EZH2 is essential for glioblastoma cancer stem cell maintenance

Hyperthermia for Targeting Cancer and Cancer Stem Cells: Insights from Novel Cellular and Clinical Approaches

The Cellular Heat Shock Response and in particular heat shock protein activation are vital stress reactions observed in both healthy and cancer cells. Hyperthermia (HT) has been proposed for several years as an advancing non-invasive cancer therapy. It selectively targets cancer cells through mechanisms influenced by temperature and temperature variations. This article delves into the impact of HT on cancer cells, especially cancer stem cells (CSCs), essential contributors to cancer recurrence and metastasis. HT has shown promise in eliminating CSCs, sensitizing them to conventional treatments and modulating the tumor microenvironment. The exploration extends to mesenchymal stem cells (MSCs), which exhibit both pro-tumorigenic and anti-tumorigenic effects. HT's potential in recruiting therapeutic MSCs for targeted delivery of antitumoral agents is also discussed. Furthermore, the article introduces Brain Thermodynamics-guided Hyperthermia (BTGH) technology, a breakthrough in temperature control and modulation of heat transfer under different conditions. This non-invasive method leverages the brain-eyelid thermal tunnel (BTT) to monitor and regulate internal brain temperature. BTGH technology, with its precision and noninvasive continuous monitoring capabilities, is under clinical investigation for applications in neurological disorders and cancer. The innovative three-phase approach involves whole-body HT, targeted brain HT, and organ-specific HT. In conclusion, the exploration of localized or whole-body HT offers promising avenues for cancer, psychiatric and neurological diseases. The ongoing clinical investigations and potential applications underscore the significance of understanding and harnessing heat's responses to enhance human health.

EZH2-mediated development of therapeutic resistance in cancer

Enhancer of zeste homolog 2 (EZH2) regulates gene expression and plays a definite role in cell proliferation, apoptosis, and senescence. Overexpression of EZH2 has been found in various human malignancies, including prostate, breast, and ovarian cancers, and is associated with increased metastasis and poor prognosis. EZH2 catalyzes trimethylation of lysine 27 of histone H3 (H3K27me3) as a canonical role in a PRC2-dependent manner. This mechanism silences various tumor suppressor genes through EZH2-mediated histone lysine methyltransferase activity. As a non-canonical role, EZH2 partners with other signaling molecules to undergo post-translational modification to orchestrate its function as a co-activator playing a critical role in cancer progression. Dysregulation of EZH2 has also been associated with therapeutic resistance in cancer cells. Given the role of EZH2 in promoting carcinogenesis and therapy resistance, both canonical and non-canonical EZH2 inhibitors have been used to combat multiple cancer types. Moreover, combining EZH2 inhibitors with other therapeutic modalities have shown to enhance the therapeutic efficacy and overcome potential resistance mechanisms in these cancerous cells. Therefore, targeting EZH2 through canonical and non-canonical modes appears to be a promising therapeutic strategy to enhance efficacy and overcome resistance in multiple cancers.

First-in-Class Dual EZH2-HSP90 Inhibitor Eliciting Striking Antiglioblastoma Activity In Vitro and In Vivo

Structural analysis of tazemetostat, an FDA-approved EZH2 inhibitor, led us to pinpoint a suitable site for appendage with a pharmacophoric fragment of second-generation HSP90 inhibitors. Resultantly, a magnificent dual EZH2/HSP90 inhibitor was pinpointed that exerted striking cell growth inhibitory efficacy against TMZ-resistant Glioblastoma (GBM) cell lines. Exhaustive explorations of chemical probe 7 led to several revelations such as (i) compound 7 increased apoptosis/necrosis-related gene expression, whereas decreased M phase/kinetochore/spindle-related gene expression as well as CENPs protein expression in Pt3R cells; (ii) dual inhibitor 7 induced cell cycle arrest at the M phase; (iii) compound 7 suppressed reactive oxygen species (ROS) catabolism pathway, causing the death of TMZ-resistant GBM cells; and (iv) compound 7 elicited substantial in vivo anti-GBM efficacy in experimental mice xenografted with TMZ-resistant Pt3R cells. Collectively, the study results confirm the potential of dual EZH2-HSP90 inhibitor 7 as a tractable anti-GBM agent.

EZH2 Inhibition Sensitizes IDH1R132H-Mutant Gliomas to Histone Deacetylase Inhibitor

Isocitrate Dehydrogenase-1 (IDH1) is commonly mutated in lower-grade diffuse gliomas. The IDH1R132H mutation is an important diagnostic tool for tumor diagnosis and prognosis; however, its role in glioma development, and its impact on response to therapy, is not fully understood. We developed a murine model of proneural IDH1R132H-mutated glioma that shows elevated production of 2-hydroxyglutarate (2-HG) and increased trimethylation of lysine residue K27 on histone H3 (H3K27me3) compared to IDH1 wild-type tumors. We found that using Tazemetostat to inhibit the methyltransferase for H3K27, Enhancer of Zeste 2 (EZH2), reduced H3K27me3 levels and increased acetylation on H3K27. We also found that, although the histone deacetylase inhibitor (HDACi) Panobinostat was less cytotoxic in IDH1R132H-mutated cells (either isolated from murine glioma or oligodendrocyte progenitor cells infected in vitro with a retrovirus expressing IDH1R132H) compared to IDH1-wild-type cells, combination treatment with Tazemetostat is synergistic in both mutant and wild-type models. These findings indicate a novel therapeutic strategy for IDH1-mutated gliomas that targets the specific epigenetic alteration in these tumors.

Cyclohexene oxide CA, a derivative of zeylenone, exhibits anti-cancer activity in glioblastoma by inducing G0/G1 phase arrest through interference with EZH2

Introduction: Due to its highly aggressiveness and malignancy, glioblastoma (GBM) urgently requires a safe and effective treatment strategy. Zeylenone, a natural polyoxygenated cyclohexenes compound isolated from Uvaria grandiflora, has exhibited potential biological activities in various human diseases, including tumors. Methods: We designed and synthesized a series of (+)-Zeylenone analogues and evaluated their anti-GBM roles through structural-activity analysis. Cell Counting Kit-8, TUNEL, transwell and flow cytometry were employed for investigating the anticancer effects of CA on GBM cells. Western blotting, molecular docking, qRT-PCR and ChIP assays were performed to reveal the underlying mechanisms by which CA regulates the GBM cell cycle. The nude mouse xenograft model, HE staining, immunohistochemistry and was used to evaluate the anticancer effect of CA in vivo. Results: We identified CA ((1R, 2R, 3S)-3-p-fluorobenzoyl-zeylenone) as having the lowest IC50 value in GBM cells. CA treatment significantly inhibited the malignant behaviors of GBM cells and induced G0/G1 phase arrest in vitro. Furthermore, we validated the molecular mechanism by which CA interferes with EZH2, attenuating the down-regulation of cyclin-dependent kinase inhibitors p27 and p16 by the PRC2 complex. By establishing orthotopic nude mice models, we further validated the inhibitory role of CA on tumorigenesis of GBM cells in vivo and its potential values to synergistically potentiate the anti-tumor effects of EZH2 inhibitors. Conclusion: Overall, this paper elucidated the anti-GBM effects and potential mechanisms of CA, and may provide a therapeutic drug candidate for GBM treatment.

Polycomb repressor complex: Its function in human cancer and therapeutic target strategy

The Polycomb Repressor Complex (PRC) plays a pivotal role in gene regulation during development and disease, with dysregulation contributing significantly to various human cancers. The intricate interplay between PRC and cellular signaling pathways sheds light on cancer complexity. PRC presents promising therapeutic opportunities, with inhibitors undergoing rigorous evaluation in preclinical and clinical studies. In this review, we emphasize the critical role of PRC complex in gene regulation, particularly PcG proteins mediated chromatin compaction through phase separation. We also highlight the pathological implications of PRC complex dysregulation in various tumors, elucidating underlying mechanisms driving cancer progression. The burgeoning field of therapeutic strategies targeting PRC complexes, notably EZH2 inhibitors, has advanced significantly. However, we explore the need for combination therapies to enhance PRC targeted treatments efficacy, providing a glimpse into the future of cancer therapeutics.

SUZ12 inhibition attenuates cell proliferation of glioblastoma via post-translational regulation of CDKN1B

BACKGROUND

Human gliomas are aggressive brain tumors characterized by uncontrolled cell proliferation. Differential expression of Polycomb repressive complex 2 (PRC2) has been reported in various subtypes of glioma. However, the role of PRC2 in uncontrolled growth in glioma and its underlying molecular mechanisms remain to be elucidated.

OBJECTIVE

We aimed to investigate the functional role of PRC2 in human glioblastoma cell growth by silencing SUZ12, the non-catalytic core component of PRC2.

METHODS

Knockdown of SUZ12 was achieved by infecting T98G cells with lentivirus carrying sequences specifically targeting SUZ12 (shSUZ12). Gene expression was examined by quantitative PCR and western analysis. The impact of shSUZ12 on cell growth was assessed using a cell proliferation assay. Cell cycle distribution was analyzed by flow cytometry, and protein stability was evaluated in cycloheximide-treated cells. Subcellular localization was examined through immunofluorescence staining and biochemical cytoplasmic-nuclear fractionation. Gene expression analysis was also performed on human specimens from normal brain and glioblastoma patients.

RESULTS

SUZ12 knockdown (SUZ12 KD) led to widespread decrease in the PRC2-specific histone mark, accompanied by a slowdown of cell proliferation through G1 arrest. In SUZ12 KD cells, the degradation of CDKN1B protein was reduced, resulting from alterations in the MYC-SKP2-CDKN1B axis. Furthermore, nuclear localization of CDKN1B was enhanced in SUZ12 KD cells. Analysis of human glioblastoma samples yielded increased expression of EZH2 and MYC along with reduced CDKN1B compared to normal human brain tissue.

CONCLUSION

Our findings suggest a novel role for SUZ12 in cell proliferation through post-translational regulation of CDKN1B in glioblastoma.

The Role of Non-Coding RNAs in Epigenetic Dysregulation in Glioblastoma Development

Glioblastoma (GBM) is a primary brain tumor arising from glial cells. The tumor is highly aggressive, the reason for which it has become the deadliest brain tumor type with the poorest prognosis. Like other cancers, it compromises molecular alteration on genetic and epigenetic levels. Epigenetics refers to changes in gene expression or cellular phenotype without the occurrence of any genetic mutations or DNA sequence alterations in the driver tumor-related genes. These epigenetic changes are reversible, making them convenient targets in cancer therapy. Therefore, we aim to review critical epigenetic dysregulation processes in glioblastoma. We will highlight the significant affected tumor-related pathways and their outcomes, such as regulation of cell cycle progression, cell growth, apoptosis, angiogenesis, cell invasiveness, immune evasion, or acquirement of drug resistance. Examples of molecular changes induced by epigenetic modifications, such as DNA epigenetic alterations, histone post-translational modifications (PTMs), and non-coding RNA (ncRNA) regulation, are highlighted. As understanding the role of epigenetic regulators and underlying molecular mechanisms in the overall pro-tumorigenic landscape of glioblastoma is essential, this literature study will provide valuable insights for establishing the prognostic or diagnostic value of various non-coding transcripts, including miRNAs.

Phosphorylation of EZH2 differs HER2-positive breast cancer invasiveness in a site-specific manner

HER2-positive breast cancer (BC) invasiveness and drug-resistance issue is the critical treatment obstacle recently. We investigated the total and phosphorylated status EZH2 expression in database and BC tissue microarray. We demonstrated for the first time that EZH2 is distributed both in cytoplasm and nucleus of breast cancer cells in a phosphorylation site-specific manner. High expressed-EZH2 cases more frequently had an advanced clinical stage (lymph node metastasis) and aggressive features than EZH2-low cases, potentially indicating the high risk of HER2-positive BC (p < 0.05). Notably, highly expressed phosphorylated EZH2 is differently located in cytoplasm or nucleus in a site-specific manner in breast cancer cells. Nucleus-located pEZH2-S21 is expressed in invasive and lymph node metastatic HER2-positive BC cases (p = 0.144, p = 0.001). Cytoplasmic pEZH2-T487 is correlated with HER2 positive status (p = 0.014).In conclusion, high expression of nucleus-located EZH2 might be a predictor of invasive BC. Activation of phosphorylated EZH2-S21 site in nucleus would be a potential predictor of HER2-positve BC and poor efficacy of HER2-target therapy. These results point to a PRC2-independent non-epigenetic mechanism and therapeutic strategy of EZH2 in HER2-positive BC.

MiR-662 is associated with metastatic relapse in early-stage breast cancer and promotes metastasis by stimulating cancer cell stemness

BACKGROUND

Breast cancer (BC) metastasis, which often occurs in bone, contributes substantially to mortality. MicroRNAs play a fundamental role in BC metastasis, although microRNA-regulated mechanisms driving metastasis progression remain poorly understood.

METHODS

MiRome analysis in serum from BC patients was performed by TaqMan™ low-density array. MiR-662 was overexpressed following MIMIC-transfection or lentivirus transduction. Animal models were used to investigate the role of miR-662 in BC (bone) metastasis. The effect of miR-662-overexpressing BC cell conditioned medium on osteoclastogenesis was investigated. ALDEFLUOR assays were performed to study BC stemness. RNA-sequencing transcriptomic analysis of miR-662-overexpressing BC cells was performed to evaluate gene expression changes.

RESULTS

High levels of hsa-miR-662 (miR-662) in serum from BC patients, at baseline (time of surgery), were associated with future recurrence in bone. At an early-stage of the metastatic disease, miR-662 could mask the presence of BC metastases in bone by inhibiting the differentiation of bone-resorbing osteoclasts. Nonetheless, metastatic miR-662-overexpressing BC cells then progressed as overt osteolytic metastases thanks to increased stem cell-like traits.

CONCLUSIONS

MiR-662 is involved in BC metastasis progression, suggesting it may be used as a prognostic marker to identify BC patients at high risk of metastasis.

Epigenetic control of cell signalling in cancer stem cells

The self-renewing cancer stem cells (CSCs) represent one of the distinct cell populations occurring in a tumour that can differentiate into multiple lineages. This group of sparsely abundant cells play a vital role in tumour survival and resistance to different treatments during cancer. The lack of exclusive markers associated with CSCs makes diagnosis and prognosis in cancer patients extremely difficult. This calls for the identification of unique regulators and markers for CSCs. Various signalling pathways like the Wnt/β-catenin pathway, Hedgehog pathway, Notch pathway, and TGFβ/BMP play a major role in the regulation and maintenance of CSCs. Epigenetic regulatory mechanisms add another layer of complexity to control these signalling pathways. In this chapter, we discuss about the role of epigenetic mechanisms in regulating the cellular signalling pathways in CSCs. The epigenetic regulatory mechanisms such as DNA methylation, histone modification and microRNAs can modulate the diverse effectors of signalling pathways and consequently the growth, differentiation and tumorigenicity of CSCs. In the end, we briefly discuss the therapeutic potential of targeting these epigenetic regulators and their target genes in CSCs.

EZH2 Contributes to Anoikis Resistance and Promotes Epithelial Ovarian Cancer Peritoneal Metastasis by Regulating m6A

OBJECTIVE

Histone modification has a significant effect on gene expression. Enhancer of zeste homolog 2 (EZH2) contributes to the epigenetic silencing of target chromatin through its roles as a histone-lysine N-methyltransferase enzyme. The development of anoikis resistance in tumor cells is considered to be a critical step in the metastatic process of primary malignant tumors. The purpose of this study was to investigate the effect and mechanism of anoikis resistance in ovarian adenocarcinoma peritoneal metastasis.

METHODS

In addition to examining EZH2 protein expression in ovarian cancer omental metastatic tissues, we established a model of ovarian cancer cell anoikis and a xenograft tumor model in nude mice. Anoikis resistance and ovarian cancer progression were tested after EZH2 and N6-methyladenosine (m6A) levels were modified.

RESULTS

EZH2 expression was significantly higher in ovarian cancer omental metastatic tissues than in normal ovarian tissues. Reducing the level of EZH2 decreased the level of m6A and ovarian cancer cell anoikis resistance in vitro and inhibited ovarian cancer progression in vivo. M6a regulation altered the effect of EZH2 on anoikis resistance.

CONCLUSION

Our results indicate that EZH2 contributes to anoikis resistance and promotes ovarian adenocarcinoma abdominal metastasis by m6A modification. Our findings imply the potential of the clinical application of m6A and EZH2 for patients with ovarian cancer.

Prediction of hub genes and key pathways associated with the radiation response of human hematopoietic stem/progenitor cells using integrated bioinformatics methods

Hematopoietic stem cells (HSCs) are indispensable for the maintenance of the entire blood program through cytokine response. However, HSCs have high radiosensitivity, which is often a problem during radiation therapy and nuclear accidents. Although our previous study has reported that the combination cytokine treatment (interleukin-3, stem cell factor, and thrombopoietin) improves the survival of human hematopoietic stem/progenitor cells (HSPCs) after radiation, the mechanism by which cytokines contribute to the survival of HSPCs is largely unclear. To address this issue, the present study characterized the effect of cytokines on the radiation-induced gene expression profile of human CD34⁺ HSPCs and explored the hub genes that play key pathways associated with the radiation response using a cDNA microarray, a protein-protein interaction-MCODE module analysis and Cytohubba plugin tool in Cytoscape. This study identified 2,733 differentially expressed genes (DEGs) and five hub genes (TOP2A, EZH2, HSPA8, GART, HDAC1) in response to radiation in only the presence of cytokines. Furthermore, functional enrichment analysis found that hub genes and top DEGs based on fold change were enriched in the chromosome organization and organelle organization. The present findings may help predict the radiation response and improve our understanding of this response of human HSPCs.

The role of histone H3 lysine demethylases in glioblastoma

Glioblastoma (GBM) is the most aggressive primary brain tumor in adults with an average survival of 15-18 months. Part of its malignancy derives from epigenetic regulation that occurs as the tumor develops and after therapeutic treatment. Specifically, enzymes involved in removing methylations from histone proteins on chromatin, i.e., lysine demethylases (KDMs), have a significant impact on GBM biology and reoccurrence. This knowledge has paved the way to considering KDMs as potential targets for GBM treatment. For example, increases in trimethylation of histone H3 on the lysine 9 residue (H3K9me3) via inhibition of KDM4C and KDM7A has been shown to lead to cell death in Glioblastoma initiating cells. KDM6 has been shown to drive Glioma resistance to receptor tyrosine kinase inhibitors and its inhibition decreases tumor resistance. In addition, increased expression of the histone methyltransferase MLL4 and UTX histone demethylase are associated with prolonged survival in a subset of GBM patients, potentially by regulating histone methylation on the promoter of the mgmt gene. Thus, the complexity of how histone modifiers contribute to glioblastoma pathology and disease progression is yet to be fully understood. To date, most of the current work on histone modifying enzymes in GBM are centered upon histone H3 demethylase enzymes. In this mini-review, we summarize the current knowledge on the role of histone H3 demethylase enzymes in Glioblastoma tumor biology and therapy resistance. The objective of this work is to highlight the current and future potential areas of research for GBM epigenetics therapy.

macroH2A2 antagonizes epigenetic programs of stemness in glioblastoma

Self-renewal is a crucial property of glioblastoma cells that is enabled by the choreographed functions of chromatin regulators and transcription factors. Identifying targetable epigenetic mechanisms of self-renewal could therefore represent an important step toward developing effective treatments for this universally lethal cancer. Here we uncover an epigenetic axis of self-renewal mediated by the histone variant macroH2A2. With omics and functional assays deploying patient-derived in vitro and in vivo models, we show that macroH2A2 shapes chromatin accessibility at enhancer elements to antagonize transcriptional programs of self-renewal. macroH2A2 also sensitizes cells to small molecule-mediated cell death via activation of a viral mimicry response. Consistent with these results, our analyses of clinical cohorts indicate that high transcriptional levels of this histone variant are associated with better prognosis of high-grade glioma patients. Our results reveal a targetable epigenetic mechanism of self-renewal controlled by macroH2A2 and suggest additional treatment approaches for glioblastoma patients.

EZH2-Myc driven glioblastoma elicited by cytomegalovirus infection of human astrocytes

Mounting evidence is identifying human cytomegalovirus (HCMV) as a potential oncogenic virus. HCMV has been detected in malignant gliomas. EZH2 and Myc play a potential oncogenic role, correlating with the glioma grade. Herewith, we present the first experimental evidence for HCMV as a reprogramming vector, straight through the dedifferentiation of mature human astrocytes, and generation of CMV-Elicited Glioblastoma Cells (CEGBCs) possessing glioblastoma-like traits. HCMV counterparts the progression of the perceived cellular and molecular mechanisms succeeding the transformation and invasion processes with CEGBCs involved in spheroid formation and invasiveness. Glioblastoma multiforme (GBM) biopsies were characterized by an elevated EZH2 and Myc expression, possessing a strong positive correlation between the aforementioned markers in the presence of HCMV. From GBM tissues, we isolated HCMV clinical strains that transformed HAs toward CEGBCs exhibiting upregulated EZH2 and Myc. Spheroids generated from CEGBCs possessed invasion potential and were sensitive to EZH2 inhibitor, ganciclovir, and temozolomide triple therapy. HCMV clinical strains transform HAs and fit with an HCMV-induced glioblastoma model of oncogenesis, and supports the tumorigenic properties of Myc and EZH2 which might be highly pertinent in the pathophysiology of astrocytic brain tumors and thereby paving the way for new therapeutic strategies.

EZH2 and NF-κB: A context-dependent crosstalk and transcriptional regulation in cancer

Epigenetic modifications regulate critical biological processes that play a pivotal role in the pathogenesis of cancer. Enhancer of Zeste Homolog 2 (EZH2), a subunit of the Polycomb-Repressive Complex 2, catalyzes trimethylation of histone H3 on Lys 27 (H3K27) involved in gene silencing. EZH2 is amplified in human cancers and has roles in regulating several cellular processes, including survival, proliferation, invasion, and self-renewal. Though EZH2 is responsible for gene silencing through its canonical role, it also regulates the transcription of several genes promoting carcinogenesis via its non-canonical role. Constitutive activation of Nuclear Factor-kappaB (NF-κB) plays a crucial role in the development and progression of human malignancies. NF-κB is essential for regulating innate and adaptive immune responses and is one of the most important molecules that increases survival during carcinogenesis. Given the evidence that increased survival and proliferation are essential for tumor development and their association with epigenetic modifications, it seems plausible that EZH2 and NF-κB crosstalk may promote cancer progression. In this review, we expand on how EZH2 and NF-κB regulate cellular responses during cancer and their crosstalk of the canonical and non-canonical roles in a context-dependent manner.

Epigenetics and immune cells in medulloblastoma

Medulloblastoma (MB) is a highly malignant childhood tumor of the cerebellum. Transcriptional and epigenetic signatures have classified MB into four molecular subgroups, further stratified into biologically different subtypes with distinct somatic copy-number aberrations, driver genes, epigenetic alterations, activated pathways, and clinical outcomes. The brain tumor microenvironment (BTME) is of importance to regulate a complex network of cells, including immune cells, involved in cancer progression in brain malignancies. MB was considered with a “cold” immunophenotype due to the low influx of immune cells across the blood brain barrier (BBB). Recently, this assumption has been reconsidered because of the identification of infiltrating immune cells showing immunosuppressive phenotypes in the BTME of MB tumors. Here, we are providing a comprehensive overview of the current status of epigenetics alterations occurring during cancer progression with a description of the genomic landscape of MB by focusing on immune cells within the BTME. We further describe how new immunotherapeutic approaches could influence concurring epigenetic mechanisms of the immunosuppressive cells in BTME. In conclusion, the modulation of these molecular genetic complexes in BTME during cancer progression might enhance the therapeutic benefit, thus firing new weapons to fight MB.

Epigenetics in cancer development, diagnosis and therapy

Cancer is a dangerous disease and one of the leading causes of death in the world. In 2020, there were nearly 10 million cancer deaths and approximately 20 million new cases. New cases and deaths from cancer are expected to increase further in the coming years. To have a deeper insight into the mechanism of carcinogenesis, epigenetics studies have been published and received much attention from scientists, doctors, and patients. Among alterations in epigenetics, DNA methylation and histone modification are studied by many scientists. They have been reported to be a major contributor in tumor formation and are involved in metastasis. From the understanding of DNA methylation and histone modification, effective, accurate and cost-effective methods for diagnosis and screening of cancer patients have been introduced. Furthermore, therapeutic approaches and drugs targeting altered epigenetics have also been clinically studied and have shown positive results in combating tumor progression. Several cancer drugs that rely on DNA methylation inactivation or histone modification have been approved by the FDA for the treatment of cancer patients. In summary, epigenetics changes such as DNA methylation or histone modification are take part in tumor growth, and they also have great prospect to study diagnostic and therapeutic methods of this dangerous disease.

EZH2 interacts with HP1BP3 to epigenetically activate WNT7B that promotes temozolomide resistance in glioblastoma

Glioblastoma (GBM) is the most lethal primary brain tumor in adults and harbors a subpopulation of glioma stem cells (GSCs). Enhancer of Zeste Homolog 2 (EZH2), a histone lysine methyltransferase, deeply involves in the stemness maintenance of GSC. However, the precise mechanism and therapeutic potential remain elusive. We postulated that the interactome of EZH2 in GSC is unique. Therefore, we performed proteomic and transcriptomic research to unveil the oncogenic mechanism of EZH2. Immunoprecipitation and mass spectrometry were used to identify proteins that co-precipitate with EZH2. We show that EZH2 binds to heterochromatin protein 1 binding protein 3 (HP1BP3) in GSCs and impairs the methylation of H3K9. Overexpression of HP1BP3 enhances the proliferation, self-renewal and temozolomide (TMZ) resistance of GBM cells. Furthermore, EZH2 and HP1BP3 co-activate WNT7B expression thereby increasing TMZ resistance and stemness of GBM cells. Importantly, inhibition of WNT7B autocrine via LGK974 effectively reverses the TMZ resistance. Our work clarifies a new oncogenic mechanism of EZH2 by which it interacts with HP1BP3 and epigenetically activates WNT7B thereby promoting TMZ resistance in GSCs. Our results provide a rationale for targeting WNT/β-catenin pathway as a promising strategy to overcome TMZ resistance in GSCs.

The function of histone methylation and acetylation regulators in GBM pathophysiology

Glioblastoma (GBM) is the most common and lethal primary brain malignancy and is characterized by a high degree of intra and intertumor cellular heterogeneity, a starkly immunosuppressive tumor microenvironment, and nearly universal recurrence. The application of various genomic approaches has allowed us to understand the core molecular signatures, transcriptional states, and DNA methylation patterns that define GBM. Histone posttranslational modifications (PTMs) have been shown to influence oncogenesis in a variety of malignancies, including other forms of glioma, yet comparatively less effort has been placed on understanding the transcriptional impact and regulation of histone PTMs in the context of GBM. In this review we discuss work that investigates the role of histone acetylating and methylating enzymes in GBM pathogenesis, as well as the effects of targeted inhibition of these enzymes. We then synthesize broader genomic and epigenomic approaches to understand the influence of histone PTMs on chromatin architecture and transcription within GBM and finally, explore the limitations of current research in this field before proposing future directions for this area of research.

Epigenetic alterations in glioblastomas: Diagnostic, prognostic and therapeutic relevance

Glioblastoma, the most common and heterogeneous tumor affecting brain parenchyma, is dismally characterized by a very poor prognosis. Thus, the search of new, more effective treatments is a vital need. Here, we will review the druggable epigenetic features of glioblastomas that are, indeed, currently explored in preclinical studies and in clinical trials for the development of more effective, personalized treatments. In detail, we will review the studies that have led to the identification of epigenetic signatures, IDH mutations, MGMT gene methylation, histone modification alterations, H3K27 mutations and epitranscriptome landscapes of glioblastomas, in each case discussing the corresponding targeted therapies and their potential efficacy. Finally, we will emphasize how recent technological improvements permit to routinely investigate many glioblastoma epigenetic biomarkers in clinical practice, further enforcing the hope that personalized drugs, targeting specific epigenetic features, could be in future a therapeutic option for selected patients.

Changing paradigms in oncology: Toward noncytotoxic treatments for advanced gliomas

Glial-lineage malignancies (gliomas) recurrently mutate and/or delete the master regulators of apoptosis p53 and/or p16/CDKN2A, undermining apoptosis-intending (cytotoxic) treatments. By contrast to disrupted p53/p16, glioma cells are live-wired with the master transcription factor circuits that specify and drive glial lineage fates: these transcription factors activate early-glial and replication programs as expected, but fail in their other usual function of forcing onward glial lineage-maturation-late-glial genes have constitutively "closed" chromatin requiring chromatin-remodeling for activation-glioma-genesis disrupts several epigenetic components needed to perform this work, and simultaneously amplifies repressing epigenetic machinery instead. Pharmacologic inhibition of repressing epigenetic enzymes thus allows activation of late-glial genes and terminates glioma self-replication (self-replication = replication without lineage-maturation), independent of p53/p16/apoptosis. Lineage-specifying master transcription factors therefore contrast with p53/p16 in being enriched in self-replicating glioma cells, reveal a cause-effect relationship between aberrant epigenetic repression of late-lineage programs and malignant self-replication, and point to specific epigenetic targets for noncytotoxic glioma-therapy.

Long noncoding RNA HOTAIR regulates the stemness of breast cancer cells via activation of the NF-κB signaling pathway

Breast cancer is the most prevalent cancer among women, and it is characterized by a high rate of tumor development and heterogeneity. Breast cancer stem cells (CSCs) may well contribute to these pathological properties, but the mechanisms underlying their self-renewal and maintenance are still elusive. Here, we found that the long noncoding RNA HOTAIR is highly expressed in breast CSCs. HOTAIR is required for breast CSC self-renewal and tumor propagation. Mechanistically, we demonstrate that HOTAIR recruits the PRC2 protein complex to the promoter of IκBα to inhibit its expression, leading to activation of the NF-κB signaling pathway. The activated NF-κB signaling promotes downstream c-Myc and Cyclin D1 expression. Furthermore, our analysis of clinical samples from the GEPIA database indicated that the IκBα level, as well as the survival rate of patients, with high HOTAIR expression was significantly lower than that of patients with relatively low HOTAIR expression. Our data suggest that HOTAIR-mediated NF-κB signaling primes breast CSC self-renewal and tumor propagation. In sum, we have identified HOTAIR-based NF-κB signaling regulatory circuit that promotes tumorigenic activity in breast CSCs, further indicating that HOTAIR could be a promising target for clinical treatment of breast cancers.

Identification of EZH2 as Cancer Stem Cell Marker in Clear Cell Renal Cell Carcinoma and the Anti-Tumor Effect of Epigallocatechin-3-Gallate (EGCG)

Simple Summary

Cancer stem cells (CSCs) refer to a group of undifferentiated heterogeneous tumor cells, defined as capable of self-renewal, differentiation, and may be linked to therapeutic resistance and tumor relapse. The development of novel therapeutic strategies to target CSCs and the identification of typical CSC markers are essential to improve therapy efficacy and prevent tumor relapse. Our study identifies CSC markers in renal cell carcinoma (RCC) and explores a potential treatment strategy and the underlying pharmacological mechanisms.

Abstract

The aim of the study was to develop a new therapeutic strategy to target cancer stem cells (CSCs) in clear cell renal cell carcinoma (ccRCC) and to identify typical CSC markers to improve therapy effectiveness. It was found that the corrected-mRNA expression-based stemness index was upregulated in kidney renal clear cell carcinoma (KIRC) tissues compared to non-tumor tissue and increased with higher tumor stage and grade. EZH2 was identified as a CSC marker and prognosis factor for KIRC patients. The expression of EZH2 was associated with several activated tumor-infiltrating immune cells. High expression of EZH2 was enriched in immune-related pathways, low expression was related to several metabolic pathways. Epigallocatechin-3-gallate (EGCG) was identified as the most potent suppressor of EZH2, was able to inhibit viability, migration, and invasion, and to increase the apoptosis rate of ccRCC CSCs. KIF11, VEGF, and MMP2 were identified as predictive EGCG target genes, suggesting a potential mechanism of how EZH2 might regulate invasiveness and migration. The percentages of FoxP3+ Treg cells in the peripheral blood mononuclear cells of ccRCC patients decreased significantly when cultured with spheres pretreated with EGCG plus sunitinib compared to spheres without treatment. Our findings provide new insights into the treatment options of ccRCC based on targeting CSCs.

PAR-Induced Harnessing of EZH2 to β-Catenin: Implications for Colorectal Cancer

G-protein-coupled receptors (GPCRs) are involved in a wide array of physiological and disease functions, yet knowledge of their role in colon cancer stem cell maintenance is still lacking. In addition, the molecular mechanisms underlying GPCR-induced post-translational signaling regulation are poorly understood. Here, we find that protease-activated receptor 4 (PAR₄) unexpectedly acts as a potent oncogene, inducing β-catenin stability and transcriptional activity. Both PAR₄ and PAR₂ are able to drive the association of methyltransferase EZH2 with β-catenin, culminating in β-catenin methylation. This methylation on a lysine residue at the N-terminal portion of β-catenin suppresses the ubiquitination of β-catenin, thereby promoting PAR-induced β-catenin stability and transcriptional activity. Indeed, EZH2 is found to be directly correlated with high PAR₄-driven tumors, and is abundantly expressed in large tumors, whereas very little to almost none is expressed in small tumors. A truncated form of β-catenin, ∆N133β-catenin, devoid of lysine, as well as serine/threonine residues, exhibits low levels of β-catenin and a markedly reduced transcriptional activity following PAR₄ activation, in contrast to wt β-catenin. Our study demonstrates the importance of β-catenin lysine methylation in terms of its sustained expression and function. Taken together, we reveal that PAR-induced post-transcriptional regulation of β-catenin is centrally involved in colon cancer.

Molecular Pathways and Genomic Landscape of Glioblastoma Stem Cells: Opportunities for Targeted Therapy

Glioblastoma (GBM) is an aggressive tumor of the central nervous system categorized by the World Health Organization as a Grade 4 astrocytoma. Despite treatment with surgical resection, adjuvant chemotherapy, and radiation therapy, outcomes remain poor, with a median survival of only 14-16 months. Although tumor regression is often observed initially after treatment, long-term recurrence or progression invariably occurs. Tumor growth, invasion, and recurrence is mediated by a unique population of glioblastoma stem cells (GSCs). Their high mutation rate and dysregulated transcriptional landscape augment their resistance to conventional chemotherapy and radiation therapy, explaining the poor outcomes observed in patients. Consequently, GSCs have emerged as targets of interest in new treatment paradigms. Here, we review the unique properties of GSCs, including their interactions with the hypoxic microenvironment that drives their proliferation. We discuss vital signaling pathways in GSCs that mediate stemness, self-renewal, proliferation, and invasion, including the Notch, epidermal growth factor receptor, phosphatidylinositol 3-kinase/Akt, sonic hedgehog, transforming growth factor beta, Wnt, signal transducer and activator of transcription 3, and inhibitors of differentiation pathways. We also review epigenomic changes in GSCs that influence their transcriptional state, including DNA methylation, histone methylation and acetylation, and miRNA expression. The constituent molecular components of the signaling pathways and epigenomic regulators represent potential sites for targeted therapy, and representative examples of inhibitory molecules and pharmaceuticals are discussed. Continued investigation into the molecular pathways of GSCs and candidate therapeutics is needed to discover new effective treatments for GBM and improve survival.

A Review of Mathematical and Computational Methods in Cancer Dynamics

Cancers are complex adaptive diseases regulated by the nonlinear feedback systems between genetic instabilities, environmental signals, cellular protein flows, and gene regulatory networks. Understanding the cybernetics of cancer requires the integration of information dynamics across multidimensional spatiotemporal scales, including genetic, transcriptional, metabolic, proteomic, epigenetic, and multi-cellular networks. However, the time-series analysis of these complex networks remains vastly absent in cancer research. With longitudinal screening and time-series analysis of cellular dynamics, universally observed causal patterns pertaining to dynamical systems, may self-organize in the signaling or gene expression state-space of cancer triggering processes. A class of these patterns, strange attractors, may be mathematical biomarkers of cancer progression. The emergence of intracellular chaos and chaotic cell population dynamics remains a new paradigm in systems medicine. As such, chaotic and complex dynamics are discussed as mathematical hallmarks of cancer cell fate dynamics herein. Given the assumption that time-resolved single-cell datasets are made available, a survey of interdisciplinary tools and algorithms from complexity theory, are hereby reviewed to investigate critical phenomena and chaotic dynamics in cancer ecosystems. To conclude, the perspective cultivates an intuition for computational systems oncology in terms of nonlinear dynamics, information theory, inverse problems, and complexity. We highlight the limitations we see in the area of statistical machine learning but the opportunity at combining it with the symbolic computational power offered by the mathematical tools explored.

The crucial role of epigenetic regulation in breast cancer anti-estrogen resistance: Current findings and future perspectives

Breast cancer (BC) cell de-sensitization to Tamoxifen (TAM) or other selective estrogen receptor (ER) modulators (SERM) is a complex process associated with BC heterogeneity and the transformation of ER signalling. The most influential resistance-related mechanisms include modifications in ER expression and gene regulation patterns. During TAM/SERM treatment, epigenetic mechanisms can effectively silence ER expression and facilitate the development of endocrine resistance. ER status is efficiently regulated by specific epigenetic tools including hypermethylation of CpG islands within ER promoters, increased histone deacetylase activity in the ER promoter, and/or translational repression by miRNAs. Over-methylation of the ER α gene (ESR1) promoter by DNA methyltransferases was associated with poor prognosis and indicated the development of resistance. Moreover, BC progression and spreading were marked by transformed chromatin remodelling, post-translational histone modifications, and expression of specific miRNAs and/or long non-coding RNAs. Therefore, targeted inhibition of histone acetyltransferases (e.g. MYST3), deacetylases (e.g. HDAC1), and/or demethylases (e.g. lysine-specific demethylase LSD1) was shown to recover and increase BC sensitivity to anti-estrogens. Indicated as a powerful molecular instrument, the administration of epigenetic drugs can regain ER expression along with the activation of tumour suppressor genes, which can in turn prevent selection of resistant cells and cancer stem cell survival. This review examines recent advances in the epigenetic regulation of endocrine drug resistance and evaluates novel anti-resistance strategies. Underlying molecular mechanisms of epigenetic regulation will be discussed, emphasising the utilization of epigenetic enzymes and their inhibitors to re-program irresponsive BCs.

EZH2, a prominent orchestrator of genetic and epigenetic regulation of solid tumor microenvironment and immunotherapy

Immune checkpoint blockade (ICB) is regarded as a promising strategy for cancer therapy. The histone methyltransferase, Enhancer of Zeste Homolog 2 (EZH2), has been implicated in the carcinogenesis of numerous solid tumors. However, the underlying mechanism of EZH2 in cancer immunotherapeutic resistance remains unknown. EZH2 orchestrates the regulation of the innate and adaptive immune systems of the tumor microenvironment (TME). Profound epigenetic and transcriptomic changes induced by EZH2 in tumor cells and immune cells mobilize the elements of the TME, leading to immune-suppressive activity of solid tumors. In this review, we summarized the dynamic functions of EZH2 on the different components of the TME, including tumor cells, T cells, macrophages, natural killer cells, myeloid-derived suppressor cells, dendritic cells, fibroblasts, and mesenchymal stem cells. Several ongoing anti-tumor clinical trials using EZH2 inhibitors have also been included as translational perspectives. In conclusion, based combinational therapy to enable ICB could offer a survival benefit in patients with cancer.

Brain Regeneration Resembles Brain Cancer at Its Early Wound Healing Stage and Diverges From Cancer Later at Its Proliferation and Differentiation Stages

Gliomas are the most frequent type of brain cancers and characterized by continuous proliferation, inflammation, angiogenesis, invasion and dedifferentiation, which are also among the initiator and sustaining factors of brain regeneration during restoration of tissue integrity and function. Thus, brain regeneration and brain cancer should share more molecular mechanisms at early stages of regeneration where cell proliferation dominates. However, the mechanisms could diverge later when the regenerative response terminates, while cancer cells sustain proliferation. To test this hypothesis, we exploited the adult zebrafish that, in contrast to the mammals, can efficiently regenerate the brain in response to injury. By comparing transcriptome profiles of the regenerating zebrafish telencephalon at its three different stages, i.e., 1 day post-lesion (dpl)-early wound healing stage, 3 dpl-early proliferative stage and 14 dpl-differentiation stage, to those of two brain cancers, i.e., low-grade glioma (LGG) and glioblastoma (GBM), we reveal the common and distinct molecular mechanisms of brain regeneration and brain cancer. While the transcriptomes of 1 dpl and 3 dpl harbor unique gene modules and gene expression profiles that are more divergent from the control, the transcriptome of 14 dpl converges to that of the control. Next, by functional analysis of the transcriptomes of brain regeneration stages to LGG and GBM, we reveal the common and distinct molecular pathways in regeneration and cancer. 1 dpl and LGG and GBM resemble with regard to signaling pathways related to metabolism and neurogenesis, while 3 dpl and LGG and GBM share pathways that control cell proliferation and differentiation. On the other hand, 14 dpl and LGG and GBM converge with respect to developmental and morphogenetic processes. Finally, our global comparison of gene expression profiles of three brain regeneration stages, LGG and GBM exhibit that 1 dpl is the most similar stage to LGG and GBM while 14 dpl is the most distant stage to both brain cancers. Therefore, early convergence and later divergence of brain regeneration and brain cancer constitutes a key starting point in comparative understanding of cellular and molecular events between the two phenomena and development of relevant targeted therapies for brain cancers.

Evaluation of an EZH2 inhibitor in patient-derived orthotopic xenograft models of pediatric brain tumors alone and in combination with chemo- and radiation therapies

Brain tumors are the leading cause of cancer-related death in children. Tazemetostat is an FDA-approved enhancer of zeste homolog (EZH2) inhibitor. To determine its role in difficult-to-treat pediatric brain tumors, we examined EZH2 levels in a panel of 22 PDOX models and confirmed EZH2 mRNA over-expression in 9 GBM (34.6 ± 12.7-fold) and 11 medulloblastoma models (6.2 ± 1.7 in group 3, 6.0 ± 2.4 in group 4) accompanied by elevated H3K27me3 expression. Therapeutic efficacy was evaluated in 4 models (1 GBM, 2 medulloblastomas and 1 ATRT) via systematically administered tazemetostat (250 and 400 mg/kg, gavaged, twice daily) alone and in combination with cisplatin (5 mg/kg, i.p., twice) and/or radiation (2 Gy/day × 5 days). Compared with the untreated controls, tazemetostat significantly (Pcorrected < 0.05) prolonged survival times in IC-L1115ATRT (101% at 400 mg/kg) and IC-2305GBM (32% at 250 mg/kg, 45% at 400 mg/kg) in a dose-dependent manner. The addition of tazemetostat with radiation was evaluated in 3 models, with only one [IC-1078MB (group 4)] showing a substantial, though not statistically significant, prolongation in survival compared to radiation treatment alone. Combining tazemetostat (250 mg/kg) with cisplatin was not superior to cisplatin alone in any model. Analysis of in vivo drug resistance detected predominance of EZH2-negative cells in the remnant PDOX tumors accompanied by decreased H3K27me2 and H3K27me3 expressions. These data supported the use of tazemetostat in a subset of pediatric brain tumors and suggests that EZH2-negative tumor cells may have caused therapy resistance and should be prioritized for the search of new therapeutic targets.

EZH2 as a new therapeutic target in brain tumors: Molecular landscape, therapeutic targeting and future prospects

Brain tumors are responsible for high mortality and morbidity worldwide. The brain tumor treatment depends on identification of molecular pathways involved in progression and malignancy. Enhancer of zeste homolog 2 (EZH2) has obtained much attention in recent years in field of cancer therapy due to its aberrant expression and capacity in modulating expression of genes by binding to their promoter and affecting methylation status. The present review focuses on EZH2 signaling in brain tumors including glioma, glioblastoma, astrocytoma, ependymomas, medulloblastoma and brain rhabdoid tumors. EZH2 signaling mainly participates in increasing proliferation and invasion of cancer cells. However, in medulloblastoma, EZH2 demonstrates tumor-suppressor activity. Furthermore, EZH2 can regulate response of brain tumors to chemotherapy and radiotherapy. Various molecular pathways can function as upstream mediators of EZH2 in brain tumors including lncRNAs and miRNAs. Owing to its enzymatic activity, EZH2 can bind to promoter of target genes to induce methylation and affects their expression. EZH2 can be considered as an independent prognostic factor in brain tumors that its upregulation provides undesirable prognosis. Both anti-tumor agents and gene therapies such as siRNA have been developed for targeting EZH2 in cancer therapy.

Cell-of-Origin and Genetic, Epigenetic, and Microenvironmental Factors Contribute to the Intra-Tumoral Heterogeneity of Pediatric Intracranial Ependymoma

Intra-tumoral heterogeneity (ITH) is a complex multifaceted phenomenon that posits major challenges for the clinical management of cancer patients. Genetic, epigenetic, and microenvironmental factors are concurrent drivers of diversity among the distinct populations of cancer cells. ITH may also be installed by cancer stem cells (CSCs), that foster unidirectional hierarchy of cellular phenotypes or, alternatively, shift dynamically between distinct cellular states. Ependymoma (EPN), a molecularly heterogeneous group of tumors, shows a specific spatiotemporal distribution that suggests a link between ependymomagenesis and alterations of the biological processes involved in embryonic brain development. In children, EPN most often arises intra-cranially and is associated with an adverse outcome. Emerging evidence shows that EPN displays large intra-patient heterogeneity. In this review, after touching on EPN inter-tumoral heterogeneity, we focus on the sources of ITH in pediatric intra-cranial EPN in the framework of the CSC paradigm. We also examine how single-cell technology has shed new light on the complexity and developmental origins of EPN and the potential impact that this understanding may have on the therapeutic strategies against this deadly pediatric malignancy.

Emerging role of G9a in cancer stemness and promises as a therapeutic target

The histone methyltransferase G9a is well-documented for its implication in neoplastic growth. However, recent investigations have demonstrated a key involvement of this chromatin writer in maintaining the self-renewal and tumor-initiating capacities of cancer stem cells (CSCs). Direct inhibition of G9a’s catalytic activity was reported as a promising therapeutic target in multiple preclinical studies. Yet, none of the available pharmacological inhibitors of G9a activity have shown success at the early stages of clinical testing. Here, we discuss central findings of oncogenic expression and activation of G9a in CSCs from different origins, as well as the impact of the suppression of G9a histone methyltransferase activity in such contexts. We will explore the challenges posed by direct and systemic inhibition of G9a activity in the perspective of clinical translation of documented small molecules. Finally, we will discuss recent advances in drug discovery as viable strategies to develop context-specific drugs, selectively targeting G9a in CSC populations.

The Pivotal Immunomodulatory and Anti-Inflammatory Effect of Histone-Lysine N-Methyltransferase in the Glioma Microenvironment: Its Biomarker and Therapy Potentials

Enhancer of zeste homolog 2 (EZH2) is a histone-lysine N-methyltransferase that encrypts a member of the Polycomb group (PcG) family. EZH2 forms a repressive chromatin structure which eventually participates in regulating the development as well as lineage propagation of stem cells and glioma progression. Posttranslational modifications are distinct approaches for the adjusted modification of EZH2 in the development of cancer. The amino acid succession of EZH2 protein makes it appropriate for covalent modifications, like phosphorylation, acetylation, O-GlcNAcylation, methylation, ubiquitination, and sumoylation. The glioma microenvironment is a dynamic component that comprises, besides glioma cells and glioma stem cells, a complex network that comprises diverse cell types like endothelial cells, astrocytes, and microglia as well as stromal components, soluble factors, and the extracellular membrane. EZH2 is well recognized as an essential modulator of cell invasion as well as metastasis in glioma. EZH2 oversecretion was implicated in the malfunction of several fundamental signaling pathways like Wnt/β-catenin signaling, Ras and NF-κB signaling, PI3K/AKT signaling, β-adrenergic receptor signaling, and bone morphogenetic protein as well as NOTCH signaling pathways. EZH2 was more secreted in glioblastoma multiforme than in low-grade gliomas as well as extremely secreted in U251 and U87 human glioma cells. Thus, the blockade of EZH2 expression in glioma could be of therapeutic value for patients with glioma. The suppression of EZH2 gene secretion was capable of reversing temozolomide resistance in patients with glioma. EZH2 is a promising therapeutic as well as prognostic biomarker for the treatment of glioma.

Histone-deacetylase 8 drives the immune response and the growth of glioma

Many epigenetic modifications occur in glioma, in particular the histone-deacetylase class proteins play a pivotal role in glioma development, driving the proliferation rate and the invasiveness of tumor cells, and modulating the tumor microenvironment. In this study, we evaluated the role of the histone deacetylase HDAC8 in the regulation of the immune response in glioma and tumor growth. We found that inhibition of HDAC8 by the specific inhibitor PCI-34051 reduces tumor volume in glioma mouse models. We reported that HDAC8 modulates the viability and the migration of human and murine glioma cells. Interestingly, HDAC8 inhibition increases the acetylation of alpha-tubulin, suggesting this epigenetic modification controls glioma migration. Furthermore, we identify HDAC8 as a key molecule that supports a poorly immunogenic tumor microenvironment, modulating microglial phenotype and regulating the gene transcription of NKG2D ligands that trigger the Natural Killer cell-mediated cytotoxicity of tumor cells. Altogether, these results identify HDAC8 as a key actor in glioma growth and tumor microenvironment, and pave the way to a better knowledge of the molecular mechanisms of immune escape in glioma.

Horizontal transfer of the stemness-related markers EZH2 and GLI1 by neuroblastoma-derived extracellular vesicles in stromal cells

Neuroblastoma (NB) is the most common extracranial pediatric solid cancer originating from undifferentiated neural crest cells. NB cells express EZH2 and GLI1 genes that are known to maintain the undifferentiated phenotype of cancer stem cells (CSC) in NB. Recent studies suggest that tumor-derived extracellular vesicles (EVs) can regulate the transformation of surrounding cells into CSC by transferring tumor-specific molecules they contain. However, the horizontal transfer of EVs molecules in NB remains largely unknown. We report the analysis of NB-derived EVs in bioengineered models of NB that are based on a collagen 1/hyaluronic acid scaffold designed to mimic the native tumor niche. Using these models, we observed an enrichment of GLI1 and EZH2 mRNAs in NB-derived EVs. As a consequence of the uptake of NB-derived EVs, the host cells increased the expression levels of GLI1 and EZH2. These results suggest the alteration of the expression profile of stromal cells through an EV-based mechanism, and point the GLI1 and EZH2 mRNAs in the EV cargo as diagnostic biomarkers in NB.

Involvement of EZH2 inhibition in lenalidomide and pomalidomide-mediated growth suppression in HTLV-1-infected cells

Immunomodulatory imide drugs (IMiDs), such as lenalidomide and pomalidomide, exert pleiotropic effects, e.g., antitumor effects in multiple myeloma, by binding the protein Cereblon and altering its substrate specificity. Lenalidomide is approved for the treatment of adult T-cell leukemia/lymphoma (ATL) caused by human T-cell leukemia virus type 1 (HTLV-1), although the precise mechanisms responsible for its effectiveness have not been fully elucidated. Here, we used HTLV-1-infected cell lines to investigate how IMiDs exert anti-ATL effects. In three of four tested HTLV-1-infected cell lines, the cells treated with lenalidomide or pomalidomide exhibited mild growth suppression without apoptosis, which was associated with decreased IRF4, c-Myc, and phosphorylated STAT3 levels as well as enhanced SOCS3 expression. Additionally, the levels of enhancer of zeste homolog 2 (EZH2) and trimethyl histone 3 Lys27 (H3K27me3) were decreased following IMiD treatment in all three susceptible cell lines. An IMiD-mediated reduction of EZH2 and H3K27me3 levels was also observed in a multiple myeloma cell line. Furthermore, treatment with an EZH2-inhibitor reproduced the IMiD-mediated effects in HTLV-1-infected cells and multiple myeloma cells. These findings strongly suggest that a reduction of EZH2 expression is involved in the mechanism underlying the antitumor effects of IMiD.

Epigenetic encoding, heritability and plasticity of glioma transcriptional cell states

Single-cell RNA sequencing has revealed extensive transcriptional cell state diversity in cancer, often observed independently of genetic heterogeneity, raising the central question of how malignant cell states are encoded epigenetically. To address this, here we performed multiomics single-cell profiling-integrating DNA methylation, transcriptome and genotype within the same cells-of diffuse gliomas, tumors characterized by defined transcriptional cell state diversity. Direct comparison of the epigenetic profiles of distinct cell states revealed key switches for state transitions recapitulating neurodevelopmental trajectories and highlighted dysregulated epigenetic mechanisms underlying gliomagenesis. We further developed a quantitative framework to directly measure cell state heritability and transition dynamics based on high-resolution lineage trees in human samples. We demonstrated heritability of malignant cell states, with key differences in hierarchal and plastic cell state architectures in IDH-mutant glioma versus IDH-wild-type glioblastoma, respectively. This work provides a framework anchoring transcriptional cancer cell states in their epigenetic encoding, inheritance and transition dynamics.

Roles of Non-coding RNAs and Angiogenesis in Glioblastoma

One of the significant hallmarks of cancer is angiogenesis. It has a crucial function in tumor development and metastasis. Thus, angiogenesis has become one of the most exciting targets for drug development in cancer treatment. Here we discuss the regulatory effects on angiogenesis in glioblastoma (GBM) of non-coding RNAs (ncRNAs), including long ncRNA (lncRNA), microRNA (miRNA), and circular RNA (circRNA). These ncRNAs may function in trans or cis forms and modify gene transcription by various mechanisms, including epigenetics. NcRNAs may also serve as crucial regulators of angiogenesis-inducing molecules. These molecules include, metalloproteinases, cytokines, several growth factors (platelet-derived growth factor, vascular endothelial growth factor, fibroblast growth factor, hypoxia-inducible factor-1, and epidermal growth factor), phosphoinositide 3-kinase, mitogen-activated protein kinase, and transforming growth factor signaling pathways.

Exploring EZH2-Proteasome Dual-Targeting Drug Discovery through a Computational Strategy to Fight Multiple Myeloma

Multiple myeloma is an incurable plasma cell neoplastic disease representing about 10–15% of all haematological malignancies diagnosed in developed countries. Proteasome is a key player in multiple myeloma and proteasome inhibitors are the current first-line of treatment. However, these are associated with limited clinical efficacy due to acquired resistance. One of the solutions to overcome this problem is a polypharmacology approach, namely combination therapy and multitargeting drugs. Several polypharmacology avenues are currently being explored. The simultaneous inhibition of EZH2 and Proteasome 20S remains to be investigated, despite the encouraging evidence of therapeutic synergy between the two. Therefore, we sought to bridge this gap by proposing a holistic in silico strategy to find new dual-target inhibitors. First, we assessed the characteristics of both pockets and compared the chemical space of EZH2 and Proteasome 20S inhibitors, to establish the feasibility of dual targeting. This was followed by molecular docking calculations performed on EZH2 and Proteasome 20S inhibitors from ChEMBL 25, from which we derived a predictive model to propose new EZH2 inhibitors among Proteasome 20S compounds, and vice versa, which yielded two dual-inhibitor hits. Complementarily, we built a machine learning QSAR model for each target but realised their application to our data is very limited as each dataset occupies a different region of chemical space. We finally proceeded with molecular dynamics simulations of the two docking hits against the two targets. Overall, we concluded that one of the hit compounds is particularly promising as a dual-inhibitor candidate exhibiting extensive hydrogen bonding with both targets. Furthermore, this work serves as a framework for how to rationally approach a dual-targeting drug discovery project, from the selection of the targets to the prediction of new hit compounds.

Going beyond Polycomb: EZH2 functions in prostate cancer

The Polycomb group (PcG) protein Enhancer of Zeste Homolog 2 (EZH2) is one of the three core subunits of the Polycomb Repressive Complex 2 (PRC2). It harbors histone methyltransferase activity (MTase) that specifically catalyze histone 3 lysine 27 (H3K27) methylation on target gene promoters. As such, PRC2 are epigenetic silencers that play important roles in cellular identity and embryonic stem cell maintenance. In the past two decades, mounting evidence supports EZH2 mutations and/or over-expression in a wide array of hematological cancers and solid tumors, including prostate cancer. Further, EZH2 is among the most upregulated genes in neuroendocrine prostate cancers, which become abundant due to the clinical use of high-affinity androgen receptor pathway inhibitors. While numerous studies have reported epigenetic functions of EZH2 that inhibit tumor suppressor genes and promote tumorigenesis, discordance between EZH2 and H3K27 methylation has been reported. Further, enzymatic EZH2 inhibitors have shown limited efficacy in prostate cancer, warranting a more comprehensive understanding of EZH2 functions. Here we first review how canonical functions of EZH2 as a histone MTase are regulated and describe the various mechanisms of PRC2 recruitment to the chromatin. We further outline non-histone substrates of EZH2 and discuss post-translational modifications to EZH2 itself that may affect substrate preference. Lastly, we summarize non-canonical functions of EZH2, beyond its MTase activity and/or PRC2, as a transcriptional cofactor and discuss prospects of its therapeutic targeting in prostate cancer.

The Impact of Epigenetic Modifications on Adaptive Resistance Evolution in Glioblastoma

Glioblastoma (GBM) is a highly lethal cancer that is universally refractory to the standard multimodal therapies of surgical resection, radiation, and chemotherapy treatment. Temozolomide (TMZ) is currently the best chemotherapy agent for GBM, but the durability of response is epigenetically dependent and often short-lived secondary to tumor resistance. Therapies that can provide synergy to chemoradiation are desperately needed in GBM. There is accumulating evidence that adaptive resistance evolution in GBM is facilitated through treatment-induced epigenetic modifications. Epigenetic alterations of DNA methylation, histone modifications, and chromatin remodeling have all been implicated as mechanisms that enhance accessibility for transcriptional activation of genes that play critical roles in GBM resistance and lethality. Hence, understanding and targeting epigenetic modifications associated with GBM resistance is of utmost priority. In this review, we summarize the latest updates on the impact of epigenetic modifications on adaptive resistance evolution in GBM to therapy.

Cancer Stem Cells as a Source of Drug Resistance in Bone Sarcomas

Bone sarcomas are commonly characterized by a high degree of intra-tumor heterogeneity, which in part is due to the presence of subpopulations of tumor cells presenting stem cell properties. Similar to normal stem cells, these cancer stem cells (CSCs) display a drug resistant phenotype and therefore are responsible for relapses and tumor dissemination. Drug resistance in bone sarcomas could be enhanced/modulated during tumor evolution though the acquisition of (epi)-genetic alterations and the adaptation to changing microenvironments, including drug treatments. Here we summarize findings supporting the involvement of pro-stemness signaling in the development of drug resistance in bone sarcomas. This include the activation of well-known pro-stemness pathways (Wnt/β-Cat, NOTCH or JAT/STAT pathways), changes in the metabolic and autophagic activities, the alteration of epigenetic pathways, the upregulation of specific non-coding RNAs and the crosstalk with different microenvironmental factors. This altered signaling is expected to be translated to the clinic in the form of biomarkers of response and new therapies able to overcome drug resistance.

Combination of AZD3463 and DZNep Prevents Bone Metastasis of Breast Cancer by Suppressing Akt Signaling

Osteolysis resulting from osteoclast overactivation is one of the severe complications of breast cancer metastasis to the bone. Previous studies reported that the anti-cancer agent DZNep induces cancer cell apoptosis by activating Akt signaling. However, the effect of DZNep on breast cancer bone metastasis is unknown. We previously found that DZNep enhances osteoclast differentiation by activating Akt. Therefore, we explored the use of the anti-cancer agent AZD3463 (an Akt inhibitor) along with DZNep, as AZD3463 can act as an anti-cancer agent and can also potentially ameliorate bone erosion. We evaluated osteoclast and breast cancer cell phenotypes and Akt signaling in vitro by treating cells with DZNep and AZD3463. Furthermore, we developed a breast cancer bone metastasis animal model in mouse tibiae to further determine their combined effects in vivo. Treatment of osteoclast precursor cells with DZNep alone increased osteoclast differentiation, bone resorption, and expression of osteoclast-specific genes. These effects were ameliorated by AZD3463. The combination of DZNep and AZD3463 inhibited breast cancer cell proliferation, colony formation, migration, and invasion. Finally, intraperitoneal injection of DZNep and AZD3463 ameliorated tumor progression and protected against bone loss. In summary, DZNep combined with AZD3463 prevented skeletal complications and inhibited breast cancer progression by suppressing Akt signaling.

lncRNA TUG1 inhibits the cancer stem cell‑like properties of temozolomide‑resistant glioma cells by interacting with EZH2

Temozolomide (TMZ) is currently one of the first-line drugs used for the treatment of high-grade gliomas. However, TMZ resistance results in unsatisfactory therapeutic effects in gliomas. Cancer stem cells (CSCs) have recently been determined to serve a pivotal regulatory role in tumor metastasis, recurrence and chemoresistance. In addition, numerous reports have shown that long non-coding RNAs (lncRNAs) exert an essential role in the occurrence and development of tumors, and can be used as biomarkers for tumor diagnosis and treatment. Among them, studies have revealed that taurine upregulated gene 1 (TUG1) exhibits an important regulatory effect on the malignant biological behavior of glioma cells. Moreover, it has been reported that enhancer of Zeste homolog 2 polycomb repressive complex subunit 2 (EZH2) promotes tumorigenesis, including in glioma. However, the underlying mechanism of the interaction of TUG1 and EZH2 with CSCs of glioma remains elusive, and thus requires further clarification. The present study aimed to explore the role of TUG1 and EZH2 in TMZ resistance in glioma. Cell Counting Kit-8, colony formation,sphere formation and Annexin V-FITC/PI assays were used to detect the proliferation, clone formation efficiency, stemness and apoptosis of TMZ-resistant glioma cells. Xenograft tumor assay was used to detect the effect of TUG1 on the tumorigenesis of TMZ-resistant glioma cells. The present findings demonstrated that TUG1 exhibited a low expression in glioma cells, while EZH2 expression was the opposite. Moreover, it was observed that A172/TMZ cells possessed higher CSCs-like properties compared with parent cells, and that TUG1 and EZH2 were abnormally expressed in A172/TMZ cells. Knockdown of TUG1 or overexpression of EZH2 promoted A172/TMZ cell proliferation and CSCs-like properties, as well as inhibited their apoptosis, thereby enhancing the TMZ resistance of A172/TMZ cells. Furthermore, it was found that TUG1 alleviated the TMZ resistance of A172/TMZ cells by inhibiting EZH2 expression. Of note, overexpression of TUG1 inhibited the tumorigenicity of A172/TMZ cells by downregulating EZH2 expression in vivo. Collectively, the present study demonstrated that TUG1 served an essential regulatory role in TMZ resistance of gliomas.