m6A mRNA methylation initiated by METTL3 directly promotes YAP translation and increases YAP activity by regulating the MALAT1-miR-1914-3p-YAP axis to induce NSCLC drug resistance and metastasis

YTHDF1 promotes hepatocellular carcinoma progression via activating PI3K/AKT/mTOR signaling pathway and inducing epithelial-mesenchymal transition

BACKGROUND

N⁶-methyladenosine (m⁶A) modification, as the most abundant RNA modification, widely participates in the physiological process and is involved in multiple disease progression, especially cancer. YTH N6-methyladenosine RNA binding protein 1 (YTHDF1) is a pivotal m⁶A "reader" protein, which has been reported in multiple cancers. However, the role and molecular mechanism of YTHDF1 in HCC are still not fully elucidated.

METHODS

Based on various bioinformatics databases, q-RT PCR, western blot, and a tissue microarray containing 90 HCC samples, we examined the expression of YTHDF1 in HCC. Then, we applied the loss-of-function experiments to explore the role of YTHDF1 in HCC by in vitro and in vivo assays. Finally, we performed the gene set enrichment analysis (GSEA) to predict the potential signaling pathway of YTHDF1 involved in HCC and further verified this prediction.

RESULTS

YTHDF1 was overexpressed in HCC and associated with HCC grade. Depletion of YTHDF1 markedly impaired the proliferation, migration, invasion, and cell cycle process of HCC cells. Mechanistically, YTHDF1 promoted the growth of HCC cells via activating the PI3K/AKT/mTOR signaling pathway. Moreover, we also demonstrated that the epithelial-mesenchymal transition (EMT) mediated the promoting effect of YTHDF1 on the migration and invasion of HCC cells.

CONCLUSIONS

YTHDF1 contributes to the progression of HCC by activating PI3K/AKT/mTOR signaling pathway and inducing EMT.

Exploration of the Role of m6 A RNA Methylation Regulators in Malignant Progression and Clinical Prognosis of Ovarian Cancer

Ovarian cancer is the most deadly gynecologic malignancy worldwide and it is warranted to dissect the critical gene regulatory network in ovarian cancer. N6-methyladenosine (m⁶A) RNA methylation, as the most prevalent RNA modification, is orchestrated by the m⁶A RNA methylation regulators and has been implicated in malignant progression of various cancers. In this study, we investigated the genetic landscape and expression profile of the m⁶A RNA methylation regulators in ovarian cancer and found that several m⁶A RNA methylation regulators were frequently amplified and up-regulated in ovarian cancer. Utilizing consensus cluster analysis, we stratified ovarian cancer samples into four clusters with distinct m⁶A methylation patterns and patients in these subgroups displayed the different clinical outcomes. Moreover, multivariate Cox proportional hazard model was used to screen the key m⁶A regulators associated with the prognosis of ovarian cancer and the last absolute shrinkage and selection operator (LASSO) Cox regression was used to construct the gene signature for prognosis prediction. The survival analysis exhibited the risk-gene signature could be used as independent prognostic markers for ovarian cancer. In conclusion, m⁶A RNA methylation regulators are associated with the malignant progression of ovarian cancer and could be a potential in prognostic prediction for ovarian cancer.

Importance of N6-methyladenosine RNA modification in lung cancer (Review)

The N6-methyladenosine (m6A) modification is the most common mRNA modification in eukaryotes and exerts biological functions by affecting RNA metabolism. The m6A modification is installed by m6A methyltransferases, removed by demethylases and recognized by m6A-binding proteins. The interaction between these three elements maintains the dynamic equilibrium of m6A in cells. Accumulating evidence indicates that m6A RNA methylation has a significant impact on RNA metabolism and is involved in the pathogenesis of cancer. Lung cancer is the leading cause of cancer-related deaths worldwide. The treatment options for lung cancer have developed considerably over the past few years; however, the survival rate of patients with lung cancer still remains very low. Although diagnostic methods and targeted therapies have been rapidly developed in recent years, the underlying mechanism and importance of m6A RNA methylation in the pathogenesis of lung cancer remains ambiguous. The current review summarized the biological functions of m6A modification and considers the potential roles of m6A regulators in the occurrence and development of lung cancer.

The Biological Function, Mechanism, and Clinical Significance of m6A RNA Modifications in Head and Neck Carcinoma: A Systematic Review

Head and neck squamous cell carcinoma (HNSCC) is one of the most common cancers, yet the molecular mechanisms underlying its onset and development have not yet been fully elucidated. Indeed, an in-depth understanding of the potential molecular mechanisms underlying HNSCC oncogenesis may aid the development of better treatment strategies. Recent epigenetic studies have revealed that the m6A RNA modification plays important roles in HNSCC. In this review, we summarize the role of m6A modification in various types of HNSCC, including thyroid, nasopharyngeal, hypopharyngeal squamous cell, and oral carcinoma. In addition, we discuss the regulatory roles of m6A in immune cells within the tumor microenvironment, as well as the potential molecular mechanisms. Finally, we review the development of potential targets for treating cancer based on the regulatory functions of m6A, with an aim to improving targeted therapies for HNSCC. Together, this review highlights the important roles that m6A modification plays in RNA synthesis, transport, and translation, and demonstrates that the regulation of m6A-related proteins can indirectly affect mRNA and ncRNA function, thus providing a novel strategy for reengineering intrinsic cell activity and developing simpler interventions to treat HNSCC.

The Role of RNA Modifications and RNA-modifying Proteins in Cancer Therapy and Drug Resistance

The advent of new genome-wide sequencing technologies has uncovered abnormal RNA modifications and RNA editing in a variety of human cancers. The discovery of reversible RNA N6-methyladenosine (RNA: m⁶A) by fat mass and obesity-associated protein (FTO) demethylase has led to exponential publications on the pathophysiological functions of m⁶A and its corresponding RNA modifying proteins (RMPs) in the past decade. Some excellent reviews have summarized the recent progress in this field. Compared to the extent of research into RNA: m⁶A and DNA 5-methylcytosine (DNA: m⁵C), much less is known about other RNA modifications and their associated RMPs, such as the role of RNA: m⁵C and its RNA cytosine methyltransferases (RCMTs) in cancer therapy and drug resistance. In this review, we will summarize the recent progress surrounding the function, intramolecular distribution and subcellular localization of several major RNA modifications, including 5' cap N7-methylguanosine (m7G) and 2'-O-methylation (Nm), m⁶A, m⁵C, A-to-I editing, and the associated RMPs. We will then discuss dysregulation of those RNA modifications and RMPs in cancer and their role in cancer therapy and drug resistance.

Role of RNA N6-Methyladenosine Modification in Male Infertility and Genital System Tumors

Epigenetic alterations, particularly RNA methylation, play a crucial role in many types of disease development and progression. Among them, N6-methyladenosine (m6A) is the most common epigenetic RNA modification, and its important roles are not only related to the occurrence, progression, and aggressiveness of tumors but also affect the progression of many non-tumor diseases. The biological effects of RNA m6A modification are dynamically and reversibly regulated by methyltransferases (writers), demethylases (erasers), and m6A binding proteins (readers). This review summarized the current finding of the RNA m6A modification regulators in male infertility and genital system tumors and discussed the role and potential clinical application of the RNA m6A modification in spermatogenesis and male genital system tumors.

MALAT1 modulated FOXP3 ubiquitination then affected GINS1 transcription and drived NSCLC proliferation

An increasing number of studies have shown that long-noncoding RNAs (lncRNAs) are involved in the post-translational modifications (PTMs) of protein in a variety of tumors. However, little is known about the exact regulation mechanism of lncRNAs in regulating PTMs in non-small-cell lung carcinoma (NSCLC) proliferation. Metastasis-associated lung adenocarcinoma transcript1 (MALAT1) and GINS complex subunit 1(GINS1) both were upregulated and promoted proliferation progression in NSCLC. In this study, the clinicopathologic significance of MALAT1 and GINS1 in NSCLC was investigated, a positive correlation in their expression was found. The silencing of MALAT1 decreased GINS1 expression and inhibited NSCLC proliferation in vitro and in vivo. The upregulation of GINS1 reversed NSCLC proliferation inhibited by MALAT1 knockdown. FOXP3 (forkhead box protein 3) was identified as the critical transcription factor for GINS1 transcription. In addition, MALAT1 could stabilize FOXP3 by binding to zinc finger (ZF) domain and leucine zipper (LZ) domain of FOXP3. Interestingly, these two domains were also interaction domains for FOXP3 binding with E3 ligase STUB1 (STIP1 homology and U-box containing protein 1). In this way, MALAT1 masked the protein-interacting domain, and inhibited FOXP3 ubiquitination by STUB1. Together, our results identified a novel regulatory axis of MALAT1-FOXP3-GINS1, and demonstrated that MALAT1 played an important modulatory role in PTM of FOXP3 which affects GINS1 transcription and drives proliferation character in NSCLC.

N6 -methyladenosine Steers RNA Metabolism and Regulation in Cancer

As one of the most studied ribonucleic acid (RNA) modifications in eukaryotes, N⁶ -methyladenosine (m⁶ A) has been shown to play a predominant role in controlling gene expression and influence physiological and pathological processes such as oncogenesis and tumor progression. Writer and eraser proteins, acting opposite to deposit and remove m⁶ A epigenetic marks, respectively, shape the cellular m⁶ A landscape, while reader proteins preferentially recognize m⁶ A modifications and mediate fate decision of the methylated RNAs, including RNA synthesis, splicing, exportation, translation, and stability. Therefore, RNA metabolism in cells is greatly influenced by these three classes of m⁶ A regulators. Aberrant expression of m⁶ A regulators has been widely reported in various types of cancer, leading to cancer initiation, progression, and drug resistance. The close links between m⁶ A and cancer shed light on the potential use of m⁶ A methylation and its regulators as prognostic biomarkers and drug targets for cancer therapy. Given the notable effects of m⁶ A in reversing chemoresistance and enhancing immune therapy, it is a promising target for combined therapy. Herein, we summarize the recent discoveries on m⁶ A and its regulators, emphasizing their influences on RNA metabolism, their dysregulation and impacts in diverse malignancies, and discuss the clinical implications of m⁶ A modification in cancer.

Epigenetics: Roles and therapeutic implications of non-coding RNA modifications in human cancers

As next-generation sequencing (NGS) is leaping forward, more than 160 covalent RNA modification processes have been reported, and they are widely present in every organism and overall RNA type. Many modification processes of RNA introduce a new layer to the gene regulation process, resulting in novel RNA epigenetics. The commonest RNA modification includes pseudouridine (Ψ), N ⁷-methylguanosine (m7G), 5-hydroxymethylcytosine (hm5C), 5-methylcytosine (m5C), N ¹-methyladenosine (m1A), N ⁶-methyladenosine (m6A), and others. In this study, we focus on non-coding RNAs (ncRNAs) to summarize the epigenetic consequences of RNA modifications, and the pathogenesis of cancer, as diagnostic markers and therapeutic targets for cancer, as well as the mechanisms affecting the immune environment of cancer. In addition, we summarize the current status of epigenetic drugs for tumor therapy based on ncRNA modifications and the progress of bioinformatics methods in elucidating RNA modifications in recent years.

METTL3 enhances the stability of MALAT1 with the assistance of HuR via m6A modification and activates NF-κB to promote the malignant progression of IDH-wildtype glioma

Understanding the role of N6-methyladenosine (m⁶A) in tumorigenesis and stem cell maintenance is an emerging field in glioma research. However, it is necessary to study the function of m⁶A in IDH-mutation and IDH-wildtype gliomas separately. Here, we aimed to elucidate the role and mechanism of the m⁶A writer METTL3 in regulating the malignant progression of IDH-wildtype gliomas. We demonstrated that METTL3 expression is positively associated with a higher malignant grade and poorer prognosis of IDH-wildtype gliomas but not IDH-mutant gliomas. METTL3 could also promote the malignant progression of gliomas in both in vitro and in vivo models. Mechanistically, METTL3 upregulated MALAT1 expression by enhancing its stability via m⁶A modification. We further revealed that HuR was essential for METTL3-mediated MALAT1 stabilization, and upregulated MALAT1 subsequently activated NF-κB. Taken together, our findings confirmed that METTL3 promoted the malignant progression of IDH-wildtype gliomas and revealed important insight into the upstream regulatory mechanism of MALAT1 and NF-κB with a primary focus on m6A modification.

N6-methyladenosine-dependent signalling in cancer progression and insights into cancer therapies

The N6-methyladenosine (m6A) modification is a dynamic and reversible epigenetic modification, which is co-transcriptionally deposited by a methyltransferase complex, removed by a demethylase, and recognized by reader proteins. Mechanistically, m6A modification regulates the expression levels of mRNA and nocoding RNA by modulating the fate of modified RNA molecules, such as RNA splicing, nuclear transport, translation, and stability. Several studies have shown that m6A modification is dysregulated in the progression of multiple diseases, especially human tumors. We emphasized that the dysregulation of m6A modification affects different signal transduction pathways and involves in the biological processes underlying tumor cell proliferation, apoptosis, invasion and migration, and metabolic reprogramming, and discuss the effects on different cancer treatment.

Methylation of microRNA-338-5p by EED promotes METTL3-mediated translation of oncogene CDCP1 in gastric cancer

Unmasking the complex regulatory pathways that mediate the malignant phenotypes of cancer cells can provide novel targets for therapies that could limit the recurrence and metastasis of gastric cancer (GC). Herein, we intended to clarify the role of embryonic ectoderm development protein (EED), microRNA-228-5p (miR-338-5p), methyltransferase like 3 (METTL3) and CUB domain containing protein 1 (CDCP1) in GC. Differentially expressed miRNAs and their target genes were extracted by in silico analysis. The studies revealed high expression of EED in GC tissues and cell lines and it high expression in GC patients was shown to be associated with poor prognosis. The chromatin immunoprecipitation assay identified that EED methylated miR-338-5p to inhibit its expression. EED knockdown could restrain the proliferative and invasive abilities of GC cells by inducing miR-338-5p. Furthermore, miR-338-5p targeted m6A methylase METTL3, while METTL3 amplified the translation of CDCP1 via m6A activity which led to accelerated proliferation and invasion of GC cells. Moreover, in vivo experiments validated that EED promoted the progression of GC through mediating the miR-338-5p/METTL3/CDCP1 axis. Collectively, EED downregulated miR-338-5p through histone methylation, which in turn impaired miR-338-5p-dependent METTL3 inhibition and enhanced CDCP1 translation, therefore contributing to the development of GC.

New Insights into YES-Associated Protein Signaling Pathways in Hematological Malignancies: Diagnostic and Therapeutic Challenges

Simple Summary

YES-associated protein (YAP) is a co-transcriptional activator that binds to transcriptional factors to increase the rate of transcription of a set of genes, and it can intervene in the onset and progression of different tumors. Most of the data in the literature refer to the effects of the YAP system in solid neoplasms. In this review, we analyze the possibility that YAP can also intervene in hematological neoplasms such as lymphomas, multiple myeloma, and acute and chronic leukemias, modifying the phenomena of cell proliferation and cell death. The possibilities of pharmacological intervention related to the YAP system in an attempt to use its modulation therapeutically are also discussed.

Abstract

The Hippo/YES-associated protein (YAP) signaling pathway is a cell survival and proliferation-control system with its main activity that of regulating cell growth and organ volume. YAP operates as a transcriptional coactivator in regulating the onset, progression, and treatment response in numerous human tumors. Moreover, there is evidence suggesting the involvement of YAP in the control of the hematopoietic system, in physiological conditions rather than in hematological diseases. Nevertheless, several reports have proposed that the effects of YAP in tumor cells are cell-dependent and cell-type-determined, even if YAP usually interrelates with extracellular signaling to stimulate the onset and progression of tumors. In the present review, we report the most recent findings in the literature on the relationship between the YAP system and hematological neoplasms. Moreover, we evaluate the possible therapeutic use of the modulation of the YAP system in the treatment of malignancies. Given the effects of the YAP system in immunosurveillance, tumorigenesis, and chemoresistance, further studies on interactions between the YAP system and hematological malignancies will offer very relevant information for the targeting of these diseases employing YAP modifiers alone or in combination with chemotherapy drugs.

Comprehensive analyses of m6A regulators and interactive coding and non-coding RNAs across 32 cancer types

N6-Methyladenosine (m6A) is an RNA modification that interacts with numerous coding and non-coding RNAs and plays important roles in the development of cancers. Nonetheless, the clinical impacts of m6A interactive genes on these cancers largely remain unclear since most studies focus only on a single cancer type. We comprehensively evaluated m6A modification patterns, including 23 m6A regulators and 83 interactive coding and non-coding RNAs among 9,804 pan-cancer samples. We used clustering analysis to identify m6A subtypes and constructed the m6A signature based on an unsupervised approach. We used the signatures to identify potential m6A modification targets across the genome. The prognostic value of one target was further validated in 3,444 samples from six external datasets. We developed three distinct m6A modification subtypes with different tumor microenvironment cell infiltration degrees: immunological, intermediate, and tumor proliferative. They were significantly associated with overall survival in 24 of 27 cancer types. Our constructed individual-level m6A signature was associated with survival, tumor mutation burden, and classical pathways. With the signature, we identified 114 novel genes as potential m6A targets. The gene shared most commonly between cancer types, BCL9L, is an oncogene and interacts with m6A patterns in the Wnt signaling pathway. In conclusion, m6A regulators and their interactive genes impact the outcome of various cancers. Evaluating the m6A subtype and the signature of individual tumors may inform the design of adjuvant treatments.

The m6A RNA methylation regulates oncogenic signaling pathways driving cell malignant transformation and carcinogenesis

The m⁶A RNA methylation is the most prevalent internal modification in mammalian mRNAs which plays critical biological roles by regulating vital cellular processes. Dysregulations of the m⁶A modification due to aberrant expression of its regulatory proteins are frequently observed in many pathological conditions, particularly in cancer. Normal cells undergo malignant transformation via activation or modulation of different oncogenic signaling pathways through complex mechanisms. Accumulating evidence showing regulation of oncogenic signaling pathways at the epitranscriptomic level has added an extra layer of the complexity. In particular, recent studies demonstrated that, in many types of cancers various oncogenic signaling pathways are modulated by the m⁶A modification in the target mRNAs as well as noncoding RNA transcripts. m⁶A modifications in these RNA molecules control their fate and metabolism by regulating their stability, translation or subcellular localizations. In this review we discussed recent exciting studies on oncogenic signaling pathways that are modulated by the m⁶A RNA modification and/or their regulators in cancer and provided perspectives for further studies. The regulation of oncogenic signaling pathways by the m⁶A modification and its regulators also render them as potential druggable targets for the treatment of cancer.

pVHL promotes lysosomal degradation of YAP in lung adenocarcinoma

Yes-associated protein (YAP) is a vital transcriptional co-activator that activates cell proliferation and evasion of apoptosis for the promotion of tumorigenesis. The von Hippel-Lindau tumor suppressor protein (pVHL), as a critical component of E3 ubiquitin ligase, targets various substrates to regulate tumor progression. However, the precise molecular mechanisms of pVHL during tumorigenesis remain largely unclear. Herein, we found that there was a significant negative correlation between pVHL and YAP at protein level in the TCGA-LUAD dataset and our cohort. Over-expression of pVHL decreased YAP protein expression and reduced its transcriptional activity. Further study indicated that pVHL did not affect YAP mRNA level but decreased YAP protein stability in a lysosome-dependent manner. In addition, the pVHL-mediated degradation of YAP inhibited cellular proliferation, migration, and enhanced chemosensitivity to cisplatin in lung adenocarcinoma cells. Interestingly, the pVHL-mediated YAP degradation was blocked by elevated O-GlcNAcylation. Collectively, our findings demonstrate that pVHL modulates the lysosomal degradation of YAP, and may provide more clues to better understanding the tumor suppressive effects of pVHL.

Linking the YTH domain to cancer: the importance of YTH family proteins in epigenetics

N6-methyladenosine (m6A), the most prevalent and reversible modification of mRNA in mammalian cells, has recently been extensively studied in epigenetic regulation. YTH family proteins, whose YTH domain can recognize and bind m6A-containing RNA, are the main "readers" of m6A modification. YTH family proteins perform different functions to determine the metabolic fate of m6A-modified RNA. The crystal structure of the YTH domain has been completely resolved, highlighting the important roles of several conserved residues of the YTH domain in the specific recognition of m6A-modified RNAs. Upstream and downstream targets have been successively revealed in different cancer types and the role of YTH family proteins has been emphasized in m6A research. This review describes the regulation of RNAs by YTH family proteins, the structural features of the YTH domain, and the connections of YTH family proteins with human cancers.

The m6A methyltransferase METTL3 regulates autophagy and sensitivity to cisplatin by targeting ATG5 in seminoma

Background

Our previous work shows Autophagy enhanced resistance to cisplatin in seminoma. The expression of the N6-methyladenosine (m6A) methyltransferases METTL3 was significantly increased in the cisplatin-resistant TCam-2 cell line of seminoma. We aimed to investigate the role of m6A methylation in autophagy and the chemosensitivity of seminoma cells.

Methods

Plasmid and siRNA were used to overexpress and knockdown METTL3. Autophagy was detected by western blot and immunofluorescence, respectively. The expression of downstream targets of METTL3 was detected by quantitative real-time PCR (qRT-PCR) and western blot, and the m6A level of them was detected by MeRIP-qPCR. Chemosensitivity of the TCam-2 cell line was identified through MTT assay.

Results

Upon METTL3 overexpression, autophagy of TCam-2 cell line was enhanced and its sensitivity to cisplatin was decreased. The use of autophagy inhibitors 3-methyladenine (3-MA) could reverse the protective effect of METTL3 on TCam-2 cells. We found that the up-regulation of METTL3 could increase the m6A modification level of ATG5 transcript, thus increased expression of ATG5. Moreover, knockdown of ATG5 reduced METTL3-induced autophagy, suggesting that ATG5 was a potential target for METTL3 to promote autophagy.

Conclusions

In summary, our research unveiled the unique mechanism by which m6A methylation regulates autophagy and chemosensitivity of the TCam-2 cell line and METTL3 was a potential target to overcome the cisplatin resistance of seminoma.

LINC00941 Promotes Progression of Non-Small Cell Lung Cancer by Sponging miR-877-3p to Regulate VEGFA Expression

Long noncoding RNAs (lncRNAs) play critical roles in carcinoma occurrence and metastasis. LINC00941 has been found to mediate the development of gastric cancer, and LINC00941 was negatively associated with the longer overall survival of lung adenocarcinoma patients. Herein, our aim was to investigate the effects and mechanisms of LINC00941 in NSCLC progression. Microarray was used to identify the change lncRNAs in NSCLC, LINC00941 was found to increase in tumor tissues and patients' plasma. Knockdown of LINC00941 didn't modulate the proliferation of NSCLC cells, but inhibition of LINC00941 in NSCLC cells suppressed the angiogenesis ability of human umbilical vein endothelial cells (HUVECs). Moreover, LINC00941 promoted tumorigenesis in vivo, while si-LINC00941 inhibited tumor development of NSCLC. VEGFA was should to be significantly modulated by LINC00941 in NSCLC cells, then luciferase assay proved that LINC00941 regulated VEGFA expression via interacting with miR-877-3p. Followed functional experiments indicated that overexpression of LINC00941 accelerated angiogenesis and NSCLC tumor progression via miR-877-3p/VEGFA axis both in vitro and in vivo. In conclusion, our results clarified the LINC00941 function for the first time, and LINC00941 promoted the progression of NSCLC, which was mediated by miR-877-3p/VEGFA axis. This study might provide new understanding and targets for NSCLC diagnosis and treatment.

m6A-dependent up-regulation of DRG1 by METTL3 and ELAVL1 promotes growth, migration, and colony formation in osteosarcoma

Osteosarcoma (OS) is a malignant tumor commonly observed in children and adolescents. Developmentally regulated GTP-binding protein (DRG) 1 plays an important role in embryonic development; aberrantly expressed DRG1 has been associated with pathological processes in cancer. The present study aimed to explore the role of DRG1 in OS and the mechanisms underlying DRG1 overexpression in OS. Clinical studies were performed to evaluate Drg1 expression in OS tissues and to identify a correlation between Drg1 expression and the clinicopathological features in patients with OS. Drg1 was knocked down in OS cells to determine its effects on cell viability, cell cycle distribution, apoptosis, migration, invasion, and colony formation rate. METTL3 and ELAVL1 were also silenced to determine their effects on the levels of N6-methyladenosine (m6A), RNA stability, and Drg1 expression. Higher levels of Drg1 mRNA and protein were observed in OS tissues than those in paracancerous tissues. High expression of DRG1 was associated with large tumor size and advanced clinical stages in OS. Silencing of Drg1 resulted in decreased viability and inhibition of the migration and colony formation abilities of OS cells; it also resulted in cell cycle arrest in the G₂/M stage and induced apoptosis. Knockdown of METTL3 led to decreased m6A and Drg1 mRNA levels. ELAVL1 knockdown impaired the stability of DRG1 mRNA, thereby reducing both the mRNA and protein levels of DRG1. In all, DRG1 exerted tumorigenic effects in OS, and the up-regulation of DRG1 in OS was induced by METTL3 and ELAVL1 in an m6A-dependent manner.

RNA methylation in hematological malignancies and its interactions with other epigenetic modifications

Hematological malignancies are a class of malignant neoplasms attributed to abnormal differentiation of hematopoietic stem cells (HSCs). The systemic involvement, poor prognosis, chemotherapy resistance, and recurrence common in hematological malignancies urge researchers to look for novel treatment targets and mechanisms. In recent years, epigenetic abnormalities have been shown to play a vital role in tumorigenesis and progression in hematological malignancies. In addition to DNA methylation and histone modifications, which are most studied, RNA methylation has become increasingly significant. In this review, we elaborate recent advances in the understanding of RNA modification in the pathogenesis, diagnosis and molecular targeted therapies of hematological malignancies and discuss its intricate interactions with other epigenetic modifications, including DNA methylation, histone modifications and noncoding RNAs.

RNA N6-methyladenosine modification, spermatogenesis, and human male infertility

RNA N6-methyladenosine (m6A) modification is one of the main forms of posttranscriptional modification, and its dysregulation is involved in a series of pathological processes. RNA m6A regulators, which mediate dynamic RNA m6A modification, are expressed in almost all types of testicular cells, including spermatogenetic cells and somatic cells. Cumulative studies have found that knockout of RNA m6A regulators in the testis leads to abnormal metabolism of the target mRNAs, which eventually causes spermatogenetic disorders and infertility. To date, a role for dysregulated RNA m6A modification in human male infertility remains elusive; however, dysregulated expression of RNA m6A regulators in abnormal human semen samples, including oligospermia, asthenozoospermia and azoospermia, has been found. Therefore, we speculate that abnormal RNA m6A methylation may be an important mechanism of male infertility. In this review, we summarize the recent findings regarding the spatiotemporal expression of RNA m6A regulators in the testes, mechanisms of RNA m6A modification in spermatogenesis and the relation between dysregulated RNA m6A regulators and human male infertility. In addition, we also discuss future directions in studying the molecular mechanism of male infertility and exploring their clinical applications from the viewpoint of RNA m6A modification.

The Important Role of N6-methyladenosine RNA Modification in Non-Small Cell Lung Cancer

N6-methyladenosine (m⁶A) is one of the most prevalent epigenetic modifications of eukaryotic RNA. The m⁶A modification is a dynamic and reversible process, regulated by three kinds of regulator, including m⁶A methyltransferases, demethylases and m⁶A-binding proteins, and this modification plays a vital role in many diseases, especially in cancers. Accumulated evidence has proven that this modification has a significant effect on cellular biological functions and cancer progression; however, little is known about the effects of the m⁶A modification in non-small cell lung cancer (NSCLC). In this review, we summarized how various m⁶A regulators modulate m⁶A RNA metabolism and demonstrated the effect of m⁶A modification on the progression and cellular biological functions of NSCLC. We also discussed how m⁶A modification affects the treatment, drug resistance, diagnosis and prognosis of NSCLC patients.

The m6A Reader YTHDF1 Facilitates the Tumorigenesis and Metastasis of Gastric Cancer via USP14 Translation in an m6A-Dependent Manner

Objectives

N⁶-methyladenosine (m⁶A) RNA methylation is implicated in the progression of multiple cancers via influencing mRNA modification. YTHDF1 can act as an oncogene in gastric cancer (GC), while the biological mechanisms via which YTHDF1 regulates gastric tumorigenesis through m⁶A modification remain largely unknown.

Methods

GEO and TCGA cohorts were analyzed for differentially expressed m⁶A modification components in GC clinical specimens and their association with clinical prognosis. Transwell and flow cytometry assays as well as subcutaneous xenograft and lung metastasis models were used to evaluate the phenotype of YTHDF1 in GC. Intersection of RNA/MeRIP-seq, luciferase assay, RIP-PCR, RNA pull-down and MeRIP-PCR was used to identify YTHDF1- modified USP14 and its m⁶A levels in GC cells.

Results

High-expressed YTHDF1 was found in GC tissues and was related to poor prognosis, acting as an independent prognostic factor of poor survival in GC patients. YTHDF1 deficiency inhibited cell proliferation and invasion (in vitro), and gastric tumorigenesis and lung metastasis (in vivo) and also induced cell apoptosis. Intersection assays revealed that YTHDF1 promoted USP14 protein translation in an m⁶A-dependent manner. USP14 upregulation was positively correlated with YTHDF1 expression and indicated a poor prognosis in GC.

Conclusion

Our data suggested that m⁶A reader YTHDF1 facilitated tumorigenesis and metastasis of GC by promoting USP14 protein translation in an m⁶A-dependent manner and might provide a potential target for GC treatment.

METTL3-mediated m6A mRNA modification of FBXW7 suppresses lung adenocarcinoma

Background

FBXW7 m⁶A modification plays an important role in lung adenocarcinoma (LUAD) progression; however, the underlying mechanisms remain unclear.

Methods

The correlation between FBXW7 and various genes related to m⁶A modification was analyzed using The Cancer Genome Atlas database. The regulatory effects of METTL3 on FBXW7 mRNA m⁶A modification were examined in a cell model, and the underlying mechanism was determined by methylated RNA immunoprecipitation, RNA immunoprecipitation, luciferase reporter, and mutagenesis assays. In vitro experiments were performed to further explore the biological effects of METTL3-mediated FBXW7 m⁶A modification on LUAD development.

Results

Decreased FBXW7 expression was accompanied by downregulated METTL3 expression in human LUAD tissues and was associated with a worse prognosis for LUAD in The Cancer Genome Atlas database. m⁶A was highly enriched in METTL3-mediated FBXW7 transcripts, and increased m⁶A modification in the coding sequence region increased its translation. Functionally, METTL3 overexpression or knockdown affected the apoptosis and proliferation phenotype of LUAD cells by regulating FBXW7 m⁶A modification and expression. Furthermore, FBXW7 overexpression in METTL3-depleted cells partially restored LUAD cell suppression in vitro and in vivo.

Conclusions

Our findings reveal that METTL3 positively regulates FBXW7 expression and confirm the tumor-suppressive role of m⁶A-modified FBXW7, thus providing insight into its epigenetic regulatory mechanisms in LUAD initiation and development.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13046-021-01880-3.

The crosstalk between m6A RNA methylation and other epigenetic regulators: a novel perspective in epigenetic remodeling

Epigenetic regulation involves a range of sophisticated processes which contribute to heritable alterations in gene expression without altering DNA sequence. Regulatory events predominantly include DNA methylation, chromatin remodeling, histone modifications, non-coding RNAs (ncRNAs), and RNA modification. As the most prevalent RNA modification in eukaryotic cells, N⁶-methyladenosine (m⁶A) RNA methylation actively participates in the modulation of RNA metabolism. Notably, accumulating evidence has revealed complicated interrelations occurring between m⁶A and other well-known epigenetic modifications. Their crosstalk conspicuously triggers epigenetic remodeling, further yielding profound impacts on a variety of physiological and pathological processes, especially tumorigenesis. Herein, we provide an up-to-date review of this emerging hot area of biological research, summarizing the interplay between m⁶A RNA methylation and other epigenetic regulators, and highlighting their underlying functions in epigenetic reprogramming.

Prognostic Roles of N6-Methyladenosine METTL3 in Different Cancers: A System Review and Meta-Analysis

BACKGROUND

Recent studies have shown that methyltransferase-like 3, a catalytic enzyme that is predominant in the N6-methyladenosine methyltransferase system, is abnormally expressed in various types of carcinoma and is correlated with poorer prognosis. However, the clinical functions of methyltransferase-like 3 in the prognosis of tumors are not fully understood.

METHODS

We identified studies by searching PubMed, Web of Science, and MedRvix for literature (up to June 30, 2020), and collected a total of 9 studies with 1257 patients for this meta-analysis. The cancer types included gastric cancer, breast cancer, non-small cell lung cancer, bladder cancer, colorectal cancer and ovarian. We further used The Cancer Genome Atlas dataset to validate the results.

RESULTS

High methyltransferase-like 3 expression clearly predicted a worse outcome (high vs. low methyltransferase-like 3 expression group; hazard ratio = 2.09, 95% confidence interval 1.53-2.89, P = 0.0001). Moreover, methyltransferase-like 3 expression was associated with differentiation (moderate + poor vs. well, pooled odds ratio = 1.76, 95% confidence interval 1.32-2.35, P = 0.0001), and gender (male vs. female, pooled odds ratio = 0.73, 95% confidence interval 0.55-0.97, P = 0.029).

CONCLUSION

Our results suggest that methyltransferase-like 3 upregulation is significantly associated with poor prognosis and could potentially function as a tumor biomarker in cancer prognosis.

The Impact of m6A RNA Modification in Therapy Resistance of Cancer: Implication in Chemotherapy, Radiotherapy, and Immunotherapy

m6A RNA methylation, which serves as a critical regulator of transcript expression, has gathered tremendous scientific interest in recent years. From RNA processing to nuclear export, RNA translation to decay, m6A modification has been studied to affect various aspects of RNA metabolism, and it is now considered as one of the most abundant epitranscriptomic modification. RNA methyltransferases (writer), m6A-binding proteins (readers), and demethylases (erasers) proteins are frequently upregulated in several neoplasms, thereby regulating oncoprotein expression, augmenting tumor initiation, enhancing cancer cell proliferation, progression, and metastasis. Though the potential role of m6A methylation in growth and proliferation of cancer cells has been well documented, its potential role in development of therapy resistance in cancer is not clear. In this review, we focus on m6A-associated regulation, mechanisms, and functions in acquired chemoresistance, radioresistance, and resistance to immunotherapy in cancer.

MTTL3 upregulates microRNA-1246 to promote occurrence and progression of NSCLC via targeting paternally expressed gene 3

Non-small cell lung cancer (NSCLC) is one of the major causes of morbidity and mortality worldwide. We aimed to investigate the role of N6-methyladenosine (m6A) methyltransferase-like 3 (METTL3) regulating microRNA-1246 (miR-1246) in the progression of NSCLC by targeting paternally expressed gene 3 (PEG3). METTL3, miR-1246, and PEG3 expression in tissues was assessed, and the predictive role of METTL3 in prognosis of patients with NSCLC was detected. NSCLC cells were relatively treated with altered expression of METTL3, miR-1246, or PEG3 to measure their roles in the proliferation, migration, invasion, apoptosis, and in vivo growth of the NSCLC cells. The RNA m6A level was determined, and the targeting relationship between miR-1246 and PEG3 was confirmed. Our results revealed that METTL3 and miR-1246 were upregulated, whereas PEG3 was downregulated in NSCLC tissues. METTL3 knockdown or PEG3 overexpression in NSCLC cells suppressed malignant behaviors of NSCLC cells. METTL3 affected the m6A modification of miR-1246, thus upregulating miR-1246 and miR-1246-targeted PEG3. The elevation of PEG3 reversed the effects of miR-1246 upregulation on NSCLC cells. This study revealed that m6A methyltransferase METTL3 affects the m6A modification of miR-1246, thus upregulating miR-1246 to promote NSCLC progression by inhibiting PEG3.

Dual effects of N6-methyladenosine on cancer progression and immunotherapy

According to the latest global cancer statistics, cancer has become a major threat to human health, but cancer treatment has encountered many bottlenecks. As an emerging topic in epigenetics, N⁶-methyladenosine (m⁶A) is the most common internal modification on eukaryotic mRNA, which has attracted increasing attention in recent years. Accumulating studies have shown that aberrant m⁶A modifications have profound effects on the characteristics of tumors, which undoubtedly led to a significant breakthrough in cancer treatment. Although m⁶A function as an oncogene or tumor suppressor is not fully revealed, determining its precise function in the development and evolution of malignant tumors is crucial in improving clinical decisions involving targeted therapies. In this review, we briefly introduce the composition of the m⁶A methylation machinery and mainly summarize the biological mechanism of m⁶A in cancer cell death, angiogenesis, epithelial-mesenchymal transition (EMT), and therapeutic resistance. Subsequently, we present the exogenous regulatory factors of m⁶A and highlight the role of m⁶A on immune cells and cancer immunotherapy. The potential therapeutic strategies of m⁶A in human cancer are also discussed, considering research gaps and future applications.

RNA methyltransferase METTL3 induces intrinsic resistance to gefitinib by combining with MET to regulate PI3K/AKT pathway in lung adenocarcinoma

Clinical research data show that gefitinib greatly improves the progression‐free survival of patients, so it is used in advanced non‐small cell lung cancer patients with EGFR mutation. However, some patients with EGFR sensitive mutations do not have good effects on initial gefitinib treatment, and this mechanism is rarely studied. METTL3, a part of N6‐adenosine‐methyltransferase, has been reported to play an important role in a variety of tumours. In this study, we found that METTL3 is up‐regulated in gefitinib‐resistant tissues compared to gefitinib‐sensitive tissues. Cell function experiments have proved that under the treatment of gefitinib, METTL3 knockdown promotes apoptosis and inhibits proliferation of lung cancer cells. Mechanistic studies have shown that METTL3 combines with MET and causes the PI3K/AKT signalling pathway to be manipulated, which affects the sensitivity of lung cancer cells to gefitinib. Therefore, our research shows that METTL3 can be used as a molecular marker to predict the efficacy of EGFR‐TKI therapy in patients, and METTL3 may be a potential therapeutic target.

The role of m6A, m5C and Ψ RNA modifications in cancer: Novel therapeutic opportunities

RNA modifications have recently emerged as critical posttranscriptional regulators of gene expression programmes. Significant advances have been made in understanding the functional role of RNA modifications in regulating coding and non-coding RNA processing and function, which in turn thoroughly shape distinct gene expression programmes. They affect diverse biological processes, and the correct deposition of many of these modifications is required for normal development. Alterations of their deposition are implicated in several diseases, including cancer. In this Review, we focus on the occurrence of N⁶-methyladenosine (m⁶A), 5-methylcytosine (m⁵C) and pseudouridine (Ψ) in coding and non-coding RNAs and describe their physiopathological role in cancer. We will highlight the latest insights into the mechanisms of how these posttranscriptional modifications influence tumour development, maintenance, and progression. Finally, we will summarize the latest advances on the development of small molecule inhibitors that target specific writers or erasers to rewind the epitranscriptome of a cancer cell and their therapeutic potential.

Long Noncoding RNAs in the Metastasis of Oral Squamous Cell Carcinoma

Oral squamous cell carcinoma (OSCC) is a common malignant tumor worldwide. Metastasis is the main cause of the death of OSCC patients. Long noncoding RNAs (lncRNAs), one of the key factors affecting OSCC metastasis, are a subtype of RNA with a length of more than 200 nucleotides that has little or no coding potential. In recent years, the important role played by lncRNAs in biological processes, such as chromatin modification, transcription regulation, RNA stability regulation, and mRNA translation, has been gradually revealed. More and more studies have shown that lncRNAs can regulate the metastasis of various tumors including OSCC at epigenetic, transcriptional, and post-transcriptional levels. In this review, we mainly discussed the role and possible mechanisms of lncRNAs in OSCC metastasis. Most lncRNAs act as oncogenes and only a few lncRNAs have been shown to inhibit OSCC metastasis. Besides, we briefly introduced the research status of cancer-associated fibroblasts-related lncRNAs in OSCC metastasis. Finally, we discussed the research prospects of lncRNAs-mediated crosstalk between OSCC cells and the tumor microenvironment in OSCC metastasis, especially the potential research value of exosomes and lymphangiogenesis. In general, lncRNAs are expected to be used for screening, treatment, and prognosis monitoring of OSCC metastasis, but more work is still required to better understand the biological function of lncRNAs.

Translation initiation in cancer at a glance

Cell division, differentiation and function are largely dependent on accurate proteome composition and regulated gene expression. To control this, protein synthesis is an intricate process governed by upstream signalling pathways. Eukaryotic translation is a multistep process and can be separated into four distinct phases: initiation, elongation, termination and recycling of ribosomal subunits. Translation initiation, the focus of this article, is highly regulated to control the activity and/or function of eukaryotic initiation factors (eIFs) and permit recruitment of mRNAs to the ribosomes. In this Cell Science at a Glance and accompanying poster, we outline the mechanisms by which tumour cells alter the process of translation initiation and discuss how this benefits tumour formation, proliferation and metastasis.

Biological functions of m6A methyltransferases

M⁶A methyltransferases, acting as a writer in N6-methyladenosine, have attracted wide attention due to their dynamic regulation of life processes. In this review, we first briefly introduce the individual components of m⁶A methyltransferases and explain their close connections to each other. Then, we concentrate on the extensive biological functions of m⁶A methyltransferases, which include cell growth, nerve development, osteogenic differentiation, metabolism, cardiovascular system homeostasis, infection and immunity, and tumour progression. We summarize the currently unresolved problems in this research field and propose expectations for m⁶A methyltransferases as novel targets for preventive and curative strategies for disease treatment in the future.

Multifaceted regulation of translation by the epitranscriptomic modification N6-methyladenosine

Translation occurring on cytoplasmic mRNA is precisely governed at three consecutive stages, including initiation, elongation and termination. A growing body of evidence has revealed that an emerging epitranscriptomic code N⁶-methyladenosine (m⁶A), asymmetrically present in a large subset of coding and non-coding transcripts, is crucially required for mediating the translatomic stability. Through recruiting translation machinery proteins, serving as a physical barrier, or directing RNA structural rearrangement and mRNA looping formation, m⁶A has been decoded to modulate translational dynamics through potentially influencing the progress of different stages, thereby forming an additional layer of complexity to the regulation of translation. In this review, we summarize the current understanding of how m⁶A guides mRNA translation under normal and stress conditions, highlighting the divergent molecular mechanisms of multifarious regulation of m⁶A-mediated translation.

METTL3 promotes adriamycin resistance in MCF-7 breast cancer cells by accelerating pri-microRNA-221-3p maturation in a m6A-dependent manner

Breast cancer (BC) is the most prevalent malignant neoplasm among women and is the fifth most common cause of cancer-associated death worldwide. Acquired chemoresistance driven by genetic and epigenetic alterations is a significant clinical challenge in treating BC. However, the mechanism of BC cell resistance to adriamycin (ADR) remains to be elucidated. In this study, we identified the methyltransferase-like 3/microRNA-221-3p/homeodomain-interacting protein kinase 2/Che-1 (METTL3/miR-221-3p/HIPK2/Che-1) axis as a novel signaling event that may be responsible for resistance of BC cells to ADR. A dual-luciferase reporter gene assay was employed to test the presence of miR-221-3p binding sites in the 3'UTR of HIPK2. Drug resistance was evaluated by immunoblotting multidrug resistance protein 1 (MDR1) and breast cancer resistance protein (BCRP). Cultured ADR-resistant MCF-7 cells were assayed for their half maximal inhibitory concentration (IC50) values and apoptosis using an MTT assay and Annexin V-FITC/PI-labeled flow cytometry, and the cells were then xenografted into nude mice. METTL3 knockdown was shown to reduce the expression of miR-221-3p by reducing pri-miR-221-3p m6A mRNA methylation, thereby reducing the IC50 value of ADR-resistant MCF-7 cells, reducing the expression of MDR1 and BCRP, and inducing apoptosis. Mechanistically, miR-221-3p was demonstrated to negatively regulate HIPK2 and upregulate its direct target Che-1, thus leading to enhanced drug resistance in ADR-resistant MCF-7 cells. In vitro results were reproduced in nude mice xenografted with ADR-resistant MCF-7 cells. Our work elucidates an epigenetic mechanism of acquired chemoresistance in BC, in support of the METTL3/miR-221-3p/HIPK2/Che-1 axis as a therapeutic target for the improvement of chemotherapy.

Diagnostic, prognostic, and therapeutic significance of long non-coding RNA MALAT1 in cancer

Metastasis Associated Lung Adenocarcinoma Transcript 1 (MALAT1) is a widely studied lncRNA in cancer. Although dispensable for normal physiology, MALAT1 is important for cancer-related pathways regulation. It is localized in the nuclear speckles periphery along with centrally located pre-RNA splicing factors. MALAT1 associated cancer signaling pathways include MAPK/ERK, PI3K/AKT, β-catenin/Wnt, Hippo, VEGF, YAP, etc. Molecular tools such as immunoprecipitation, RNA pull-down, reporter assay, Northern blotting, microarray, and q-RT-PCR has been used to elucidate MALAT1's function in cancer pathogenesis. MALAT1 can regulate multiple steps in the development of tumours. The diagnostic and prognostic significance of MALAT1 has been demonstrated in cancers of the breast, cervix, colorectum, gallbladder, lung, ovary, pancreas, prostate, glioma, hepatocellular carcinoma, and multiple myeloma. MALAT1 has also emerged as a novel therapeutic target for solid as well as hematological malignancies. In experimental models, siRNA and antisense oligonucleotide (ASO) based strategy has been used for targeting MALAT1. The lncRNA has also been targeted for the chemosensitization and radiosensitization of cancer cells. However, most studies have been performed in preclinical models. How the cross-talk of MALAT1 with other signaling pathways affect cancer pathogenesis is the focus of this article. The diagnostic, prognostic, and therapeutic significance of MALAT1 in multiple cancer types are discussed.

The emerging roles of m6A modification in liver carcinogenesis

The 'epitranscriptome', a collective term for chemical modifications that influence the structure, metabolism, and functions of RNA, has recently emerged as vitally important for the regulation of gene expression. N⁶-methyladenosine (m⁶A), the most prevalent mammalian mRNA internal modification, has been demonstrated to have a pivotal role in almost all vital bioprocesses, such as stem cell self-renewal and differentiation, heat shock or DNA damage response, tissue development, and maternal-to-zygotic transition. Hepatocellular carcinoma (HCC) is prevalent worldwide with high morbidity and mortality because of late diagnosis at an advanced stage and lack of effective treatment strategies. Epigenetic modifications including DNA methylation and histone modification have been demonstrated to be crucial for liver carcinogenesis. However, the role and underlying molecular mechanism of m⁶A in liver carcinogenesis are mostly unknown. In this review, we summarize recent advances in the m⁶A region and how these new findings remodel our understanding of m⁶A regulation of gene expression. We also describe the influence of m⁶A modification on liver carcinoma and lipid metabolism to instigate further investigations of the role of m⁶A in liver biological diseases and its potential application in the development of therapeutic strategies.

Emerging roles of RNA methylation in gastrointestinal cancers

RNA methylation has emerged as a fundamental process in epigenetic regulation. Accumulating evidences indicate that RNA methylation is essential for many biological functions, and its dysregulation is associated with human cancer progression, particularly in gastrointestinal cancers. RNA methylation has a variety of biological properties, including N6-methyladenosine (m6A), 2-O-dimethyladenosine (m6Am), N1-methyladenosine (m1A), 5-methylcytosine (m5C) and 7-methyl guanosine (m7G). Dynamic and reversible methylation on RNA is mediated by RNA modifying proteins called "writers" (methyltransferases) and "erasers" (demethylases). "Readers" (modified RNA binding proteins) recognize and bind to RNA methylation sites, which influence the splicing, stability or translation of modified RNAs. Herein, we summarize the biological functions and mechanisms of these well-known RNA methylations, especially focusing on the roles of m6A in gastrointestinal cancer development.

Loading MicroRNA-376c in Extracellular Vesicles Inhibits Properties of Non-Small Cell Lung Cancer Cells by Targeting YTHDF1

Objective:

Extracellular vesicles (Evs) secreted from cells have been revealed to mediate signal transduction between cells. Nevertheless, the mechanisms through which molecules transported by EVs function remain to be elucidated. In the present study, the functional relevance of endothelial cells (ECs)-secreted Evs carrying microRNA-376c (miR-376c) in the biological activities of non-small cell lung cancer (NSCLC) cells was investigated, including the related mechanisms.

Methods:

Two cell lines with the highest YTH N6-methyladenosine (m6A) RNA binding protein 1 (YTHDF1) expression were selected for subsequent experiments. Cellular proliferation, migration, invasion and apoptosis were measured by EdU, wound healing, Transwell assays and flow cytometry, respectively. The binding relationship between miR-376c and YTHDF1 was analyzed by dual-luciferase reporter assays. The miR-376c, YTHDF1 and β-catenin expression was evaluated by qPCR assays and western blot assays.

Results:

The expression patterns of YTHDF1 were higher in NSCLC cells, whereas miR-376c was reduced versus the normal bronchial epithelial cells. Silencing of YTHDF1 repressed NSCLC cell proliferation, invasion and migration abilities, whereas enhanced apoptosis. miR-376c negatively modulated YTHDF1 expression. Under co-culture conditions, ECs transmitted miR-376c into NSCLC cells through Evs, and inhibited the intracellular YTHDF1 expression and the Wnt/β-catenin pathway activation. Rescue experiments revealed that YTHDF1 overexpression reversed the inhibitory role of miR-376c released by EC-Evs in NSCLC cells.

Conclusion:

EC-delivered Evs inhibit YTHDF1 expression and the Wnt/β-catenin pathway induction via miR-376c overexpression, thus inhibiting the malignant phenotypes of NSCLC cells.

[Research Advances of m⁶A RNA Methylation in Non-small Cell Lung Cancer]

m⁶A修饰是真核生物mRNA中最丰富的修饰之一，该过程受m⁶A甲基转移酶和去甲基化酶的共同调控。m⁶A修饰后的RNA能够被m⁶A识别蛋白特异性识别并结合，进而介导RNA的剪接、成熟、出核、降解和翻译等。目前国内外对于m⁶A修饰及其相关蛋白如何参与非小细胞肺癌发生发展的研究，主要集中于细胞恶性增殖、迁移、侵袭、转移和耐药等方面。m⁶A修饰相关蛋白在肺癌组织标本和血液循环肿瘤细胞（circulating tumor cell, CTC）中表达异常，有望成为肺癌诊断和预后判断的潜在分子标志物。本文围绕m⁶A修饰相关蛋白的组成、作用方式、在非小细胞肺癌恶性进展中的生物学功能，以及针对m⁶A修饰的靶向治疗等方面的研究进展进行综述，旨在为非小细胞肺癌的早期临床诊断和靶向药物的开发提供新思路。

N6-methyladenine modification in noncoding RNAs and its function in cancer

Non-coding RNAs are the main component of the extensive transcription results of the mammalian genome. They are not transcribed into proteins but play critical roles in regulating multiple biological processes and affecting cancer progression. m6A modification is one of the most abundant internal RNA modification of mammalian cells, and it involves almost all aspects of RNA metabolism. Recent research revealed tight correlations between m6A modification and ncRNAs and indicated the interaction between m6A and ncRNAs act a pivotal part in the development of cancer. The correlation between m6A modification and ncRNAs provides a new perspective for exploring the potential regulatory mechanism of tumor gene expression, and suggest that m6A modification and ncRNAs may be important prognostic markers and therapeutic targets for multiple cancers. In this review, we summarize the potential regulatory mechanisms between m6A methylation and ncRNAs, highlighting how their relationship affects biological functions in cancer.

Silencing of METTL3 attenuates cardiac fibrosis induced by myocardial infarction via inhibiting the activation of cardiac fibroblasts

Cardiac fibrosis is characterized by the activation of cardiac fibroblasts and accumulation of extracellular matrix. METTL3, a component of methyltransferase complex, participates in multiple biological processes associated with mammalian development and disease progression. However, the role of METTL3 in cardiac fibrosis is still unknown. We performed fibroblasts activation with TGF-β1 (20 ng/mL) in vitro and established in vivo mouse models with lentivirus to assess the effects of METTL3 on cardiac fibroblasts proliferation and collagen formation. Methylated RNA immunoprecipitation (MeRIP) was used to define the potential fibrosis-regulated gene. The expression level of METTL3 was increased in cardiac fibrotic tissue of mice with chronic myocardial infarction and cultured cardiac fibroblats (CFs) treated with TGF-β1. Enforced expression of METTL3 promoted proliferation and fibroblast-to-myofibroblast transition and collagens accumulation, while silence of METTL3 did the opposite. Silence of METTL3 by lentivirus carrying METTL3 siRNA markedly alleviated cardiac fibrosis in MI mice. Transcriptome and N6-methyladenosine (m⁶ A) profiling analyses revealed that the expression and m⁶ A level of collagen-related genes were altered after silence of METTL3. METTL3-mediated m⁶ A modification is critical for the development of cardiac fibrosis, providing a molecular target for manipulating fibrosis and the associated cardiac diseases.

RNA m6A Modification in Cancers: Molecular Mechanisms and Potential Clinical Applications

N⁶-Methyladenosine (m⁶A) RNA modification brings a new dawn for RNA modification researches in recent years. This posttranscriptional RNA modification is dynamic and reversible, and is regulated by methylases ("writers"), demethylases ("erasers"), and proteins that preferentially recognize m⁶A modifications ("readers"). The change of RNA m⁶A modification regulates RNA metabolism in eucaryon, including translation, splicing, exporting, decay, and processing. Thereby the dysregulation of m⁶A may lead to tumorigenesis and progression. Given the tumorigenic role of abnormal m⁶A expression, m⁶A regulators may function as potential clinical therapeutic targets for cancers. In this review, we emphasize on the underlying mechanisms of m⁶A modifications in tumorigenesis and further introduce the potential m⁶A regulators-associated therapeutic targets for tumor therapy.

The m6A epitranscriptome opens a new charter in immune system logic

N6-methyladenosine (m6A), the most prevalent RNA internal modification, is present in most eukaryotic species and prokaryotes. Studies have highlighted an intricate network architecture by which m6A epitranscriptome impacts on immune response and function. However, it was only until recently that the mechanisms underlying the involvement of m6A modification in immune system were uncovered. Here, we systematically review the m6A involvement in the regulation of innate and adaptive immune cells. Further, the interplay between m6A modification and anti-inflammatory, anti-viral and anti-tumour immunity is also comprehensively summarized. Finally, we focus on the future prospects of m6A modification in immune modulation. A better understanding of the crosstalk between m6A modification and immune system is of great significance to reveal new pathogenic pathways and to develop promising therapeutic targets of diseases.

N6-methyladenosine RNA modification in cancer therapeutic resistance: Current status and perspectives

Several strategies, including chemotherapy and radiotherapy, have improved therapeutic outcomes among cancer patients in clinical practice. However, due to their heterogeneity, cancer cells frequently display primary or acquired therapeutic resistance, thereby resulting in treatment failure. The mechanisms underlying cancer therapeutic resistance are complex and varied. Among them, N6-methyladenosine (m6A) RNA modification has gained increasing attention as a potential determinant of therapy resistance within various cancers. In this review, we primarily describe evidence for the effect of the m6A epitranscriptome on RNA homeostasis modulation, which has been shown to alter multiple cellular pathways in cancer research and treatment. Additionally, we discuss the profiles and biological implications of m6A RNA methylation, which is undergoing intensive investigation for its effect on the control of therapeutic resistance.