EZH2 T367 phosphorylation activates p38 signaling through lysine methylation to promote breast cancer progression

The role of lncRNAs in the interplay of signaling pathways and epigenetic mechanisms in glioma

Gliomas, highly aggressive tumors of the central nervous system, present overwhelming challenges due to their heterogeneity and therapeutic resistance. Glioblastoma multiforme (GBM), the most malignant form, underscores this clinical urgency due to dismal prognosis despite aggressive treatment regimens. Recent advances in cancer research revealed signaling pathways and epigenetic mechanisms that intricately govern glioma progression, offering multifaceted targets for therapeutic intervention. This review explores the dynamic interplay between signaling events and epigenetic regulation in the context of glioma, with a particular focus on the crucial roles played by non-coding RNAs (ncRNAs). Through direct and indirect epigenetic targeting, ncRNAs emerge as key regulators shaping the molecular landscape of glioblastoma across its various stages. By dissecting these intricate regulatory networks, novel and patient-tailored therapeutic strategies could be devised to improve patient outcomes with this devastating disease.

MAPK14/p38α shapes the molecular landscape of endometrial cancer and promotes tumorigenic characteristics

The molecular underpinnings of high-grade endometrial carcinoma (HGEC) metastatic growth and survival are poorly understood. Here, we show that ascites-derived and primary tumor HGEC cell lines in 3D spheroid culture faithfully recapitulate key features of malignant peritoneal effusion and exhibit fundamentally distinct transcriptomic, proteomic, and metabolomic landscapes compared with conventional 2D monolayers. Using a genetic screening platform, we identify MAPK14 (which encodes the protein kinase p38α) as a specific requirement for HGEC in spheroid culture. MAPK14/p38α has broad roles in programming the phosphoproteome, transcriptome, and metabolome of HGEC spheroids, yet has negligible impact on monolayer cultures. MAPK14 promotes tumorigenicity in vivo and is specifically required to sustain a sub-population of spheroid cells that is enriched in cancer stemness markers. Therefore, spheroid growth of HGEC activates unique biological programs, including p38α signaling, that cannot be captured using 2D culture models and are highly relevant to malignant disease pathology.

Exploring oncogenic roles and clinical significance of EZH2: focus on non-canonical activities

The enhancer of zeste homolog 2 (EZH2) is a catalytic component of Polycomb repressive complex 2 (PRC2) mediating the methylation of histone 3 lysine 27 (H3K27me3) and hence the epigenetic repression of target genes, known as canonical function. Growing evidence indicates that EZH2 has non-canonical roles that are exerted as PRC2-dependent and PRC2-independent methylation of non-histone proteins, and methyltransferase-independent interactions of EZH2 with various proteins contributing to gene expression regulation and alterations in the protein stability. EZH2 is frequently mutated and/or its expression is deregulated in various cancer types. The cancer sensitivity to inhibitors of EZH2 enzymatic activity and state-of-the-art approaches to deplete EZH2 with chemical degraders are discussed. This review also presents the clinical trials in various phases that evaluate the use of EZH2 inhibitors, both as monotherapy and in combination with other agents for the treatment of patients with diverse types of cancers.

KDM5D histone demethylase mediates p38α inactivation via its enzymatic activity to inhibit cancer progression

The p38 MAP kinase (MAPK) signaling pathway plays pivotal roles in various cellular processes. Phosphorylation serves as a canonical way to regulate p38α activation through a phosphorylation cascade. Thus, understanding the mechanism governing p38α phosphorylation is important. The present study demonstrated that p38α undergoes methylation at K165, which promote its phosphorylation in tumor cells. Inhibition of p38α methylation impairs p38α phosphorylation, repressing tumor progression in vitro and in vivo. Mechanistically, KDM5D is a demethylase that interacts with p38α, mediating demethylation at K165 and inhibiting p38α phosphorylation. Moreover, KDM5D is expressed at low levels in non-small cell lung cancer (NSCLC), and high KDM5D expression is positively correlated with cancer survival. KDM5D markedly inhibits cell proliferation and migration via inactivating p38α, thereby slowing cancer progression in xenograft models. In summary, these findings highlight KDM5D as a demethylase of p38α at K165, elucidating a unique role for lysine demethylation in integrating cytoplasmic kinase-signaling cascades. The present results revealed the critical role of KDM5D in suppressing tumor progression, suggesting that KDM5D can serve as a potential drug target for combating hyperactive p38α-driven lung cancer.

Integration of epigenomic and transcriptomic profiling uncovers EZH2 target genes linked to cysteine metabolism in hepatocellular carcinoma

Enhancer of zeste homolog 2 (EZH2), a key protein implicated in various cancers including hepatocellular carcinoma (HCC), is recognized for its association with epigenetic dysregulation and pathogenesis. Despite clinical explorations into EZH2-targeting therapies, the mechanisms underlying its role in gene suppression in HCC have remained largely unexplored. Here, we integrate epigenomic and transcriptomic analyses to uncover the transcriptional landscape modulated by selective EZH2 inhibition in HCC. By reanalyzing transcriptomic data of HCC patients, we demonstrate that EZH2 overexpression correlates with poor patient survival. Treatment with the EZH2 inhibitor tazemetostat restored expression of genes involved in cysteine-methionine metabolism and lipid homeostasis, while suppressing angiogenesis and oxidative stress-related genes. Mechanistically, we demonstrate EZH2-mediated H3K27me3 enrichment at cis-regulatory elements of transsulfuration pathway genes, which is reversed upon inhibition, leading to increased chromatin accessibility. Among 16 EZH2-targeted candidate genes, BHMT and CDO1 were notably correlated with poor HCC prognosis. Tazemetostat treatment of HCC cells increased BHMT and CDO1 expression while reducing levels of ferroptosis markers FSP1, NFS1, and SLC7A11. Functionally, EZH2 inhibition dose-dependently reduced cell viability and increased lipid peroxidation in HCC cells. Our findings reveal a novel epigenetic mechanism controlling lipid peroxidation and ferroptosis susceptibility in HCC, providing a rationale for exploring EZH2-targeted therapies in this malignancy.

CCN6 Suppresses Metaplastic Breast Carcinoma by Antagonizing Wnt/β-Catenin Signaling to Inhibit EZH2-Driven EMT

Metaplastic breast carcinomas (mBrCA) are a highly aggressive subtype of triple-negative breast cancer with histologic evidence of epithelial-to-mesenchymal transition and aberrant differentiation. Inactivation of the tumor suppressor gene cellular communication network factor 6 (CCN6; also known as Wnt1-induced secreted protein 3) is a feature of mBrCAs, and mice with conditional inactivation of Ccn6 in mammary epithelium (Ccn6-KO) develop spindle mBrCAs with epithelial-to-mesenchymal transition. Elucidation of the precise mechanistic details of how CCN6 acts as a tumor suppressor in mBrCA could help identify improved treatment strategies. In this study, we showed that CCN6 interacts with the Wnt receptor FZD8 and coreceptor LRP6 on mBrCA cells to antagonize Wnt-induced activation of β-catenin/TCF-mediated transcription. The histone methyltransferase EZH2 was identified as a β-catenin/TCF transcriptional target in Ccn6-KO mBrCA cells. Inhibiting Wnt/β-catenin/TCF signaling in Ccn6-KO mBrCA cells led to reduced EZH2 expression, decreased histone H3 lysine 27 trimethylation, and deregulation of specific target genes. Pharmacologic inhibition of EZH2 reduced growth and metastasis of Ccn6-KO mBrCA mammary tumors in vivo. Low CCN6 is significantly associated with activated β-catenin and high EZH2 in human spindle mBrCAs compared with other subtypes. Collectively, these findings establish CCN6 as a key negative regulator of a β-catenin/TCF/EZH2 axis and highlight the inhibition of β-catenin or EZH2 as a potential therapeutic approach for patients with spindle mBrCAs.  Significance: CCN6 deficiency drives metaplastic breast carcinoma growth and metastasis by increasing Wnt/β-catenin activation to upregulate EZH2, identifying EZH2 inhibition as a mechanistically guided treatment strategy for this deadly form of breast cancer.

Methylation modification of non-histone proteins in breast cancer: an emerging targeted therapeutic strategy

Breast cancer is a major public health concern worldwide, being the most commonly diagnosed cancer among women and a leading cause of cancer-related deaths. Recent studies have highlighted the significance of non-histone methylation in breast cancer, which modulates the activity, interaction, localization, and stability of target proteins. This regulation affects critical processes such as oncogenesis, tumor growth, proliferation, invasion, migration, and immune responses. This review delves into the enzymes responsible for non-histone methylation, such as protein arginine methyltransferases (PRMTs), lysine methyltransferases (KMTs), and demethylases, and explores their roles in breast cancer. By elucidating the molecular mechanisms and functional consequences of non-histone methylation, this review aims to provide insights into novel therapeutic strategies targeting these pathways. The therapeutic potential of targeting non-histone methylation to overcome drug resistance and enhance treatment efficacy in breast cancer is also discussed, highlighting promising avenues for future research and clinical applications.

Regulation of EZH2 protein stability: new mechanisms, roles in tumorigenesis, and roads to the clinic

The importance of EZH2 as a key methyltransferase has been well documented theoretically. Practically, the first EZH2 inhibitor Tazemetostat (EPZ6438), was approved by FDA in 2020 and is used in clinic. However, for most solid tumors it is not as effective as desired and the scope of clinical indications is limited, suggesting that targeting its enzymatic activity may not be sufficient. Recent technologies focusing on the degradation of EZH2 protein have drawn attention due to their potential robust effects. This review focuses on the molecular mechanisms that regulate EZH2 protein stability via post-translational modifications (PTMs), mainly including ubiquitination, phosphorylation, and acetylation. In addition, we discuss recent advancements of multiple proteolysis targeting chimeras (PROTACs) strategies and the latest degraders that can downregulate EZH2 protein. We aim to highlight future directions to expand the application of novel EZH2 inhibitors by targeting both EZH2 enzymatic activity and protein stability.

Cancer metastasis under the magnifying glass of epigenetics and epitranscriptomics

Most of the cancer-associated mortality and morbidity can be attributed to metastasis. The role of epigenetic and epitranscriptomic alterations in cancer origin and progression has been extensively demonstrated during the last years. Both regulations share similar mechanisms driven by DNA or RNA modifiers, namely writers, readers, and erasers; enzymes responsible of respectively introducing, recognizing, or removing the epigenetic or epitranscriptomic modifications. Epigenetic regulation is achieved by DNA methylation, histone modifications, non-coding RNAs, chromatin accessibility, and enhancer reprogramming. In parallel, regulation at RNA level, named epitranscriptomic, is driven by a wide diversity of chemical modifications in mostly all RNA molecules. These two-layer regulatory mechanisms are finely controlled in normal tissue, and dysregulations are associated with every hallmark of human cancer. In this review, we provide an overview of the current state of knowledge regarding epigenetic and epitranscriptomic alterations governing tumor metastasis, and compare pathways regulated at DNA or RNA levels to shed light on a possible epi-crosstalk in cancer metastasis. A deeper understanding on these mechanisms could have important clinical implications for the prevention of advanced malignancies and the management of the disseminated diseases. Additionally, as these epi-alterations can potentially be reversed by small molecules or inhibitors against epi-modifiers, novel therapeutic alternatives could be envisioned.

Landscape of internal N7-methylguanosine of long non-coding RNA modifications in resistant acute myeloid leukemia

BACKGROUND

Growing evidence indicates that RNA methylation plays a fundamental role in epigenetic regulation, which is associated with the tumorigenesis and drug resistance. Among them, acute myeloid leukemia (AML), as the top acute leukemia for adults, is a deadly disease threatening human health. Although N7-methylguanosine (m7G) has been identified as an important regulatory modification, its distribution has still remained elusive.

METHODS

The present study aimed to explore the long non-coding RNA (lncRNA) functional profile of m7G in AML and drug-resistant AML cells. The transcriptome-wide m7G methylation of lncRNA was analyzed in AML and drug-resistant AML cells. RNA MeRIP-seq was performed to identify m7G peaks on lncRNA and differences in m7G distribution between AML and drug-resistant AML cells. The Gene Ontology (GO) and the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses were conducted to predict the possible roles and m7G-associated pathway.

RESULTS

Using m7G peak sequencing, it was found that a sequence motif was necessary for m7G methylation in drug-resistant AML lncRNA. Unsupervised hierarchical cluster analysis confirmed that lncRNA m7G methylation occurred more frequently in drug-resistant AML cells than in AML cells. RNA sequencing demonstrated that more genes were upregulated by methylation in drug-resistant AML cells, while methylation downregulated more genes in AML cells. The GO and KEGG pathway enrichment analyses revealed that genes having a significant correlation with m7G sites in lncRNA were involved in drug-resistant AML signaling pathways.

CONCLUSION

Significant differences in the levels and patterns of m7G methylation between drug-resistant AML cells and AML cells were revealed. Furthermore, the cellular functions potentially influenced by m7G in drug-resistant AML cells were predicted, providing evidence implicating m7G-mediated lncRNA epigenetic regulation in the progression of drug resistance in AML. These findings highlight the involvement of m7G in the development of drug resistance in AML.