HATs off: selective synthetic inhibitors of the histone acetyltransferases p300 and PCAF

Concurrent inhibition of p300/CBP and FLT3 enhances cytotoxicity and overcomes resistance in acute myeloid leukemia

FMS-like tyrosine kinase-3 (FLT3), a class 3 receptor tyrosine kinase, can be activated by mutations of internal tandem duplication (FLT3-ITD) or point mutations in the tyrosine kinase domain (FLT3-TKD), leading to constitutive activation of downstream signaling cascades, including the JAK/STAT5, PI3K/AKT/mTOR and RAS/MAPK pathways, which promote the progression of leukemic cells. Despite the initial promise of FLT3 inhibitors, the discouraging outcomes in the treatment of FLT3-ITD-positive acute myeloid leukemia (AML) promote the pursuit of more potent and enduring therapeutic approaches. The histone acetyltransferase complex comprising the E1A binding protein P300 and its paralog CREB-binding protein (p300/CBP) is a promising therapeutic target, but the development of effective p300/CBP inhibitors faces challenges due to inherent resistance and low efficacy, often exacerbated by the absence of reliable clinical biomarkers for patient stratification. In this study we investigated the role of p300/CBP in FLT3-ITD AML and evaluated the therapeutic potential of targeting p300/CBP alone or in combination with FLT3 inhibitors. We showed that high expression of p300 was significantly associated with poor prognosis in AML patients and positively correlated with FLT3 expression. We unveiled that the p300/CBP inhibitors A485 or CCS1477 dose-dependently downregulated FLT3 transcription via abrogation of histone acetylation in FLT3-ITD AML cells; in contrast, the FLT3 inhibitor quizartinib reduced the level of H3K27Ac. Concurrent inhibition of p300/CBP and FLT3 enhanced the suppression of FLT3 signaling and H3K27 acetylation, concomitantly reducing the phosphorylation of STAT5, AKT, ERK and the expression of c-Myc, thereby leading to synergistic antileukemic effects both in vitro and in vivo. Moreover, we found that p300/CBP-associated transcripts were highly expressed in quizartinib-resistant AML cells with FLT3-TKD mutation. Targeting p300/CBP with A485 or CCS1477 retained the efficacy of quizartinib, suggesting marked synergy when combined with p300/CBP inhibitors in quizartinib-resistant AML models, as well as primary FLT3-ITD+ AML samples. These results demonstrate a potential therapeutic strategy of combining p300/CBP and FLT3 inhibitors to treat FLT3-ITD and FLT3-TKD AML.

Potential therapeutic targets for ischemic stroke in pre-clinical studies: Epigenetic-modifying enzymes DNMT/TET and HAT/HDAC

Ischemic stroke (IS) remains a leading cause of mortality and disability worldwide, driven by genetic predispositions and environmental interactions, with epigenetics playing a pivotal role in mediating these processes. Specific modifying enzymes that regulate epigenetic changes have emerged as promising targets for IS treatment. DNA methyltransferases (DNMTs), ten-eleven translocation (TET) dioxygenases, histone acetyltransferases (HATs), and histone deacetylases (HDACs) are central to epigenetic regulation. These enzymes maintain a dynamic balance between DNA methylation/demethylation and histone acetylation/deacetylation, which critically influences gene expression and neuronal survival in IS. This review is based on both in vivo and in vitro experimental studies, exploring the roles of DNMT/TET and HAT/HDAC in IS, evaluating their potential as therapeutic targets, and discussing the use of natural compounds as modulators of these enzymes to develop novel treatment strategies.

Tip60 HAT activators as therapeutic modulators for Alzheimer's disease

Reduced histone acetylation in the brain causes transcriptional dysregulation and cognitive impairment that are key initial steps in Alzheimer's disease (AD) etiology. Unfortunately, current treatment strategies primarily focus on histone deacetylase inhibition (HDACi) that causes detrimental side effects due to non-specific acetylation. Here, we test Tip60 histone acetyltransferase (HAT) activation as a therapeutic strategy for selectively restoring cognition-associated histone acetylation depleted in AD by developing compounds that enhance Tip60's neuroprotective HAT function. Several compounds show high Tip60-binding affinity predictions in silico, enhanced Tip60 HAT action in vitro, and restore Tip60 knockdown mediated functional deficits in Drosophila in vivo. Furthermore, compounds prevent neuronal deficits and lethality in an AD-associated amyloid precursor protein neurodegenerative Drosophila model and remarkably, restore expression of repressed neuroplasticity genes in the AD brain, underscoring compound specificity and therapeutic effectiveness. Our results highlight Tip60 HAT activators as a promising therapeutic neuroepigenetic modulator strategy for AD treatment.

Targeting lysine acetylation readers and writers

Lysine acetylation is a major post-translational modification in histones and other proteins that is catalysed by the 'writer' lysine acetyltransferases (KATs) and mediates interactions with bromodomains (BrDs) and other 'reader' proteins. KATs and BrDs play key roles in regulating gene expression, cell growth, chromatin structure, and epigenetics and are often dysregulated in disease states, including cancer. There have been accelerating efforts to identify potent and selective small molecules that can target individual KATs and BrDs with the goal of developing new therapeutics, and some of these agents are in clinical trials. Here, we summarize the different families of KATs and BrDs, discuss their functions and structures, and highlight key advances in the design and development of chemical agents that show promise in blocking the action of these chromatin proteins for disease treatment.

Dysregulation of the p300/CBP histone acetyltransferases in human cancer

p300 (E1A binding protein 300) and CBP (CREB-binding protein) are critical regulators of chromatin dynamics and gene expression, playing essential roles in various cellular processes, including proliferation, differentiation, apoptosis, and immune responses. These homologous histone acetyltransferases (HATs) function as transcriptional co-activators by acetylating histones and non-histone proteins. p300/CBP is essential for development, and dysregulation of p300 and CBP has been implicated in several human diseases, particularly cancer. Somatic mutations that inactivate p300/CBP are frequently observed across various cancer types. Additionally, other mutations leading to translocations or truncations of p300/CBP can result in enhanced catalytic activity, potentially representing novel gain-of-function mutations that promote tumor progression. In this review, we discuss the mechanisms underlying the regulation of p300/CBP HAT activity, its dysregulation in cancer, and the development of p300/CBP inhibitors and their potential in cancer therapies.

The important role of the histone acetyltransferases p300/CBP in cancer and the promising anticancer effects of p300/CBP inhibitors

Histone acetyltransferases p300 (E1A-associated protein p300) and CBP (CREB binding protein), collectively known as p300/CBP due to shared sequence and functional synergy, catalyze histone H3K27 acetylation and consequently induce gene transcription. p300/CBP over-expression or over-activity activates the transcription of oncogenes, leading to cancer cell growth, resistance to apoptosis, tumor initiation and development. The discovery of small molecule inhibitors targeting p300/CBP histone acetyltransferase activity, bromodomains, dual inhibitors of p300/CBP and BRD4 bromodomains, as well as proteolysis-targeted-chimaera p300/CBP protein degraders, marks significant progress in cancer therapeutics. These inhibitors and degraders induce histone H3K27 deacetylation, reduce oncogene expression and cancer cell proliferation, promote cancer cell death, and decrease tumor progression in mice. Furthermore, p300/CBP inhibitors and protein degraders have been demonstrated to exert synergy when in combination with conventional radiotherapy, chemotherapy and BRD4 inhibitors in vitro as well as in mice. Importantly, two p300/CBP bromodomain inhibitors, CCS1477 and FT-7051, as well as the dual p300/CBP and BRD4 bromodomain inhibitor NEO2734 have entered Phase I and IIa clinical trials in patients with advanced and refractory hematological malignancies or solid tumors. Taken together, the identification of p300/CBP as critical drivers of tumorigenesis and the development of p300/CBP inhibitors and proteolysis-targeted-chimaera protein degraders represent promising avenues for clinical translation of novel cancer therapeutics.

Grammar rules and exceptions for the language of transcriptional activation domains

Transcriptional activation domains (ADs) of gene activators have remained enigmatic for decades as short, extremely variable, and structurally disordered sequences. Using a rational design and high throughput in vivo experimentation, we determine the grammar rules and exceptions for the language of ADs. According to identified rules, billions of highly active ADs can be composed of balanced amounts of acidic/aromatic amino acids, with either mixed composition of aromatic residues, or using only one aromatic residue mixed with acidic residues. However, equally active sequences can be composed of only aliphatic leucine and aspartic acid residues. The much rarer LD exceptions have a higher ratio of hydrophobic/acidic balance and display a specific LDL(L/D)DLL motif. For aromatic/acidic Ads, the intermixing of proline residues in context of amphipathic α-helix structures significantly increases the AD activity. The identified grammar rules and exceptions are interpreted in application to the biochemistry of AD function and eukaryotic gene expression.

The Enigma of Transcriptional Activation Domains

Activation domains (ADs) of eukaryotic gene activators remain enigmatic for decades as short, extremely variable sequences which often are intrinsically disordered in structure and interact with an uncertain number of targets. The general absence of specificity increasingly complicates the utilization of the widely accepted mechanism of AD function by recruitment of coactivators. The long-standing enigma at the heart of molecular biology demands a fundamental rethinking of established concepts. Here, we review the experimental evidence supporting a novel mechanistic model of gene activation, based on ADs functioning via surfactant-like near-stochastic interactions with gene promoter nucleosomes. This new model is consistent with recent information-rich experimental data obtained using high-throughput synthetic biology and bioinformatics analysis methods, including machine learning. We clarify why the conventional biochemical principle of specificity for sequence, structures, and interactions fails to explain activation domain function. This perspective provides connections to the liquid-liquid phase separation model, signifies near-stochastic interactions as fundamental for the biochemical function, and can be generalized to other cellular functions.

Targeting histone modifiers in bladder cancer therapy - preclinical and clinical evidence

Bladder cancer in the most advanced, muscle-invasive stage is lethal, and very limited therapeutic advances have been reported for decades. To date, cisplatin-based chemotherapy remains the first-line therapy for advanced bladder cancer. Late-line options have historically been limited. In the past few years, next-generation sequencing technology has enabled chromatin remodelling gene mutations to be characterized, showing that these alterations are more frequent in urothelial bladder carcinoma than in other cancer types. Histone modifiers have functional roles in tumour progression by modulating the expression of tumour suppressors and oncogenes and, therefore, have been considered as novel drug targets for cancer therapy. The roles of epigenetic reprogramming through histone modifications have been increasingly studied in bladder cancer, and the therapeutic efficacy of targeting those histone modifiers genetically or chemically is being assessed in preclinical studies. Results from preclinical studies in bladder cancer encouraged the investigation of some of these drugs in clinical trials, which yield mixed results. Further understanding of how alterations of histone modification mechanistically contribute to bladder cancer progression, drug resistance and tumour microenvironment remodelling will be required to facilitate clinical application of epigenetic drugs in bladder cancer.

Peptide-based inhibitors of epigenetic proteins

Epigenetic drug discovery has become an integral part of medicinal chemistry in the past two decades. Targeting epigenetic proteins-enzymes that modify histone proteins and DNA (writers and erasers) and proteins that recognize such modifications (readers)-has been firmly established as a medicinal strategy for treatment of many human diseases, including cancer and neurological disorders. In this chapter, we systematically describe peptide-based inhibitors of structurally and functionally diverse classes of epigenetic proteins. We show that epigenetic writers, such as DNA methyltransferases, histone methyltransferases and histone acetyltransferases, can be efficiently inhibited by peptides possessing nonproteinogenic amino acids. Moreover, the activity of epigenetic erasers, including TET enzymes, histone demethylases, and histone deacetylases, can be selectively modulated by diverse linear and cyclic peptides. Furthermore, we discuss chromatin-binding epigenetic reader proteins that can be inhibited by histone-mimicking peptides. Overall, this chapter highlights that peptides provide an important molecular platform for epigenetic drug discovery programmes in academia and industry.

Discovery of novel nucleoside derivatives as selective lysine acetyltransferase p300 inhibitors for cancer therapy

P300 and CBP are two closely related histone acetyltransferases that are important transcriptional coactivators of many cellular processes. Inhibition of the transcriptional regulator p300/CBP is a promising therapeutic approach in oncology. However, there are no reported single selective p300 or CBP inhibitors to date. In this study, we designed and optimized a series of lysine acetyltransferase p300 selective inhibitors bearing a nucleoside scaffold. Most compounds showed excellent inhibitory activity against p300 with IC50 ranging from 0.18 to 9.90 μM, except for J16, J29, J40, and J48. None of the compounds showed inhibitory activity against CBP (inhibition rate < 50 % at 10 µM). Then the cytotoxicity of the compounds against a series of cancer cells were evaluated. Compounds J31 and J32 showed excellent proliferation inhibitory activity on cancer cells T47D and H520 with desirable selectivity profile of p300 over CBP. These compounds could be promising lead compounds for the development of novel epigenetic inhibitors as antitumor agents.

Histone lysine acetyltransferase inhibitors: an emerging class of drugs for cancer therapy

Lysine acetyltransferases (KATs) are a family of epigenetic enzymes involved in the regulation of gene expression; they represent a promising class of emerging drug targets. The frequent molecular dysregulation of these enzymes, as well as their mechanistic links to biological functions that are crucial to cancer, have led to exploration around the development of small-molecule inhibitors against KATs. Despite early challenges, recent advances have led to the development of potent and selective enzymatic and bromodomain (BRD) KAT inhibitors. In this review we discuss the discovery and development of new KAT inhibitors and their application as oncology therapeutics. Additionally, new chemically induced proximity approaches are presented, offering opportunities for unique target selectivity profiles and tissue-specific targeting of KATs. Emerging clinical data for CREB binding protein (CREBBP)/EP300 BRD inhibitors and KAT6 catalytic inhibitors indicate the promise of this target class in cancer therapeutics.

Reprogramming of regulatory T cells in inflammatory tumor microenvironment: can it become immunotherapy turning point?

Overcoming the immunosuppressive tumor microenvironment and identifying widely used immunosuppressants with minimal side effects are two major challenges currently hampering cancer immunotherapy. Regulatory T cells (Tregs) are present in almost all cancer tissues and play an important role in preserving autoimmune tolerance and tissue homeostasis. The tumor inflammatory microenvironment causes the reprogramming of Tregs, resulting in the conversion of Tregs to immunosuppressive phenotypes. This process ultimately facilitates tumor immune escape or tumor progression. However, current systemic Treg depletion therapies may lead to severe autoimmune toxicity. Therefore, it is crucial to understand the mechanism of Treg reprogramming and develop immunotherapies that selectively target Tregs within tumors. This article provides a comprehensive review of the potential mechanisms involved in Treg cell reprogramming and explores the application of Treg cell immunotherapy. The interference with reprogramming pathways has shown promise in reducing the number of tumor-associated Tregs or impairing their function during immunotherapy, thereby improving anti-tumor immune responses. Furthermore, a deeper understanding of the mechanisms that drive Treg cell reprogramming could reveal new molecular targets for future treatments.

Epigenetic alterations fuel brain metastasis via regulating inflammatory cascade

Brain metastasis (BrM) is a major threat to the survival of melanoma, breast, and lung cancer patients. Circulating tumor cells (CTCs) cross the blood-brain barrier (BBB) and sustain in the brain microenvironment. Genetic mutations and epigenetic modifications have been found to be critical in controlling key aspects of cancer metastasis. Metastasizing cells confront inflammation and gradually adapt in the unique brain microenvironment. Currently, it is one of the major areas that has gained momentum. Researchers are interested in the factors that modulate neuroinflammation during BrM. We review here various epigenetic factors and mechanisms modulating neuroinflammation and how this helps CTCs to adapt and survive in the brain microenvironment. Since epigenetic changes could be modulated by targeting enzymes such as histone/DNA methyltransferase, deacetylases, acetyltransferases, and demethylases, we also summarize our current understanding of potential drugs targeting various aspects of epigenetic regulation in BrM.

Novel berberine derivatives as p300 histone acetyltransferase inhibitors in combination treatment for breast cancer

Adenoviral E1A binding protein p300 (EP300 or p300) and its similar paralog, cyclic-AMP response element binding protein (CBP), are important histone acetyltransferases (HAT) and transcriptional co-activators in epigenetics, participating in numerous cellular pathways including proliferation, differentiation and apoptosis. The overexpression or dysregulation of p300/CBP is closely related to oncology-relevant disease. The inhibition of p300 HAT has been found to be a potential drug target. Berberine has been reported to show anticancer activity and synergistic effect in combination with some of the clinical anticancer drugs via modulation of various pathways. Here, the present study sought to discover more chemotypes of berberine derivatives as p300 HAT inhibitors and to examine the combination of these novel analogues with doxorubicin for the treatment of breast cancer. A series of novel berberine derivatives with modifications of A/B/D rings of berberine have been designed, synthesized and screened. Compound 7b was found to exhibit inhibitory potency against p300 HAT with IC50 values of 1.51 μM. Western blotting proved that 7b decreased H3K27Ac and interfered with the expression of oncology-relevant protein in MCF-7 cells. Further bioactive evaluation showed that combination of compound 7b with doxorubicin could significantly inhibit tumor growth and invasion in vitro and in vivo.

Protein lysine acetyltransferase CBP/p300: A promising target for small molecules in cancer treatment

CBP and p300 are homologous proteins exhibiting remarkable structural and functional similarity. Both proteins function as acetyltransferase and coactivator, underscoring their significant roles in cellular processes. The function of histone acetyltransferases is to facilitate the release of DNA from nucleosomes and act as transcriptional co-activators to promote gene transcription. Transcription factors recruit CBP/p300 by co-condensation and induce transcriptional bursting. Disruption of CBP or p300 functions is associated with different diseases, especially cancer, which can result from either loss of function or gain of function. CBP and p300 are multidomain proteins containing HAT (histone acetyltransferase) and BRD (bromodomain) domains, which perform acetyltransferase activity and maintenance of HAT signaling, respectively. Inhibitors targeting HAT and BRD have been explored for decades, and some BRD inhibitors have been evaluated in clinical trials for treating hematologic malignancies or advanced solid tumors. Here, we review the development and application of CBP/p300 inhibitors. Several inhibitors have been evaluated in vivo, exhibiting notable potency but limited selectivity. Exploring these inhibitors emphasizes the promise of targeting CBP and p300 with small molecules in cancer therapy.

Garcinia kola: a critical review on chemistry and pharmacology of an important West African medicinal plant

Garcinia kola Heckel (Clusiaceae) is a tree indigenous to West and Central Africa. All plant parts, but especially the seeds, are of value in local folklore medicine. Garcinia kola is used in treatment of numerous diseases, including gastric disorders, bronchial diseases, fever, malaria and is used to induce a stimulating and aphrodisiac effect. The plant is now attracting considerable interest as a possible source of pharmaceutically important drugs. Several different classes of compounds such as biflavonoids, benzophenones, benzofurans, benzopyran, vitamin E derivatives, xanthones, and phytosterols, have been isolated from G. kola, of which many appears to be found only in this species, such as garcinianin (found in seeds and roots), kolanone (fruit pulp, seeds, roots), gakolanone (stem bark), garcinoic acid, garcinal (both in seeds), garcifuran A and B, and garcipyran (all in roots). They showed a wide range of pharmacological activities (e.g. analgesic, anticancer, antidiabetic, anti-inflammatory, antimalarial, antimicrobial, hepatoprotective and neuroprotective effects), though this has only been confirmed in animal models. Kolaviron is the most studied compound and is perceived by many studies as the active principle of G. kola. However, its research is associated with significant flaws (e.g. too high doses tested, inappropriate positive control). Garcinol has been tested under better conditions and is perhaps showing more promising results and should attract deeper research interest (especially in the area of anticancer, antimicrobial, and neuroprotective activity). Human clinical trials and mechanism-of-action studies must be carried out to verify whether any of the compounds present in G. kola may be used as a lead in the drug development.

Acetyl-Click Screening Platform Identifies Small-Molecule Inhibitors of Histone Acetyltransferase 1 (HAT1)

HAT1 is a central regulator of chromatin synthesis that acetylates nascent histone H4. To ascertain whether targeting HAT1 is a viable anticancer treatment strategy, we sought to identify small-molecule inhibitors of HAT1 by developing a high-throughput HAT1 acetyl-click assay. Screening of small-molecule libraries led to the discovery of multiple riboflavin analogs that inhibited HAT1 enzymatic activity. Compounds were refined by synthesis and testing of over 70 analogs, which yielded structure-activity relationships. The isoalloxazine core was required for enzymatic inhibition, whereas modifications of the ribityl side chain improved enzymatic potency and cellular growth suppression. One compound (JG-2016 [24a]) showed relative specificity toward HAT1 compared to other acetyltransferases, suppressed the growth of human cancer cell lines, impaired enzymatic activity in cellulo, and interfered with tumor growth. This is the first report of a small-molecule inhibitor of the HAT1 enzyme complex and represents a step toward targeting this pathway for cancer therapy.

KATs off: Biomedical insights from lysine acetyltransferase inhibitors

Lysine acetyltransferase (KAT) enzymes including the p300, MYST, and GCN5 families play major roles in modulating the structure of chromatin and regulating transcription. Because of their dysregulation in various disease states including cancer, efforts to develop inhibitors of KATs have steadily gained momentum. Here we provide an overview of recent progress on the development of high quality chemical probes of the p300 and MYST family of KATs and how they are emerging as useful tools for basic and translational investigation.

The protective role of EP300 in monocrotaline-induced pulmonary hypertension

Background

Pulmonary hypertension (PH) is a lethal disease characterized by pulmonary vascular remodeling, which is mediated by the abnormal proliferation/migration of pulmonary arterial smooth muscle cells (PASMCs). Recent reports suggest the involvement of histone acetylation in PAH development and that histone deacetylase (HDAC) inhibitors have therapeutic potential for the treatment of PAH. EP300 is an acetyltransferase that plays diverse roles in cell proliferation, differentiation, and apoptosis. However, the functions of EP3000 in PH are rarely studied.

Results

In this work, we found that the expression of EP300 was increased in the pulmonary arteries of monocrotaline (MCT)-induced PH rats. Knockdown of EP300 by AAV-mediated shRNA exacerbated the PH, with a higher right ventricular systolic pressure (RVSP), right ventricular hypertrophy index (RVHI), and wall thickness in the pulmonary artery of MCT-induced PH rat. On the cellular level, the proliferation of PASMCs was promoted by EP300 knockdown. In addition, the expression of EP300 was increased in PASMCs by the overexpression of EGR1, while the deletion of EGR1 binding sites in the EP300 promoter region decreased the activity of EP300 promoter. Moreover, deleting the EP300 promoter region containing EGR1 binding sites using CRISPR/Cas9 abolished the upregulation of EP300 in MCT-induced rats and exacerbated MCT-induced PH. To summarize, our data indicate that EP300 upregulation mediated by EGR1 has a protective effect on MCT-induced PH.

Conclusion

These findings showed EP300 expression was increased in the MCT-induced PH model in rats, which could be mediated by EGR1; the EP300 also displayed the potential to provide protection from PH.

Histone modification and histone modification-targeted anti-cancer drugs in breast cancer: Fundamentals and beyond

Dysregulated epigenetic enzymes and resultant abnormal epigenetic modifications (EMs) have been suggested to be closely related to tumor occurrence and progression. Histone modifications (HMs) can assist in maintaining genome stability, DNA repair, transcription, and chromatin modulation within breast cancer (BC) cells. In addition, HMs are reversible, dynamic processes involving the associations of different enzymes with molecular compounds. Abnormal HMs (e.g. histone methylation and histone acetylation) have been identified to be tightly related to BC occurrence and development, even though their underlying mechanisms remain largely unclear. EMs are reversible, and as a result, epigenetic enzymes have aroused wide attention as anti-tumor therapeutic targets. At present, treatments to restore aberrant EMs within BC cells have entered preclinical or clinical trials. In addition, no existing studies have comprehensively analyzed aberrant HMs within BC cells; in addition, HM-targeting BC treatments remain to be further investigated. Histone and non-histone protein methylation is becoming an attractive anti-tumor epigenetic therapeutic target; such methylation-related enzyme inhibitors are under development at present. Consequently, the present work focuses on summarizing relevant studies on HMs related to BC and the possible mechanisms associated with abnormal HMs. Additionally, we also aim to analyze existing therapeutic agents together with those drugs approved and tested through pre-clinical and clinical trials, to assess their roles in HMs. Moreover, epi-drugs that target HMT inhibitors and HDAC inhibitors should be tested in preclinical and clinical studies for the treatment of BC. Epi-drugs that target histone methylation (HMT inhibitors) and histone acetylation (HDAC inhibitors) have now entered clinical trials or are approved by the US Food and Drug Administration (FDA). Therefore, the review covers the difficulties in applying HM-targeting treatments in clinics and proposes feasible approaches for overcoming such difficulties and promoting their use in treating BC cases.

Structure-activity relationship and antitumor activity of 1,4-pyrazine-containing inhibitors of histone acetyltransferases P300/CBP

Acetylation of histone lysine residues by histone acetyltransferase (HAT) p300 and its paralog CBP play important roles in gene regulation in health and diseases. The HAT domain of p300/CBP has been found to be a potential drug target for cancer. Compound screening followed by structure-activity relationship studies yielded a novel series of 1,4-pyrazine-containing inhibitors of p300/CBP HAT with their IC50s as low as 1.4 μM. Enzyme kinetics and other studies support the most potent compound 29 is a competitive inhibitor of p300 HAT against the substrate histone. It exhibited a high selectivity for p300 and CBP, with negligible activity on other classes of HATs in human. Compound 29 inhibited cellular acetylation of several histone lysine residues and showed strong activity against proliferation of a panel of solid and blood cancer cells. These results indicate it is a novel pharmacological lead for drug development targeting these cancers as well as a useful chemical probe for biological studies of p300/CBP.

Investigating peptide-Coenzyme A-conjugates as chemical probes for proteomic profiling of N-terminal and lysine acetyltransferases

Acetyl groups are transferred from acetyl‐coenzyme A (Ac‐CoA) to protein N‐termini and lysine side chains by N‐terminal acetyltransferases (NATs) and lysine acetyltransferases (KATs), respectively. Building on lysine‐CoA conjugates as KAT probes, we have synthesized peptide probes with CoA conjugated to N‐terminal alanine (α‐Ala‐CoA), proline (α‐Pro‐CoA) or tri‐glutamic acid (α‐3Glu‐CoA) units for interactome profiling of NAT complexes. The α‐Ala‐CoA probe enriched the majority of NAT catalytic and auxiliary subunits, while a lysine CoA‐conjugate bound only a subset of endogenous KATs. Interactome profiling with the α‐Pro‐CoA probe showed reduced NAT recruitment in favor of metabolic CoA binding proteins and α‐3Glu‐CoA steered the interactome towards NAA80 and NatB. These findings agreed with the inherent substrate specificities of the target proteins and showed that N‐terminal CoA‐conjugated peptides are versatile probes for NAT complex profiling in lysates of physiological and pathological backgrounds.

Histone acetyltransferases CBP/p300 in tumorigenesis and CBP/p300 inhibitors as promising novel anticancer agents

The histone acetyltransferases CBP and p300, often referred to as CBP/p300 due to their sequence homology and functional overlap and co-operation, are emerging as critical drivers of oncogenesis in the past several years. CBP/p300 induces histone H3 lysine 27 acetylation (H3K27ac) at target gene promoters, enhancers and super-enhancers, thereby activating gene transcription. While earlier studies indicate that CBP/p300 deletion/loss can promote tumorigenesis, CBP/p300 have more recently been shown to be over-expressed in cancer cells and drug-resistant cancer cells, activate oncogene transcription and induce cancer cell proliferation, survival, tumorigenesis, metastasis, immune evasion and drug-resistance. Small molecule CBP/p300 histone acetyltransferase inhibitors, bromodomain inhibitors, CBP/p300 and BET bromodomain dual inhibitors and p300 protein degraders have recently been discovered. The CBP/p300 inhibitors and degraders reduce H3K27ac, down-regulate oncogene transcription, induce cancer cell growth inhibition and cell death, activate immune response, overcome drug resistance and suppress tumor progression in vivo. In addition, CBP/p300 inhibitors enhance the anticancer efficacy of chemotherapy, radiotherapy and epigenetic anticancer agents, including BET bromodomain inhibitors; and the combination therapies exert substantial anticancer effects in mouse models of human cancers including drug-resistant cancers. Currently, two CBP/p300 inhibitors are under clinical evaluation in patients with advanced and drug-resistant solid tumors or hematological malignancies. In summary, CBP/p300 have recently been identified as critical tumorigenic drivers, and CBP/p300 inhibitors and protein degraders are emerging as promising novel anticancer agents for clinical translation.

Chemical Biology Tools for Protein Lysine Acylation

Lysine acylation plays pivotal roles in cell physiology, including DNA transcription and repair, signal transduction, immune defense, metabolism, and many other key cellular processes. Molecular mechanisms of dysregulated lysine acylation are closely involved in the pathophysiological progress of many human diseases, most notably cancers. In recent years, chemical biology tools have become instrumental in studying the function of post-translational modifications (PTMs), identifying new "writers", "erasers" and "readers", and in targeted therapies. Here, we describe key developments in chemical biology approaches that have advanced the study of lysine acylation and its regulatory proteins (2016-2021). We further discuss the discovery of ligands (inhibitors and PROTACs) that are capable of targeting regulators of lysine acylation. Next, we discuss some current challenges of these chemical biology probes and suggest how chemists and biologists can utilize chemical probes with more discriminating capacity. Finally, we suggest some critical considerations in future studies of PTMs from our perspective.

The P300 acetyltransferase inhibitor C646 promotes membrane translocation of insulin receptor protein substrate and interaction with the insulin receptor

Inhibition of P300 acetyltransferase activity by specific inhibitor C646 has been shown to improve insulin signaling. However, the underlying molecular mechanism of this improvement remains unclear. In this study, we analyzed P300 levels of obese patients and found that they were significantly increased in liver hepatocytes. In addition, large amounts of P300 appeared in the cytoplasm. Inhibition of P300 acetyltransferase activity by C646 drastically increased tyrosine phosphorylation of the insulin receptor protein substrates (IRS1/2) without affecting the tyrosine phosphorylation of the beta subunit of the insulin receptor (IRβ) in hepatocytes in the absence of insulin. Since IRS1/2 requires membrane translocation and binding to inositol compounds for normal functions, we also examined the role of acetylation on binding to phosphatidylinositol(4,5)P2, and found that IRS1/2 acetylation by P300 reduced this binding. In contrast, we show that inhibition of IRS1/2 acetylation by C646 facilitates IRS1/2 membrane translocation. Intriguingly, we demonstrate that C646 activates IRβ's tyrosine kinase activity and directly promotes IRβ interaction with IRS1/2, leading to the tyrosine phosphorylation of IRS1/2 and subsequent activation of insulin signaling even in the absence of insulin. In conclusion, these data reveal the unique effects of C646 in activating insulin signaling in patients with obesity and diabetes.

Design, synthesis and biological evaluation of a novel spiro oxazolidinedione as potent p300/CBP HAT inhibitor for the treatment of ovarian cancer

Histone acetylation is one of the most essential parts of epigenetic modification, mediating a variety of complex biological functions. In these procedure, p300/CBP could catalyze the acetylation of lysine 27 on histone 3 (H3K27ac), and had been reported to mediate tumorigenesis and development in a variety of tumors by enhancing chromatin transcription activity. Ovarian cancer, as an extremely malignant tumor, has also been observed to undergo abnormal acetylation of histones. However, whether the treatment of ovarian cancer could be achieved by inhibiting the acetylation activity of p300/CBP on H3K27 has not been well investigated. In this article, we modified the structure of p300/CBP HAT domain inhibitor A-485 and obtained a highly active small molecule known as 13f, which has an IC₅₀ value of 0.49 nM for inhibiting the in vitro enzyme activity of p300, as well as the anti-proliferation IC₅₀ value on ovarian cancer cell line OVCAR-3 was 153 nM. In addition, 13f had strong acetylase family selectivity, good metabolic stability and promising in vivo anti-tumor activity in OVCAR-3 xenograft model. The discovery of 13f revealed a more active chemical entity of the HATs domain of p300/CBP and provided a novel idea for the application of epigenetic inhibitors in the treatment of ovarian cancer.

Targeting Histone Modifications in Breast Cancer: A Precise Weapon on the Way

Histone modifications (HMs) contribute to maintaining genomic stability, transcription, DNA repair, and modulating chromatin in cancer cells. Furthermore, HMs are dynamic and reversible processes that involve interactions between numerous enzymes and molecular components. Aberrant HMs are strongly associated with tumorigenesis and progression of breast cancer (BC), although the specific mechanisms are not completely understood. Moreover, there is no comprehensive overview of abnormal HMs in BC, and BC therapies that target HMs are still in their infancy. Therefore, this review summarizes the existing evidence regarding HMs that are involved in BC and the potential mechanisms that are related to aberrant HMs. Moreover, this review examines the currently available agents and approved drugs that have been tested in pre-clinical and clinical studies to evaluate their effects on HMs. Finally, this review covers the barriers to the clinical application of therapies that target HMs, and possible strategies that could help overcome these barriers and accelerate the use of these therapies to cure patients.

Molecular Epigenetics: Chemical Biology Tools Come of Age

The field of epigenetics has exploded over the last two decades, revealing an astonishing level of complexity in the way genetic information is stored and accessed in eukaryotes. This expansion of knowledge, which is very much ongoing, has been made possible by the availability of evermore sensitive and precise molecular tools. This review focuses on the increasingly important role that chemistry plays in this burgeoning field. In an effort to make these contributions more accessible to the nonspecialist, we group available chemical approaches into those that allow the covalent structure of the protein and DNA components of chromatin to be manipulated, those that allow the activity of myriad factors that act on chromatin to be controlled, and those that allow the covalent structure and folding of chromatin to be characterized. The application of these tools is illustrated through a series of case studies that highlight how the molecular precision afforded by chemistry is being used to establish causal biochemical relationships at the heart of epigenetic regulation.

Viral Manipulation of the Host Epigenome as a Driver of Virus-Induced Oncogenesis

Tumorigenesis due to viral infection accounts for a high fraction of the total global cancer burden (15–20%) of all human cancers. A comprehensive understanding of the mechanisms by which viral infection leads to tumor development is extremely important. One of the main mechanisms by which viruses induce host cell proliferation programs is through controlling the host’s epigenetic machinery. In this review, we dissect the epigenetic pathways through which oncogenic viruses can integrate their genome into host cell chromosomes and lead to tumor progression. In addition, we highlight the potential use of drugs based on histone modifiers in reducing the global impact of cancer development due to viral infection.

PROTACs: Promising Approaches for Epigenetic Strategies to Overcome Drug Resistance

Epigenetic modulation of gene expression is essential for tissue-specific development and maintenance in mammalian cells. Disruption of epigenetic processes, and the subsequent alteration of gene functions, can result in inappropriate activation or inhibition of various cellular signaling pathways, leading to cancer. Recent advancements in the understanding of the role of epigenetics in cancer initiation and progression have uncovered functions for DNA methylation, histone modifications, nucleosome positioning, and non-coding RNAs. Epigenetic therapies have shown some promise for hematological malignancies, and a wide range of epigenetic-based drugs are undergoing clinical trials. However, in a dynamic survival strategy, cancer cells exploit their heterogeneous population which frequently results in the rapid acquisition of therapy resistance. Here, we describe novel approaches in drug discovery targeting the epigenome, highlighting recent advances the selective degradation of target proteins using Proteolysis Targeting Chimera (PROTAC) to address drug resistance.

Synthesis and Biological Evaluation of Spirocyclic Chromane Derivatives as a Potential Treatment of Prostate Cancer

As a significant co-activator involved in cell cycle and cell growth, differentiation and development, p300/CBP has shown extraordinary potential target in cancer therapy. Herein we designed new compounds from the lead compound A-485 based on molecular dynamic simulations. A series of new spirocyclic chroman derivatives was prepared, characterized and proven to be a potential treatment of prostate cancer. The most potent compound B16 inhibited the proliferation of enzalutamide-resistant 22Rv1 cells with an IC₅₀ value of 96 nM. Furthermore, compounds B16–P2 displayed favorable overall pharmacokinetic profiles, and better tumor growth inhibition than A-485 in an in vivo xenograft model.

Targeted degradation of the enhancer lysine acetyltransferases CBP and p300

The enhancer factors CREB-binding protein (CBP) and p300 (also known as KAT3A and KAT3B) maintain gene expression programs through lysine acetylation of chromatin and transcriptional regulators and by scaffolding functions mediated by several protein-protein interaction domains. Small molecule inhibitors that target some of these domains have been developed; however, they cannot completely ablate p300/CBP function in cells. Here we describe a chemical degrader of p300/CBP, dCBP-1. Leveraging structures of ligand-bound p300/CBP domains, we use in silico modeling of ternary complex formation with the E3 ubiquitin ligase cereblon to enable degrader design. dCBP-1 is exceptionally potent at killing multiple myeloma cells and can abolish the enhancer that drives MYC oncogene expression. As an efficient degrader of this unique class of acetyltransferases, dCBP-1 is a useful tool alongside domain inhibitors for dissecting the mechanism by which these factors coordinate enhancer activity in normal and diseased cells.

Tackle Epithelial-Mesenchymal Transition With Epigenetic Drugs in Cancer

Epithelial-mesenchymal Transition (EMT) is a de-differentiation process in which epithelial cells lose their epithelial properties to acquire mesenchymal features. EMT is essential for embryogenesis and wound healing but is aberrantly activated in pathological conditions like fibrosis and cancer. Tumor-associated EMT contributes to cancer cell initiation, invasion, metastasis, drug resistance and recurrence. This dynamic and reversible event is governed by EMT-transcription factors (EMT-TFs) with epigenetic complexes. In this review, we discuss recent advances regarding the mechanisms that modulate EMT in the context of epigenetic regulation, with emphasis on epigenetic drugs, such as DNA demethylating reagents, inhibitors of histone modifiers and non-coding RNA medication. Therapeutic contributions that improve epigenetic regulation of EMT will translate the clinical manifestation as treating cancer progression more efficiently.

Recent insights into Histone Acetyltransferase-1: biological function and involvement in pathogenesis

Acetylation of histone and non-histone proteins is a post-translational modification mostly associated with activation of gene transcription. The first histone acetyltransferase (HAT) identified as modifying newly synthesized histone H4 in yeast was a type B HAT named HAT1. Although it was the first HAT to be discovered, HAT1 remains one of the most poorly studied enzymes in its class. In addition to its well-established role in the cytoplasm, recent findings have revealed new and intriguing aspects of the function of HAT1 in the nucleus. Several studies have described its involvement in regulating different pathways associated with a wide range of diseases, including cancer. This review focuses on our current understanding of HAT1, highlighting its importance in regulating chromatin replication and gene expression. This previously unknown role for HAT1 opens up novel scenarios in which further studies will be required to better understand its function.

Role of histone acetyltransferase inhibitors in cancer therapy

The development of cancer is a complex phenomenon driven by various extrinsic as well as intrinsic risk factors including epigenetic modifications. These post-translational modifications are encountered in diverse cancer cells and appear for a relatively short span of time. These changes can significantly affect various oncogenic genes and proteins involved in cancer initiation and progression. Histone lysine acetylation and deacetylation processes are controlled by two opposing classes of enzymes that modulate gene regulation either by adding an acetyl moiety on a histone lysine residue by histone lysine acetyltransferases (KATs) or via removing it by histone deacetylases (KDACs). Deregulated KAT activity has been implicated in the development of several diseases including cancer and can be targeted for the development of anti-neoplastic drugs. Here, we describe the predominant epigenetic changes that can affect key KAT superfamily members during carcinogenesis and briefly highlight the pharmacological potential of employing lysine acetyltransferase inhibitors (KATi) for cancer therapy.

Computational insights into the binding mode of curcumin analogues against EP300 HAT domain as potent acetyltransferase inhibitors

Acetylation plays a key role in maintaining and balancing cellular regulation and homeostasis. Acetyltransferases are an important class of enzymes which mediate this acetylation process. EP300 is a type 3 major lysine (K) acetyl transferase, and its aberrant activity is implicated in many human diseases. Hence, targeting EP300 mediated acetylation is a necessary step to control the associated diseases. Currently, a few EP300 inhibitors are known, among which curcumin is the most widely investigated molecule. However, due to its instability, chemical aggregation and reactivity, its inhibitory activity against the EP300 acetyltransferase domain is disputable. To address this curcumin problem, different curcumin analogues have been synthesized. These molecules were selected for screening against the EP300 acetyltransferase domain using in silico docking and MD analysis. We have successfully elucidated that the curcumin analogue CNB001 is a potential EP300 inhibitor with good drug-like characteristics.

Catalysis by protein acetyltransferase Gcn5

Gcn5 serves as the defining member of the Gcn5-related N-acetyltransferase (GNAT) superfamily of proteins that display a common structural fold and catalytic mechanism involving the transfer of the acyl-group, primarily acetyl-, from CoA to an acceptor nucleophile. In the case of Gcn5, the target is the ε-amino group of lysine primarily on histones. Over the years, studies on Gcn5 structure-function have often formed the basis by which we understand the complex activities and regulation of the entire protein acetyltransferase family. It is now appreciated that protein acetylation occurs on thousands of proteins and can reversibly regulate the function of many cellular processes. In this review, we provide an overview of our fundamental understanding of catalysis, regulation of activity and substrate selection, and inhibitor development for this archetypal acetyltransferase.

Targeting a critical step in fungal hexosamine biosynthesis

Aspergillus fumigatus is a human opportunistic fungal pathogen whose cell wall protects it from the extracellular environment including host defenses. Chitin, an essential component of the fungal cell wall, is synthesized from UDP-GlcNAc produced in the hexosamine biosynthetic pathway. As this pathway is critical for fungal cell wall integrity, the hexosamine biosynthesis enzymes represent potential targets of antifungal drugs. Here, we provide genetic and chemical evidence that glucosamine 6-phosphate N-acetyltransferase (Gna1), a key enzyme in this pathway, is an exploitable antifungal drug target. GNA1 deletion resulted in loss of fungal viability and disruption of the cell wall, phenotypes that could be rescued by exogenous GlcNAc, the product of the Gna1 enzyme. In a murine model of aspergillosis, the Δgna1 mutant strain exhibited attenuated virulence. Using a fragment-based approach, we discovered a small heterocyclic scaffold that binds proximal to the Gna1 active site and can be optimized to a selective submicromolar binder. Taken together, we have provided genetic, structural, and chemical evidence that Gna1 is an antifungal target in A. fumigatus.

Correction of Niemann-Pick type C1 trafficking and activity with the histone deacetylase inhibitor valproic acid

Niemann-Pick type C (NPC) disease is primarily caused by mutations in the NPC1 gene and is characterized by the accumulation of unesterified cholesterol and lipids in the late endosomal (LE) and lysosomal (Ly) compartments. The most prevalent disease-linked mutation is the I1061T variant of NPC1, which exhibits defective folding and trafficking from the endoplasmic reticulum to the LE/Ly compartments. We now show that the FDA-approved histone deacetylase inhibitor (HDACi) valproic acid (VPA) corrects the folding and trafficking defect associated with I1061T-NPC1 leading to restoration of cholesterol homeostasis, an effect that is largely driven by a reduction in HDAC7 expression. The VPA-mediated trafficking correction is in part associated with an increase in the acetylation of lysine residues in the cysteine-rich domain of NPC1. The HDACi-mediated correction is synergistically improved by combining it with the FDA-approved anti-malarial, chloroquine, a known lysosomotropic compound, which improved the stability of the LE/Ly-localized fraction of the I1061T variant. We posit that combining the activity of VPA, to modulate epigenetically the cellular acetylome, with chloroquine, to alter the lysosomal environment to favor stability of the trafficked I1061T variant protein can have a significant therapeutic benefit in patients carrying at least one copy of the I1061T variant of NPC1, the most common disease-associated mutation leading to NPC disease. Given its ability to cross the blood-brain barrier, we posit VPA provides a potential mechanism to improve the response to 2-hydroxypropyl-β-cyclodextrin, by restoring a functional NPC1 to the cholesterol managing compartment as an adjunct therapy.

Discovery, Structure-Activity Relationship, and Biological Activity of Histone-Competitive Inhibitors of Histone Acetyltransferases P300/CBP

Histone acetyltransferase (HAT) p300 and its paralog CBP acetylate histone lysine side chains and play critical roles in regulating gene transcription. The HAT domain of p300/CBP is a potential drug target for cancer. Through compound screening and medicinal chemistry, novel inhibitors of p300/CBP HAT with their IC₅₀ values as low as 620 nM were discovered. The most potent inhibitor is competitive against histone substrates and exhibits a high selectivity for p300/CBP. It inhibited cellular acetylation and had strong activity with EC₅₀ of 1-3 μM against proliferation of several tumor cell lines. Gene expression profiling in estrogen receptor (ER)-positive breast cancer MCF-7 cells showed that inhibitor treatment recapitulated siRNA-mediated p300 knockdown, inhibited ER-mediated gene transcription, and suppressed expression of numerous cancer-related gene signatures. These results demonstrate that the inhibitor is not only a useful probe for biological studies of p300/CBP HAT but also a pharmacological lead for further drug development targeting cancer.

Early Drug-Discovery Efforts towards the Identification of EP300/CBP Histone Acetyltransferase (HAT) Inhibitors

EP300 and CBP (KAT3A/3B) are two highly homologous, multidomain, epigenetic coregulators that play central roles in transcription through the acetylation of lysine residues on histones and other proteins. Both enzymes have been implicated in human diseases, especially cancer. From a high-throughput screen of 191 000 compounds searching for EP300/CBP histone acetyltransferase (HAT) inhibitors, 18 compounds were characterized by a suite of biochemical enzymatic assays and biophysical methods, including X-ray crystallography and native mass spectrometry. This work resulted in the discovery of three distinct mechanistic classes of EP300/CBP HAT inhibitors, including two classes not previously described. The profiles of an example of each class of inhibitor are described in detail. A subsequent medicinal chemistry effort led to the development of a novel class of orally bioavailable AcCoA-competitive EP300/CBP HAT inhibitors with in vivo activity. We believe that this work will prove to be a useful guide for other groups interested in the development of HAT inhibitors.

A Systems Chemoproteomic Analysis of Acyl-CoA/Protein Interaction Networks

Acyl-coenzyme A (CoA)/protein interactions are essential for life. Despite this importance, their global scope and selectivity remains undefined. Here, we describe CATNIP (CoA/AcetylTraNsferase Interaction Profiling), a chemoproteomic platform for the high-throughput analysis of acyl-CoA/protein interactions in endogenous proteomes. First, we apply CATNIP to identify acetyl-CoA-binding proteins through unbiased clustering of competitive dose-response data. Next, we use this method to profile the selectivity of acyl-CoA/protein interactions, leading to the identification of specific acyl-CoA engagement signatures. Finally, we apply systems-level analyses to assess the features of protein networks that may interact with acyl-CoAs, and use a strategy for high-confidence proteomic annotation of acetyl-CoA-binding proteins to identify a site of non-enzymatic acylation in the NAT10 acetyltransferase domain that is likely driven by acyl-CoA binding. Overall, our studies illustrate how chemoproteomics and systems biology can be integrated to understand the roles of acyl-CoA metabolism in biology and disease.

A novel histone acetyltransferase inhibitor A485 improves sensitivity of non-small-cell lung carcinoma cells to TRAIL

Transcriptional coactivators p300 and CBP catalyze the acetylation of lysine residues in histone proteins. Upregulation of p300 and CBP has been associated with lung, colorectal and hepatocellular cancer, indicating an important role of p300 and CBP in tumorigenesis. Recently, the novel p300 and CBP-selective inhibitor A485 became available, which was shown to inhibit proliferation of 124 different cancer cell lines. Here, we found that downregulation of EP300 or CREBBP enhances apoptosis upon TRAIL stimulation in non-small-cell lung cancer (NSCLC) cells. A485 upregulates pro- and anti-apoptotic genes at the mRNA level, implying an apoptosis-modulating effect in NSCLC cells. However, A485 alone does not induce apoptosis. Interestingly, we observed that the number of apoptotic cells increases upon combined treatment with A485 and TRAIL. Therefore, A485, as a TRAIL-sensitizer, was used in combination with TRAIL in wild type of NSCLC cell lines (HCC827 and H1650) and cells with acquired erlotinib resistance (HCC827-ER and H1650-ER). Our results show that the combination of A485 and TRAIL synergistically increases cell death and inhibits long-term cell proliferation. Furthermore, this combination inhibits the growth of 3D spheroids of EGFR-TKI-resistant cells. Taken together, we demonstrate a successful combination of A485 and TRAIL in EGFR-TKI-sensitive and resistant NSCLC cells.

Discovery of Highly Potent, Selective, and Orally Efficacious p300/CBP Histone Acetyltransferases Inhibitors

p300 and CREB-binding protein (CBP) are ubiquitously expressed pleiotropic lysine acetyltransferases and play a key role as transcriptional co-activators that are essential for a multitude of cellular processes. Despite great importance, there is a lack of highly selective, potent, druglike p300/CBP inhibitors. Through the artificial-intelligence-assisted drug discovery pipeline and further optimization, we reported the discovery of novel, highly selective, potent small-molecule inhibitors of p300/CBP histone acetyltransferases (HAT) with desired druglike properties, exemplified by B026. Our data demonstrated that B026, with half maximal inhibitory concentration (IC50) values of 1.8 nM to p300 and 9.5 nM to CBP enzyme inhibitory activity, is the most potent, selective p300/CBP HAT inhibitor. Moreover, B026 achieves significant and dose-dependent tumor growth inhibition in an animal model of human cancer, suggesting that B026 is a highly promising p300/CBP HAT inhibitor and warrants extensive preclinical investigation as a potential clinical development candidate.

Epigenetic Modifications Associated with the Pathogenesis of Type 2 Diabetes Mellitus

BACKGROUND AND OBJECTIVE

Type 2 diabetes mellitus (T2DM) is a multifactorial metabolic disorder. Pancreatic β-cell dysfunction and insulin resistance are the most common and crucial events of T2DM. Increasing evidence suggests the association of epigenetic modifications with the pathogenesis of T2DM through the changes in important biological processes including pancreatic β- cell differentiation, development and maintenance of normal β-cell function. Insulin sensitivity by the peripheral glucose uptake tissues is also changed by the altered epigenetic mechanisms. In this review, we discussed the major epigenetic alterations and their effects on β-cell function, insulin secretion and insulin resistance in context of T2DM.

METHODS

We investigated the presently available epigenetic modifications including DNA methylation, posttranslational histone modifications, ATP-dependent chromatin remodeling and non-coding RNAs related to the pathogenesis of T2DM. Published literatures on this topic were searched both on Google Scholar and Pubmed with related keywords and investigated for relevant information.

RESULTS

The epigenetic modifications introduce changes in gene expression which are essential for appropriate β-cell development and functions, insulin secretion and sensitivity resulting in the pathogenesis of T2DM. Interestingly, T2DM could also be a prominent reason for the mentioned epigenetic alterations.

CONCLUSION

This review article emphasized on the epigenetic modifications associated with T2DM and discussed the consequences in deterioration of the disease condition.