy. This trial is registered with NCT03473639.

Recent Developments and Future Perspectives of Purine Derivatives as a Promising Scaffold in Drug Discovery

Numerous purine-containing compounds have undergone extensive investigation for their medical efficacy across various diseases. The swift progress in purine-based medicinal chemistry has brought to light the therapeutic capabilities of purine-derived compounds in addressing challenging medical conditions. Defined by a heterocyclic ring comprising a pyrimidine ring linked with an imidazole ring, purine exhibits a diverse array of therapeutic attributes. This review systematically addresses the multifaceted potential of purine derivatives in combating various diseases, including their roles as anticancer agents, antiviral compounds (anti-herpes, anti-HIV, and anti-influenzae), autoimmune and anti-inflammatory agents, antihyperuricemic and anti-gout solutions, antimicrobial agents, antitubercular compounds, anti-leishmanial agents, and anticonvulsants. Emphasis is placed on the remarkable progress made in developing purine-based compounds, elucidating their significant target sites. The article provides a comprehensive exploration of developments in both natural and synthetic purines, offering insights into their role in managing a diverse range of illnesses. Additionally, the discussion delves into the structure-activity relationships and biological activities of the most promising purine molecules. The intriguing capabilities revealed by these purine-based scaffolds unequivocally position them at the forefront of drug candidate development. As such, this review holds potential significance for researchers actively involved in synthesizing purine-based drug candidates, providing a roadmap for the continued advancement of this promising field.

Epigenetic meets metabolism: novel vulnerabilities to fight cancer

Histones undergo a plethora of post-translational modifications (PTMs) that regulate nucleosome and chromatin dynamics and thus dictate cell fate. Several evidences suggest that the accumulation of epigenetic alterations is one of the key driving forces triggering aberrant cellular proliferation, invasion, metastasis and chemoresistance pathways. Recently a novel class of histone "non-enzymatic covalent modifications" (NECMs), correlating epigenome landscape and metabolic rewiring, have been described. These modifications are tightly related to cell metabolic fitness and are able to impair chromatin architecture. During metabolic reprogramming, the high metabolic flux induces the accumulation of metabolic intermediate and/or by-products able to react with histone tails altering epigenome homeostasis. The accumulation of histone NECMs is a damaging condition that cancer cells counteracts by overexpressing peculiar "eraser" enzymes capable of removing these modifications preserving histones architecture. In this review we explored the well-established NECMs, emphasizing the role of their corresponding eraser enzymes. Additionally, we provide a parterre of drugs aiming to target those eraser enzymes with the intent to propose novel routes of personalized medicine based on the identification of epi-biomarkers which might be selectively targeted for therapy. Video Abstract.

HDAC inhibition regulates oxidative stress in CD4+Thelper cells of chronic obstructive pulmonary disease and non-small cell lung cancer patients via mitochondrial transcription factor a (mtTFA) modulating NF-κB/HIF1α axis

Histone deacetylases (HDACs) play a crucial role in the epigenetic regulation of gene expression by remodelling chromatin. Isoenzymes of the HDAC family exhibit aberrant regulation in a wide variety of cancers as well as several inflammatory lung disorders like chronic obstructive pulmonary disease (COPD). Inhibition of HDACs is a potential therapeutic strategy that could be used to reverse epigenetic modification. Trichostatin A (TSA), a powerful histone deacetylase (HDAC) inhibitor, has anti-cancer effects in numerous cancer types. However, it is not yet apparent how HDAC inhibitors affect human non-small cell lung cancer cells (NSCLC) and COPD. This study aims to investigate TSA's role in restoring mitochondrial dysfunction and its effect on hypoxia and inflammation in CD4+T cells obtained from patients with COPD and lung cancer. As a result of treatment with TSA, there is a reduction in the expression of inflammatory cytokines and a decreased enrichment of transcriptional factors associated with inflammation at VEGFA gene loci. We have seen a substantial decrease in the expression of NF-κB and HIF1α, which are the critical mediators of inflammation and hypoxia, respectively. Following TSA treatment, mtTFA expression was increased, facilitating patients with COPD and NSCLC in the recovery of their dysfunctional mitochondria. Furthermore, we have discovered that TSA treatment in patients with COPD and NSCLC may lead to immunoprotective ness by inducing Th1ness. Our finding gives a new insight into the existing body of knowledge regarding TSA-based therapeutic methods and highlights the necessity of epigenetic therapy for these devastating lung disorders.

Design, Synthesis, and Biological Evaluation of Histone Deacetylase Inhibitors Derived from Erianin and Its Derivatives

Multi-target histone deacetylase (HDAC) inhibitors can be designed by introducing dominant structures of natural products to enhance activity and efficacy while avoiding the toxicity from other targets. In this study, we reported a series of novel HDAC inhibitors based on erianin and amino erianin upon pharmacophore fusion strategy. Two representative compounds, N-hydroxy-2-(2-methoxy-5- (3,4,5-trimethoxyphenethyl)phenoxy)acetamide and N-Hydroxy-8-((2-methoxy-5- (3,4,5-trimethoxyphenethyl)phenyl)amino)octanamide, possessed good inhibitory effect against five cancer cells tested (IC50 =0.30-1.29 μΜ, 0.29-1.70 μΜ) with strong HDAC inhibition, and low toxicity toward L02 cells, which were selected for subsequent biological studies in PANC-1 cells. They were also found to promote the intracellular generation of reactive oxygen species, cause DNA damage, block the cell cycle at G2/M phase, and activate the mitochondria-related apoptotic pathway to induce cell apoptosis, which are significant for the discovery of new HDAC inhibitors.

Discovery of (S)-N-(2-Amino-4-fluorophenyl)-4-(1-(3-(4-((dimethylamino)methyl)phenyl)-6-oxopyridazin-1(6H)-yl)ethyl)benzamide as Potent Class I Selective HDAC Inhibitor for Oral Anticancer Drug Candidate

A novel series of benzamide derivatives were successively designed and synthesized prepared from the pyridazinone scaffold. Among them, (S)-17b, demonstrated potent inhibitory activity in vitro toward human class I HDAC isoforms and human myelodysplastic syndrome (SKM-1) cell line. Also, (S)-17b strongly increased the intracellular level of acetyl-histone H3 and P21 simultaneously and effectively induced G1 cell cycle arrest and apoptosis. Through oral dosing in SKM-1 xenograft models, (S)-17b exhibited excellent in vivo antitumor activity. In addition, compound (S)-17b showed better antitumor efficacy on mouse models with intact immune system than those with thymus deficiencies. Furthermore, this compound displayed a favorable pharmacokinetic profile in ICR mice and SD rat, respectively, minimal metabolic property differences among hepatocytes from five species, and a low inhibition upon the human ether-a-go-go (hERG) channel with an IC₅₀ value of 34.6 μΜ. This novel compound (S)-17b may serve as a new drug candidate for further investigation.

Engaging plasticity: Differentiation therapy in solid tumors

Cancer is a systemic heterogeneous disease that can undergo several rounds of latency and activation. Tumor progression evolves by increasing diversity, adaptation to signals from the microenvironment and escape mechanisms from therapy. These dynamic processes indicate necessity for cell plasticity. Epithelial-mesenchymal transition (EMT) plays a major role in facilitating cell plasticity in solid tumors by inducing dedifferentiation and cell type transitions. These two practices, plasticity and dedifferentiation enhance tumor heterogeneity creating a key challenge in cancer treatment. In this review we will explore cancer cell plasticity and elaborate treatment modalities that aspire to overcome such dynamic processes in solid tumors. We will further discuss the therapeutic potential of utilizing enhanced cell plasticity for differentiation therapy.

Propolin G-Suppressed Epithelial-to-Mesenchymal Transition in Triple-Negative Breast Cancer Cells via Glycogen Synthase Kinase 3β-Mediated Snail and HDAC6-Regulated Vimentin Degradation

Triple-negative breast cancer (TNBC) is a highly aggressive breast cancer with a poor prognosis. The incidence and mortality rate of TNBC are frequently found in younger women. Due to the absence of a good therapeutic strategy, effective remedies for inhibiting TNBC have been developed for improving the cure rate. Epithelial-to-mesenchymal transition (EMT) is a critical mechanism to regulate cancer cell motility and invasion. Furthermore, ectopic expression of EMT molecules correlates with the metastasis and poor prognosis of TNBC. Targeting EMT might be a strategy for the therapy and prevention of TNBC. Propolin G, an active c-prenylflavanone in Taiwanese propolis, has been shown to possess anti-cancer activity in many cancers. However, the anti-metastasis activity of propolin G on TNBC is still unclear. The present study showed that the migration and invasion activities of TNBC cells was suppressed by propolin G. Down-regulated expression of Snail and vimentin and up-regulated expression of E-cadherin were dose- and time-dependently observed in propolin G-treated MDA-MB-231 cells. Propolin G inhibited Snail and vimentin expressions via the signaling pathways associated with post-translational modification. The activation of glycogen synthase kinase 3β (GSK-3β) by propolin G resulted in increasing GSK-3β interaction with Snail. Consequently, the nuclear localization and stability of Snail was disrupted resulting in promoting the degradation. Propolin G-inhibited Snail expression and the activities of migration and invasion were reversed by GSK-3β inhibitor pretreatment. Meanwhile, the outcomes also revealed that histone deacetylase 6 (HDAC6) activity was dose-dependently suppressed by propolin G. Correspondently, the amounts of acetyl-α-tubulin, a down-stream substrate of HDAC6, were increased. Dissociation of HDAC6/Hsp90 with vimentin leading to increased vimentin acetylation and degradation was perceived in the cells with the addition of propolin G. Moreover, up-regulated expression of acetyl-α-tubulin by propolin G was attenuated by HDAC6 overexpression. On the contrary, down-regulated expression of vimentin, cell migration and invasion by propolin G were overturned by HDAC6 overexpression. Conclusively, restraint cell migration and invasion of TNBC by propolin G were activated by the expression of GSK-3β-suppressed Snail and the interruption of HDAC6-mediated vimentin protein stability. Aiming at EMT, propolin G might be a potential candidate for TNBC therapy.

Opposite effects of the triple target (DNA-PK/PI3K/mTOR) inhibitor PI-103 on the radiation sensitivity of glioblastoma cell lines proficient and deficient in DNA-PKcs

BACKGROUND

Radiotherapy is routinely used to combat glioblastoma (GBM). However, the treatment efficacy is often limited by the radioresistance of GBM cells.

METHODS

Two GBM lines MO59K and MO59J, differing in intrinsic radiosensitivity and mutational status of DNA-PK and ATM, were analyzed regarding their response to DNA-PK/PI3K/mTOR inhibition by PI-103 in combination with radiation. To this end we assessed colony-forming ability, induction and repair of DNA damage by γH2AX and 53BP1, expression of marker proteins, including those belonging to NHEJ and HR repair pathways, degree of apoptosis, autophagy, and cell cycle alterations.

RESULTS

We found that PI-103 radiosensitized MO59K cells but, surprisingly, it induced radiation resistance in MO59J cells. Treatment of MO59K cells with PI-103 lead to protraction of the DNA damage repair as compared to drug-free irradiated cells. In PI-103-treated and irradiated MO59J cells the foci numbers of both proteins was higher than in the drug-free samples, but a large portion of DNA damage was quickly repaired. Another cell line-specific difference includes diminished expression of p53 in MO59J cells, which was further reduced by PI-103. Additionally, PI-103-treated MO59K cells exhibited an increased expression of the apoptosis marker cleaved PARP and increased subG1 fraction. Moreover, irradiation induced a strong G2 arrest in MO59J cells (~ 80% vs. ~ 50% in MO59K), which was, however, partially reduced in the presence of PI-103. In contrast, treatment with PI-103 increased the G2 fraction in irradiated MO59K cells.

CONCLUSIONS

The triple-target inhibitor PI-103 exerted radiosensitization on MO59K cells, but, unexpectedly, caused radioresistance in the MO59J line, lacking DNA-PK. The difference is most likely due to low expression of the DNA-PK substrate p53 in MO59J cells, which was further reduced by PI-103. This led to less apoptosis as compared to drug-free MO59J cells and enhanced survival via partially abolished cell-cycle arrest. The findings suggest that the lack of DNA-PK-dependent NHEJ in MO59J line might be compensated by DNA-PK independent DSB repair via a yet unknown mechanism.

Histone deacetylase (HDAC) 9: versatile biological functions and emerging roles in human cancer

BACKGROUND

HDAC9 (histone deacetylase 9) belongs to the class IIa family of histone deacetylases. This enzyme can shuttle freely between the nucleus and cytoplasm and promotes tissue-specific transcriptional regulation by interacting with histone and non-histone substrates. HDAC9 plays an essential role in diverse physiological processes including cardiac muscle development, bone formation, adipocyte differentiation and innate immunity. HDAC9 inhibition or activation is therefore a promising avenue for therapeutic intervention in several diseases. HDAC9 overexpression is also common in cancer cells, where HDAC9 alters the expression and activity of numerous relevant proteins involved in carcinogenesis.

CONCLUSIONS

This review summarizes the most recent discoveries regarding HDAC9 as a crucial regulator of specific physiological systems and, more importantly, highlights the diverse spectrum of HDAC9-mediated posttranslational modifications and their contributions to cancer pathogenesis. HDAC9 is a potential novel therapeutic target, and the restoration of aberrant expression patterns observed among HDAC9 target genes and their related signaling pathways may provide opportunities to the design of novel anticancer therapeutic strategies.

Non-enzymatic Covalent Modifications as a New Chapter in the Histone Code

The interior of the cell abounds with reactive species that can accumulate as non-enzymatic covalent modifications (NECMs) on biological macromolecules. These adducts interfere with many cellular processes, for example, by altering proteins' surface topology, enzymatic activity, or interactomes. Here, we discuss dynamic NECMs on chromatin, which serves as the cellular blueprint. We first outline the chemistry of NECM formation and then focus on the recently identified effects of their accumulation on chromatin structure and transcriptional output. We next describe the known cellular regulatory mechanisms that prevent or reverse NECM formation. Finally, we discuss recently developed chemical biology platforms for probing and manipulating these NECMs in vitro and in vivo.

Chidamide increases the sensitivity of refractory or relapsed acute myeloid leukemia cells to anthracyclines via regulation of the HDAC3 -AKT-P21-CDK2 signaling pathway

BACKGROUND

Induction therapy for acute myeloid leukemia (AML) is an anthracycline-based chemotherapy regimen. However, many patients experience a relapse or exhibit refractory disease (R/R). There is an urgent need for more effective regimens to reverse anthracycline resistance in these patients.

METHODS

In this paper, Twenty-seven R/R AML patients with anthracycline resistance consecutively received chidamide in combination with anthracycline-based regimen as salvage therapy at the Chinese PLA General Hospital.

RESULTS

Of the 27 patients who had received one course of salvage therapy, 13 achieved a complete response and 1 achieved a partial response. We found that the HDAC3-AKT-P21-CDK2 signaling pathway was significantly upregulated in anthracycline-resistant AML cells compared to non-resistant cells. AML patients with higher levels of HDAC3 had lower event-free survival (EFS) and overall survival (OS) rates. Moreover, anthracycline-resistant AML cells are susceptible to chidamide, a histone deacetylase inhibitor which can inhibit cell proliferation, increase cell apoptosis and induce cell-cycle arrest in a time- and dose-dependent manner. Chidamide increases the sensitivity of anthracycline-resistant cells to anthracycline drugs, and these effects are associated with the inhibition of the HDAC3-AKT-P21-CDK2 signaling pathway.

CONCLUSION

Chidamide can increase anthracycline drug sensitivity by inhibiting HDAC3-AKT-P21-CDK2 signaling pathway, thus demonstrating the potential for application.

Transcription tipping points for T follicular helper cell and T-helper 1 cell fate commitment

During viral infection, immune cells coordinate the induction of inflammatory responses that clear infection and humoral responses that promote protection. CD4⁺ T-cell differentiation sits at the center of this axis. Differentiation toward T-helper 1 (Th1) cells mediates inflammation and pathogen clearance, while T follicular helper (Tfh) cells facilitate germinal center (GC) reactions for the generation of high-affinity antibodies and immune memory. While Th1 and Tfh differentiation occurs in parallel, these CD4⁺ T-cell identities are mutually exclusive, and progression toward these ends is determined via the upregulation of T-bet and Bcl6, respectively. These lineage-defining transcription factors act in concert with multiple networks of transcriptional regulators that tip the T-bet and Bcl6 axis in CD4⁺ T-cell progenitors to either a Th1 or Tfh fate. It is now clear that these transcriptional networks are guided by cytokine cues that are not only varied between distinct viral infections but also dynamically altered throughout the duration of infection. Thus, multiple intrinsic and extrinsic factors combine to specify the fate, plasticity, and function of Th1 and Tfh cells during infection. Here, we review the current information on the mode of action of the lineage-defining transcription factors Bcl6 and T-bet and how they act individually and in complex to govern CD4⁺ T-cell ontogeny. Furthermore, we outline the multifaceted transcriptional regulatory networks that act upstream and downstream of Bcl6 and T-bet to tip the differentiation equilibrium toward either a Tfh or Th1 fate and how these are impacted by dynamic inflammatory cues.

Histone modifications in epigenetic regulation of cancer: Perspectives and achieved progress

Epigenetic changes associated with histone modifications play an important role in the emergence and maintenance of the phenotype of various cancer types. In contrast to direct mutations in the main DNA sequence, these changes are reversible, which makes the development of inhibitors of enzymes of post-translational histone modifications one of the most promising strategies for the creation of anticancer drugs. To date, a wide variety of histone modifications have been found that play an important role in the regulation of chromatin state, gene expression, and other nuclear events. This review examines the main features of the most common and studied epigenetic histone modifications with a proven role in the pathogenesis of a wide range of malignant neoplasms: acetylation / deacetylation and methylation / demethylation of histone proteins, as well as the role of enzymes of the HAT / HDAC and HMT / HDMT families in the development of oncological pathologies. The data on the relationship between histone modifications and certain types of cancer are presented and discussed. Special attention is devoted to the consideration of various strategies for the development of epigenetic inhibitors. The main directions of the development of inhibitors of histone modifications are analyzed and effective strategies for their creation are identified and discussed. The most promising strategy is the use of multitarget drugs, which will affect multiple molecular targets of cancer. A critical analysis of the current status of approved epigenetic anticancer drugs has also been performed.

Epigenetic Regulation of Multidrug Resistance Protein 1 and Breast Cancer Resistance Protein Transporters by Histone Deacetylase Inhibition

Multidrug resistance protein 1 (MDR1, ABCB1, P-glycoprotein) and breast cancer resistance protein (BCRP, ABCG2) are key efflux transporters that mediate the extrusion of drugs and toxicants in cancer cells and healthy tissues, including the liver, kidneys, and the brain. Altering the expression and activity of MDR1 and BCRP influences the disposition, pharmacodynamics, and toxicity of chemicals, including a number of commonly prescribed medications. Histone acetylation is an epigenetic modification that can regulate gene expression by changing the accessibility of the genome to transcriptional regulators and transcriptional machinery. Recently, studies have suggested that pharmacological inhibition of histone deacetylases (HDACs) modulates the expression and function of MDR1 and BCRP transporters as a result of enhanced histone acetylation. This review addresses the ability of HDAC inhibitors to modulate the expression and the function of MDR1 and BCRP transporters and explores the molecular mechanisms by which HDAC inhibition regulates these transporters. While the majority of studies have focused on histone regulation of MDR1 and BCRP in drug-resistant and drug-sensitive cancer cells, emerging data point to similar responses in nonmalignant cells and tissues. Elucidating epigenetic mechanisms regulating MDR1 and BCRP is important to expand our understanding of the basic biology of these two key transporters and subsequent consequences on chemoresistance as well as tissue exposure and responses to drugs and toxicants. SIGNIFICANCE STATEMENT: Histone deacetylase inhibitors alter the expression of key efflux transporters multidrug resistance protein 1 and breast cancer resistance protein in healthy and malignant cells.

Suppressing migration and invasion of H1299 lung cancer cells by honokiol through disrupting expression of an HDAC6-mediated matrix metalloproteinase 9

Metastasis is the crucial mechanism to cause high mortality in lung cancer. Degradation of extracellular matrix (ECM) by proteolytic enzymes, especially matrix metalloproteinases (MMPs), is a key process for promoting cancer cell migration and invasion. Therefore, targeting MMPs might be a strategy for lung cancer metastasis suppression. Honokiol, a biological active component of Magnolia officinalis, has been indicated to suppress lung cancer tumorigenesis through epigenetic regulation. However, the regulation of MMPs‐mediated migration and invasion by honokiol through epigenetic regulation in lung cancer is still a mystery. In the present study, the migration and invasion ability of H1299 lung cancer was suppressed by noncytotoxic concentrations of honokiol treatment. The proteolytic activity of MMP‐9, rather than MMP‐2, was inhibited in honokiol‐treated H1299 cells. Honokiol‐inhibited MMP‐9 expression was through promoting MMP‐9 protein degradation rather than suppressing transcription mechanism. Furthermore, the expression of specific histone deacetylases 6 (HDAC6) substrate, acetyl‐α‐tubulin, was accumulated after honokiol incubation. The disassociation of MMP‐9 with hyper‐acetylated heat shock protein 90 (Hsp90) was observed resulting in MMP‐9 degradation after honokiol treatment. Meanwhile, honokiol‐suppressed MMP‐9 expression and invasion ability of H1299 lung cancer cells was rescued by HDAC6 overexpression. Accordingly, the results suggested that the suppression of migration and invasion activities by honokiol was through inhibiting HDAC6‐mediated Hsp90/MMP‐9 interaction and followed by MMP‐9 degradation in lung cancer.

Clinical Role of Epigenetics and Network Analysis in Eye Diseases: A Translational Science Review

Network medicine is a molecular-bioinformatic approach analyzing gene-gene interactions that can perturb the human interactome. This review focuses on epigenetic changes involved in several ocular diseases, such as DNA methylation, histone and nonhistone post-translational modifications, and noncoding RNA regulators. Although changes in aberrant DNA methylation play a major role in the pathogenesis of most ocular diseases, histone modifications are seldom investigated. Hypermethylation in TGM-2 and hypomethylation in MMP-2/CD24 promoter genes may play a crucial role in pterygium development; hypermethylation in regulatory regions of GSTP1 and OGG1 genes appear to be diagnostic biomarkers of cataract; hypomethylation of TGF-β1 promoter may trigger glaucoma onset; hypermethylation of the LOXL1 gene might be associated with pseudoexfoliation syndrome. A large panel of upregulated micro-RNAs (miRNAs), including hsa-hsa-miR-494, hsa-let-7e, hsa-miR-513-1, hsa-miR-513-2, hsa-miR-518c, hsa-miR-129-1, hsa-miR-129-2, hsa-miR-198, hsa-miR-492, hsa-miR-498, hsa-miR-320, hsa-miR-503, and hsa-miR-373, ^∗ may have a putative role in the development of retinoblastoma. Hypermethylation of H3K4 and hypomethylation of H3K27 at the TGFBIp locus are putative pathogenic mechanisms involved in corneal dystrophies. Determining how, where, and when specific epigenetic changes trigger ocular diseases may provide useful clinical biomarkers for their prevention, diagnosis, and management, as well as innovative drug targets. PF-04523655, a 19-nucleotide methylated double-stranded siRNA targeting the RTP80 gene, showed a dose-related improvement in best-corrected visual acuity (BCVA) in patients affected by diabetic macular edema. The observed results support a clinical network-based research program aimed to clarify the role of epigenetic regulators in the development of ocular diseases and personalized therapy.

Induction of Apoptosis and Autophagy in Breast Cancer Cells by a Novel HDAC8 Inhibitor

Epigenetic therapy has been demonstrated to be a viable strategy for breast cancer treatment. In this study, we report the anti-tumor activity of a hydroxamate-based histone deacetylase (HDAC)8-selective inhibitor, HMC, in breast cancer cells. MTT assays showed that HMC inhibited cell viability of MCF-7 and MDA-MB-231 cells with IC₅₀ values of 7.7 μM and 9.5 μM, respectively. HMC induced caspase-dependent apoptosis in MCF-7 cells, which was associated with its ability to modulate a series of cell survival-related signaling effectors, including Akt, mTOR, Bax, Mcl-1, and Bcl-2. Additionally, HMC was capable of activating PPARγ, which was accompanied by reduced expression of PPARγ target gene products, such as cyclin D1 and CDK6. HMC increased the production of ROS in MCF-7 cells, which could be partially reversed by the cotreatment with a ROS scavenger (N-acetylcysteine or glutathione). Furthermore, HMC induced autophagy, as characterized by the formation of acidic vesicular organelles and autophagic biomarkers including LC3B-II and Atg5. Notably, pharmacological blockade of autophagy by 3-MA or CQ could attenuate HMC-induced apoptosis, suggesting that autophagy played a self-protective role in HMC-induced cell death. Together, these data suggest the translational potential of HMC to be developed into a potential therapeutic agent for breast cancer therapy.

Histone Deacetylases and Histone Deacetylase Inhibitors: Molecular Mechanisms of Action in Various Cancers

Epigenetic modifications such as histone modification play an important role in tumorigenesis. There are several evidence that histone deacetylases (HDACs) play a key role in cancer induction and progression by histone deacetylation. Besides, histone acetylation is being accessed as a therapeutic target because of its role in regulating gene expression. HDAC inhibitors (HDACIs) are a family of synthetic and natural compounds that differ in their target specificities and activities. They affect markedly cancer cells, inducing cell differentiation, cell cycle arrest and cell death, reduction of angiogenesis, and modulation of the immune system. Here, we summarize the mechanisms of HDACs and the HDACIs in several cancers. An online search of different sources such as PubMed, ISI, and Scopus was performed to find available data on mechanisms and pathways of HDACs and HDACIs in different cancers. The result indicated that HDACs induce cancer through multiple mechanisms in various tissues. This effect can be inhibited by HDACIs which affect cancer cell by different pathways such as cell differentiation, cell cycle arrest, and cell death. In conclusion, these findings indicate that the HDACs play a major role in carcinogenesis through various pathways, and HDACIs can inhibit HDAC activity by multiple mechanisms resulting in cell cycle arrest, cell growth inhibition, and apoptosis induction.

Safety and Tolerability of Histone Deacetylase (HDAC) Inhibitors in Oncology

Histone deacetylases (HDACs) are expressed at increased levels in cells of various malignancies, and the use of HDAC inhibitors has improved outcomes in patients with haematological malignancies (T-cell lymphomas and multiple myeloma). However, they are not as effective in solid tumours. Five agents are currently approved under various jurisdictions, namely belinostat, chidamide, panobinostat, romidepsin and vorinostat. These agents are associated with a range of class-related and agent-specific serious and/or severe adverse effects, notably myelosuppression, diarrhoea and various cardiac effects. Among the cardiac effects are ST-T segment abnormalities and QTc interval prolongation of the electrocardiogram, isolated cases of atrial fibrillation and, in rare instances, ventricular tachyarrhythmias. In order to improve the safety profile of this class of drugs as well as their efficacy in indications already approved and to further widen their indications, a large number of newer HDAC inhibitors with varying degrees of HDAC isoform selectivity have been synthesised and are currently under clinical development. Preliminary evidence from early studies suggests that they may be effective in non-haematological cancers as well when used in combination with other therapeutic modalities, but that they too appear to be associated with the above class-related adverse effects. As the database accumulates, the safety, efficacy and risk/benefit of the newer agents and their indications will become clearer.

Effect of DNA Methyltransferase in Comparison to and in Combination with Histone Deacetylase Inhibitors on Hepatocellular Carcinoma HepG2 Cell Line

Background:

DNA demethylating agents and histone deacetylase inhibitors can affect reactivation of gene expression and apoptosis induction by DNA acetylation and demethylation. The aim of the present study was to analyze the effects of DNA demethylating agent genistein (GE) and histone deacetylase inhibitor valproic acid VPA), alone and combined, on hepatocellular carcinoma Hep G2 cell line.

Methods:

The cells were treated with various doses of genistein and valproic acid (alone and combined) and the MTT assay and flow cytometry were used to determine cell viability and apoptosis.

Results:

Genistein and valproic acid inhibited the growth of HepG 2 cells significantly. Result of flow cytometry demonstrated that genistein and valproic acid (alone and combined) induce apoptosis significantly in a timedependent manner.

Conclusions:

Genistein and valproic acid can significantly inhibit proliferation and induce apoptosis in HepG2 cell line. The apoptotic effects of GE in combination with VPA were more significant that of each compound alone.

Proteomic analysis of Plasmodium falciparum histone deacetylase 1 complex proteins

Plasmodium falciparum histone deacetylases (PfHDACs) are an important class of epigenetic regulators that alter protein lysine acetylation, contributing to regulation of gene expression and normal parasite growth and development. PfHDACs are therefore under investigation as drug targets for malaria. Despite this, our understanding of the biological roles of these enzymes is only just beginning to emerge. In higher eukaryotes, HDACs function as part of multi-protein complexes and act on both histone and non-histone substrates. Here, we present a proteomics analysis of PfHDAC1 immunoprecipitates, identifying 26 putative P. falciparum complex proteins in trophozoite-stage asexual intraerythrocytic parasites. The co-migration of two of these (P. falciparum heat shock proteins 70-1 and 90) with PfHDAC1 was validated using Blue Native PAGE combined with Western blot. These data provide a snapshot of possible PfHDAC1 interactions and a starting point for future studies focused on elucidating the broader function of PfHDACs in Plasmodium parasites.

SIRT1 rs3758391 polymorphism and risk of diffuse large B cell lymphoma in a Chinese population

Background

The aim of the study was to explore the association between the SIRT1 single nucleotide polymorphism (SNP) rs3758391 and diffuse large B cell lymphoma (DLBCL) in a Chinese Han population.

Methods

206 patients diagnosed with DLBCL and 219 healthy individuals were recruited in the present study. The genotyping of SIRT1 rs3758391 polymorphism was detected by polymerase chain reaction–restriction fragment length polymorphism. The SIRT1 mRNA expression was detected by the Taqman real-time quantitative PCR.

Results

Our study showed that the genotype TT and allele T frequency were significantly higher in DLBCL patients than that of controls (p = 0.02 and 0.01, respectively). No statistical differences were observed between SIRT1 rs3758391 and clinical characteristics of DLBCL patients. Analysis of the polymorphism revealed an increased risk of DLBCL associated with TC and TT genotype when compared with CC genotype [odds ratio = 2.621 and 3.518, respectively; 95% confidence interval (CI) 1.249–5.501 and 1.675–7.390, respectively; p = 0.011 and 0.001, respectively]. The survival analysis indicated that the patients with C allele had higher overall survival rate than those with genotype TT (p = 0.005). Furthermore, multivariate Cox regression analysis showed that the TT genotype of SIRT1 SNP rs3758391 was an independent poor prognostic factor for DLBCL patients (p = 0.006, HR 1.981, 95% CI 1.215–3.231). The SIRT1 mRNA expression was significantly upregulated in DLBCL patients than that of controls (p < 0.001). In addition, the SIRT1 mRNA expression of TT subgroup was upregulated compared with TC/CC subgroup in DLBCL patients (p < 0.001).

Conclusion

These results suggest that the SIRT1 rs3758391 polymorphism is associated with the risk and survival rate of DLBCL in Chinese Han population.

Repurposing old drugs in oncology: Opportunities with clinical and regulatory challenges ahead

WHAT IS KNOWN AND OBJECTIVE

In order to expedite the availability of drugs to treat cancers in a cost-effective manner, repurposing of old drugs for oncological indications is gathering momentum. Revolutionary advances in pharmacology and genomics have demonstrated many old drugs to have activity at novel antioncogenic pharmacological targets. We decided to investigate whether prospective studies support the promises of nonclinical and retrospective clinical studies on repurposing three old drugs, namely metformin, valproate and astemizole.

METHODS

We conducted an extensive literature search through PubMed to gather representative nonclinical and retrospective clinical studies that investigated the potential repurposing of these three drugs for oncological indications. We then searched for prospective studies aimed at confirming the promises of retrospective data.

RESULTS AND DISCUSSION

While evidence from nonclinical and retrospective clinical studies with these drugs appears highly promising, large scale prospective studies are either lacking or have failed to substantiate this promise. We provide a brief discussion of some of the challenges in repurposing. Principal challenges and obstacles relate to heterogeneity of cancers studied without considering their molecular signatures, trials with small sample size and short duration, failure consider issues of ethnicity of study population and effective antioncogenic doses of the drug studied.

WHAT IS NEW AND CONCLUSION

Well-designed prospective studies demonstrating efficacy are required for repurposing old drugs for oncology indications, just as they are for new chemical entities for any indication. Early and ongoing interactions with regulatory authorities are invaluable. We outline a tentative framework for a structured approach to repurposing old drugs for novel indications in oncology.

Molecular testing in the diagnosis of differentiated thyroid carcinomas

Different genetic mutations and other molecular alterations in papillary thyroid cancer (PTC) and follicular thyroid cancer (FTC) can be detected in fine-needle aspiration (FNA) of thyroid nodules, and can be used successfully to ameliorate cancer diagnosis and management of patients with thyroid nodules. The greatest experience has been obtained with the diagnostic use of BRAF mutation that is strongly specific for malignancy when detected using well-validated techniques. The strongest diagnostic result can be obtained testing FNA samples for a panel of mutations that typically involve TERT, BRAF, PAX8/PPARγ, RAS, and RET/PTC. Finding any of these mutations in a thyroid nodule provides strong indication for malignancy and helps to refine clinical management for a significant proportion of patients with indeterminate cytology. The use of molecular markers, as TERT, BRAF, PAX8/PPARγ, RAS, and RET/PTC, may be considered for patients with indeterminate FNA cytology (FNAC) to help guide management. In patients with indeterminate TIR3 FNA, the combination of precise molecular marker expression analysis with molecular mutations evaluations could ameliorate significantly the accuracy of cancer diagnosis. However other prospective studies are needed to identify more accurate molecular markers. Finally, the knowledge of these molecular pathways has permitted the development of new targeted therapies for aggressive TC.

Syntheses and Biological Evaluation of Novel Hydroxamic Acid Derivatives Containing Purine Moiety as Histone Deacetylase Inhibitors

The novel hydroxamates containing purine scaffold were designed, synthesized and screened for their biological activities as histone deacetylase (HDAC) inhibitors. Some of them exhibited excellent acti-HDACs activities and antiproliferative activities, the most promising compound was 7m'. Western blot analysis indicated the compounds 7f', 7l', 7m', 7o' could increase histone H3 acetylation levels in HCT116 and K562 cell lines, and 7m' increased the level of acetyl histone H3 in a dose-dependent manner, which is similar to the behavior of suberoylanilide hydroxamic acid (SAHA). Molecular docking study revealed that the conformation of 7m' in the active site of HDAC2 was similar to positive drug SAHA, which were oriented with the hydroxamic acid towards the catalytic center and formed metal binding with zinc ion.

Epimutational profile of hematologic malignancies as attractive target for new epigenetic therapies

In recent years, recurrent somatic mutations in epigenetic regulators have been identified in patients with hematological malignancies. Furthermore, chromosomal translocations in which the fusion protein partners are themselves epigenetic regulators or where epigenetic regulators are recruited/targeted by oncogenic fusion proteins have also been described. Evidence has accumulated showing that "epigenetic drugs" are likely to provide clinical benefits in several hematological malignancies, granting their approval for the treatment of myelodysplastic syndromes and cutaneous T-cell lymphomas. A large number of pre-clinical and clinical trials evaluating epigenetic drugs alone or in combination therapies are ongoing. The aim of this review is to provide a comprehensive summary of known epigenetic alterations and of the current use of epigenetic drugs for the treatment of hematological malignancies.

Sirtuin 3 enhanced drug sensitivity of human hepatoma cells through glutathione S-transferase pi 1/JNK signaling pathway

SIRT3, a class III histone deacetylase, has been implicated in various cancers as a novel therapeutic target. In hepatocellular carcinoma (HCC), we previously reported that SIRT3 induced cell apoptosis by regulating GSK-3β/Bax signaling pathway. Downregulation of SIRT3 in HCC cells facilitates tumor cell survival. In this study, we found that chemotherapeutic agents (doxorubicin, cisplatin and epirubicin) and sorafenib treatment downregulated SIRT3 mRNA and protein levels in three HCC cell lines. MTS assay found that SIRT3 overexpression sensitized liver cancer cells to chemotherapeutic agents and sorafenib in SMMC-7721, Huh-7 and PLC/PRF/5 cell lines. Moreover, SIRT3 overexpression promoted chemotherapeutic agents-induced or sorafenib-induced apoptosis as evidenced by flow cytometry, enhanced PARP cleavage and enhanced Caspase-9 cleavage in three HCC cells. In contrast, SIRT3 silencing increased drug resistance of HCC cells to chemotherapeutic agents. Mechanistic study found that SIRT3 downregulated the mRNA and protein levels of glutathione S-transferase pi 1 (GSTP1), which is a member of phase II detoxification enzymes families involved in metabolizing for chemotherapeutic agents. Moreover, SIRT3 decreased the amount of GSTP1 that was associated with JNK, which finally contributed the activation of JNK activity and activation of downstream target c-Jun and Bim. Importantly, GSTP1 overexpression or JNK inhibitor abolished SIRT3-induced apoptosis in HCC cells exposed to chemotherapeutic agents. Finally, there was a negative correlation between SIRT3 expression and GSTP1 expression in human HCC tissues. Together, our findings revealed SIRT3 could enhance the drug sensitivity of HCC cells to an array of chemotherapeutic agents. SIRT3 may serve as a potential target for improving the chemosensitivity of HCC patients.

A Phase I/II Study Targeting Angiogenesis Using Bevacizumab Combined with Chemotherapy and a Histone Deacetylase Inhibitor (Valproic Acid) in Advanced Sarcomas

Epigenetic events and genetic alterations under the control of the tumor microenvironment potentially mediate tumor induced angiogenesis involved in soft tissue sarcoma (STS) metastasis. Addition of antiangiogenic agent, such as bevacizumab, to standard chemotherapy in treatment of sarcoma has been studied in clinical trials, but most of the findings have not supported its use. We hypothesized the existence of an epigenetically mediated "angiogenic switch", and the tumor microenvironment, prevents bevacizumab from truly blocking angiogenesis. The addition of valproic acid (VPA), a weak histone deacetylase inhibitor, and bevacizumab, a monoclonal antibody against vascular endothelial growth factor, together with the cytotoxic effects of gemcitabine and docetaxel, may enhance responses and alter chemoresistance. This was designed as a phase I/II trial with primary endpoints including safety of the treatment combination and tumor response. Unresectable or metastatic sarcoma patients >18 years of age, irrespective of number of prior treatments, received VPA 40 mg/kg orally for 5 days prior to day 1, bevacizumab at 15 mg/kg IV on day 1, gemcitabine 900 mg/m² (day 1, day 8), and docetaxel 75 mg/m² (day 8). Cycles were of 28 day duration. Bevacizumab and VPA were continued as maintenance after 6 cycles, until disease progression. A standard 3 + 3 phase I dose de-escalation design was utilized to evaluate safety. Gain of function p53 gene mutation testing was performed on available archival tissue specimens. A total of 46 patients (30 female, 16 male) with median age of 60 (range 24-81) years were enrolled; 34 (73.9%) patients received prior chemotherapy, 14 (30%) of which received prior gemcitabine and docetaxel. Patients received a median of 5.5 cycles (range 0-24 of treatment (min 0, one patient died prior to completing the first cycle; max: 24, one patient received 6 cycles and 18 maintenance cycles before progressing). Seventeen patients underwent dose reduction, of which VPA was reduced in 6 patients. Forty-one patients were evaluable for response. There was a confirmed complete response in 1 (epithelioid sarcoma), and a partial response (PR) in 6 (1 carcinosarcoma, 2 extrauterine leiomyosarcoma (LMS), 2 undifferentiated pleomorphic sarcoma, and 1 uterine LMS) patients. Stable disease (SD) was seen in 21 patients for at least 2 months. One subject with prior gemcitabine and docetaxel had PR, and 7 had SD. Median progression-free survival (PFS) was 5.7 months (95% CI: 2.1-8.0), and overall survival (OS) was 12.9 months (95% CI: 8.3-14.5). Three patients died due to tumor progression while on the study. The combination of VPA, bevacizumab, gemcitabine, and docetaxel appears to be moderately safe and well tolerated. Given that there are very limited options for patients with relapsed refractory STS, this drug combination may be an important therapy to consider. This combination treatment deserves further investigation in epithelioid and carcinosarcoma subtypes.

Total synthesis of the natural HDAC inhibitor Cyl-1

A chelate enolate Claisen rearrangement was used as a key step in the first total synthesis of Cyl-1, a cyclic tetrapeptide from Cylindrocladium scoparium.

Acetylation- and Methylation-Related Epigenetic Proteins in the Context of Their Targets

The nucleosome surface is covered with multiple modifications that are perpetuated by eight different classes of enzymes. These enzymes modify specific target sites both on DNA and histone proteins, and these modifications have been well identified and termed “epigenetics”. These modifications play critical roles, either by affecting non-histone protein recruitment to chromatin or by disturbing chromatin contacts. Their presence dictates the condensed packaging of DNA and can coordinate the orderly recruitment of various enzyme complexes for DNA manipulation. This genetic modification machinery involves various writers, readers, and erasers that have unique structures, functions, and modes of action. Regarding human disease, studies have mainly focused on the genetic mechanisms; however, alteration in the balance of epigenetic networks can result in major pathologies including mental retardation, chromosome instability syndromes, and various types of cancers. Owing to its critical influence, great potential lies in developing epigenetic therapies. In this regard, this review has highlighted mechanistic and structural interactions of the main epigenetic families with their targets, which will help to identify more efficient and safe drugs against several diseases.

Immunoexpression of HDAC1, HDAC2, and HAT1 in actinic cheilitis and lip squamous cell carcinoma

BACKGROUND

Acetylation and deacetylation are the most studied covalent histone modifications resulting in transcriptional regulation with histone deacetylases (HDAC) and histone acetyltransferases (HAT) as the main associated enzymes. These enzymes overexpression induces abnormal transcription of key genes that regulate important cellular functions, such as proliferation, cell cycle regulation, and apoptosis. Thus, the expression of different HATs and HDACs has been evaluated in various cancers.

OBJECTIVE

To investigate HDAC1, HDAC2 and HAT1 expression in lip squamous cell carcinoma (LSCC) and actinic cheilitis (AC) and to demonstrate their correlation with DNA metyltransferases (DNMTs).

MATERIAL AND METHODS

Thirty cases of lip squamous cell carcinoma (LSCC), thirty cases of actinic cheilitis (AC), and 28 cases of non-neoplastic epithelium as control were selected for immunohistochemical investigation.

RESULTS

Nuclear HDAC2 immunopositivity was significantly higher in AC (75.07% ± 29.70) when compared with LSCC (51.06% ± 39.02). HDAC1 and HAT1 nuclear immunostaining were higher in AC, with no statistical significance. When comparing data with our previous study, we found a positive correlation between HDAC1 X DNMT1/DNMT3b, HDAC2 X DNMT3b, and HAT1 X DNMT1/DNMT3b for certain studied groups.

CONCLUSION

This study showed higher levels of nuclear HDAC2 immunopositivity in AC, possibly indicating that this enzyme plays a key role in lip photocarcinogenesis early stages.

Role of TCTP for Cellular Differentiation and Cancer Therapy

The translationally controlled tumor protein (TCTP) is a highly conserved protein that is regulated due to a high number of extracellular stimuli. TCTP has an important role for cell cycle and normal development. On the other side, tumor reversion and malignant transformation have been associated with TCTP. TCTP has been found among the 12 genes that are differentially expressed during mouse oocyte maturation, and an overexpression of this gene was reported in a wide variety of different cancer types. Its antiapoptotic effect is indicated by the interaction with several proapoptotic proteins of the Bcl-2 family and the p53 tumor suppressor protein. In this article, we draw attention to the role of TCTP in cancer, especially, focusing on cell differentiation and tumor reversion, a biological process by which highly tumorigenic cells lose their malignant phenotype. This protein has been shown to be the most strongly downregulated protein in revertant cells compared to the parental cancer cells. Decreased expression of TCTP results either in the reprogramming of cancer cells into reversion or apoptosis. As conventional chemotherapy is frequently associated with the development of drug resistance and high toxicity, the urge for the development of new or additional scientific approaches falls into place. Differentiation therapy aims at reinducing differentiation backward to the nonmalignant cellular state. Here, different approaches have been reported such as the induction of retinoid pathways and the use of histone deacetylase inhibitors. Also, PPARγ agonists and the activation of the vitamin D receptor have been reported as potential targets in differentiation therapy. As TCTP is known as the histamine-releasing factor, antihistaminic drugs have been shown to target this protein. Antihistaminic compounds, hydroxyzine and promethazine, inhibited cell growth of cancer cells and decreased TCTP expression of breast cancer and leukemia cells. Recently, we found that two antihistaminics, levomepromazine and buclizine, inhibited cancer cell growth by direct binding to TCTP and induction of cell differentiation. These data confirmed that TCTP is an exquisite target for anticancer differentiation therapy and antihistaminics have potential to be lead compounds for the direct interaction with TCTP as new inhibitors of human TCTP and tumor growth.

Epigenomics in Waldenstrom's macroglobulinaemia

Epigenomics refers to study of the epigenome, which represents changes in gene expression that are not induced by DNA sequence aberrations. For instance, DNA methylation, histone acetylation and microRNAs may modulate gene expression without altering the gene sequence. Waldenström's macroglobulinaemia (WM) is a low-grade B-cell lymphoma, classified as lymphoplasmacytic lymphoma, characterized by the presence of clonal lymphoplasmacytic cells in the bone marrow and serum monoclonal immunoglobulin-M in the circulation. It is a rare disease and, although indolent, it remains incurable with a median overall survival of 5-6 years. Most patients succumb to disease progression. WM cells present with aberrant histone hypoacetylation that may be explained, at least in part, via deregulated microRNAs, thus suggesting the use of histone deacetylase inhibitors or microRNA-based therapies in this disease.

Epigenetic regulation of human retinoblastoma

Retinoblastoma is a rare type of eye cancer of the retina that commonly occurs in early childhood and mostly affects the children before the age of 5. It occurs due to the mutations in the retinoblastoma gene (RB1) which inactivates both alleles of the RB1. RB1 was first identified as a tumor suppressor gene, which regulates cell cycle components and associated with retinoblastoma. Previously, genetic alteration was known as the major cause of its occurrence, but later, it is revealed that besides genetic changes, epigenetic changes also play a significant role in the disease. Initiation and progression of retinoblastoma could be due to independent or combined genetic and epigenetic events. Remarkable work has been done in understanding retinoblastoma pathogenesis in terms of genetic alterations, but not much in the context of epigenetic modification. Epigenetic modifications that silence tumor suppressor genes and activate oncogenes include DNA methylation, chromatin remodeling, histone modification and noncoding RNA-mediated gene silencing. Epigenetic changes can lead to altered gene function and transform normal cell into tumor cells. This review focuses on important epigenetic alteration which occurs in retinoblastoma and its current state of knowledge. The critical role of epigenetic regulation in retinoblastoma is now an emerging area, and better understanding of epigenetic changes in retinoblastoma will open the door for future therapy and diagnosis.

Flow-induced HDAC1 phosphorylation and nuclear export in angiogenic sprouting

Angiogenesis requires the coordinated growth and migration of endothelial cells (ECs), with each EC residing in the vessel wall integrating local signals to determine whether to remain quiescent or undergo morphogenesis. These signals include vascular endothelial growth factor (VEGF) and flow-induced mechanical stimuli such as interstitial flow, which are both elevated in the tumor microenvironment. However, it is not clear how VEGF signaling and mechanobiological activation due to interstitial flow cooperate during angiogenesis. Here, we show that endothelial morphogenesis is histone deacetylase-1- (HDAC1) dependent and that interstitial flow increases the phosphorylation of HDAC1, its activity, and its export from the nucleus. Furthermore, we show that HDAC1 inhibition decreases endothelial morphogenesis and matrix metalloproteinase-14 (MMP14) expression. Our results suggest that HDAC1 modulates angiogenesis in response to flow, providing a new target for modulating vascularization in the clinic.

JNJ-26481585 primes rhabdomyosarcoma cells for chemotherapeutics by engaging the mitochondrial pathway of apoptosis

Rhabdomyosarcoma (RMS) is a common soft-tissue sarcoma in childhood with a poor prognosis, highlighting the need for new treatment strategies. Here we identify a synergistic interaction of the second-generation histone deacetylase inhibitor (HDACI) JNJ-26481585 and common chemotherapeutic drugs (i.e. Doxorubicin, Etoposide, Vincristine, Cyclophosphamide and Actinomycin D) to trigger apoptosis in RMS cells. Importantly, JNJ-26481585/Doxorubicin cotreatment also significantly suppresses long-term clonogenic survival of RMS cells and tumor growth in vivo in a preclinical RMS model. Mechanistically, JNJ-26481585/Doxorubicin cotreatment causes upregulation of the BH3-only proteins Bim and Noxa as well as downregulation of the antiapoptotic proteins Mcl-1 and Bcl-xL. These changes in the ratio of pro- and antiapoptotic Bcl-2 proteins contribute to JNJ-26481585/Doxorubicin-mediated apoptosis, since knockdown of Bim or Noxa significantly inhibits cell death. Also, JNJ-26481585 and Doxorubicin cooperate to stimulate activation of Bax and Bak, which is required for JNJ-26481585/Doxorubicin-induced apoptosis, since silencing of Bax or Bak protects against apoptosis. Consistently, overexpression of Bcl-2 significantly reduces JNJ-26481585/Doxorubicin-mediated apoptosis. JNJ-26481585/Doxorubicin cotreatment leads to caspase activation and caspase-dependent apoptosis, since the broad-range caspase inhibitor N-benzyloxycarbonyl-Val-Ala-Asp-fluoromethylketone (zVAD.fmk) rescues cells from apoptosis. In conclusion, the second-generation HDACI JNJ-26481585 cooperates with chemotherapeutics to engage mitochondrial apoptosis in RMS cells, demonstrating that JNJ-26481585 represents a promising strategy for chemosensitization of RMS.