3-deazaneplanocin A, a histone methyltransferase inhibitor, improved the chemoresistance induced under hypoxia in melanoma cells

One of common characteristics of solid tumors is low O2 level, so-called hypoxia, which plays a critical role in chemoresistance. Epigenetic mechanism such as DNA methylation and histone modification is involved in cancer development and progression. There is ample evidence that epigenetic drugs reversed acquired chemoresistance in cancer cells under normal O2 level, normoxia. However, it remains unknown whether epigenetic drugs improve acquired chemoresistance under hypoxia. The aim of our study was to investigate whether epigenetic drugs can improve the chemoresistance induced under hypoxia in cancer cells. In murine melanoma B16-BL6 (B16) cells, the culture under hypoxia, 1%O2 caused the elevated expression of hypoxia-inducible factor-1α (HIF-1α) and its target genes. The chemoresistance to 7-ethyl-10-hydroxycamptothecin (SN-38, the active metabolite of irinotecan) was also acquired under hypoxia in B16 cells. In addition, as epigenetic mechanisms, the protein expression of the enhancer of zeste homolog 2 (EZH2), histone methyltransferase and its target histone H3 trimethylation at lysine 27 (H3K27Me3) level increased under hypoxia. The induction of H3K27Me3 under hypoxia was suppressed by EZH2 siRNA and 3-deazaneplanocin A (DZNep), an EZH2 inhibitor. Furthermore, both EZH2 siRNA and DZNep significantly reduced the cell viability after SN-38 treatment and improved the chemoresistance to SN-38 under hypoxia. These results indicated that the chemoresistance to SN-38 under hypoxia would arise from epigenetic mechanism, H3K27Me3 elevation due to EZH2 induction. In conclusion, a histone methyltransferase EZH2 inhibitor, DZNep was capable of tackling acquired chemoresistance via the suppression of histone methylation induced under hypoxic tumor microenvironment.

Hypoxia-cleavable and specific targeted nanomedicine delivers epigenetic drugs for enhanced treatment of breast cancer and bone metastasis

Breast cancer bone metastasis has become a common cancer type that still lacks an effective treatment method. Although epigenetic drugs have demonstrated promise in cancer therapy, their nontargeted accumulation and drug resistance remain nonnegligible limiting factors. Herein, we first found that icaritin had a strong synergistic effect with an epigenetic drug (JQ1) in the suppression of breast cancer, which could help to relieve drug resistance to JQ1. To improve tumor-targeted efficacy, we developed a hypoxia-cleavable, RGD peptide-modified poly(D,L-lactide-co-glycolide) (PLGA) nanoparticle (termed ARNP) for the targeted delivery of JQ1 and icaritin. The decoration of long cleavable PEG chains can shield RGD peptides during blood circulation and reduce cellular uptake at nonspecific sites. ARNP actively targets breast cancer cells via an RGD-αvβ3 integrin interaction after PEG chain cleavage by responding to hypoxic tumor microenvironment. In vitro and in vivo assays revealed that ARNP exhibited good biodistribution and effectively suppressed primary tumor and bone metastasis. Meanwhile, ARNP could alleviate bone erosion to a certain extent. Furthermore, ARNP significantly inhibited pulmonary metastasis secondary to bone metastasis. The present study suggests that ARNP has great promise in the treatment of breast cancer and bone metastasis due to its simple and practical potential.

Use of histone methyltransferase inhibitors in cancer treatment: A systematic review

Histone modifications are an epigenetic mechanism, and the dysregulation of these proteins is known to be associated with the initiation and progression of cancer. In the search for the development of new and more effective drugs, histone modifications were identified as possible therapeutic targets. Histone methyltransferase (HMT) inhibitors correspond to the third generation of epigenetic drugs capable of writing or deleting epigenetic information. This systematic review summarized the development and prospect for the use of different HMT inhibitors in cancer therapy. An electronic search was applied across CENTRAL, Clinical Trials, Embase, LILACS, LIVIVO, Open Gray, PubMed, Scopus, and Web of Science. Based on the title and abstracts, two authors independently selected eligible studies. After the complete reading of the articles, based on the eligibility criteria, 11 studies were included in the review. Different inhibitors of HMT have been explored in multiple clinical studies, and have shown considerable anti-tumor effects. However, few phase 2 studies have been completed and/or have available results. The most advanced clinical trials mainly include tazemetostat, an Enhancer of zeste homolog 2 (EZH2) inhibitor approved for follicular lymphoma (FL). The use of HMT inhibitors has presented, so far, concise results in the treatment of hematological cancers, moreover, the adverse effects presented after the use of these medicines (alone or in combination) did not show a high level of risk for the patient. These findings, in addition to ongoing clinical studies, can represent a promising future regarding the use of HMT inhibitors in treating different types of cancer.

Epigenetic drug screen identified IOX1 as an inhibitor of Th17-mediated inflammation through targeting TET2

BACKGROUND

Targeting helper T cells, especially Th17 cells, has become a plausible therapy for many autoimmune diseases.

METHODS

Using an in vitro culture system, we screened an epigenetics compound library for inhibitors of IFN-γ and IL-17 expression in murine Th1 and Th17 cultures.

FINDINGS

This identified IOX1 as an effective suppressor of IL-17 expression in both murine and human CD4⁺ T cells. Furthermore, we found that IOX1 suppresses Il17a expression directly by targeting TET2 activity on its promoter in Th17 cells. Using established pre-clinical models of intraocular inflammation, treatment with IOX1 in vivo reduced the migration/infiltration of Th17 cells into the site of inflammation and tissue damage.

INTERPRETATION

These results provide evidence of the strong potential for IOX1 as a viable therapy for inflammatory diseases, in particular of the eye.

FUNDING

This study was supported by the National Key Research and Development Program of China 2021YFA1101200 (2021YFA1101204) to LW and XW; the National Natural Science Foundation of China 81900844 to XH and 82171041 to LW; the China Postdoctoral Science Foundation 2021M700776 and the Scientific Research Project of Guangdong Provincial Bureau of Traditional Chinese Medicine 20221373 to YZ; and the National Institute for Health Research (NIHR) Biomedical Research Centre at Moorfields Eye Hospital NHS (National Health Service) Foundation Trust and University College London Institute of Ophthalmology, UK (DAC, LPS, PJPL, MS, ADD and RWJL). The views expressed are those of the authors and not necessarily those of the NIHR or the UK's Department of Health and Social Care.

Screening for Small-Molecule Inhibitors of Histone Methyltransferases

Potent and highly selective small-molecule inhibitors are needed to unravel the biological complexities of histone methyltransferases and to reveal their therapeutic potential. A prerequisite to developing these inhibitors is the identification of validated chemical matter for initiating a medicinal chemistry campaign. For the most part, finding these initial starting points occurs through screening of large, unbiased compound libraries. The size and nature of these libraries, coupled with the complexities of the bisubstrate utilizing histone methyltransferases, necessitates that the primary screen and subsequent hit triage be carefully considered.In this chapter, using EZH2 as a representative example, we describe a screening and hit triage campaign that identified validated chemical matter allowing initiation of medicinal chemistry studies. Moreover, we discuss a cell-based assay to support lead identification and optimization. The approach described here entailing a mixture of biochemical, biophysical and cell-based assays should be applicable to identifying validated starting points for other histone methyltransferases.

Targeting cancer epigenetic pathways with small-molecule compounds: Therapeutic efficacy and combination therapies

Epigenetics mainly refers to covalent modifications to DNA or histones without affecting genomes, which ultimately lead to phenotypic changes in cells or organisms. Given the abundance of regulatory targets in epigenetic pathways and their pivotal roles in tumorigenesis and drug resistance, the development of epigenetic drugs holds a great promise for the current cancer therapy. However, lack of potent, selective, and clinically tractable small-molecule compounds makes the strategy to target cancer epigenetic pathways still challenging. Therefore, this review focuses on epigenetic pathways, small molecule inhibitors targeting DNA methyltransferase (DNMT) and small molecule inhibitors targeting histone modification (the main regulatory targets are histone acetyltransferases (HAT), histone deacetylases (HDACs) and histone methyltransferases (HMTS)), as well as the combination strategies of the existing epigenetic therapeutic drugs and more new therapies to improve the efficacy, which will shed light on a new clue on discovery of more small-molecule drugs targeting cancer epigenetic pathways as promising strategies in the future.

Epigenetic Regulation in Breast Cancer

Aberrant epigenetic alteration has been associated with development of various cancers, including breast cancer. Since epigenetic modifications such as DNA methylation and histone modification are reversible, epigenetic enzymes, including histone modifying enzymes and DNA methyltransferases, emerge as attractive targets for cancer therapy. Although epi-drugs targeting histone deacetylation or DNA methylation have received FDA approval for cancer therapy, a very modest anti-tumor activity has been observed with monotherapy in clinical studies of breast cancer. To improve efficacy of epi-drugs in breast cancer, combination of epi-drugs with other therapies currently has been investigated. Additionally, basic researches to elucidate molecular causes of cancer should be extensively and intensively conducted in order to find novel epigenetic druggable targets. In this chapter, we summarize how epigenetic regulation affects the development of breast cancer and how to control cancer phenotype by modulating abnormal epigenetic modifications, and then suggest future research directions in epigenetics for breast cancer treatment.

SOX9 is controlled by the BRD4 inhibitor JQ1 via multiple regulation mechanisms

SOX9 is a key transcription factor during cell differentiation, sex determination, and tumorigenesis. However, the detailed mechanisms of its targeting strategy remain elusive. To investigate possibilities of targeting SOX9 with epigenetic drugs and the precise underlying mechanisms, two human cancer cell lines were chosen as model systems, which showed high SOX9 expression and anti-tumorigenic effects upon loss of SOX9. Histone acetylation-related screening of a small panel of epigenetic drugs revealed that the bromodomain reader inhibitor JQ1 dramatically downregulated SOX9 through multiple regulation steps, namely, transcription, BRD4-SOX9 protein-protein interaction, and further protein stability. These findings suggest that BRD4 inhibition is a novel therapeutic strategy for diseases characterized by SOX9 overexpression.

[Epigenetic aberrations in adult T-cell leukemia/lymphoma and development of a novel EZH1/2 inhibitor]

Histone H3 lysine 27 tri-methylation (H3K27me3) -dependent transcription regulation is a fundamental process of gene control. Although EZH2 mutation is observed in certain lymphoma types, many other cancers show global H3K27me3 accumulation irrespective of mutation. However, the underlying mechanisms of gene silencing and therapeutic efficacies of epigenetic drugs remain unclear. In this study, we showed that globally-accumulated H3K27me3 is induced by both cis-bound EZH1 and EZH2 in mature lymphocyte-derived malignancies. Mutual interference and compensatory functions of co-expressed EZH1/2 rearrange the genome-wide distribution, establishing restricted chromatin and gene expression signatures. Using novel EZH1/2 dual inhibitors, we found that both EZH1 and EZH2 are required for the maintenance and induction of H3K27me3. The synthetic lethality of targeting EZH1 and EZH2 was observed in lymphoma models and primary adult T-cell leukemia/lymphoma (ATL) cells harboring H3K27me3 accumulation. This heritable EZH1/2 dysfunctional state was epigenetically imprinted at the virus-infected, immortalized phase. EZH1/2 dual inhibition could eliminate infected cell populations more effectively than EZH2 inhibition. Regarding the frequent observation of H3K27me3 accumulation in advanced-stage and early-phase malignant progenitors, the emerging EZH1- and EZH2-dependent epigenetic reprograming is an incipient process of fate decision within developmental pathways of cancers.

Glioma epigenetics: From subclassification to novel treatment options

Gliomas are the most common malignant primary brain tumors, of which glioblastoma is the most malignant form (WHO grade IV), and notorious for treatment resistance. Over the last decade mutations in epigenetic regulator genes have been identified as key drivers of subtypes of gliomas with distinct clinical features. Most characteristic are mutations in IDH1 or IDH2 in lower grade gliomas, and histone 3 mutations in pediatric high grade gliomas that are also associated with characteristic DNA methylation patterns. Furthermore, in adult glioblastoma patients epigenetic silencing of the DNA repair gene MGMT by promoter methylation is predictive for benefit from alkylating agent therapy. These epigenetic alterations are used as biomarkers and play a central role for classification of gliomas (WHO 2016) and treatment decisions. Here we review the pivotal role of epigenetic alterations in the etiology and biology of gliomas. We summarize the complex interactions between "driver" mutations, DNA methylation, histone post-translational modifications, and overall chromatin organization, and how they inform current efforts of testing epigenetic compounds and combinations in preclinical and clinical studies.

The epigenetic promotion of osteogenic differentiation of human adipose-derived stem cells by the genetic and chemical blockade of histone demethylase LSD1

Human adipose-derived stem cells (hASCs) are a highly attractive source in bone tissue engineering. It has become increasingly clear that chromatin regulators play an important role in cell fate determination. However, how osteogenic differentiation of hASCs is controlled by epigenetic mechanisms is not fully understood. Here we use genetic tools and chemical inhibitors to modify the epigenetic program of hASCs and identify lysine-specific demethylase 1 (LSD1), a histone demethylase that specifically catalyzes demethylation of di- and mono- methyl histone H3 lysine 4 (H3K4me2/1), as a key regulator in osteogenic differentiation of hASCs. Specifically, we demonstrated that genetic depletion of LSD1 with lentiviral strategy for gene knockdown promoted osteogenic differentiation of hASCs by cell studies and xenograft assays. At the molecular level, we found that LSD1 regulates osteogenesis-associated genes expression through its histone demethylase activity. Significantly, we demonstrated LSD1 demethylase inhibitors could efficiently block its catalytic activity and epigenetically boost osteogenic differentiation of hASCs. Altogether, our study defined the functional and biological roles of LSD1 and extensively explored the effects of its enzymatic activity in osteogenic differentiation of hASCs. A better understanding of how LSD1 influences on osteogenesis associated epigenetic events will provide new insights into the modulation of hASCs based cell therapy and improve the development of bone tissue engineering with epigenetic intervention.