PRMT7 ablation stimulates anti-tumor immunity and sensitizes melanoma to immune checkpoint blockade

Epigenetic Dysregulation of Retrotransposons in Cancer

Approximately 97% of the human genome comprises noncoding sequences, with nearly half originating from transposable elements. Among these, retrotransposons represent a critical subclass that replicates via a "copy-and-paste" mechanism and significantly influences the regulation of host genomes. In both normal and pathologic contexts, retrotransposons contribute to a vast reservoir of regulatory elements that can modulate the expression of genes. If left unchecked, retrotransposons can substantially affect host transcriptional programs and genomic integrity. Therefore, various mechanisms, including epigenetic modifications, have been employed to mitigate their potentially deleterious effects. In diseases such as cancer, the epigenome is often significantly reprogrammed, which can lead to retrotransposon dysregulation. Drawing insights from recent studies conducted in human and murine cells, this review examines how retrotransposons expand the complexity of mammalian genomes, describes the impact of their epigenetic dysregulation on cancer development, and highlights the potential of targeting these sequences for therapeutic strategies.

Development of Novel PRMT7 Inhibitors for the Treatment of Prostate Cancer

Prostate cancer (PCa) remains a prevalent malignancy in men and warrants novel and efficacious therapy. Protein arginine methyltransferase 7 (PRMT7) has been recently identified as a promising target for PCa treatment, however, the development of efficacious PRMT7 inhibitors is limited. Herein, we reported an effective and selective PRMT7 inhibitor, A33, which was obtained through structural optimization and exhibited potent anti-PCa efficacy in vitro and in vivo. A33 significantly inhibited the proliferation, colony formation, migration, and invasion of PCa cells and induced substantial cell cycle arrest and apoptosis. Mechanistically, A33 decreased the monomethylarginine level in PCa cells, regulated tumor metastasis-, proliferation-, and apoptosis-associated proteins, and enhanced antitumor innate immunity by targeting PRMT7. More importantly, A33 exhibited low toxicity and effectively suppressed PCa tumor growth in the DU-145 xenograft tumor model. Collectively, this study provides a novel potent PRMT7 inhibitor for further anti-PCa drug discovery.

PRMT7 Inhibitor SGC3027 Enhances Radiotherapy Efficacy via Activating ATM Kinase in Non-Small Cell Lung Carcinoma

Non-small-cell lung cancer (NSCLC) is the leading cause of tumor-related death in humans. Radiotherapy is a crucial strategy for NSCLC treatment, although its effectiveness is limited by the radio-resistance of tumor cells. Our current research finds that the protein arginine methyltransferase 7 (PRMT7) is upregulated in NSCLC and correlates with poor prognosis. Pharmacological inhibition of PRMT7 by SGC3027, a specific small-molecule PRMT7 inhibitor, suppresses the proliferation, migration and invasion of NSCLC. Combining irradiation with SGC3027 strengthens the impact of irradiation on the biological behaviors of NSCLC cells. We also find that SGC3027 specifically activates ATM kinase and its downstream cell cycle checkpoint kinases to enhance radiobiological response in NSCLC. These findings underscore the promising therapeutic potential of PRMT7 inhibitors as well as combining PRMT7 inhibition with irradiation exposure for effective NSCLC therapies.

METTL3/IGF2BP1 promotes the development of triple-negative breast cancer by mediating m6A methylation modification of PRMT7

BACKGROUND

PRMT7 is upregulated in breast cancer and promotes tumor metastasis. Here we aimed to explore the function and mechanism of PRMT7 in triple-negative breast cancer (TNBC).

METHODS

The expression of PRMT7, METTL3 and IGF2BP1 was detected by immunohistochemistry (IHC), qRT-PCR and western blot. Cell viability and proliferation were measured using MTT and EdU assay. Flow cytometry and TUNEL assays were used to evaluate apoptosis. Invasion and migration were assessed by transwell and wound healing assays, respectively. Glucose consumption and lactate production were measured to assess glycolysis. In addition, the interaction between METTL3 and PRMT was verified by methylated RNA immunoprecipitation. The roles of METTL3 and PRMT in vivo were investigated through a xenograft model.

RESULTS

PRMT7 was upregulated in TNBC tissues and cells, and the knockdown of PRMT7 inhibited cell proliferation, invasion, migration and glycolysis, but induced apoptosis in TNBC cells. METTL3/IGF2BP1 enhanced PRMT7 expression by mediating the m6A methylation modification of PRMT7. Besides, METTL3 knockdown suppressed the progression of TNBC cells and regulated the WNT/β-catenin pathway via PRMT7. Moreover, silencing METTL3 restrained TNBC tumor growth in vivo through regulating PRMT7.

CONCLUSION

METTL3/IGF2BP1 facilitates the progression of TNBC by mediating m6A methylation modification of PRMT7.

Multidimensional bioinformatics perspective on smoking-linked driver genes and immune regulatory mechanisms in non-small cell lung cancer

BACKGROUND

Lung cancer, one of the leading causes of cancer-related morbidity and mortality worldwide, is strongly associated with smoking as its primary carcinogenic factor. However, despite the strong link between smoking and lung cancer, not all smokers develop the disease, suggesting that individual genetic susceptibility and molecular mechanisms may play a critical role in the onset of lung cancer. Understanding the gene-driving mechanisms and immune regulatory pathways involved in smoking-related lung cancer remains one of the key challenges in current lung cancer research.

METHODS

This study employs an integrative bioinformatics approach to explore gene expression differences and immune microenvironment characteristics between smokers with non-small cell lung cancer (NSCLC) and normal individuals. First, smoking-linked lung cancer driver genes (SLDCGs) were identified, followed by Mendelian Randomization (MR) and Summary-based Mendelian Randomization (SMR) analyses to further validate their causal relationships. Next, public databases, including TCGA, GEO, and GTEx, were used to systematically analyze the expression differences of SLDCGs across various clinical subgroups, and immune infiltration analysis was conducted to explore their potential roles in the immune microenvironment of NSCLC.

RESULTS

The study identified HLA-J and PRMT7 as core driver genes for smoking-associated NSCLC. MR analysis confirmed the potential causal relationship of HLA-J and PRMT7 in the development of NSCLC. Specifically, high expression of PRMT7 was closely associated with the occurrence of NSCLC, while low expression of HLA-J was implicated in immune evasion mechanisms in NSCLC. Additionally, immune microenvironment analysis revealed that HLA-J enhances the activity of immune cells, particularly T cells, to promote tumor immune recognition, whereas PRMT7 suppresses immune cell function, weakening immune surveillance and facilitating immune evasion.

CONCLUSION

This study systematically reveals the molecular mechanisms of smoking-linked NSCLC through multidimensional bioinformatics analysis, highlighting the key roles of SLDCGs in immune evasion. The discovery of HLA-J and PRMT7 provides new theoretical foundations for targeted immunotherapy, with significant potential for early diagnosis and personalized treatment of smoking-induced NSCLC. Future research should focus on validating these genes in clinical samples and exploring their potential in immunotherapy.

Arginine and colorectal cancer: Exploring arginine-related therapeutic strategies and novel insights into cancer immunotherapies

Concerning the progression of societies and the evolution of lifestyle and dietary habits, the potential for the development of human malignancies, particularly colorectal cancer (CRC), has markedly escalated, positioning it as one of the most prevalent and lethal forms of cancer globally. Empirical evidence indicates that the metabolic processes of cancerous and healthy cells can significantly impact immune responses and the fate of tumors. Arginine, a multifaceted amino acid, assumes a crucial and paradoxical role in various metabolic pathways, as certain tumors exhibit arginine auxotrophy while others do not. Notably, CRC is classified as arginine non-auxotrophic, possessing the ability to synthesize arginine from citrulline. Systemic arginine deprivation and the inhibition of arginine uptake represent two prevalent therapeutic strategies in oncological treatment. However, given the divergent behaviors of tumors concerning the metabolism and synthesis of arginine, one of these therapeutic approaches-namely systemic arginine deprivation-does not apply to CRC. This review elucidates the characteristics of arginine uptake inhibition and systemic arginine deprivation alongside their respective benefits and limitations in CRC. Furthermore, the involvement of arginine in immunotherapeutic strategies is examined in light of the most recent discoveries on various human malignancies.

PRMT7 in cancer: Structure, effects, and therapeutic potentials

Protein arginine methyltransferase 7 (PRMT7), a type III methyltransferase responsible solely for arginine mono-methylation, plays a critical role in numerous physiological and pathological processes. Recent studies have highlighted its aberrant expression or mutation in various cancers, implicating it in tumorigenesis, cancer progression, and drug resistance. Consequently, PRMT7 has emerged as a promising target for cancer diagnosis and therapeutic intervention. In this review, we present an overview of the molecular structure of PRMT7, discuss its roles and mechanisms in different cancer types, and analyze the binding modes and structure-activity relationships of reported PRMT7 inhibitors. Furthermore, we identify the challenges encountered in functional exploration and drug development targeting PRMT7, propose potential solutions to these challenges, and outline future directions for the development of PRMT7 inhibitors to inform future drug discovery efforts.

Protein arginine methyltransferase 7 modulators in disease therapy: Current progress and emerged opportunity

Protein arginine methyltransferase 7 (PRMT7) is an essential epigenetic and post-translational regulator in eukaryotic organisms. Dysregulation of PRMT7 is intimately related to multiple types of human diseases, particularly cancer. In addition, PRMT7 exerts multiple effects on cellular processes such as growth, migration, invasion, apoptosis, and drug resistance in various cancers, making it as a promising target for anti-tumor therapeutics. In this review, we initially provide an overview of the structure and biological functions of PRMT7, along with its association with diseases. Subsequently, we summarized the PRMT inhibitors in clinical trials and the co-crystal structural of PRMT7 inhibitors. Moreover, we also focus on recent progress in the design and development of modulators targeting PRMT7, including isoform-selective and non-selective PRMT7 inhibitors, and the dual-target inhibitors based on PRMT7, from the perspectives of rational design, pharmacodynamics, pharmacokinetics, and the clinical status of these modulators. Finally, we also provided the challenges and prospective directions for PRMT7 targeting drug discovery in cancer therapy.

Dual roles of human endogenous retroviruses in cancer progression and antitumor immune response

Human endogenous retroviruses (HERVs) are a class of transposable elements formed by the integration of ancient retroviruses into the germline genome. They are inherited in a Mendelian manner and approximately constitute 8 % of the human genome. HERVs were considered as "junk DNA" for decades, but increasing evidence suggests that they play significant roles in pathological inflammation, neural differentiation, and oncogenesis. Specifically, HERVs expression has been implicated in several oncogenic processes and the formation of the tumor microenvironment. Indeed, the dual roles of HERVs in cancer, serving as both promoters of oncogenesis and forerunners of the innate antitumor immune response, remain a subject of debate. In this review, we will discuss how HERVs participate in cancer progression and how they are regulated. Our aim is to provide a comprehensive understanding of the fundamental properties and potential function of HERVs in propagating oncogenesis and activating the antitumor immune response. We hope that updated knowledge will reshape our understanding of the critical roles played by HERVs in human evolution and cancer progression.

KDM3A Ablation Activates Endogenous Retrovirus Expression to Stimulate Antitumor Immunity in Gastric Cancer

The success of immunotherapy for cancer treatment is limited by the presence of an immunosuppressive tumor microenvironment (TME); Therefore, identifying novel targets to that can reverse this immunosuppressive TME and enhance immunotherapy efficacy is essential. In this study, enrichment analysis based on publicly available single-cell and bulk RNA sequencing data from gastric cancer patients are conducted, and found that tumor-intrinsic interferon (IFN) plays a central role in TME regulation. The results shows that KDM3A over-expression suppresses the tumor-intrinsic IFN response and inhibits KDM3A, either genomically or pharmacologically, which effectively promotes IFN responses by activating endogenous retroviruses (ERVs). KDM3A ablation reconfigures the dsRNA-MAVS-IFN axis by modulating H3K4me2, enhancing the infiltration and function of CD8 T cells, and simultaneously reducing the presence of regulatory T cells, resulting in a reshaped TME in vivo. In addition, combining anti-PD1 therapy with KDM3A inhibition effectively inhibited tumor growth. In conclusions, this study highlights KDM3A as a potential target for TME remodeling and the enhancement of antitumor immunity in gastric cancer through the regulation of the ERV-MAVS-IFN axis.

RARRES1 identified by comprehensive bioinformatic analysis and experimental validation as a promising biomarker in Skin Cutaneous Melanoma

Skin cutaneous melanoma (SKCM) is a highly malignant form of skin cancer, known for its unfavorable prognosis and elevated mortality rate. RARRES1, a gene responsive to retinoic acid receptors, displays varied functions in various cancer types. However, the specific role and underlying mechanisms of RARRES1 in SKCM are still unclear. GSE15605 was utilized to analyze the expression of RARRES1 in SKCM. Subsequently, the TCGA and GEO databases were employed to investigate the relationships between RARRES1 and clinicopathological parameters, as well as the prognostic implications and diagnostic efficacy of RARRES1 in SKCM. GO, KEGG, and GSEA analyses were conducted to explore the potential functions of RARRES1. Furthermore, the associations between RARRES1 and immune infiltration were examined. Genomic alterations and promoter methylation levels of RARRES1 in SKCM were assessed using cBioPortal, UALCAN, and the GEO database. Finally, RARRES1 expression in SKCM was validated through immunohistochemistry, and its functional role in SKCM progression was elucidated via in vivo and in vitro experiments. We found that RARRES1 was downregulated in SKCM compared with normal tissues, and this low expression was associated with worse clinicopathological features and poor prognosis of SKCM. The diagnostic efficacy of RARRES1, as determined by ROC analysis, was 0.732. Through GO, KEGG, and GSEA enrichment analysis, we identified 30 correlated genes and pathways that were mainly enriched in the tumor immune microenvironment, proliferation, apoptosis, and autophagy. Additionally, RARRES1 expression was found to be positively related to the infiltration of various immune cells in SKCM, particularly macrophages and T helper cells, among others. Analysis of genomic alterations and promoter methylation revealed that shallow deletion and hypermethylation of the RARRES1 promoter could lead to reduced RARRES1 expression. IHC validation confirmed the downregulation of RARRES1 in SKCM. Moreover, overexpression of RARRES1 inhibited the proliferation and migration of A375 cells, promoted apoptosis, and inhibited autophagic flux. In the mouse xenograft model, RARRES1 overexpression also suppressed SKCM tumor growth. Collectively, these findings suggest that RARRES1 may function as a suppressor and could potentially serve as a prognostic biomarker and therapeutic target for SKCM.

PRMT1 promotes epigenetic reprogramming associated with acquired chemoresistance in pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) carries a dismal prognosis due to therapeutic resistance. We show that PDAC cells undergo global epigenetic reprogramming to acquire chemoresistance, a process that is driven at least in part by protein arginine methyltransferase 1 (PRMT1). Genetic or pharmacological PRMT1 inhibition impairs adaptive epigenetic reprogramming and delays acquired resistance to gemcitabine and other common chemo drugs. Mechanistically, gemcitabine treatment induces translocation of PRMT1 into the nucleus, where its enzymatic activity limits the assembly of chromatin-bound MAFF/BACH1 transcriptional complexes. Cut&Tag chromatin profiling of H3K27Ac, MAFF, and BACH1 suggests a pivotal role for MAFF/BACH1 in global epigenetic response to gemcitabine, which is confirmed by genetically silencing MAFF. PRMT1 and MAFF/BACH1 signature genes identified by Cut&Tag analysis distinguish gemcitabine-resistant from gemcitabine-sensitive patient-derived xenografts of PDAC, supporting the PRMT1-MAFF/BACH1 epigenetic regulatory axis as a potential therapeutic avenue for improving the efficacy and durability of chemotherapies in patients of PDAC.

Type-I protein arginine methyltransferase inhibition primes anti-programmed cell death protein 1 immunotherapy in triple-negative breast cancer

BACKGROUND

Immune-checkpoint blockade (ICB) therapy shows promise for treating aggressive triple-negative breast cancer (TNBC). However, only some patients benefit from ICB, revealing an urgent need for identifying novel strategies for sensitizing patients to ICB. Previously, the authors demonstrated that type-I protein arginine methyltransferases (PRMTs) regulated antiviral innate-immune responses in TNBC by altering RNA splicing. This study aimed to explore the effects of targeting type-I PRMTs on the tumor microenvironment (TME) and the efficacy of ICB therapy against TNBC.

METHODS

Single-cell transcriptomic analysis was performed to investigate the effects of type-I PRMT inhibition on the TME, especially T-cell subsets. Single-cell T-cell receptor sequencing was performed to analyze the diversity and dynamics of the T-cell repertoire. A syngeneic murine model of TNBC was used to evaluate the therapeutic efficacy and immune memory effect of combining a type-I PRMT inhibitor (MS023) with an anti-programmed cell death protein 1 (PD-1) antibody.

RESULTS

Type-I PRMT inhibition combined with anti-PD-1 therapy reduced tumor growth. Mechanistically, type-I PRMT inhibition reshaped the TME. Increased CD8 T-cell infiltration was verified using flow cytometry. Increased clonotypes and clonal diversity were also observed after MS023 treatment, which contributed to immune memory following combination treatment.

CONCLUSIONS

Targeting type-I PRMT can potentially improve immunotherapeutic efficacies in patients with TNBC. By enhancing the tumor immunogenicity and promoting a more favorable immune microenvironment, this combined approach may enable more patients with TNBC to benefit from immunotherapies.

Protein arginine methyltransferase 1, a major regulator of biological processes

Protein arginine methyltransferase 1 (PRMT1) is a major type I arginine methyltransferase that catalyzes the formation of monomethyl and asymmetric dimethylarginine in protein substrates. It was first identified to asymmetrically methylate histone H4 at the third arginine residue forming the H4R3me2a active histone mark. However, several protein substrates are now identified as being methylated by PRMT1. As a result of its association with diverse classes of substrates, PRMT1 regulates several biological processes like chromatin dynamics, transcription, RNA processing, and signal transduction. The review provides an overview of PRMT1 structure, biochemical features, specificity, regulation, and role in cellular functions. We discuss the genomic distribution of PRMT1 and its association with tRNA genes. Further, we explore the different substrates of PRMT1 involved in splicing. In the end, we discuss the proteins that interact with PRMT1 and their downstream effects in diseased states.

Melanoma differentiation-associated protein 5 prevents cardiac hypertrophy via apoptosis signal-regulating kinase 1-c-Jun N-terminal kinase/p38 signaling

Pathological cardiac hypertrophy (CH) is driven by maladaptive changes in myocardial cells in response to pressure overload or other stimuli. CH has been identified as a significant risk factor for the development of various cardiovascular diseases, ultimately resulting in heart failure. Melanoma differentiation-associated protein 5 (MDA5), encoded by interferon-induced with helicase C domain 1 (IFIH1), is a cytoplasmic sensor that primarily functions as a detector of double-stranded ribonucleic acid (dsRNA) viruses in innate immune responses; however, its role in CH pathogenesis remains unclear. Thus, the aim of this study was to examine the relationship between MDA5 and CH using cellular and animal models generated by stimulating neonatal rat cardiomyocytes with phenylephrine and by performing transverse aortic constriction on mice, respectively. MDA5 expression was upregulated in all models. MDA5 deficiency exacerbated myocardial pachynsis, fibrosis, and inflammation in vivo, whereas its overexpression hindered CH development in vitro. In terms of the underlying molecular mechanism, MDA5 inhibited CH development by promoting apoptosis signal-regulating kinase 1 (ASK1) phosphorylation, thereby suppressing c-Jun N-terminal kinase/p38 signaling pathway activation. Rescue experiments using an ASK1 activation inhibitor confirmed that ASK1 phosphorylation was essential for MDA5-mediated cell death. Thus, MDA5 protects against CH and is a potential therapeutic target.

PRMT1 acts as a suppressor of MHC-I and anti-tumor immunity

Cancer immunotherapies have demonstrated remarkable success; however, the majority of patients do not respond or develop resistance. Here, we conduct epigenetic gene-targeted CRISPR-Cas9 screens to identify epigenomic factors that limit CD8+ T cell-mediated anti-tumor immunity. We identify that PRMT1 suppresses interferon gamma (Ifnγ)-induced MHC-I expression, thus dampening CD8+ T cell-mediated killing. Indeed, PRMT1 knockout or pharmacological targeting of type I PRMT with the clinical inhibitor GSK3368715 enhances Ifnγ-induced MHC-I expression through elevated STAT1 expression and activation, while re-introduction of PRMT1 in PRMT1-deficient cells reverses this effect. Importantly, loss of PRMT1 enhances the efficacy of anti-PD-1 immunotherapy, and The Cancer Genome Atlas analysis reveals that PRMT1 expression in human melanoma is inversely correlated with expression of human leukocyte antigen molecules, infiltration of CD8+ T cells, and overall survival. Taken together, we identify PRMT1 as a negative regulator of anti-tumor immunity, unveiling clinical type I PRMT inhibitors as immunotherapeutic agents or as adjuncts to existing immunotherapies.

PRMT7-Dependent Transcriptional Activation of Hmgb2 Aggravates Severe Acute Pancreatitis by Promoting Acsl1-Induced Ferroptosis

Severe acute pancreatitis (SAP) is a highly fatal abdominal emergency, and its association with protein arginine methyltransferase 7 (PRMT7), the sole known type III enzyme responsible for the monomethylation of arginine residue, remains unexplored. In this study, we observe an increase in the PRMT7 levels in the pancreas of SAP mice and Cerulein-LPS-stimulated AR42J cells. Overexpression of Prmt7 exacerbated pancreatic damage in SAP, while the inhibition of PRMT7 improved SAP-induced pancreatic damage. Furthermore, PRMT7 overexpression promoted inflammation, oxidative stress, and ferroptosis during SAP. Mechanically, PRMT7 catalyzed monomethylation at histone H4 arginine 3 (H4R3me1) at the promoter region of high mobility group proteins 2 (HMGB2), thereby enhancing its transcriptional activity. Subsequently, HMGB2 facilitated Acyl CoA synthase long-chain family member 1 (ACSL1) transcription by binding to its promoter region, resulting in the activation of ferroptosis. Inhibition of PRMT7 effectively alleviated ferroptosis in Cerulein-LPS-induced AR42J cells by suppressing the HMGB2-ACSL1 pathway. Overall, our study reveals that PRMT7 plays a crucial role in promoting SAP through its regulation of the HMGB2-ACSL1 pathway to accelerate ferroptosis.

Protein arginine methyltransferases (PRMTs): Orchestrators of cancer pathogenesis, immunotherapy dynamics, and drug resistance

Protein Arginine Methyltransferases (PRMTs) are a family of enzymes regulating protein arginine methylation, which is a post-translational modification crucial for various cellular processes. Recent studies have highlighted the mechanistic role of PRMTs in cancer pathogenesis, immunotherapy, and drug resistance. PRMTs are involved in diverse oncogenic processes, including cell proliferation, apoptosis, and metastasis. They exert their effects by methylation of histones, transcription factors, and other regulatory proteins, resulting in altered gene expression patterns. PRMT-mediated histone methylation can lead to aberrant chromatin remodeling and epigenetic changes that drive oncogenesis. Additionally, PRMTs can directly interact with key signaling pathways involved in cancer progression, such as the PI3K/Akt and MAPK pathways, thereby modulating cell survival and proliferation. In the context of cancer immunotherapy, PRMTs have emerged as critical regulators of immune responses. They modulate immune checkpoint molecules, including programmed cell death protein 1 (PD-1), through arginine methylation. Drug resistance is a significant challenge in cancer treatment, and PRMTs have been implicated in this phenomenon. PRMTs can contribute to drug resistance through multiple mechanisms, including the epigenetic regulation of drug efflux pumps, altered DNA damage repair, and modulation of cell survival pathways. In conclusion, PRMTs play critical roles in cancer pathogenesis, immunotherapy, and drug resistance. In this overview, we have endeavored to illuminate the mechanistic intricacies of PRMT-mediated processes. Shedding light on these aspects will offer valuable insights into the fundamental biology of cancer and establish PRMTs as promising therapeutic targets.

PRMT1 Integrates Immune Microenvironment and Fatty Acid Metabolism Response in Progression of Hepatocellular Carcinoma

Background

Protein arginine methyltransferase (PRMT) family members have important roles in cancer processes. However, its functions in the regulation of cancer immunotherapy of hepatocellular carcinoma (HCC) are incompletely understood. This study aimed to investigate the roles of PRMT1 in HCC.

Methods

Single-cell RNA sequencing (scRNA-seq) and clinicopathological data were obtained and used to explore the diagnostic and prognostic value, cellular functions and roles in immune microenvironment regulation of PRMT1 in HCC. The functions of PRMT1 were explored using Kyoto Encyclopedia of Genes and Genomes (KEGG) and Gene Ontology (GO), as well as gene set enrichment analysis (GSEA). TIMER and CIBERSORT were used to analyze the relationships between PRMT1 expression and immune cell infiltration. The STRING database was used to construct a protein-protein interaction (PPI) network.

Results

PRMT1 was aberrantly expressed in HCC, which high expression was associated with tumor progression, worse overall survival (OS) and disease-free survival (DFS) of patients with HCC. PRMT1 was also associated with immune cell infiltration. Moreover, it was specifically expressed in immune cells, including exhausted CD8 T cells, B cells, and mono/macro cells in patients with immunotherapy. The expression of immune checkpoints was significantly increased in the high-PRMT1 expression groups of HCC patients. Regarding biological mechanisms, cell viability, migration and invasion, and the expression of genes related to fatty acid metabolism were suppressed in PRMT1 knockdown HCC cells. Moreover, genes co-expressed with PRMT1 were involved in the fatty acid metabolic process and enriched in fatty and drug-induced liver disease.

Conclusion

Taken together, these results indicate that PRMT1 might exert its oncogenic effects via immune microenvironment regulation and fatty acid metabolism in HCC. Our finding will provide a foundation for further studies and indicate a potential clinical therapeutic target for liver cancer.

Promising role of protein arginine methyltransferases in overcoming anti-cancer drug resistance

Drug resistance remains a major challenge in cancer treatment, necessitating the development of novel strategies to overcome it. Protein arginine methyltransferases (PRMTs) are enzymes responsible for epigenetic arginine methylation, which regulates various biological and pathological processes, as a result, they are attractive therapeutic targets for overcoming anti-cancer drug resistance. The ongoing development of small molecules targeting PRMTs has resulted in the generation of chemical probes for modulating most PRMTs and facilitated clinical treatment for the most advanced oncology targets, including PRMT1 and PRMT5. In this review, we summarize various mechanisms underlying protein arginine methylation and the roles of specific PRMTs in driving cancer drug resistance. Furthermore, we highlight the potential clinical implications of PRMT inhibitors in decreasing cancer drug resistance. PRMTs promote the formation and maintenance of drug-tolerant cells via several mechanisms, including altered drug efflux transporters, autophagy, DNA damage repair, cancer stem cell-related function, epithelial-mesenchymal transition, and disordered tumor microenvironment. Multiple preclinical and ongoing clinical trials have demonstrated that PRMT inhibitors, particularly PRMT5 inhibitors, can sensitize cancer cells to various anti-cancer drugs, including chemotherapeutic, targeted therapeutic, and immunotherapeutic agents. Combining PRMT inhibitors with existing anti-cancer strategies will be a promising approach for overcoming anti-cancer drug resistance. Furthermore, enhanced knowledge of the complex functions of arginine methylation and PRMTs in drug resistance will guide the future development of PRMT inhibitors and may help identify new clinical indications.

Genetic Control of Alternative Splicing and its Distinct Role in Colorectal Cancer Mechanisms

BACKGROUND & AIMS

Dysregulation of alternative splicing is implicated in many human diseases, and understanding the genetic variation underlying transcript splicing is essential to dissect the molecular mechanisms of cancers. We aimed to provide a comprehensive functional dissection of splicing quantitative trait loci (sQTLs) in cancer and focus on elucidating its distinct role in colorectal cancer (CRC) mechanisms.

METHODS

We performed a comprehensive sQTL analysis to identify genetic variants that control messenger RNA splicing across 33 cancer types from The Cancer Genome Atlas and independently validated in our 154 CRC tissues. Then, large-scale, multicenter, multi-ethnic case-control studies (34,585 cases and 76,023 controls) were conducted to examine the association of these sQTLs with CRC risk. A series of biological experiments in vitro and in vivo were performed to investigate the potential mechanisms of the candidate sQTLs and target genes.

RESULTS

The molecular characterization of sQTL revealed its distinct role in cancer susceptibility. Tumor-specific sQTL further showed better response to cancer development. In addition, functionally informed polygenic risk score highlighted the potentiality of sQTLs in the CRC prediction. Complemented by large-scale population studies, we identified that the risk allele (T) of a multi-ancestry-associated sQTL rs61746794 significantly increased the risk of CRC in Chinese (odds ratio, 1.20; 95% CI, 1.12-1.29; P = 8.82 × 10-7) and European (odds ratio, 1.11; 95% CI, 1.07-1.16; P = 1.13 × 10-7) populations. rs61746794-T facilitated PRMT7 exon 16 splicing mediated by the RNA-binding protein PRPF8, thus increasing the level of canonical PRMT7 isoform (PRMT7-V2). Overexpression of PRMT7-V2 significantly enhanced the growth of CRC cells and xenograft tumors compared with PRMT7-V1. Mechanistically, PRMT7-V2 functions as an epigenetic writer that catalyzes the arginine methylation of H4R3 and H3R2, subsequently regulating diverse biological processes, including YAP, AKT, and KRAS pathway. A selective PRMT7 inhibitor, SGC3027, exhibited antitumor effects on human CRC cells.

CONCLUSIONS

Our study provides an informative sQTLs resource and insights into the regulatory mechanisms linking splicing variants to cancer risk and serving as biomarkers and therapeutic targets.

Protein arginine methylation in viral infection and antiviral immunity

Protein arginine methyltransferase (PRMT)-mediated arginine methylation is an important post-transcriptional modification that regulates various cellular processes including epigenetic gene regulation, genome stability maintenance, RNA metabolism, and stress-responsive signal transduction. The varying substrates and biological functions of arginine methylation in cancer and neurological diseases have been extensively discussed, providing a rationale for targeting PRMTs in clinical applications. An increasing number of studies have demonstrated an interplay between arginine methylation and viral infections. PRMTs have been found to methylate and regulate several host cell proteins and different functional types of viral proteins, such as viral capsids, mRNA exporters, transcription factors, and latency regulators. This modulation affects their activity, subcellular localization, protein-nucleic acid and protein-protein interactions, ultimately impacting their roles in various virus-associated processes. In this review, we discuss the classification, structure, and regulation of PRMTs and their pleiotropic biological functions through the methylation of histones and non-histones. Additionally, we summarize the broad spectrum of PRMT substrates and explore their intricate effects on various viral infection processes and antiviral innate immunity. Thus, comprehending the regulation of arginine methylation provides a critical foundation for understanding the pathogenesis of viral diseases and uncovering opportunities for antiviral therapy.

Critical Roles of Protein Arginine Methylation in the Central Nervous System

A remarkable post-transitional modification of both histones and non-histone proteins is arginine methylation. Methylation of arginine residues is crucial for a wide range of cellular process, including signal transduction, DNA repair, gene expression, mRNA splicing, and protein interaction. Arginine methylation is modulated by arginine methyltransferases and demethylases, like protein arginine methyltransferase (PRMTs) and Jumonji C (JmjC) domain containing (JMJD) proteins. Symmetric dimethylarginine and asymmetric dimethylarginine, metabolic products of the PRMTs and JMJD proteins, can be changed by abnormal expression of these proteins. Many pathologies including cancer, inflammation and immune responses have been closely linked to aberrant arginine methylation. Currently, the majority of the literature discusses the substrate specificity and function of arginine methylation in the pathogenesis and prognosis of cancers. Numerous investigations on the roles of arginine methylation in the central nervous system (CNS) have so far been conducted. In this review, we display the biochemistry of arginine methylation and provide an overview of the regulatory mechanism of arginine methyltransferases and demethylases. We also highlight physiological functions of arginine methylation in the CNS and the significance of arginine methylation in a variety of neurological diseases such as brain cancers, neurodegenerative diseases and neurodevelopmental disorders. Furthermore, we summarize PRMT inhibitors and molecular functions of arginine methylation. Finally, we pose important questions that require further research to comprehend the roles of arginine methylation in the CNS and discover more effective targets for the treatment of neurological diseases.

PRMT7 Inhibits the Proliferation and Migration of Gastric Cancer Cells by Suppressing the PI3K/AKT Pathway via PTEN

Protein arginine methyltransferase 7 (PRMT7) plays a crucial role in tumor occurrence and development; however, its expression pattern, biological function, and specific mechanism in gastric cancer (GC) remain poorly defined. The present study aimed to investigate the role of PRMT7 during GC carcinogenesis and its underlying mechanism. We found that PRMT7 is expressed at low levels in GC tissues, and this low expression is associated with tumor size, differentiation degree, lymph node metastasis, and TNM stage. Functionally, PRMT7 inhibits GC cell proliferation and migration. Mechanistically, PRMT7 induces PTEN expression and suppresses the downstream PI3K/AKT signaling cascade. Finally, we confirmed that PRMT7 interacts with PTEN protein and promotes PTEN arginine methylation. Taken together, our findings suggest that PRMT7 can inhibit PI3K/AKT signaling pathway activation by regulating PTEN, thereby inhibiting GC cell proliferation and migration. PRMT7 may be a promising therapeutic target for the prevention of GC.

Retinoic acid-inducible gene-I like receptor pathway in cancer: modification and treatment

Retinoic acid-inducible gene-I (RIG-I) like receptor (RLR) pathway is one of the most significant pathways supervising aberrant RNA in cells. In predominant conditions, the RLR pathway initiates anti-infection function via activating inflammatory effects, while recently it is discovered to be involved in cancer development as well, acting as a virus-mimicry responder. On one hand, the product IFNs induces tumor elimination. On the other hand, the NF-κB pathway is activated which may lead to tumor progression. Emerging evidence demonstrates that a wide range of modifications are involved in regulating RLR pathways in cancer, which either boost tumor suppression effect or prompt tumor development. This review summarized current epigenetic modulations including DNA methylation, histone modification, and ncRNA interference, as well as post-transcriptional modification like m6A and A-to-I editing of the upstream ligand dsRNA in cancer cells. The post-translational modulations like phosphorylation and ubiquitylation of the pathway's key components were also discussed. Ultimately, we provided an overview of the current therapeutic strategies targeting the RLR pathway in cancers.

Comprehensive Analysis and Drug Modulation of Human Endogenous Retrovirus in Hepatocellular Carcinomas

BACKGROUND

Human endogenous retroviruses (HERVs) play an important role in the development of cancer and many diseases. Here, we comprehensively explored the impact of HERVs on hepatocellular carcinomas (HCCs).

METHODS

We employed Telescope to identify HERVs and quantify their expression in the total RNA sequencing data obtained from 254 HCC samples, comprising 254 tumor tissues and 34 matched normal tissues.

RESULTS

In total, 3357 locus-specific activations of HERVs were differentially expressed, and 180 were correlated with patient survival. Using these 180 HERVs for classification, we found four subgroups with survival correlation. Higher expression levels of the 180 HERVs were correlated with poorer survival, while age, AFP, some mutations, and copy and structural variants differed among subgroups. The differential expression of host genes in high expression of these 180 HERVs primarily involved the activation of pathways related to immunity and infection, lipid and atherosclerosis, MAPK and NF-kB signaling, and cytokine-cytokine receptor interactions. Conversely, there was a suppression of pathways associated with RNA processing, including nucleocytoplasmic transport, surveillance and ribosome biogenesis, and transcriptional misregulation in cancer pathways. Almost all genes involved in HERV activation restriction, KRAB zinc finger proteins, RNA nucleocytoplasmic transport, stemness, HLA and antigen processing and presentation, and immune checkpoints were overexpressed in cancerous tissues, and many over-expressed HERV-related nearby genes were correlated with high HERV activation and poor survival. Twenty-three immune and stromal cells showed higher expression in non-cancerous than cancerous tissues, and seven were correlated with HERV activation. Small-molecule modulation of alternative splicing (AS) altered the expression of survival-related HERVs and their activation-related genes, as well as nearby genes.

CONCLUSION

Comprehensive and integrated approaches for evaluating HERV expression and their correlation with specific pathways have the potential to provide new companion diagnostics and therapeutic strategies for HCC.

Reshaping the tumour immune microenvironment in solid tumours via tumour cell and immune cell DNA methylation: from mechanisms to therapeutics

In recent years, the tumour microenvironment (TME) of solid tumours has attracted more and more attention from researchers, especially those non-tumour components such as immune cells. Infiltration of various immune cells causes tumour immune microenvironment (TIME) heterogeneity, and results in different therapeutic effects. Accumulating evidence showed that DNA methylation plays a crucial role in remodelling TIME and is associated with the response towards immune checkpoint inhibitors (ICIs). During carcinogenesis, DNA methylation profoundly changes, specifically, there is a global loss of DNA methylation and increased DNA methylation at the promoters of suppressor genes. Immune cell differentiation is disturbed, and exclusion of immune cells from the TME occurs at least in part due to DNA methylation reprogramming. Therefore, pharmaceutical interventions targeting DNA methylation are promising. DNA methyltransferase inhibitors (DNMTis) enhance antitumor immunity by inducing transcription of transposable elements and consequent viral mimicry. DNMTis upregulate the expression of tumour antigens, mediate immune cells recruitment and reactivate exhausted immune cells. In preclinical studies, DNMTis have shown synergistic effect when combined with immunotherapies, suggesting new strategies to treat refractory solid tumours.

The Crucial Roles and Research Advances of cGAS-STING Pathway in Cutaneous Disorders

The cGAS-STING signaling pathway senses the presence of cytosolic DNA, induces strong type I interferon responses, and enhances inflammatory cytokine production, placing it as an important axis in infection, autoimmunity, and tumor immunity. Recent studies have shown that the abnormalities and/or dysfunctions of cGAS-STING signaling are closely related to the pathogenesis of skin diseases and/or cancers. Additionally, a variety of new therapeutics targeting the cGAS-STING signaling are in development for the treatment of skin disorders. However, the precise molecular mechanisms of cGAS-STING-mediated cutaneous disorders have not been fully elucidated. In this review, we will summarize the regulatory roles and mechanisms of cGAS-STING signaling in skin disorders and recent progresses of cGAS-STING-related drugs as well as their potential clinical applications.

The Role of PRMT5 in Immuno-Oncology

Immune checkpoint inhibitor (ICI) therapy has caused a paradigm shift in cancer therapeutic strategy. However, this therapy only benefits a subset of patients. The difference in responses to ICIs is believed to be dependent on cancer type and its tumor microenvironment (TME). The TME is favorable for cancer progression and metastasis and can also help cancer cells to evade immune attacks. To improve the response to ICIs, it is crucial to understand the mechanism of how the TME is maintained. Protein arginine methyltransferase 5 (PRMT5) di-methylates arginine residues in its substrates and has essential roles in the epigenetic regulation of gene expression, signal transduction, and the fidelity of mRNA splicing. Through these functions, PRMT5 can support cancer cell immune evasion. PRMT5 is necessary for regulatory T cell (Treg) functions and promotes cancer stemness and the epithelial-mesenchymal transition. Specific factors in the TME can help recruit Tregs, tumor-associated macrophages, and myeloid-derived suppressor cells into tumors. In addition, PRMT5 suppresses antigen presentation and the production of interferon and chemokines, which are necessary to recruit T cells into tumors. Overall, PRMT5 supports an immunosuppressive TME. Therefore, PRMT5 inhibition would help recover the immune cycle and enable the immune system-mediated elimination of cancer cells.

S-adenosylmethionine blocks tumorigenesis and with immune checkpoint inhibitor enhances anti-cancer efficacy against BRAF mutant and wildtype melanomas

Despite marked success in treatment with immune checkpoint inhibitor (CPI), only a third of patients are responsive. Thus, melanoma still has one of the highest prevalence and mortality rates; which has led to a search for novel combination therapies that might complement CPI. Aberrant methylomes are one of the mechanisms of resistance to CPI therapy. S-adenosylmethionine (SAM), methyl donor of important epigenetic processes, has significant anti-cancer effects in several malignancies; however, SAM's effect has never been extensively investigated in melanoma. We demonstrate that SAM modulates phenotype switching of melanoma cells and directs the cells towards differentiation indicated by increased melanogenesis (melanin and melanosome synthesis), melanocyte-like morphology, elevated Mitf and Mitf activators' expression, increased antigen expression, reduced proliferation, and reduced stemness genes' expression. Consistently, providing SAM orally, reduced tumor growth and progression, and metastasis of syngeneic BRAF mutant and wild-type (WT) melanoma mouse models. Of note, SAM and anti-PD-1 antibody combination treatment had enhanced anti-cancer efficacy compared to monotherapies, showed significant reduction in tumor growth and progression, and increased survival. Furthermore, SAM and anti-PD-1 antibody combination triggered significantly higher immune cell infiltration, higher CD8+ T cells infiltration and effector functions, and polyfunctionality of CD8+ T cells in YUMMER1.7 tumors. Therefore, SAM combined with CPI provides a novel therapeutic strategy against BRAF mutant and WT melanomas and provides potential to be translated into clinic.

Epigenetic Mechanisms Underlying Melanoma Resistance to Immune and Targeted Therapies

Melanoma is an aggressive skin cancer reliant on early detection for high likelihood of successful treatment. Solar UV exposure transforms melanocytes into highly mutated tumor cells that metastasize to the liver, lungs, and brain. Even upon resection of the primary tumor, almost thirty percent of patients succumb to melanoma within twenty years. Identification of key melanoma genetic drivers led to the development of pharmacological BRAF^V600E and MEK inhibitors, significantly improving metastatic patient outcomes over traditional cytotoxic chemotherapy or pioneering IFN-α and IL-2 immune therapies. Checkpoint blockade inhibitors releasing the immunosuppressive effects of CTLA-4 or PD-1 proved to be even more effective and are the standard first-line treatment. Despite these major improvements, durable responses to immunotherapy and targeted therapy have been hindered by intrinsic or acquired resistance. In addition to gained or selected genetic alterations, cellular plasticity conferred by epigenetic reprogramming is emerging as a driver of therapy resistance. Epigenetic regulation of chromatin accessibility drives gene expression and establishes distinct transcriptional cell states. Here we review how aberrant chromatin, transcriptional, and epigenetic regulation contribute to therapy resistance and discuss how targeting these programs sensitizes melanoma cells to immune and targeted therapies.

The Influence of Arginine Methylation in Immunity and Inflammation

Exploration in the field of epigenetics has revealed that protein arginine methyltransferases (PRMTs) contribute to disease, and this has given way to the development of specific small molecule compounds that inhibit arginine methylation. Protein arginine methylation is known to regulate fundamental cellular processes, such as transcription; pre-mRNA splicing and other RNA processing mechanisms; signal transduction, including the anti-viral response; and cellular metabolism. PRMTs are also implicated in the regulation of physiological processes, including embryonic development, myogenesis, and the immune system. Finally, the dysregulation of PRMTs is apparent in cancer, neurodegeneration, muscular disorders, and during inflammation. Herein, we review the functions of PRMTs in immunity and inflammation. We also discuss recent progress with PRMTs regarding the modulation of gene expression related to T and B lymphocyte differentiation, germinal center dynamics, and anti-viral signaling responses, as well as the clinical relevance of using PRMT inhibitors alone or in combination with other drugs to treat cancer, immune, and inflammatory-related diseases.