Metformin exhibits antiproliferation activity in breast cancer via miR-483-3p/METTL3/m6A/p21 pathway

RNA m6A modification in ferroptosis: implications for advancing tumor immunotherapy

The pursuit of innovative therapeutic strategies in oncology remains imperative, given the persistent global impact of cancer as a leading cause of mortality. Immunotherapy is regarded as one of the most promising techniques for systemic cancer therapies among the several therapeutic options available. Nevertheless, limited immune response rates and immune resistance urge us on an augmentation for therapeutic efficacy rather than sticking to conventional approaches. Ferroptosis, a novel reprogrammed cell death, is tightly correlated with the tumor immune environment and interferes with cancer progression. Highly mutant or metastasis-prone tumor cells are more susceptible to iron-dependent nonapoptotic cell death. Consequently, ferroptosis-induction therapies hold the promise of overcoming resistance to conventional treatments. The most prevalent post-transcriptional modification, RNA m6A modification, regulates the metabolic processes of targeted RNAs and is involved in numerous physiological and pathological processes. Aberrant m6A modification influences cell susceptibility to ferroptosis, as well as the expression of immune checkpoints. Clarifying the regulation of m6A modification on ferroptosis and its significance in tumor cell response will provide a distinct method for finding potential targets to enhance the effectiveness of immunotherapy. In this review, we comprehensively summarized regulatory characteristics of RNA m6A modification on ferroptosis and discussed the role of RNA m6A-mediated ferroptosis on immunotherapy, aiming to enhance the effectiveness of ferroptosis-sensitive immunotherapy as a treatment for immune-resistant malignancies.

RNA modifications in cancer immune therapy: regulators of immune cells and immune checkpoints

RNA modifications are epigenetic changes that alter the structure and function of RNA molecules, playing a crucial role in the onset, progression, and treatment of cancer. Immune checkpoint inhibitor (ICI) therapies, particularly PD-1 blockade and anti-CTLA-4 treatments, have changed the treatment landscape of virous cancers, showing great potential in the treatment of different cancer patients, but sensitivity to these therapies is limited to certain individuals. This review offers a comprehensive survey of the functions and therapeutic implications of the four principal RNA modifications, particularly highlighting the significance of m6A in the realms of immune cells in tumor and immunotherapy. This review starts by providing a foundational summary of the roles RNA modifications assume within the immune cell community, focusing on T cells, NK cells, macrophages, and dendritic cells. We then discuss how RNA modifications influence the intricate regulatory mechanisms governing immune checkpoint expression, modulation of ICI efficacy, and prediction of ICI treatment outcomes, and review drug therapies targeting genes regulated by RNA modifications. Finally, we explore the role of RNA modifications in gene editing, cancer vaccines, and adoptive T cell therapies, offering valuable insights into the use of RNA modifications in cancer immunotherapy.

Virtual Screening and Molecular Docking: Discovering Novel METTL3 Inhibitors

Methyltransferase-like 3 (METTL3) is an RNA methyltransferase that catalyzes the N6 -methyladenosine (m6A) modification of mRNA in eukaryotic cells. Past studies have shown that METTL3 is highly expressed in various cancers and is closely related to tumor development. Therefore, METTL3 inhibitors have received widespread attention as effective treatments for different types of tumors. This study proposes a hybrid high-throughput virtual screening (HTVS) protocol that combines structure-based methods with geometric deep learning-based DeepDock algorithms. We identified unique skeleton inhibitors of METTL3 from our self-built internal database. Among them, compound C3 showed significant inhibitory activity on METTL3, and further molecular dynamics simulations were performed to provide more details about the binding conformation. Overall, our research demonstrates the effectiveness of hybrid virtual algorithms, which is of great significance for understanding the biological functions of METTL3 and developing treatment methods for related diseases.

Functions of methyltransferase-like 3 in breast cancer: pathogenesis, drug resistance, and therapeutic target

Breast cancer (BC) is a highly prevalent malignancy worldwide, with complex pathogenesis and treatment challenges. Research reveals that methyltransferase-like 3 (METTL3) is widely involved in the pathogenesis of several tumors through methylation of its target RNAs, and its role and mechanisms in BC are also extensively studied. In this review, we aim to provide a comprehensive interpretation of available studies and elucidate the relationship between METTL3 and BC. This review suggests that high levels of METTL3 are associated with the pathogenesis, poor prognosis, and drug resistance of BC, suggesting METTL3 as a potential diagnostic or prognostic biomarker and therapeutic target. Collectively, this review provides a comprehensive understanding of how METTL3 functions through RNA methylation, which provides a valuable reference for future fundamental studies and clinical applications.

Unraveling the cross-talk between N6-methyladenosine modification and non-coding RNAs in breast cancer: Mechanisms and clinical implications

In recent years, breast cancer (BC) has surpassed lung cancer as the most common malignant tumor worldwide and remains the leading cause of cancer death in women. The etiology of BC usually involves dysregulation of epigenetic mechanisms and aberrant expression of certain non-coding RNAs (ncRNAs). N6-methyladenosine (m6A), the most prevalent RNA modification in eukaryotes, widely exists in ncRNAs to affect its biosynthesis and function, and is an important regulator of tumor-related signaling pathways. Interestingly, ncRNAs can also regulate or target m6A modification, playing a key role in cancer progression. However, the m6A-ncRNAs regulatory network in BC has not been fully elucidated, especially the regulation of m6A modification by ncRNAs. Therefore, in this review, we comprehensively summarize the interaction mechanisms and biological significance of m6A modifications and ncRNAs in BC. Meanwhile, we also focused on the clinical application value of m6A modification in BC diagnosis and prognosis, intending to explore new biomarkers and potential therapeutic targets.

Small molecule inhibitors targeting m6A regulators

As the most common form of epigenetic regulation by RNA, N6 methyladenosine (m6A) modification is closely involved in physiological processes, such as growth and development, stem cell renewal and differentiation, and DNA damage response. Meanwhile, its aberrant expression in cancer tissues promotes the development of malignant tumors, as well as plays important roles in proliferation, metastasis, drug resistance, immunity and prognosis. This close association between m6A and cancers has garnered substantial attention in recent years. An increasing number of small molecules have emerged as potential agents to target m6A regulators for cancer treatment. These molecules target the epigenetic level, enabling precise intervention in RNA modifications and efficiently disrupting the survival mechanisms of tumor cells, thus paving the way for novel approaches in cancer treatment. However, there is currently a lack of a comprehensive review on small molecules targeting m6A regulators for anti-tumor. Here, we have comprehensively summarized the classification and functions of m6A regulators, elucidating their interactions with the proliferation, metastasis, drug resistance, and immune responses in common cancers. Furthermore, we have provided a comprehensive overview on the development, mode of action, pharmacology and structure-activity relationships of small molecules targeting m6A regulators. Our aim is to offer insights for subsequent drug design and optimization, while also providing an outlook on future prospects for small molecule development targeting m6A.

FTO ameliorates doxorubicin-induced cardiotoxicity by inhibiting ferroptosis via P53-P21/Nrf2 activation in a HuR-dependent m6A manner

Doxorubicin (DOX)-induced cardiotoxicity seriously limits its clinical applicability, and no therapeutic interventions are available. Ferroptosis, an iron-dependent regulated cell death characterised by lipid peroxidation, plays a pivotal role in DOX-induced cardiotoxicity. N6-methyladenosine (m6A) methylation is the most frequent type of RNA modification and involved in DOX-induced ferroptosis, however, its underlying mechanism remains unclear. P21 was recently found to inhibit ferroptosis by interacting with Nrf2 and is regulated in a P53-dependent or independent manner, such as through m6A modification. In the present study, we investigated the mechanism underlying m6A modification in DOX-induced ferroptosis by focusing on P21. Our results show that fat mass and obesity-associated protein (FTO) down-regulation was associated with DOX-induced cardiotoxicity. FTO over-expression significantly improved cardiac function and cell viability in DOX-treated mouse hearts and H9C2 cells. FTO over-expression significantly inhibited DOX-induced ferroptosis, and the Fer-1 inhibition of ferroptosis significantly reduced DOX-induced cardiotoxicity. P21 was significantly upregulated by FTO and activated Nrf2, playing a crucial role in the anti-ferroptotic effect. FTO upregulated P21/Nrf2 in a P53-dependent manner by mediating the demethylation of P53 or in a P53-independent manner by mediating P21/Nrf2 directly. Human antigen R (HuR) is crucial for FTO-mediated regulation of ferroptosis and P53-P21/Nrf2. Notably, we also found that P21 inhibition in turn inhibited HuR and P53 expression, while HuR inhibition further inhibited FTO expression. RNA immunoprecipitation assay showed that HuR binds to the transcripts of FTO and itself. Collectively, FTO inhibited DOX-induced ferroptosis via P21/Nrf2 activation by mediating the m6A demethylation of P53 or P21/Nrf2 in a HuR-dependent manner and constituted a positive feedback loop with HuR and P53-P21. Our findings provide novel insight into key functional mechanisms associated with DOX-induced cardiotoxicity and elucidate a possible therapeutic approach.

Metformin and Breast Cancer: Current Findings and Future Perspectives from Preclinical and Clinical Studies

Over the last several decades, a growing body of research has investigated the potential to repurpose the anti-diabetic drug metformin for breast cancer prevention and/or treatment. Observational studies in the early 2000s demonstrated that patients with diabetes taking metformin had decreased cancer risk, providing the first evidence supporting the potential role of metformin as an anti-cancer agent. Despite substantial efforts, two decades later, the exact mechanisms and clinical efficacy of metformin for breast cancer remain ambiguous. Here, we have summarized key findings from studies examining the effect of metformin on breast cancer across the translational spectrum including in vitro, in vivo, and human studies. Importantly, we discuss critical factors that may help explain the significant heterogeneity in study outcomes, highlighting how metformin dose, underlying metabolic health, menopausal status, tumor subtype, membrane transporter expression, diet, and other factors may play a role in modulating metformin's anti-cancer effects. We hope that these insights will help with interpreting data from completed studies, improve the design of future studies, and aid in the identification of patient subsets with breast cancer or at high risk for the disease who are most likely to benefit from metformin treatment.

Modification patterns and metabolic characteristics of m6A regulators in digestive tract tumors

M6A is essential for tumor occurrence and progression. The expression patterns of m6A regulators differ in various kinds of tumors. Transcriptomic expression statistics together with clinical data from a database were analyzed to distinguish patients with digestive tract tumors. Based on the expression patterns of diverse m6A regulators, patients were divided into several clusters. Survival analysis suggested significant differences in patient prognosis among the m6A clusters. The results showed overlapping of m6A expression patterns with energy metabolism and nucleotide metabolism. Functional analyses imply that m6A modifications in tumor cells probably drive metabolic reprogramming to sustain rapid proliferation of cancer cells. Our analysis highlights the m6A risk characterizes various kinds of metabolic features and predicts chemotherapy sensitivity in digestive tract tumors, providing evidence for m6A regulators as markers to predict patient outcomes.

A review on the role of RNA methylation in aging-related diseases

Senescence is the underlying mechanism of organism aging and is robustly regulated at the post-transcriptional level. This regulation involves the chemical modifications, of which the RNA methylation is the most common. Recently, a rapidly growing number of studies have demonstrated that methylation is relevant to aging and aging-associated diseases. Owing to the rapid development of detection methods, the understanding on RNA methylation has gone deeper. In this review, we summarize the current understanding on the influence of RNA modification on cellular senescence, with a focus on mRNA methylation in aging-related diseases, and discuss the emerging potential of RNA modification in diagnosis and therapy.

New insights into the regulation of METTL3 and its role in tumors

As one of the most abundant epigenetic modifications in RNA, N6-methyladenosine (m6A) affects RNA transcription, splicing, stability, and posttranscriptional translation. Methyltransferase-like 3 (METTL3), a key component of the m6A methyltransferase complex, dynamically regulates target genes expression through m6A modification. METTL3 has been found to play a critical role in tumorigenesis, tumor growth, metastasis, metabolic reprogramming, immune cell infiltration, and tumor drug resistance. As a result, the development of targeted drugs against METTL3 is becoming increasingly popular. This review systematically summarizes the factors that regulate METTL3 expression and explores the specific mechanisms by which METTL3 affects multiple tumor biological behaviors. We aim to provide fundamental support for tumor diagnosis and treatment, at the same time, to offer new ideas for the development of tumor-targeting drugs.

The crucial roles of m6A RNA modifications in cutaneous cancers: Implications in pathogenesis, metastasis, drug resistance, and targeted therapies

N6-methyladenosine (m6A) is the most abundant internal modification on RNA. It is a dynamical and reversible process, which is regulated by m6A methyltransferase and m6A demethylase. The m6A modified RNA can be specifically recognized by the m6A reader, leading to RNA splicing, maturation, degradation or translation. The abnormality of m6A RNA modification is closely related to a variety of biological processes, especially the occurrence and development of tumors. Recent studies have shown that m6A RNA modification is involved in the pathogenesis of skin cancers. However, the precise molecular mechanisms of m6A-mediated cutaneous tumorigenesis have not been fully elucidated. Therefore, this review will summarize the biological characteristics of m6A modification, its regulatory role and mechanism in skin cancers, and the recent research progress of m6A-related molecular drugs, aiming to provide new ideas for clinical diagnosis and targeted therapy of cutaneous cancers.

Mechanisms of Regulation of the Expression of miRNAs and lncRNAs by Metformin in Ovarian Cancer

Ovarian cancer (OC) is one of the most lethal gynecological malignancies. The use of biological compounds such as non-coding RNAs (ncRNAs) is being considered as a therapeutic option to improve or complement current treatments since the deregulation of ncRNAs has been implicated in the pathogenesis and progression of OC. Old drugs with antitumoral properties have also been studied in the context of cancer, although their antitumor mechanisms are not fully clear. For instance, the antidiabetic drug metformin has shown pleiotropic effects in several in vitro models of cancer, including OC. Interestingly, metformin has been reported to regulate ncRNAs, which could explain its diverse effects on tumor cells. In this review, we discuss the mechanism of epigenetic regulation described for metformin, with a focus on the evidence of metformin-dependent microRNA (miRNAs) and long non-coding RNA (lncRNAs) regulation in OC.

Development of a N6-methyladenosine-directed single quantum dot-based biosensor for sensitive detection of METTL3/14 complex activity in breast cancer tissues

The METTL3/14 complex is an important RNA N6-Methyladenosine (m6A) methyltransferase in organisms, and the abnormal METTL3/14 complex activity is associated with the pathogenesis and various cancers. Sensitive detection of METTL3/14 complex is essential to tumor pathogenesis study, cancer diagnosis, and anti-cancer drug discovery. However, traditional methods for METTL3/14 complex assay suffer from poor specificity, costly antibodies, unstable RNA substrates, and low sensitivity. Herein, we construct a single quantum dot (QD)-based förster resonance energy transfer (FRET) biosensor for sensitive detection of METTL3/14 complex activity. In the presence of METTL3/14 complex, it catalyzes the methylation of adenine in the substrate probe, leading to the formation of m6A that protects the substrate probes from MazF-mediated cleavage. The hybridization of methylated DNA substrate with biotinylated capture probe initiates polymerization reaction to obtain a biotinylated double-stranded DNA (dsDNA) with the incorporation of numerous Cy5 fluorophores. Subsequently, the Cy5-incorporated dsDNA can self-assembly onto the 605QD surface to form the 605QD-dsDNA-Cy5 nanostructure, causing FRET between 605QD donor and Cy5 acceptor. This biosensor has excellent sensitivity with a limit of detection (LOD) of 3.11 × 10-17 M, and it can measure the METTL3/14 complex activity in a single cell. Moreover, this biosensor can be used to evaluate the METTL3/14 complex kinetic parameters and screen potential inhibitors. Furthermore, it can differentiate the METTL3/14 complex expression in healthy human tissues and breast cancer patient tissues, providing a powerful tool for cancer pathogenesis study, clinical diagnosis, prognosis monitoring, and drug discovery.

Non-coding RNA genes modulate PI3K/AKT signaling pathway in polycystic ovary syndrome

BACKGROUND

The PI3K protein kinase B (PI3K/AKT) signaling pathway has crucial roles in insulin signaling and other endocrine disorders. The purpose of this study is to validate the association of PCOS with PI3K/AKT pathway target genes, miRNA486-5p, and miRNA483-5p as well as to evaluate the outcome of metformin on the pathogenesis of PCOS.  METHODS: This case-controlled study included 3 subject groups: twenty healthy females (control group), twenty PCOS females before treatment, and twenty PCOS females treated with metformin at a dose (500 mg 3 times per day for 3 months). The following gene expressions were assessed by real-time PCR: PI3K, AKT, ERK, GLUT4, miRNA486-5p, and miRNA483-5p in the whole blood.

RESULTS

There was a significant decrease in miRNA486-5p and miRNA483-5p in the PCOS group with a significant negative correlation between miRNA486-5p and PI3K and a significant negative correlation between miRNA483-5p and ERK. Metformin treatment resulted in significant elevation of the studied miRNA, significant downregulation of PI3K/AKT target genes, and significant amelioration of the gonadotrophic hormonal imbalance and insulin resistance markers: fasting blood glucose, HBA1C, fasting insulin, and GLUT4 gene expression.

CONCLUSIONS

miRNA486 and miRNA483 downregulation may contribute to the etiology of PCOS, influence glucose metabolism, and result in IR in PCOS. Metformin's upregulation of those miRNAs affects glucose metabolism by controlling the expression of GLUT4, ameliorates PCOS-related insulin resistance, and improves PCOS-related hormonal imbalance by controlling the PI3K/AKT signaling pathway.

N6-methyladenosine modification of REG1α facilitates colorectal cancer progression via β-catenin/MYC/LDHA axis mediated glycolytic reprogramming

Aerobic glycolysis has been considered as a hallmark of colorectal cancer (CRC). However, the potential functional regulators of glycolysis in CRC remains to be elucidated. In the current study, we found that Regenerating islet-derived protein 1-alpha (REG1α) was significantly increased in both CRC tissues and serum, and positively associated with CRC patients' lymph node metastasis, advanced tumor stage, and unfavorable prognosis. Ectopic expression of REG1α contributed to various tumorigenic properties, including cell proliferation, cell cycle, migration, invasion, and glycolysis. In contrast, REG1α deficiency in CRC cells attenuated malignant properties and glucose metabolism. Mechanically, REG1α promoted CRC proliferation and metastasis via β-catenin/MYC axis-mediated glycolysis upregulation. Moreover, the malignant behaviors governed by REG1α could be effectively abolished by silencing of Wnt/β-catenin/MYC axis or glycolysis process using specific inhibitors. Besides, REG1α expression was mediated by METTL3 in an m6A-dependent manner. Overall, our work defines a novel regulatory model of the METTL3/REG1α/β-catenin/MYC axis in CRC, which indicates that REG1α could function as a novel biomarker and a potential therapeutic target for patients with CRC.

The role of m6A and m6Am RNA modifications in the pathogenesis of diabetes mellitus

The rapidly developing research field of epitranscriptomics has recently emerged into the spotlight of researchers due to its vast regulatory effects on gene expression and thereby cellular physiology and pathophysiology. N⁶-methyladenosine (m⁶A) and N⁶,2'-O-dimethyladenosine (m⁶Am) are among the most prevalent and well-characterized modified nucleosides in eukaryotic RNA. Both of these modifications are dynamically regulated by a complex set of epitranscriptomic regulators called writers, readers, and erasers. Altered levels of m⁶A and also several regulatory proteins were already associated with diabetic tissues. This review summarizes the current knowledge and gaps about m⁶A and m⁶Am modifications and their respective regulators in the pathophysiology of diabetes mellitus. It focuses mainly on the more prevalent type 2 diabetes mellitus (T2DM) and its treatment by metformin, the first-line antidiabetic agent. A better understanding of epitranscriptomic modifications in this highly prevalent disease deserves further investigation and might reveal clinically relevant discoveries in the future.

Value of negatively correlated miR-205-5p/HMGB3 and miR-96-5p/FOXO1 on the diagnosis of breast cancer and benign breast diseases

Background

MicroRNA (miRNA) and mRNA levels in matching specimens were used to identify miRNA-mRNA interactions. We aimed to integrate transcriptome, immunophenotype, methylation, mutation, and survival data analyses to examine the profiles of miRNAs and target mRNAs and their associations with breast cancer (BC) diagnosis.

Methods

Based on the Gene Expression Omnibus (GEO) database and The Cancer Genome Atlas (TCGA), differentially expressed miRNAs and targeted mRNAs were screened from experimentally verified miRNA-target interaction databases using Pearson's correlation analysis. We used real-time quantitative reverse transcription polymerase chain reaction to verify BC and benign disease samples, and logistic regression analysis was used to establish a diagnostic model based on miRNAs and target mRNAs. Receiver operating characteristic curve analysis was performed to test the ability to recognize the miRNA-mRNA pairs. Next, we investigated the complex interactions between miRNA-mRNA regulatory pairs and phenotypic hallmarks.

Results

We identified 27 and 359 dysregulated miRNAs and mRNAs, respectively, based on the GEO and TCGA databases. Using Pearson's correlation analysis, 10 negative miRNA-mRNA regulatory pairs were identified after screening both databases, and the related miRNA and target mRNA levels were assessed in 40 BC tissues and 40 benign breast disease tissues. Two key regulatory pairs (miR-205-5p/High mobility group box 3 (HMGB3) and miR-96-5p/Forkhead Box O1 (FOXO1)) were selected to establish the diagnostic model. They also had utility in survival and clinical analyses.

Conclusions

A diagnostic model including two miRNAs and their respective target mRNAs was established to distinguish between BC and benign breast diseases. These markers play essential roles in BC pathogenesis.

The m6A methyltransferase METTL16 inhibits the proliferation of pancreatic adenocarcinoma cancer cells via the p21 signaling pathway

Background

Many studies have reported that N6-methyladenosine (m6A) modification plays a critical role in the epigenetic regulation of organisms and especially in the pathogenesis of malignant diseases. However, m6A research has mainly focused on methyltransferase activity mediated by METTL3, and few studies have focused on METTL16. The aim of this study was to investigate the mechanism of METTL16, which mediates m6A modification, and its role in pancreatic adenocarcinoma (PDAC) cell proliferation.

Methods

Clinicopathologic and survival data were retrospectively collected from 175 PDAC patients from multiple clinical centers to detect the expression of METTL16. CCK-8, cell cycle, EdU and xenograft mouse model experiments were used to evaluate the proliferation effect of METTL16. Potential downstream pathways and mechanisms were explored via RNA sequencing, m6A sequencing, and bioinformatic analyses. Regulatory mechanisms were studied through methyltransferase inhibition, RIP, MeRIP‒qPCR assays.

Results

We found that METTL16 expression was markedly downregulated in PDAC, and multivariate Cox regression analyses revealed that METTL16 was a protective factor for PDAC patients. We also demonstrated that METTL16 overexpression inhibited PDAC cell proliferation. Furthermore, we identified a METTL16-p21 signaling axis, with downregulation of METTL16 resulting in inhibition of CDKN1A (p21). Additionally, METTL16 silencing and overexpression experiments highlighted m6A modification alterations in PDAC.

Conclusions

METTL16 plays a tumor-suppressive role and suppresses PDAC cell proliferation through the p21 pathway by mediating m6A modification. METTL16 may be a novel marker of PDAC carcinogenesis and target for the treatment of PDAC.

Metformin attenuates multiple myeloma cell proliferation and encourages apoptosis by suppressing METTL3-mediated m6A methylation of THRAP3, RBM25, and USP4

Based on the results of epidemiological and preclinical studies, metformin can improve the prognosis of patients with malignant tumors. Studies have confirmed that metformin inhibits multiple myeloma (MM) cell proliferation and promotes apoptosis. Nevertheless, the specific mechanism remains to be elucidated. MM cells were intervened with different doses of metformin to detect cell proliferation and apoptosis. Western blotting and RT-qPCR were employed to assess the expression of METTL3, METTL14, WTAP, FTO, and ALKBH5 after metformin intervention. The microarray dataset GSE29023 was retrieved from the Gene Expression Omnibus (GEO) database and calculated using the R language (limma package) to authenticate differentially expressed genes (DEGs). The database for annotation, visualization, and integrated discovery (David) was applied for GO annotation analysis of DEGs. Subsequently, the string database and Cytoscape software were applied to construct protein-protein interaction (PPI) and DEM hub gene networks. Bioinformatics analysis and MeRIP were applied to predict and test METTL3-mediated m6A levels on mRNA of THRAP3, RBM25, and USP4 in METTL3 knocked-down cells. Then rescue experiments were performed to explore effects of METTL3 and THRAP3, RBM25, or USP4 on cell proliferation and apoptosis. The effect on MM cell xenograft tumor growth was observed by injection of metformin or/and overexpression of METTL3 in in vivo experiments. Metformin decreased cell proliferation and encouraged cell apoptosis in a dose-dependent manner. Global m6A modification was elevated in MM cells compared to normal cells, which was counteracted by metformin treatment. Furthermore, THRAP3, RBM25, and USP4 were identified as possible candidate genes for metformin treatment by GSE29023 data mining. METTL3 interference impaired m6A modification on mRNA of THRAP3, RBM25, and USP4 as well as expression levels. The mRNA stability and expression of THRAP3, RBM25, and USP4 was decreased after metformin treatment, which was reversed by METTL3 overexpression. THRAP3, RBM25 or USP4 knockdown reversed the assistance of METTL3 overexpression on the malignant behavior of MM cells. Finally, upregulation of METTL3 was shown to exert facilitative effects on xenograft tumor growth by blocking metformin injection. The present study demonstrates that metformin can repress the expression of THRAP3, RBM25, and USP4 by inhibiting METTL3-mediated m6A modification, which in turn hamper cell proliferation and promotes cell apoptosis.Abbreviations: multiple myeloma (MM), Gene Expression Omnibus (GEO), differentially expressed genes (DEGs), database for annotation, visualization and integrated discovery (David), protein-protein interaction (PPI), epithelial‑mesenchymal transition (EMT), methyltransferase like 3 (METTL3), methyltransferase like 14 (METTL14), wilms tumor 1-associated protein (WTAP), methyltransferase like 16 (METTL16), acute myeloid leukemia (AML), non-small lung cancer (NSCLC), glioma stem cells (GSCs), normal bone marrow-derived plasma cells (nPCs), false discovery rate (FDR), biological process (BP), optical density (OD), horseradish peroxidase (HRP), M6A RNA immunoprecipitation assay (MeRIP).

Hypoxia-responsive PPARGC1A/BAMBI/ACSL5 axis promotes progression and resistance to lenvatinib in hepatocellular carcinoma

Emerging evidence has indicated that peroxisome proliferator-activated receptor-gamma coactivator-1α (PPARGC1A) is involved in hepatocellular carcinoma (HCC). However, its detailed function and up- and downstream mechanisms are incompletely understood. In this study, we confirmed that PPAGC1A is lowly expressed in HCC and is associated with poor prognosis using large-scale public datasets and in-house cohorts. PPAGC1A was found to impair the progression and sensitivity of HCC to lenvatinib. Mechanistically, PPAGC1A repressed bone morphogenetic protein and activin membrane-bound inhibitor (BAMBI) by inhibiting WNT/β-catenin signaling. BAMBI mediated the function of PPARGC1A and regulated ACSL5 through TGF-β/SMAD signaling. PPARGC1A/BAMBI regulated ROS production and ferroptosis-related cell death by controlling ACSL5. PPARGC1A/BAMBI/ACSL5 axis was hypoxia-responsive. METTL3 and WTAP silenced PPARGC1A in an m6A-YTHDF2-dependent way under normoxia and hypoxia, respectively. Metformin restored PPARGC1A expression by reducing its m6A modification via inhibiting METTL3. In animal models and patient-derived organoids, consistent functional data of PPARGC1A/BAMBI/ACSL5 were observed. Conclusions: These findings provide new insights into the role of the aberrant PPARGC1A/BAMBI/ACSL5 axis in HCC. And the mechanism of PPARGC1A dysregulation was explained by m6A modification. Metformin may benefit HCC patients with PPARGC1A dysregulation.

Roles and therapeutic implications of m6A modification in cancer immunotherapy

Recent studies have demonstrated that N6-methyladenosine (m6A), the most abundant, dynamic, and reversible epigenetic RNA modification in eukaryotes, is regulated by a series of enzymes, including methyltransferases (writers), demethylases (erasers), and m6A recognition proteins (readers). Aberrant regulation of m6A modification is pivotal for tumorigenesis, progression, invasion, metastasis, and apoptosis of malignant tumors. Immune checkpoint inhibitors (ICIs) has revolutionized cancer treatment, as recognized by the 2018 Nobel Prize in Medicine and Physiology. However, not all cancer patients response to ICI therapy, which is thought to be the result of intricate immune escape mechanisms. Recently, numerous studies have suggested a novel role for m6A epigenetic modification in the regulation of tumor immune evasion. Herein, we review the relevant mechanisms of m6A regulators in regulating various key signaling pathways in cancer biology and how m6A epigenetic modifications regulate the expression of immune checkpoints, opening a new window to understand the roles and mechanisms of m6A epigenetic modifications in regulating tumor immune evasion. In addition, we highlight the prospects and development directions of future combined immunotherapy strategies based on m6A modification targeting, providing directions for promoting the treatment outcomes of immune checkpoint inhibitors.

METTL3 stabilization by PIN1 promotes breast tumorigenesis via enhanced m6A-dependent translation

Methyltransferase-like 3 (METTL3) is the catalytic subunit of the N⁶-adenosine methyltransferase complex responsible for N⁶-methyladenosine (m⁶A) modification of mRNA in mammalian cells. Although METTL3 expression is increased in several cancers, the regulatory mechanisms are unclear. We explored the regulatory roles of peptidyl-prolyl cis-trans isomerase NIMA-interacting 1 (PIN1) in METTL3 stability and m⁶A modification of mRNA. PIN1 interacted with METTL3 and prevented its ubiquitin-dependent proteasomal and lysosomal degradation. It stabilized METTL3, which increased the m⁶A modification of transcriptional coactivator with PDZ-binding motif (TAZ) and epidermal growth factor receptor (EGFR) mRNA, resulting in their efficient translation. PIN1 knockout altered the distribution of TAZ and EGFR mRNA from polysomes into monosomes. Inhibition of MEK1/2 kinases and PIN1 destabilized METTL3, which impeded breast cancer cell proliferation and induced cell cycle arrest at the G0/G1 phases. METTL3 knockout reduced PIN1 overexpression-induced colony formation in MCF7 cells and enhanced tumor growth in 4T1 cells in an orthotopic mouse model. In clinical settings, METTL3 expression significantly increased with tumor progression and was positively correlated with PIN1 expression in breast cancer tissues. Thus, PIN1 plays a regulatory role in mRNA translation, and the PIN1/METTL3 axis may be an alternative therapeutic target in breast cancer.

Epi-miRNAs: Modern mediators of methylation status in human cancers

Methylation of the fundamental macromolecules, DNA/RNA, and proteins, is remarkably abundant, evolutionarily conserved, and functionally significant in cellular homeostasis and normal tissue/organism development. Disrupted methylation imprinting is strongly linked to loss of the physiological equilibrium and numerous human pathologies, and most importantly to carcinogenesis, tumor heterogeneity, and cancer progression. Mounting recent evidence has documented the active implication of miRNAs in the orchestration of the multicomponent cellular methylation machineries and the deregulation of methylation profile in the epigenetic, epitranscriptomic, and epiproteomic levels during cancer onset and progression. The elucidation of such regulatory networks between the miRNome and the cellular methylation machineries has led to the emergence of a novel subclass of miRNAs, namely "epi-miRNAs" or "epi-miRs." Herein, we have summarized the existing knowledge on the functional role of epi-miRs in the methylation dynamic landscape of human cancers and their clinical utility in modern cancer diagnostics and tailored therapeutics. This article is categorized under: RNA in Disease and Development > RNA in Disease.

Effect of circular RNAs and N6-methyladenosine (m6A) modification on cancer biology

N6-methyladenosine (m6A), as the most abundant and well-known RNA modification, has been found to play an important role in cancer. Circular RNAs (circRNAs) are a class of single-stranded covalently closed RNA molecules generated by the reverse splicing process. Recent studies have revealed the vital roles of circRNAs in many diseases, including tumorigenesis. Accumulating evidence also shows an association between m6A modification and circRNAs. This study aimed to review the interactions between m6A modification and circRNAs and illustrate their roles in tumorigenesis. m6A modification can modulate the biogenesis, translation, cytoplasmic export, degradation, and other functions of circRNAs in different tumors. circRNAs can also modulate m6A modification by affecting writers, erasers, and readers. We focused on the potential regulatory mechanisms and the biological consequences of m6A modification of circRNAs, as well as the interactions in tumors of different systems. Finally, we listed the possible development directions of m6A modification and circRNAs, which might facilitate the clinical application of tumor therapy. AVAILABILITY OF DATA AND MATERIALS: Not applicable. Keywords.

METTL3 from Target Validation to the First Small-Molecule Inhibitors: A Medicinal Chemistry Journey

RNA methylation is a critical mechanism for regulating the transcription and translation of specific sequences or for eliminating unnecessary sequences during RNA maturation. METTL3, an RNA methyltransferase that catalyzes the transfer of a methyl group to the N⁶-adenosine of RNA, is one of the key mediators of this process. METTL3 dysregulation may result in the emergence of a variety of diseases ranging from cancer to cardiovascular and neurological disorders beyond contributing to viral infections. Hence, the discovery of METTL3 inhibitors may assist in furthering the understanding of the biological roles of this enzyme, in addition to contributing to the development of novel therapeutics. Through this work, we will examine the existing correlations between METTL3 and diseases. We will also analyze the development, mode of action, pharmacology, and structure-activity relationships of the currently known METTL3 inhibitors. They include both nucleoside and non-nucleoside compounds, with the latter comprising both competitive and allosteric inhibitors.

The N6-methyladenosine METTL3 regulates tumorigenesis and glycolysis by mediating m6A methylation of the tumor suppressor LATS1 in breast cancer

BACKGROUND

Posttranscriptional modification of tumor-associated factors plays a pivotal role in breast cancer progression. However, the underlying mechanism remains unknown. M6A modifications in cancer cells are dynamic and reversible and have been found to impact tumor initiation and progression through various mechanisms. In this study, we explored the regulatory mechanism of breast cancer cell proliferation and metabolism through m6A methylation in the Hippo pathway.  METHODS: A combination of MeRIP-seq, RNA-seq and metabolomics-seq was utilized to reveal a map of m6A modifications in breast cancer tissues and cells. We conducted RNA pull-down assays, RIP-qPCR, MeRIP-qPCR, and RNA stability analysis to identify the relationship between m6A proteins and LATS1 in m6A regulation in breast cancer cells. The expression and biological functions of m6A proteins were confirmed in breast cancer cells in vitro and in vivo. Furthermore, we investigated the phosphorylation levels and localization of YAP/TAZ to reveal that the activity of the Hippo pathway was affected by m6A regulation of LATS1 in breast cancer cells.  RESULTS: We demonstrated that m6A regulation plays an important role in proliferation and glycolytic metabolism in breast cancer through the Hippo pathway factor, LATS1. METTL3 was identified as the m6A writer, with YTHDF2 as the reader protein of LATS1 mRNA, which plays a positive role in promoting both tumorigenesis and glycolysis in breast cancer. High levels of m6A modification were induced by METTL3 in LATS1 mRNA. YTHDF2 identified m6A sites in LATS1 mRNA and reduced its stability. Knockout of the protein expression of METTL3 or YTHDF2 increased the expression of LATS1 mRNA and suppressed breast cancer tumorigenesis by activating YAP/TAZ in the Hippo pathway.

CONCLUSIONS

In summary, we discovered that the METTL3-LATS1-YTHDF2 pathway plays an important role in the progression of breast cancer by activating YAP/TAZ in the Hippo pathway.

METTLing in Stem Cell and Cancer Biology

The methyltransferase-like (METTL) family is a diverse group of methyltransferases that can methylate nucleotides, proteins, and small molecules. Despite this diverse array of substrates, they all share a characteristic seven-beta-strand catalytic domain, and recent evidence suggests many also share an important role in stem cell biology. The most well characterized family members METTL3 and METTL14 dimerize to form an N6-methyladenosine (m6A) RNA methyltransferase with established roles in cancer progression. However, new mouse models indicate that METTL3/METTL14 are also important for embryonic stem cell (ESC) development and postnatal hematopoietic and neural stem cell self-renewal and differentiation. METTL1, METTL5, METTL6, METTL8, and METTL17 also have recently identified roles in ESC pluripotency and differentiation, while METTL11A/11B, METTL4, METTL7A, and METTL22 have been shown to play roles in neural, mesenchymal, bone, and hematopoietic stem cell development, respectively. Additionally, a variety of other METTL family members are translational regulators, a role that could place them as important players in the transition from stem cell quiescence to differentiation. Here we will summarize what is known about the role of METTL proteins in stem cell differentiation and highlight the connection between their growing importance in development and their established roles in oncogenesis.

Multilevel regulation of N6-methyladenosine RNA modifications: Implications in tumorigenesis and therapeutic opportunities

N⁶-methyladenosine (m⁶A) RNA modification is widely perceived as the most abundant and common modification in transcripts. This modification is dynamically regulated by specific m⁶A "writers", "erasers" and "readers" and is reportedly involved in the occurrence and development of many diseases. Since m⁶A RNA modification was discovered in the 1970s, with the progress of relevant research technologies, an increasing number of functions of m⁶A have been reported, and a preliminary understanding of m⁶A has been obtained. In this review, we summarize the mechanisms through which m⁶A RNA modification is regulated from the perspectives of expression, posttranslational modification and protein interaction. In addition, we also summarize how external and internal environmental factors affect m⁶A RNA modification and its functions in tumors. The mechanisms through which m⁶A methylases, m⁶A demethylases and m⁶A-binding proteins are regulated are complicated and have not been fully elucidated. Therefore, we hope to promote further research in this field by summarizing these mechanisms and look forward to the future application of m⁶A in tumors.

NIR-light-controlled G-quadruplex hydrogel for synergistically enhancing photodynamic therapy via sustained delivery of metformin and catalase-like activity in breast cancer

Severely hypoxic condition of tumour represents a notable obstacle against the efficiency of photodynamic therapy (PDT). While mitochondria targeted therapy by metformin has been considered as a promising strategy for reducing oxygen consumption in tumours, its low treatment sensitivity, short half-life and narrow absorption window in vivo remain the intractable challenges. In this report, 5′-guanosine monophosphate (5′GMP), indocyanine green (ICG), hemin and metformin, were combined to construct a smart G-quadruplex (G4) hydrogel named HMI@GEL for breast cancer (BC) treatment. Benefiting from the photothermal (PTT) effect of ICG, HMI@GEL exhibited excellent characteristics of NIR-light-triggered and persistent drug delivery to maintain high intratumoral concentration of metformin. Furthermore, drug loading concentration of metformin reached an amazing 300 ​mg ​mL⁻¹ in HMI@GEL. To our knowledge, it might be the highest loading efficiency in the reported literatures. With the combination of catalase-mimicking Hemin@mil88, metformin could inhibit tumour mitochondrial respiratory significantly, which sequentially permitted in situ efficient oxygen generation. Remarkable apoptosis and necrosis were achieved by the combination of PTT and synergistically enhanced PDT as well as the activated tumour immunotherapy. Collectively, the HMI@GEL in situ injectable platform showed a promising strategy for enhanced PDT by metformin, and opened new perspectives for treating BC versatilely.

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A NIR-light-controlled G-quadruplex hydrogel HMI@GEL loading metformin was prepared for precision breast cancer therapy.

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The extremely high drug loading capacity (300 ​mg ​mL⁻¹) and persistent delivery of metformin was realized for the first time.

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The combination of catalase-mimicking Hemin@mil88 and metformin dual enhanced intracellular ROS generation.

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The tumour immune microenvironment was dramatically reshaped by synthetic photodynamic/photothermal therapy.

Super-Resolution Quantification of T2DM-Induced Mitochondrial Morphology Changes and Their Implications in Pharmacodynamics of Metformin and Sorafenib

Mitochondria, as the powerhouse of cells, are involved in various processes of cellular homeostasis, especially energy metabolism. The morphology of mitochondria is a critical indicator for their functions, referring to mitochondrial fusion and fission. Here, we performed structured illumination microscopy (SIM) to measure the mitochondrial morphology in living cells. Benefitting from its nano-scale resolution, this SIM-based strategy can quantify the fusion and fission of mitochondria with high sensitivity. Furthermore, as type 2 diabetes mellitus (T2DM) is caused by a disorder of energy substrate utilization, this strategy has the potential to study T2DM by analyzing the mitochondrial morphology of insulin-resistant (IR) cells. With SIM, we found that mitochondrial fission was increased in IR MRC-5, LO2, FHs 74 Int, and HepG2 cells but not in IR Huh7 cells with high-invasiveness ability. Furthermore, we found that metformin could inhibit mitochondrial fission in IR cells, and sorafenib could promote mitochondrial fusion in HepG2 cancer cells, especially in those IR cells. To conclude, mitochondrial fission is involved in T2DM, and cancer cells with high-invasiveness ability may be equipped with stronger resistance to energy metabolism disorder. In addition, the pharmacodynamics of metformin and sorafenib in cancer may be related to the inhibition of mitochondrial fission, especially for patients with T2DM.

Novel insights into m6A modification of coding and non-coding RNAs in tumor biology: From molecular mechanisms to therapeutic significance

Accumulating evidence has revealed that m⁶A modification, the predominant RNA modification in eukaryotes, adds a novel layer of regulation to the gene expression. Dynamic and reversible m⁶A modification implements sophisticated and crucial functions in RNA metabolism, including generation, splicing, stability, and translation in messenger RNAs (mRNAs) and non-coding RNAs (ncRNAs). Furthermore, m⁶A modification plays a determining role in producing various m⁶A-labeling RNA outcomes, thereby affecting several functional processes, including tumorigenesis and progression. Herein, we highlighted current advances in m⁶A modification and the regulatory mechanisms underlying mRNAs and ncRNAs in distinct cancer stages. Meanwhile, we also focused on the therapeutic significance of m⁶A regulators in clinical cancer treatment.

METTL3 plays a crucial function in multiple biological processes

The N6-methyladenosine (m⁶A) refers to the methylation of the N6 position of adenosine of RNA adenine. The modification of m⁶A is one of the most abundant epigenetic modifications in eukaryotic mRNA and non-coding RNA and is controlled by methyltransferases and demethylases. The biological mechanism and significance of m⁶A have been discovered with the development of m⁶A sequencing. Various m⁶A complex components regulate the function of m⁶A on mRNA. Methyltransferase-like 3 (METTL3) is one of the earliest identified m⁶A methyltransferases which regulate the functions of m⁶A. A large number of studies have shown that METTL3 establishes a cross-talk with tumor cells and development of various human diseases. In this review, we will briefly elaborate on the role of METTL3 in biological function, epithelial-mesenchymal transition (EMT), inflammatory response and sensitivity to the resistance of chemo radiotherapies. The underlying molecular mechanism demonstrated by METTL3 may provide a possible target for treating and diagnosing human diseases.

Metformin counteracts stimulatory effects induced by insulin in primary breast cancer cells

Background

Metabolic disorders are associated with increased incidence, aggressive phenotype and poor outcome of breast cancer (BC) patients. For instance, hyperinsulinemia is an independent risk factor for BC and the insulin/insulin receptor (IR) axis is involved in BC growth and metastasis. Of note, the anti-diabetic metformin may be considered in comprehensive therapeutic approaches in BC on the basis of its antiproliferative effects obtained in diverse pre-clinical and clinical studies.

Methods

Bioinformatics analysis were performed using the information provided by The Invasive Breast Cancer Cohort of The Cancer Genome Atlas (TCGA) project. The naturally immortalized BC cell line, named BCAHC-1, as well as cancer-associated fibroblasts (CAFs) derived from BC patients were used as model systems. In order to identify further mechanisms that characterize the anticancer action of metformin in BC, we performed gene expression and promoter studies as well as western blotting experiments. Moreover, cell cycle analysis, colony and spheroid formation, actin cytoskeleton reorganization, cell migration and matrigel drops evasion assays were carried out to provide novel insights on the anticancer properties of metformin.

Results

We first assessed that elevated expression and activation of IR correlate with a worse prognostic outcome in estrogen receptor (ER)-positive BC. Thereafter, we established that metformin inhibits the insulin/IR-mediated activation of transduction pathways, gene changes and proliferative responses in BCAHC-1 cells. Then, we found that metformin interferes with the insulin-induced expression of the metastatic gene CXC chemokine receptor 4 (CXCR4), which we found to be associated with poor disease-free survival in BC patients exhibiting high levels of IR. Next, we ascertained that metformin prevents a motile phenotype of BCAHC-1 cells triggered by the paracrine liaison between tumor cells and CAFs upon insulin activated CXCL12/CXCR4 axis.

Conclusions

Our findings provide novel mechanistic insights regarding the anti-proliferative and anti-migratory effects of metformin in both BC cells and important components of the tumor microenvironment like CAFs. Further investigations are warranted to corroborate the anticancer action of metformin on the tumor mass toward the assessment of more comprehensive strategies halting BC progression, in particular in patients exhibiting metabolic disorders and altered insulin/IR functions.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12967-022-03463-y.

The Key Role of RNA Modification in Breast Cancer

The modulation of the function and expression of epigenetic regulators of RNA modification has gradually become the hotspot of cancer research. Studies have shown that alteration of epigenetic modifications can promote the development and metastasis of breast cancer. This review highlights the progress in characterization of the link between RNA modification and the prognosis, carcinogenesis and treatment of breast cancer, which may provide a new theoretical basis for development of effective strategies for monitoring of breast cancer based on epigenetics.

Metformin combats obesity by targeting FTO in an m6A-YTHDF2-dependent manner

Obesity has become a health threat and hard enough to deal with. Evidences show that metformin could inhibit adipogenesis and combat obesity, while its mechanisms remain to be elucidated more comprehensively. In this study, we found that administration of metformin could combat obesity induced by high-fat diet (HFD), indicated by strikingly decreased body weight and weight of inguinal white adipose tissue (iWAT) and epidydimal white adipose tissue (eWAT) compared to the control group. Mechanically, we revealed that metformin could inhibit protein expression of FTO, leading to increased m⁶A methylation levels of cyclin D1 (Ccnd1) and cyclin dependent kinase 2 (Cdk2), two crucial regulators in cell cycle. Ccnd1 and Cdk2 with increased m⁶A levels were recognized by YTH m⁶A RNA binding protein 2 (YTHDF2), causing a YTHDF2-dependent decay and decreased protein expressions. In consequence, mitotic clonal expansion (MCE) process was blocked and adipogenesis was inhibited.

The Emerging Role of N6-Methyladenosine RNA Methylation as Regulators in Cancer Therapy and Drug Resistance

N6-methyladenosine (m6A) RNA methylation has been considered the most prevalent, abundant, and conserved internal transcriptional modification throughout the eukaryotic mRNAs. Typically, m6A RNA methylation is catalyzed by the RNA methyltransferases (writers), is removed by its demethylases (erasers), and interacts with m6A-binding proteins (readers). Accumulating evidence shows that abnormal changes in the m6A levels of these regulators are increasingly associated with human tumorigenesis and drug resistance. However, the molecular mechanisms underlying m6A RNA methylation in tumor occurrence and development have not been comprehensively clarified. We reviewed the recent findings on biological regulation of m6A RNA methylation and summarized its potential therapeutic strategies in various human cancers.

m6A modification: recent advances, anticancer targeted drug discovery and beyond

Abnormal N6-methyladenosine (m6A) modification is closely associated with the occurrence, development, progression and prognosis of cancer, and aberrant m6A regulators have been identified as novel anticancer drug targets. Both traditional medicine-related approaches and modern drug discovery platforms have been used in an attempt to develop m6A-targeted drugs. Here, we provide an update of the latest findings on m6A modification and the critical roles of m6A modification in cancer progression, and we summarize rational sources for the discovery of m6A-targeted anticancer agents from traditional medicines and computer-based chemosynthetic compounds. This review highlights the potential agents targeting m6A modification for cancer treatment and proposes the advantage of artificial intelligence (AI) in the discovery of m6A-targeting anticancer drugs. Three stages of m6A-targeting anticancer drug discovery: traditional medicine-based natural products, modern chemical modification or synthesis, and artificial intelligence (AI)-assisted approaches for the future.

Processing body (P-body) and its mediators in cancer

In recent years, processing bodies (P-bodies) formed by liquid-liquid phase separation, have attracted growing scientific attention due to their involvement in numerous cellular activities, including the regulation of mRNAs decay or storage. These cytoplasmic dynamic membraneless granules contain mRNA storage and decay components such as deadenylase and decapping factors. In addition, different mRNA metabolic regulators, including m⁶A readers and gene-mediated miRNA-silencing, are also associated with such P-bodies. Cancerous cells may profit from these mRNA decay shredders by up-regulating the expression level of oncogenes and down-regulating tumor suppressor genes. The main challenges of cancer treatment are drug resistance, metastasis, and cancer relapse likely associated with cancer stem cells, heterogeneity, and plasticity features of different tumors. The mRNA metabolic regulators based on P-bodies play a great role in cancer development and progression. The dysregulation of P-bodies mediators affects mRNA metabolism. However, less is known about the relationship between P-bodies mediators and cancerous behavior. The current review summarizes the recent studies on P-bodies mediators, their contribution to tumor development, and their potential in the clinical setting, particularly highlighting the P-bodies as potential drug-carriers such as exosomes to anticancer in the future.

Metformin for Cardiovascular Protection, Inflammatory Bowel Disease, Osteoporosis, Periodontitis, Polycystic Ovarian Syndrome, Neurodegeneration, Cancer, Inflammation and Senescence: What Is Next?

Diabetes is accompanied by several complications. Higher prevalence of cancers, cardiovascular diseases, chronic kidney disease (CKD), obesity, osteoporosis, and neurodegenerative diseases has been reported among patients with diabetes. Metformin is the oldest oral antidiabetic drug and can improve coexisting complications of diabetes. Clinical trials and observational studies uncovered that metformin can remarkably prevent or alleviate cardiovascular diseases, obesity, polycystic ovarian syndrome (PCOS), osteoporosis, cancer, periodontitis, neuronal damage and neurodegenerative diseases, inflammation, inflammatory bowel disease (IBD), tuberculosis, and COVID-19. In addition, metformin has been proposed as an antiaging agent. Numerous mechanisms were shown to be involved in the protective effects of metformin. Metformin activates the LKB1/AMPK pathway to interact with several intracellular signaling pathways and molecular mechanisms. The drug modifies the biologic function of NF-κB, PI3K/AKT/mTOR, SIRT1/PGC-1α, NLRP3, ERK, P38 MAPK, Wnt/β-catenin, Nrf2, JNK, and other major molecules in the intracellular signaling network. It also regulates the expression of noncoding RNAs. Thereby, metformin can regulate metabolism, growth, proliferation, inflammation, tumorigenesis, and senescence. Additionally, metformin modulates immune response, autophagy, mitophagy, endoplasmic reticulum (ER) stress, and apoptosis and exerts epigenetic effects. Furthermore, metformin protects against oxidative stress and genomic instability, preserves telomere length, and prevents stem cell exhaustion. In this review, the protective effects of metformin on each disease will be discussed using the results of recent meta-analyses, clinical trials, and observational studies. Thereafter, it will be meticulously explained how metformin reprograms intracellular signaling pathways and alters molecular and cellular interactions to modify the clinical presentations of several diseases.

The M6A methyltransferase METTL3 regulates proliferation in esophageal squamous cell carcinoma

Esophageal squamous cell carcinoma (ESCC) is one of the most lethal human cancers with a lower 5-year survival rate. N6-methyladenosine (m6A) methylation, an important epigenetic modification, has been reported to associate with physiological and pathological processes of cancers. However, its role in ESCC remains unclear. In this work, we found that the m6A levels were elevated in ESCC cancer tissues and ESCC cells. The PPI network demonstrated that METTL3, METTL14, WTAP, RBM15, and KIAA1429 were all significantly associated with each other. Moreover, we found a significant upregulation of METTL3 mRNA and protein amounts in ESCC tissues. The METTL3 mRNA expression level of tissues had associations with ESCC differentiation extent and sex (p < 0.05). The METTL3 mRNA expression level of tissues, sensitivity for diagnosing ESCC was 75.00%, specificity was 72.06% and area under the ROC curve was 0.8030. Depletion of METTL3 markedly diminished m6A levels in human ESCC cell lines and METTL3 overexpression restored the reduction in m6A levels. These results suggested that METTL3 is the primary enzyme that modulates m6A methylation and a critical regulatory factor in ESCC. Additionally, METTL3 knockdown significantly suppressed the ESCC cell proliferation, while METTL3 overexpression markedly promoted ESCC cell proliferation both in cell and animal models. These results demonstrated that METTL3 promotes ESCC development. Furthermore, METTL3 may modulate the cell cycle of ESCC cells through a p21-dependent pattern. METTL3-guided m6A modification may contribute to the progression of ESCC via the p21-axis. Our study is the first investigation to report that METTL3-mediated m6A methylation plays a crucial role in ESCC oncogenesis and highlights that METTL3 might be a potential biomarker and therapeutic target for ESCC patients.

Function of N6-Methyladenosine Modification in Tumors

N6-Methyladenosine (m6A) modification is a dynamic and reversible methylation modification at the N6-position of adenosine. As one of the most prevalent posttranscriptional methylation modifications of RNA, m6A modification participates in several mRNA processes, including nuclear export, splicing, translation, and degradation. Some proteins, such as METTL3, METTL14, WTAP, ALKBH5, FTO, and YTHDF1/2/3, are involved in methylation. These proteins are subdivided into writers (METTL3, METTL14, WTAP), erasers (ALKBH5, FTO), and readers (YTHDF1/2/3) according to their functions in m6A modification. Several studies have shown that abnormal m6A modification occurs in tumors, including colorectal cancer, liver cancer, breast cancer, nasopharyngeal carcinoma, and gastric cancer. The proteins for m6A modification are involved in tumor proliferation, angiogenesis, metastasis, immunity, and other processes. Herein, the roles of m6A modification in cancer are discussed, which will improve the understanding of tumorigenesis, as well as the diagnosis, treatment, and prognosis of tumors.

Regulatory roles of RNA modifications in breast cancer

Collectively referred to as the epitranscriptome, RNA modifications play important roles in gene expression control regulating relevant cellular processes. In the last few decades, growing numbers of RNA modifications have been identified not only in abundant ribosomal (rRNA) and transfer RNA (tRNA) but also in messenger RNA (mRNA). In addition, many writers, erasers and readers that dynamically regulate the chemical marks have also been characterized. Correct deposition of RNA modifications is prerequisite for cellular homeostasis, and its alteration results in aberrant transcriptional programs that dictate human disease, including breast cancer, the most frequent female malignancy, and the leading cause of cancer-related death in women. In this review, we emphasize the major RNA modifications that are present in tRNA, rRNA and mRNA. We have categorized breast cancer-associated chemical marks and summarize their contribution to breast tumorigenesis. In addition, we describe less abundant tRNA modifications with related pathways implicated in breast cancer. Finally, we discuss current limitations and perspectives on epitranscriptomics for use in therapeutic strategies against breast and other cancers.

N6-Methyladenosine-Regulated mRNAs: Potential Prognostic Biomarkers for Patients With Lung Adenocarcinoma

Aberrant regulation of m6A mRNA modification can lead to changes in gene expression, thus contributing to tumorigenesis in several types of solid tumors. In this study, by integrating analyses of m6A methylation and mRNA expression, we identified 84 m6A-regulated mRNAs in lung adenocarcinoma (LUAD). Although the m6A methylation levels of total RNA in LUAD patient tumor tissue were reduced, the majority (75.2%) of m6A-regulated mRNAs were hypermethylated. The m6A-hypermethylated mRNAs were mainly enriched in terms related to transcription factor activity. We established a 10-m6A-regulated-mRNA signature score system through least absolute shrinkage and selection operator Cox regression analysis, with its predictive value validated by Kaplan–Meier curve and time-dependent receiver operating characteristic curves. RFXAP and KHDRBS2 from the signature also exhibited an independent prognostic value. The co-expression and interaction network analyses demonstrated the strong correlation between m6A regulators and the genes in the signature, further supporting the results of the m6A methylation modification patterns. These findings highlight the potential utility of integrating multi-omics data (m6A methylation level and mRNA expression) to accurately obtain potential prognostic biomarkers, which may provide important insights into developing novel and effective therapies for LUAD.

Biguanides drugs: Past success stories and promising future for drug discovery

Biguanides have attracted much attention a century ago and showed resurgent interest in recent years after a long period of dormancy. They constitute an important class of therapeutic agents suitable for the treatment of a wide spectrum of diseases. Therapeutic indications of biguanides include antidiabetic, antimalarial, antiviral, antiplaque, and bactericidal applications. This review presents an extensive overview of the biological activity of biguanides and different mechanisms of action of currently marketed biguanide-containing drugs, as well as their pharmacological properties when applicable. We highlight the recent developments in research on biguanide compounds, with a primary focus on studies on metformin in the field of oncology. We aim to provide a critical overview of all main bioactive biguanide compounds and discuss future perspectives for the design of new drugs based on the biguanide fragment.

N6-methyladenosine methyltransferases: functions, regulation, and clinical potential

N6-methyladenosine (m6A) has emerged as an abundant modification throughout the transcriptome with widespread functions in protein-coding and noncoding RNAs. It affects the fates of modified RNAs, including their stability, splicing, and/or translation, and thus plays important roles in posttranscriptional regulation. To date, m6A methyltransferases have been reported to execute m6A deposition on distinct RNAs by their own or forming different complexes with additional partner proteins. In this review, we summarize the function of these m6A methyltransferases or complexes in regulating the key genes and pathways of cancer biology. We also highlight the progress in the use of m6A methyltransferases in mediating therapy resistance, including chemotherapy, targeted therapy, immunotherapy and radiotherapy. Finally, we discuss the current approaches and clinical potential of m6A methyltransferase-targeting strategies.

lncRNA MALAT1 participates in metformin inhibiting the proliferation of breast cancer cell

In recent years, the repurposing of conventional and chemotherapeutic drugs is recognized as an alternative strategy for health care. The main purpose of this study is to strengthen the application of non‐oncological drug metformin on breast cancer treatment in the perspective of epigenetics. In the present study, metformin was found to inhibit cell proliferation, promote apoptosis and induce cell cycle arrest in breast cancer cells at a dose‐dependent manner. In addition, metformin treatment elevated acH3K9 abundance and decreased acH3K18 level. The expression of lncRNA MALAT1, HOTAIR, DICER1‐AS1, LINC01121 and TUG1 was up‐regulated by metformin treatment. In metformin‐treated cells, MALAT1 knock‐down increased the Bax/Bcl2 ratio and enhanced p21 but decreased cyclin B1 expression. The expression of Beclin1, VDAC1, LC3‐II, CHOP and Bip was promoted in the cells received combinatorial treatment of metformin and MALAT1 knock‐down. The reduced phosphorylation of c‐Myc was further decreased in the metformin‐treated cells in combination with MALAT1 knock‐down than metformin treatment alone. Taken together, these results provide a promising repurposed strategy for metformin on cancer treatment by modulating epigenetic modifiers.

m6A RNA methylation and beyond - The epigenetic machinery and potential treatment options

m6A is emerging as one of the most important RNA modifications because of its involvement in pathological and physiological events. Here, we provide an overview of this epitranscriptomic modification, beginning with a description of the molecular players involved and continuing with a focus on the role of m6A in the maintenance of stemness, induction of the epithelial to mesenchymal transition (EMT), and tumor progression. Finally, we discuss the state of the art regarding the design and validation of inhibitors of m6A writers or erasers to provide a background for future investigations and for the development of specific therapeutics.

Understanding the roles of N6-methyladenosine writers, readers and erasers in breast cancer

Breast cancer is believed to be driven by epigenetic regulation of genes implicated in cell proliferation, survival, and differentiation. Recently, aberrant N⁶-methyladenosine (m⁶A) decorations turned up as crucial epigenetic regulator for malignant breast cancer, which may serve as new targets for breast cancer treatment. Here we briefly outline the functions of m⁶A and its regulatory proteins, including m⁶A “writers,” “readers,” and “erasers” on RNA life fate, recapitulate the latest breakthroughs in understanding m⁶A modification and its regulatory proteins, and the underlying molecular mechanisms that contribute to the carcinogenesis and the progression of breast cancer, so as to provide potential epigenetic targets for diagnosis, treatment and prognosis in breast cancer.

Novel insights into the m6A-RNA methyltransferase METTL3 in cancer

N6-methyladenosine (m⁶A) is a prevalent internal RNA modification in higher eukaryotic cells. As the pivotal m⁶A regulator, RNA methyltransferase-like 3 (METTL3) is responsible for methyl group transfer in the progression of m⁶A modification. This epigenetic regulation contributes to the structure and functional regulation of RNA and further promotes tumorigenesis and tumor progression. Accumulating evidence has illustrated the pivotal roles of METTL3 in a variety of human cancers. Here, we systemically summarize the interaction between METTL3 and RNAs, and illustrate the multiple functions of METTL3 in human cancer. METLL3 is aberrantly expressed in a variety of tumors. Elevation of METTL3 is usually associated with rapid progression and poor prognosis of tumors. On the other hand, METTL3 may also function as a tumor suppressor in several cancers. Based on the tumor-promoting effect of METTL3, the possibility of applying METTL3 inhibitors is further discussed, which is expected to provide novel insights into antitumor therapy.