Crosstalk Between m6A RNA Methylation and miRNA Biogenesis in Cancer: An Unholy Nexus

METTL3 promotes oral squamous cell carcinoma by regulating miR-146a-5p/SMAD4 axis

N6-methyladenosine (m6A), one of the most prominent and reversible internal modifications of eukaryotic RNAs, has emerged as a critical regulator of gene expression in various cancers including oral squamous cell carcinoma (OSCC), wherein it shapes the tumor-specific epitranscriptomic gene-regulatory networks. METTL3, the primary m6A RNA methyltransferase, is significantly upregulated in OSCC cells leading to increased global m6A levels. Interestingly, METTL3 positively regulates miRNA biogenesis by modulating the processing of primary miRNAs in a m6A-dependent manner. We identified miR-146a-5p, an oncogenic miRNA as one of the METTL3-regulated miRNAs in OSCC. METTL3-depletion or inhibition of its catalytic activity leads to a reduction of miR-146a-5p and an appreciable accumulation of primary miR-146a in OSCC cells. Functional assays examining the effects of miR-146a-5p inhibition or overexpression confirm its oncogenic role in OSCC pathophysiology. Further, SMAD4, a central transducer in TGF-β signaling, was identified as a miR-146a-5p target. In OSCC cells, SMAD4-depletion exacerbates the oncogenic traits, whereas its overexpression exerts the opposite effect. Additionally, METTL3-depletion dysregulates SMAD4-regulated genes suggesting its potential involvement in SMAD4-dependent TGF-β signaling. Taken together, we report that METTL3, an oncogene regulates the expression of SMAD4, a tumor-suppressor via miR-146a-5p, thus unveiling a novel regulatory axis of METTL3/miR-146a-5p/SMAD4 in OSCC, which can potentially have therapeutic implications.

M6A Modified miR-31-5p Suppresses M1 Macrophage Polarization and Autoimmune Dry Eye by Targeting P2RX7

The dysregulation of the M1/M2 macrophage balance plays a pivotal role in autoimmune diseases. However, the interplay between microRNAs (miRNAs) and N6-methyladenosine (m6A) modulation in regulating this balance remains poorly understood. Here, a significant reduction in miR-31-5p levels is observed in the lacrimal glands of rabbit autoimmune dacryoadenitis and the peripheral blood mononuclear cells (PBMCs) of Sjögren's syndrome (SS) dry eye patients. Overexpression of miR-31-5p exhibits preventive and therapeutic effects on rabbit autoimmune dacryoadenitis. Further investigation revealed that miR-31-5p overexpression significantly restored the M1/M2 macrophage balance both in vivo and in vitro. Mechanistically, miR-31-5p directly targets the P2x7 receptor (P2RX7), leading to the inactivation of p38 mitogen-activated protein kinases (MAPK) signaling and reduced expression of M1 markers. Furthermore, methylated RNA immunoprecipitation and luciferase reporter assays demonstrated that fat mass and obesity-associated protein (FTO)-mediated m6A demethylation, which sustains pri-miR-31 stability, is responsible for the decreased miR-31-5p levels in autoimmune dry eye. Notably, PBMC samples from SS dry eye patients further support the link between reduced miR-31-5p levels and M1 macrophage activation observed in rabbits. Overall, these data highlight the critical role of the FTO/miR-31-5p/P2RX7/p38 MAPK axis in autoimmune inflammation, suggesting their potential as therapeutic targets for autoimmune dry eye.

YTHDC1-Mediated lncRNA MSC-AS1 m6A Modification Potentiates Laryngeal Squamous Cell Carcinoma Development via Repressing ATXN7 Transcription

Laryngeal squamous cell carcinoma (LSCC) has the highest mortality rate among head and neck squamous cell carcinoma. This study was designed to investigate the biological effect of long noncoding RNA (lncRNA) MSC antisense RNA 1 (MSC-AS1) on LSCC development and the underlying mechanism. The expression and prognostic value of lncRNAs in head and neck squamous cell carcinoma were predicted in the bioinformatics tools. The overexpression of MSC-AS1 in LSCC patients predicted a poor prognosis. Depletion of MSC-AS1 using shRNA repressed the malignant phenotype of AMC-HN-8 and TU-177 cells. MSC-AS1, mainly localized in the nucleus, interacted closely with the transcription factor CCCTC-binding factor (CTCF). CTCF played anti-tumor effects in vitro and in vivo. Ataxin-7 (ATXN7) was predicted to be a downstream target of CTCF, whose expression was negatively controlled by MSC-AS1. MSC-AS1 was found to block the expression of CTCF, thereby repressing ATXN7. Finally, MSC-AS1 overexpression in LSCC was governed by YTH domain-containing protein 1 (YTHDC1)-mediated m6A modification. In summary, our research identified the YTHDC1/MSC-AS1/CTCF/ATXN7 axis in LSCC development, which indicated that MSC-AS1 is an attractive biomarker in the LSCC treatment.

Research progress on N6-methyladenosine RNA modification in osteosarcoma: functions, mechanisms, and potential clinical applications

Osteosarcoma (OS) is the most commonly diagnosed primary malignant bone tumor in children and adolescents. Despite significant advancements in therapeutic strategies against OS over the past few decades, the prognosis for this disease remains poor, largely due to its high invasiveness and challenges associated with its treatment. N6-methyladenosine (m6A) modification is one of the most abundant epigenetic modifications of RNAs, and many studies have highlighted its crucial role in OS. This article provides a comprehensive summary and introduction to m6A regulators, including methyltransferases, demethylases, and binding proteins. The article emphasizes how regulated m6A modifications can either promote or inhibit OS. It also delves into the mechanisms by which m6A-modified messenger RNAs (mRNAs) and noncoding RNAs (ncRNAs) participate in signaling pathways such as the Wnt/β-catenin, PI3K/AKT, and STAT3 pathways, and discusses these mechanisms in detail. Given the abnormal expression of m6A regulators in OS, the article also explores their potential applications as biomarkers or therapeutic targets in clinical settings. It is anticipated that this review will provide new insights into the diagnosis and treatment of OS.

N6-methyladenosine RNA modification in head and neck squamous cell carcinoma (HNSCC): current status and future insights

N6-methyladenosine (m6A) plays a pivotal role in regulating epitranscriptomic mechanisms and is closely linked to the normal functioning of diverse classes of RNAs, both coding as well as noncoding. Recent research highlights the role of m6A RNA methylation in the onset and progression of several cancers, including head and neck squamous cell carcinoma (HNSCC). HNSCC ranks as the seventh most common cancer globally, with a five-year patient survival rate of just 50%. Elevated m6A RNA methylation levels and deregulated expression of various m6A modifiers, i.e. writers, readers, and erasers, have been reported across nearly all HNSCC subtypes. Numerous studies have demonstrated that m6A modifications significantly impact key hallmarks of HNSCC, such as proliferation, apoptosis, migration, and invasion. Furthermore, m6A impacts epithelial-mesenchymal transition (EMT), drug resistance, and aerobic glycolysis, and disrupts the tumor microenvironment. Additionally, transcripts regulated by m6A in HNSCC present themselves as potential diagnostic and prognostic biomarkers. This review attempts to comprehensively summarize the role of m6A RNA methylation and its modifiers in regulating various facets of HNSCC pathogenesis.

The role of epigenetic methylations in thyroid Cancer

Thyroid cancer (TC) represents one of the most prevalent endocrine malignancies, with a rising incidence worldwide. Epigenetic alterations, which modify gene expression without altering the underlying DNA sequence, have garnered significant attention in recent years. Increasing evidence underscores the pivotal role of epigenetic modifications, including DNA methylation, RNA methylation, and histone methylation, in the pathogenesis of TC. This review provides a comprehensive overview of these reversible and environmentally influenced epigenetic modifications, highlighting their molecular mechanisms and functional roles in TC. Additionally, the clinical implications, challenges associated with studying these epigenetic modifications, and potential future research directions are explored.

YTHDF2-Mediated m6A methylation inhibition by miR27a as a protective mechanism against hormonal osteonecrosis in BMSCs

BACKGROUND

With the increasing incidence of steroid-induced necrosis of the femoral head (SNFH), numerous scholars have investigated its pathogenesis. Current evidence suggests that the imbalance between lipogenesis and osteoblast differentiation in bone marrow mesenchymal stem cells (BMSCs) is a key pathological feature of SNFH. MicroRNAs (miRNAs) have strong gene regulatory effects and can influence the direction of cell differentiation. N6-methyladenosine (m6A) is a prevalent epigenetic modification involved in diverse pathophysiological processes. However, knowledge of how miRNAs regulate m6A-related factors that affect BMSC differentiation is limited.

OBJECTIVE

We aimed to investigate the role of miR27a in regulating the expression of YTHDF2 in BMSCs.

METHODS

We compared miR27a, YTHDF2, and total m6A mRNA levels in SNFH-affected and control BMSCs. CCK-8 and TUNEL assays were used to assess BMSC proliferation and apoptosis. Western blotting and qRT‒PCR were used to measure the expression of osteogenic (ALP, RUNX2, and OCN) and lipogenic (PPARγ and C/EBPα) markers. Alizarin Red and Oil Red O staining were used to quantify osteogenic and lipogenic differentiation, respectively. miR27a was knocked down or overexpressed to evaluate its impact on BMSC differentiation and its relationship with YTHDF2. Bioinformatics analyses identified YTHDF2 as a differentially expressed gene in SNFH (ROC analysis) and revealed potential signaling pathways through GSEA. The effects of YTHDF2 silencing on the lipogenic and osteogenic functions of BMSCs were assessed.

RESULTS

miR27a downregulation and YTHDF2 upregulation were observed in the SNFH BMSCs. miR27a knockdown/overexpression modulated YTHDF2 expression, impacting BMSC differentiation. miR27a silencing decreased m6A methylation and promoted osteogenic differentiation, while YTHDF2 silencing exerted similar effects. GSEA suggested potential signaling pathways associated with YTHDF2 in SNFH.

CONCLUSION

miR27a regulates BMSC differentiation through YTHDF2, affecting m6A methylation and promoting osteogenesis. This finding suggests a potential therapeutic target for SNFH.