G9a Modulates Lipid Metabolism in CD4 T Cells to Regulate Intestinal Inflammation

Current and Emerging Approaches Targeting G9a for the Treatment of Various Diseases

G9a, a histone lysine methyltransferase, is instrumental in regulating gene expression through epigenetic modifications. Its overexpression is closely linked to the progression of various human diseases, including cancers. Therefore, targeting G9a enzyme is a promising strategy for treating various diseases. Although no G9a inhibitors have yet reached clinical trials, several small molecule inhibitors have demonstrated strong preclinical efficacy. For instance, the orally available inhibitor 16 (DS79932728) shows significant potential for treating sickle cell disease, while 34 (compound 15h) has shown promising treatment of rhabdomyosarcoma. This Perspective summarizes the protein structure and biological functions of G9a, along with its association with various diseases. We highlight the design strategies, structure-activity relationships, and biological activity assessments of G9a inhibitors. Additionally, we discuss the unique advantages of the mechanisms of novel G9a inhibitors, offering insights for the future development of more effective drugs targeting G9a.

Git2 deficiency promotes MDSCs recruitment in intestine via NF-κB-CXCL1/CXCL12 pathway and ameliorates necrotizing enterocolitis

Necrotizing enterocolitis (NEC) is a severe gastrointestinal disease in preterm infants and the most common cause of neonatal death, whereas the molecular mechanism of intestinal injury remains unclear accompanied by deficiency of effective therapeutic approaches. GIT2 (G-protein-coupled receptor kinase interacting proteins 2) can affect innate and adaptive immunity and has been involved in multiple inflammatory disorders. In this study, we investigated whether GIT2 participates in the pathogenesis of NEC. Here we found that intestinal Git2 gene expression was significantly increased in NEC patients and NEC mice, which positively correlated with the tissue damage severity, and Git2 deficiency could potently protect against NEC development in mice. Mechanistically, Git2 gene knockout dramatically increased the recruitment of MDSCs in the intestine, and in vivo depletion of MDSCs almost completely abrogated the protective effect of Git2 deficiency on NEC. Moreover, Git2 deficiency induced MDSCs intestinal accumulation mainly relied on CXCL1/CXCL12 signaling, as evidenced by the significant increment of CXCL1 and CXCL12 levels in intestinal epithelium of Git2-/- mice and dramatically decrease of MDSCs accumulation in intestine as well as increase of NEC severity upon treatment of CXCL1/CXCL12 pathway inhibitors. In addition, Git2 deficiency induced up-regulation of CXCL1 and CXCL12 is at least partially mediated through activating NF-κB signaling. Thus, our findings suggest that GIT2 is involved in the pathogenesis of NEC, and targeting GIT2 may be a potential preventive and therapeutic approach for NEC.

Metabolic reprogramming and immune evasion: the interplay in the tumor microenvironment

Tumor cells possess complex immune evasion mechanisms to evade immune system attacks, primarily through metabolic reprogramming, which significantly alters the tumor microenvironment (TME) to modulate immune cell functions. When a tumor is sufficiently immunogenic, it can activate cytotoxic T-cells to target and destroy it. However, tumors adapt by manipulating their metabolic pathways, particularly glucose, amino acid, and lipid metabolism, to create an immunosuppressive TME that promotes immune escape. These metabolic alterations impact the function and differentiation of non-tumor cells within the TME, such as inhibiting effector T-cell activity while expanding regulatory T-cells and myeloid-derived suppressor cells. Additionally, these changes lead to an imbalance in cytokine and chemokine secretion, further enhancing the immunosuppressive landscape. Emerging research is increasingly focusing on the regulatory roles of non-tumor cells within the TME, evaluating how their reprogrammed glucose, amino acid, and lipid metabolism influence their functional changes and ultimately aid in tumor immune evasion. Despite our incomplete understanding of the intricate metabolic interactions between tumor and non-tumor cells, the connection between these elements presents significant challenges for cancer immunotherapy. This review highlights the impact of altered glucose, amino acid, and lipid metabolism in the TME on the metabolism and function of non-tumor cells, providing new insights that could facilitate the development of novel cancer immunotherapies.

Intestinal NSD2 Aggravates Nonalcoholic Steatohepatitis Through Histone Modifications

Mounting clinical evidence suggests that a comprised intestinal barrier contributes to the progression of nonalcoholic steatohepatitis (NASH); nevertheless, the precise mechanism remains elusive. This study unveils a significant upregulation of nuclear receptor-binding SET domain protein 2 (NSD2) in the intestines of obese humans and mice subjected to a high-fat cholesterol diet (HFCD). Intestine-specific NSD2 knockout attenuated the progression of intestinal barrier impairment and NASH, whereas NSD2 overexpression exacerbated this progression. Mechanistically, NSD2 directly regulates the transcriptional activation of Ern1 by demethylating histone H3 at lysine 36 (H3K36me2), thus activating the ERN1-JNK axis to intensify intestinal barrier impairment and subsequently foster NASH progression. These findings elucidate the crucial role of NSD2-mediated H3K36me2 in intestinal barrier impairment, suggesting that targeting intestinal NSD2 can represent a novel therapeutic approach for NASH.

Ehmt2 inactivation in pancreatic epithelial cells shapes the transcriptional landscape and inflammation response of the whole pancreas

Introduction: The Euchromatic Histone Methyl Transferase Protein 2 (EHMT2), also known as G9a, deposits transcriptionally repressive chromatin marks that play pivotal roles in the maturation and homeostasis of multiple organs. Recently, we have shown that Ehmt2 inactivation in the mouse pancreas alters growth and immune gene expression networks, antagonizing Kras-mediated pancreatic cancer initiation and promotion. Here, we elucidate the essential role of Ehmt2 in maintaining a transcriptional landscape that protects organs from inflammation. Methods: Comparative RNA-seq studies between normal postnatal and young adult pancreatic tissue from Ehmt2 conditional knockout animals (Ehmt2 fl/fl ) targeted to the exocrine pancreatic epithelial cells (Pdx1-Cre and P48 Cre/+ ), reveal alterations in gene expression networks in the whole organ related to injury-inflammation-repair, suggesting an increased predisposition to damage. Thus, we induced an inflammation repair response in the Ehmt2 fl/fl pancreas and used a data science-based approach to integrate RNA-seq-derived pathways and networks, deconvolution digital cytology, and spatial transcriptomics. We also analyzed the tissue response to damage at the morphological, biochemical, and molecular pathology levels. Results and discussion: The Ehmt2 fl/fl pancreas displays an enhanced injury-inflammation-repair response, offering insights into fundamental molecular and cellular mechanisms involved in this process. More importantly, these data show that conditional Ehmt2 inactivation in exocrine cells reprograms the local environment to recruit mesenchymal and immunological cells needed to mount an increased inflammatory response. Mechanistically, this response is an enhanced injury-inflammation-repair reaction with a small contribution of specific Ehmt2-regulated transcripts. Thus, this new knowledge extends the mechanisms underlying the role of the Ehmt2-mediated pathway in suppressing pancreatic cancer initiation and modulating inflammatory pancreatic diseases.

Metabolic heterogeneity in tumor microenvironment - A novel landmark for immunotherapy

The surrounding non-cancer cells and tumor cells that make up the tumor microenvironment (TME) have various metabolic rhythms. TME metabolic heterogeneity is influenced by the intricate network of metabolic control within and between cells. DNA, protein, transport, and microbial levels are important regulators of TME metabolic homeostasis. The effectiveness of immunotherapy is also closely correlated with alterations in TME metabolism. The response of a tumor patient to immunotherapy is influenced by a variety of variables, including intracellular metabolic reprogramming, metabolic interaction between cells, ecological changes within and between tumors, and general dietary preferences. Although immunotherapy and targeted therapy have made great strides, their use in the accurate identification and treatment of tumors still has several limitations. The function of TME metabolic heterogeneity in tumor immunotherapy is summarized in this article. It focuses on how metabolic heterogeneity develops and is regulated as a tumor progresses, the precise molecular mechanisms and potential clinical significance of imbalances in intracellular metabolic homeostasis and intercellular metabolic coupling and interaction, as well as the benefits and drawbacks of targeted metabolism used in conjunction with immunotherapy. This offers insightful knowledge and important implications for individualized tumor patient diagnosis and treatment plans in the future.

Lipid metabolism in tumor-infiltrating regulatory T cells: perspective to precision immunotherapy

Regulatory T cells (Tregs) are essential to the negative regulation of the immune system, as they avoid excessive inflammation and mediate tumor development. The abundance of Tregs in tumor tissues suggests that Tregs may be eliminated or functionally inhibited to stimulate antitumor immunity. However, immunotherapy targeting Tregs has been severely hampered by autoimmune diseases due to the systemic elimination of Tregs. Recently, emerging studies have shown that metabolic regulation can specifically target tumor-infiltrating immune cells, and lipid accumulation in TME is associated with immunosuppression. Nevertheless, how Tregs actively regulate metabolic reprogramming to outcompete effector T cells (Teffs), and how lipid metabolic reprogramming contributes to the immunomodulatory capacity of Tregs have not been fully discussed. This review will discuss the physiological processes by which lipid accumulation confers a metabolic advantage to tumor-infiltrating Tregs (TI-Tregs) and amplifies their immunosuppressive functions. Furthermore, we will provide a summary of the driving effects of various metabolic regulators on the metabolic reprogramming of Tregs. Finally, we propose that targeting the lipid metabolism of TI-Tregs could be efficacious either alone or in conjunction with immune checkpoint therapy.

EHMT2 Inactivation in Pancreatic Epithelial Cells Shapes the Transcriptional Landscape and Inflammation Response of the Whole Pancreas

The Euchromatic Histone Methyl Transferase Protein 2 (EHMT2), also known as G9a, deposits transcriptionally repressive chromatin marks that play pivotal roles in the maturation and homeostasis of multiple organs. Recently, we have shown that EHMT2 inactivation alters growth and immune gene expression networks, antagonizing KRAS-mediated pancreatic cancer initiation and promotion. Here, we elucidate the essential role of EHMT2 in maintaining a transcriptional landscape that protects organs from inflammation. Comparative RNA-seq studies between normal postnatal and young adult pancreatic tissue from EHMT2 conditional knockout animals ( EHMT2 fl/fl ) targeted to the exocrine pancreatic epithelial cells ( Pdx1-Cre and P48 Cre/+ ), reveal alterations in gene expression networks in the whole organ related to injury-inflammation-repair, suggesting an increased predisposition to damage. Thus, we induced an inflammation repair response in the EHMT2 fl/fl pancreas and used a data science-based approach to integrate RNA-seq-derived pathways and networks, deconvolution digital cytology, and spatial transcriptomics. We also analyzed the tissue response to damage at the morphological, biochemical, and molecular pathology levels. The EHMT2 fl/fl pancreas displays an enhanced injury-inflammation-repair response, offering insights into fundamental molecular and cellular mechanisms involved in this process. More importantly, these data show that conditional EHMT2 inactivation in exocrine cells reprograms the local environment to recruit mesenchymal and immunological cells needed to mount an increased inflammatory response. Mechanistically, this response is an enhanced injury-inflammation-repair reaction with a small contribution of specific EHMT2-regulated transcripts. Thus, this new knowledge extends the mechanisms underlying the role of the EHMT2-mediated pathway in suppressing pancreatic cancer initiation and modulating inflammatory pancreatic diseases.

Galectin-7 Induction by EHMT2 Inhibition Enhances Immunity in Microsatellite Stability Colorectal Cancer

BACKGROUND & AIMS

Although immunotherapy shows substantial advancement in colorectal cancer (CRC) with microsatellite instability high, it has limited efficacy for CRC with microsatellite stability (MSS). Identifying combinations that reverse immune suppression and prime MSS tumors for current immunotherapy approaches remains an urgent need.

METHODS

An in vitro CRISPR screen was performed using coculture models of primary tumor cells and autologous immune cells from MSS CRC patients to identify epigenetic targets that could enhance immunotherapy efficacy in MSS tumors.

RESULTS

We revealed EHMT2, a histone methyltransferase, as a potential target for MSS CRC. EHMT2 inhibition transformed the immunosuppressive microenvironment of MSS tumors into an immunomodulatory one by altering cytokine expression, leading to T-cell-mediated cytotoxicity activation and improved responsiveness to anti-PD1 treatment. We observed galectin-7 up-regulation upon EHMT2 inhibition, which converted a "cold" MSS tumor environment into a T-cell-inflamed one. Mechanistically, CHD4 repressed galectin-7 expression by recruiting EHMT2 to form a cotranscriptional silencing complex. Galectin-7 administration enhanced anti-PD1 efficacy in MSS CRC, serving as a potent adjunct cytokine therapy.

CONCLUSIONS

Our findings suggest that targeting the EHMT2/galectin-7 axis could provide a novel combination strategy for immunotherapy in MSS CRC.

The Genetics of Inflammatory Bowel Disease

The genetic background of inflammatory bowel disease, both Crohn's disease and ulcerative colitis, has been known for more than 2 decades. In the last 20 years, genome-wide association studies have dramatically increased our knowledge on the genetics of inflammatory bowel disease with more than 200 risk genes having been identified. Paralleling this increasing knowledge, the armamentarium of inflammatory bowel disease medications has been growing constantly. With more available therapeutic options, treatment decisions become more complex, with still many patients experiencing a debilitating disease course and a loss of response to treatment over time. With a better understanding of the disease, more effective personalized treatment strategies are looming on the horizon. Genotyping has long been considered a strategy for treatment decisions, such as the detection of thiopurine S-methyltransferase and nudix hydrolase 15 polymorphisms before the initiation of azathioprine. However, although many risk genes have been identified in inflammatory bowel disease, a substantial impact of genetic risk assessment on therapeutic strategies and disease outcome is still missing. In this review, we discuss the genetic background of inflammatory bowel disease, with a particular focus on the latest advances in the field and their potential impact on management decisions.

Hypomethylation and Overexpression of Th17-Associated Genes is a Hallmark of Intestinal CD4+ Lymphocytes in Crohn's Disease

BACKGROUND

The development of Crohn's disease [CD] involves immune cell signalling pathways regulated by epigenetic modifications. Aberrant DNA methylation has been identified in peripheral blood and bulk intestinal tissue from CD patients. However, the DNA methylome of disease-associated intestinal CD4+ lymphocytes has not been evaluated.

MATERIALS AND METHODS

Genome-wide DNA methylation sequencing was performed from terminal ileum CD4+ cells from 21 CD patients and 12 age- and sex-matched controls. Data were analysed for differentially methylated CpGs [DMCs] and methylated regions [DMRs]. Integration was performed with RNA-sequencing data to evaluate the functional impact of DNA methylation changes on gene expression. DMRs were overlapped with regions of differentially open chromatin [by ATAC-seq] and CCCTC-binding factor [CTCF] binding sites [by ChIP-seq] between peripherally derived Th17 and Treg cells.

RESULTS

CD4+ cells in CD patients had significantly increased DNA methylation compared to those from the controls. A total of 119 051 DMCs and 8113 DMRs were detected. While hypermethylated genes were mostly related to cell metabolism and homeostasis, hypomethylated genes were significantly enriched within the Th17 signalling pathway. The differentially enriched ATAC regions in Th17 cells [compared to Tregs] were hypomethylated in CD patients, suggesting heightened Th17 activity. There was significant overlap between hypomethylated DNA regions and CTCF-associated binding sites.

CONCLUSIONS

The methylome of CD patients shows an overall dominant hypermethylation yet hypomethylation is more concentrated in proinflammatory pathways, including Th17 differentiation. Hypomethylation of Th17-related genes associated with areas of open chromatin and CTCF binding sites constitutes a hallmark of CD-associated intestinal CD4+ cells.

NSD2 methylates AROS to promote SIRT1 activation and regulates fatty acid metabolism-mediated cancer radiotherapy

Fatty acid metabolism plays a critical role in both tumorigenesis and cancer radiotherapy. However, the regulatory mechanism of fatty acid metabolism has not been fully elucidated. NSD2, a histone methyltransferase that catalyzes di-methylation of histone H3 at lysine 36, has been shown to play an essential role in tumorigenesis and cancer progression. Here, we show that NSD2 promotes fatty acid oxidation (FAO) by methylating AROS (active regulator of SIRT1) at lysine 27, facilitating the physical interaction between AROS and SIRT1. The mutation of lysine 27 to arginine weakens the interaction between AROS and SIRT1 and impairs AROS-SIRT1-mediated FAO. Additionally, we examine the effect of NSD2 inhibition on radiotherapy efficacy and find an enhanced effectiveness of radiotherapy. Together, our findings identify a NSD2-dependent methylation regulation pattern of the AROS-SIRT1 axis, suggesting that NSD2 inhibition may be a potential adjunct for tumor radiotherapy.

Unlocking the potential of targeting histone-modifying enzymes for treating IBD and CRC

Dysregulation of histone modifications has been implicated in the pathogenesis of both inflammatory bowel disease (IBD) and colorectal cancer (CRC). These diseases are characterized by chronic inflammation, and alterations in histone modifications have been linked to their development and progression. Furthermore, the gut microbiota plays a crucial role in regulating immune responses and maintaining gut homeostasis, and it has been shown to exert effects on histone modifications and gene expression in host cells. Recent advances in our understanding of the roles of histone-modifying enzymes and their associated chromatin modifications in IBD and CRC have provided new insights into potential therapeutic interventions. In particular, inhibitors of histone-modifying enzymes have been explored in clinical trials as a possible therapeutic approach for these diseases. This review aims to explore these potential therapeutic interventions and analyze previous and ongoing clinical trials that examined the use of histone-modifying enzyme inhibitors for the treatment of IBD and CRC. This paper will contribute to the current body of knowledge by exploring the latest advances in the field and discussing the limitations of existing approaches. By providing a comprehensive analysis of the potential benefits of targeting histone-modifying enzymes for the treatment of IBD and CRC, this review will help to inform future research in this area and highlight the significance of understanding the functions of histone-modifying enzymes and their associated chromatin modifications in gastrointestinal disorders for the development of potential therapeutic interventions.

Unraveling the Complex Interplay between Epigenetics and Immunity in Alcohol-Associated Liver Disease: A Comprehensive Review

The mechanisms of immune dysfunction in alcohol-associated liver disease (ALD) have garnered growing research interest in recent times. Alcohol-mediated immune dysfunction has been implicated as a potential cause of ALD-associated microbial infection and inflammatory response. The immune microenvironment of an organism is essentially a complex network of interactions between immune cells, cytokines, extracellular matrix, and other immune-related molecules. This microenvironment is highly adaptive and responsive to environmental cues. Epigenetic reprogramming of the immune microenvironment has recently emerged as a key driver of ALD progression, particularly in the context of endotoxin tolerance and immune disorders. Although epigenetic modifications are known to play an important role in the regulation of the immune microenvironment in ALD, the specific mechanisms and molecular processes by which this regulation is achieved are yet to be fully understood. This paper aims to provide an overview of the current knowledge on the effects of alcohol consumption on epigenetics, with special focus on summarizing the data on the epigenetic regulatory mechanisms involved in the effects of alcohol consumption on the immune microenvironment. In addition, this paper aims to present a review of the epigenetic modifications involved in different forms of ALD. This review is expected to offer new perspectives for the diagnosis, treatment, monitoring, and prognostic assessment of ALD from an epigenetic perspective.