Methyltransferase-like 3 Expression Research Articles

METTL3-mediated m6A modification enhances lncRNA H19 stability to promote endothelial cell inflammation and pyroptosis to aggravate atherosclerosis.

This study explored the impact of N6-methyladenosine (m6A) modification on the regulation of long noncoding RNA (lncRNA) and atherosclerosis progression. An atherosclerosis cell model was established by treating human aortic endothelial cells (HAECs) with oxidized low-density lipoprotein. Additionally, an atherosclerotic animal model was developed using ApoE-/- C57BL/6 male mice fed a high-fat diet. Both models were employed to assess the expression changes of proteins associated with m6A modification. First, the effect of m6A modification writer protein methyltransferase-like 3 (METTL3) knockdown on changes in the level of pyroptosis in HAECs was investigated, and bioinformatic analysis confirmed that lncRNA H19 (H19) was the potential target of m6A modification. RNA-binding protein immunoprecipitation assays were subsequently performed to explore the interaction between H19 and the m6A writer protein METTL3, as well as the reader protein recombinant insulin-like growth factor 2 mRNA-binding protein 2 (IGF2BP2). Finally, the effect of H19 expression on pyroptosis levels in HAECs was evaluated. In the aortas of atherosclerosis mice, overall m6A levels were significantly elevated compared with controls (p < .05), with METTL3 and METTL14 mRNA and protein levels notably increased (p < .05). Similarly, ox-LDL-treated HAECs showed a significant rise in m6A levels, along with increased METTL3 and METTL14 expression (p < .05). METTL3 knockdown in HAECs led to decreased pyroptosis, as evidenced by reduced lactate dehydrogenase release and lower levels of IL-1β, IL-18, and IL-6 (p < .05). Overexpression of H19 reversed these effects, indicating METTL3's role in promoting atherosclerosis by stabilizing H19 through m6A modification. H19 was the primary target lncRNA molecule of METTL3-mediated m6A modification in the pathogenesis of atherosclerosis. METTL3-mediated m6A modification regulated H19 expression, thereby aggravating atherosclerosis by activating pyroptosis.

Notch-Driven Cholangiocarcinogenesis Involves the Hippo Pathway Effector TAZ via METTL3-m6A-YTHDF1

Background and AimsNotch and TAZ are implicated in cholangiocarcinogenesis, but whether and how these oncogenic molecules interact remain unknown. MethodsThe development of CCA was induced by hydrodynamic tail vein (HDTV) injection of oncogenes (NICD/AKT) to the FVB/NJ mice. CCA xenograft was developed by inoculation of human CCA cells into the livers of SCID mice. Tissues and cells were analyzed using qRT-PCR, Western blotting analyses, Immunohistochemistry, ChIP-qPCR and WST-1 cell proliferation Assay. ResultsOur experimental findings show that TAZ is indispensable in NICD-driven cholangiocarcinogenesis. Notch activation induces the expression of METTL3 (Methyltransferase like-3) which catalyzes N6-methyladenosine (m6A) modification of TAZ mRNA and that this mechanism plays a central role in the crosstalk between Notch and TAZ in CCA cells. Mechanistically, Notch regulates the expression of METTL3 through the binding of NICD to its downstream transcription factor CSL in the promoter region of METTL3. METTL3 in turn mediates m6A modification of TAZ mRNA which is recognized by the m6A reader YTHDF1 to enhance TAZ protein translation. We observed that inhibition of Notch signaling decreased the protein levels of both MELLT3 and TAZ. Depletion of METTL3 by shRNAs or by the next generation GapmeR antisense oligonucleotides (ASOs) decreased the level of TAZ protein and inhibited the growth of human CCA cells in vitro and in mice. ConclusionThis study describes a novel Notch-METTL3-TAZ signaling cascade which is important in CCA development and progression. Our experimental results provide new insight into how the Notch pathway cooperates with TAZ signaling in CCA, and the findings may have important therapeutic implications.

ZNF740 facilitates the malignant progression of hepatocellular carcinoma via the METTL3/HIF‑1A signaling axis.

Hepatocellular carcinoma (HCC) is the second leading cause of cancer‑related death, and efficient treatments to facilitate recovery and enhance long‑term outcomes are lacking. Zinc finger proteins (ZNFs), known as the largest group of transcription factors, have gained interest for their roles in HCC by stimulating the transcription of well‑known tumor‑causing genes. However, the specific roles and molecular mechanisms of ZNF740 in HCC remain unknown. The present study performed bioinformatics analysis and RNA‑sequencing analysis of differentially expressed genes in HCC, detected ZNF740 expression levels in HCC using reverse transcription‑quantitative PCR, western blotting and immunohistochemistry, and explored the effects of ZNF740 on the progression of liver cancer in vitro and in vivo using cellular functionality assays and cell‑derived xenografts. In addition, a dual‑luciferase reporter assay was performed to analyze the binding of ZNF740 with the METTL3 promoter. Furthermore, cell functionality experiments were performed to analyze whether ZNF740 promotes the proliferation of liver cancer cells in a METTL3‑dependent manner. Bioinformatics and immunoprecipitation assays were further used to analyze the molecular mechanism of ZNF740 in liver cancer. The present study demonstrated that ZNF740 expression was upregulated in HCC. Mechanistically, overexpressed ZNF740 interacted with the methyltransferase‑like 3 (METTL3) promoter and increased METTL3 expression, leading to the stabilization of hypoxia‑inducible factor‑1A (HIF1A) mRNA in an N6‑methyladenosine/YTH N6‑methyladenosine RNA‑binding protein 1‑dependent manner. Eventually, the ZNF740/METTL3/HIF1A signaling axis may facilitate the proliferation, invasion and metastasis of liver cancer via METTL3/HIF‑1A signaling. The present findings revealed the important role of ZNF740 and suggested a potential therapeutic approach that might improve clinical therapies for liver cancer.

METTL3 silencing inhibits ferroptosis to suppress ovarian fibrosis in PCOS by upregulating m6A modification of GPX4.

Methyltransferase-like 3 (METTL3) is extensively reported to be involved in organ fibrosis. Ovarian fibrosis is a main characteristic of polycystic ovary syndrome (PCOS). However, the reaction mechanism of METTL3 in PCOS is poorly investigated. This paper was intended to reveal the role and the mechanism of METTL3 in PCOS. Animal and cell models of PCOS were induced by dehydroepiandrosterone (DHEA). H&E staining was performed to detect the pathological alterations in ovary tissues. Masson staining, immunofluorescence, along with western blot measured fibrosis both in vitro and in vivo. To evaluate estrous cycle, vaginal smear was performed. Lipid peroxidation and ferroptosis were evaluated by MDA assay kits, GSH assay kits, immunohistochemistry, Prussian blue staining and western blot. qRT-PCRand western blot were adopted to estimate METTL3 and GPX4 expression. The m6A and hormone secretion levels were respectively assessed by m6A RNA Methylation Quantitative Kit and corresponding kits. The interaction between METTL3 and GPX4 was testified by immunoprecipitation. The fibrosis and ferroptosis were aggravated and m6A and METTL3 expression were increased in ovarian tissues of DHEA-induced PCOS mice. METTL3 silencing alleviated pathological changes, affected hormone secretion level, and repressed fibrosis, lipid peroxidation and ferroptosis in the ovarian tissues of PCOS mice. In vitro, DHEA stimulation increased m6A and METTL3 expression and induced ferroptosis and fibrosis. METTL3 knockdown promoted GPX4 expression in DHEA-induced granulosa cells by m6A modification and restrained DHEA-induced fibrosis, lipid peroxidation and ferroptosis in granulosa cells via elevating GPX4. METTL3 silence inhibited ovarian fibrosis in PCOS, which was mediated through suppressing ferroptosis by upregulating GPX4 in m6A-dependent manner.

METTL3 Regulates the Translation of Oncogene Myc through m6A Modification and Promotes the Occurrence and Development of Cervical Cancer.

Cervical cancer (CC) is one of the major types of gynecological cancer, with a high global incidence and mortality rate. Methyltransferase-like 3 (METTL3), a key constituent of methyltransferase, plays a crucial role in various biological processes. Still, only a rare report has been made on its involvement in the progression of CC. Therefore, this study aims to investigate the impact of METTL3 in CC and its molecular mechanisms. Gene expression datasets about CC were obtained from the Gene Expression Omnibus (GEO) database, and the expression of METTL3 and Myc was analyzed. Cell viability was detected after METTL3 knockdown in HeLa and SiHa cells, followed by cell counting Kit-8 (CCK-8) assays. The relative expression of METTL3 and Myc was detected via real-time quantitative PCR (qPCR) assays, and the protein expression was determined using Western blot. Meanwhile, cell invasion and migration capabilities were assessed utilizing transwell assays, and cell proliferation was detected using the EdU experiment. Furthermore, RNA methylation immunoprecipitation-qPCR detection was performed to determine the expression of Myc after N6-methyladenosine (m6A) modification. Analysis of the GEO database indicated elevated expression of METTL3 and Myc in CC tissues. Patients with high METTL3 expression had shorter disease-free survival, and patients with high Myc expression had shorter overall survival. Following the knockdown of METTL3, there was a significant reduction in the viability, proliferation, invasion, and migration abilities of HeLa and SiHa cells. Besides, the expression of METTL3 and Myc mRNAs and proteins was greatly reduced. The level of m6A Myc decreased significantly after METTL3 knockdown. METTL3 plays an important role in regulating cervical cancer cells. METTL3 promotes CC development through m6A modification to regulate the expression of the oncogene Myc.

METTL3-STAT5B interaction facilitates the co-transcriptional m6A modification of mRNA to promote breast tumorigenesis

Enhanced expression of methyltransferase-like 3 (METTL3) promotes the m6A modification of specific mRNAs, contributing to breast tumorigenesis. While the mRNA substrates targeted by METTL3 are well characterized, the factors dictating the selection of these specific mRNA remain elusive. This study aimed to examine the regulatory role of the transcription factor STAT5B in METTL3-induced m6A modification. METTL3 specifically interacts with STAT5B in response to mitogenic stimulation by epidermal growth factor (EGF). Chromatin immunoprecipitation and CRISPR/Cas9 mutagenesis showed that STAT5B recruits METTL3 to gene promoters like CCND1, where METTL3 interacts with RPB1, dependent on CDK9-mediated RPB1 (Ser2) phosphorylation during transcription elongation. Inhibition and depletion of either STAT5B or CDK9 prevented the EGF-induced m6A modification of CCND1. The translation efficiency of CCND1 was increased following m6A modification, thereby increasing cell proliferation. STAT5B facilitated METTL3-induced tumor formation by increasing CCND1 expression in an orthotopic mouse model. In clinical context, a positive correlation was observed between p-STAT5B and METTL3 expression in high-grade breast tumors. This study elucidates a novel mechanism that underlies the specificity of m6A modification in breast cancer cells, thereby underscoring its potential therapeutic value.

LINC01410 accelerates the invasion of trophoblast cells by modulating METTL3/Fas.

Insufficient trophoblast invasion, culminating in suboptimal uterine spiral artery remodeling, is pinpointed as a pivotal contributor to preeclampsia (PE) development. LINC01410 has been documented to be increased in various neoplasms, and is significantly associated with the invasive capabilities of tumor cells. Nonetheless, its function and the mechanisms in the pathogenesis of PE require further investigation. LINC01410 and methyltransferase-like 3 (METTL3) were ectopically expressed in HTR-8/Svneo cells via lentiviral transduction. Subsequently, the cells' invasive capabilities and apoptosis rates were evaluated employing Transwell assays and flow cytometry, respectively. The interplay between LINC01410 and METTL3, alongside the m6A methylation of FAS, was probed through RNA immunoprecipitation (RIP). Additionally, the association between FAS and METTL3 was elucidated via Coimmunoprecipitation (Co-IP) assays. The protein level of NF-κB, BAX, and BCL-2 in LINC01410-overexpressing cells was detected by Western blot. Our findings revealed that LINC01410 elevation increased the invasive ability of HTR-8/Svneo cells, directly impacting METTL3 then leading to its reduced expression. Conversely, heightened METTL3 expression mitigated invasiveness while enhancing apoptosis in these cells. Moreover, METTL3's interaction with FAS led to increased FAS expression, subject to m6A methylation. A surge in LINC01410 markedly decreased both mRNA and protein levels of FAS. Furthermore, LINC01410 overexpression significantly reduced NF-κB and BAX protein levels while augmenting BCL-2. Upregulation of LINC01410 expression promotes trophoblast cell invasion by inhibiting FAS levels through modified m6A alteration and suppressing the NF-κB pathway. These findings underscore the pivotal role of LINC01410 in regulating trophoblast cell invasion and propose it as a promising therapeutic strategy for preventing or alleviating PE. This offers valuable insights for the clinical treatment of PE, for which definitive targeted therapy methods are currently lacking.

METTL3 aggravates cell damage induced by Streptococcus pneumoniae via the NEAT1/CTCF/MUC19 axis.

Disruption of the alveolar barrier can trigger acute lung injury. This study elucidated the association of methyltransferase-like 3 (METTL3) with Streptococcus pneumoniae (SP)-induced apoptosis and inflammatory injury of alveolar epithelial cells (AECs). AECs were cultured and then infected with SP. Furthermore, the expression of METTL3, interleukin (IL)-10, IL-6, tumor necrosis factor-alpha (TNF-α), monocyte chemoattractant protein-1 (MCP-1), long noncoding RNA nuclear paraspeckle assembly transcript 1 (NEAT1), mucin 19 (MUC19), N6-methyladenosine (m6A), and NEAT1 after m6A modification were detected by qRT-PCR, Western blot, and enzyme-linked immunosorbent, m6A quantification, and methylated RNA immunoprecipitation-qPCR analyses, respectively. Moreover, the subcellular localization of NEAT1 was analyzed by nuclear/cytosol fractionation assay, and the binding between NEAT1 and CCCTC-binding factor (CTCF) was also analyzed. The results of this investigation revealed that SP-induced apoptosis and inflammatory injury in AECs and upregulated METTL3 expression. In addition, the downregulation of METTL3 alleviated apoptosis and inflammatory injury in AECs. METTL3-mediated m6A modification increased NEAT1 and promoted its binding with CTCF to facilitate MUC19 transcription. NEAT1 or MUC19 overexpression disrupted their protective role of silencing METTL3 in AECs, thereby increasing apoptosis and inflammatory injury. In conclusion, this is the first study to suggest that METTL3 aggravates SP-induced cell damage via the NEAT1/CTCF/MUC19 axis.

METTL3 shapes m6A epitranscriptomic landscape for successful human placentation.

Methyltransferase-like 3 (METTL3), the catalytic enzyme of methyltransferase complex for m6A methylation of RNA, is essential for mammalian development. However, the importance of METTL3 in human placentation remains largely unexplored. Here, we show that a fine balance of METTL3 function in trophoblast cells is essential for successful human placentation. Both loss-of and gain-in METTL3 functions are associated with adverse human pregnancies. A subset of recurrent pregnancy losses and preterm pregnancies are often associated with loss of METTL3 expression in trophoblast progenitors. In contrast, METTL3 is induced in pregnancies associated with fetal growth restriction (FGR). Our loss of function analyses showed that METTL3 is essential for the maintenance of human TSC self-renewal and their differentiation to extravillous trophoblast cells (EVTs). In contrast, loss of METTL3 in human TSCs promotes syncytiotrophoblast (STB) development. Global analyses of RNA m6A modification and METTL3-RNA interaction in human TSCs showed that METTL3 regulates m6A modifications on the mRNA molecules of critical trophoblast regulators, including GATA2, GATA3, TEAD1, TEAD4, WWTR1, YAP1, TFAP2C and ASCL2, and loss of METTL3 leads to depletion of mRNA molecules of these critical regulators. Importantly, conditional deletion of Mettl3 in trophoblast progenitors of an early post-implantation mouse embryo also leads to arrested self-renewal. Hence, our findings indicate that METLL3 is a conserved epitranscriptomic governor in trophoblast progenitors and ensures successful placentation by regulating their self-renewal and dictating their differentiation fate.

RNA methylation machinery and m6A target genes as circulating biomarkers of ulcerative colitis and Crohn’s disease: Correlation with disease activity, location, and inflammatory cytokines

Accurate diagnosis of ulcerative colitis (UC) and Crohn’s disease (CD), the main subtypes of inflammatory bowel disease (IBD), has been challenging due to the constraints of the current techniques. N6-methyl adenosine (m6A) regulators have evolved as key players in IBD pathogenesis; however, their relation to its clinical setting is largely unexplored. This study investigated the potential of selected RNA methylation machinery and m6A target genes as serum biomarkers of UC and CD, their predictive and discriminating capabilities, and their correlations with laboratory data, interleukin (IL)-6, interferon-γ, disease activity scores, and pathological features. Fifty UC and 45 CD patients, along with 30 healthy volunteers were enlisted. The mRNA expression levels of the m6A writers methyltransferase-like 3 (METTL3) and Wilms-tumor associated protein (WTAP), and the reader YTH domain family, member 1 (YTHDF1), along with the m6A candidate genes sex determining region Y-box 2 (SOX2), hexokinase 2 (HK2), and ubiquitin-conjugating enzyme E2 L3 (UBE2L3) were upregulated in UC patients, whereas only METTL3, HK2, and UBE2L3 were upregulated in CD patients versus controls. Serum WTAP (AUC = 0.94, 95 %CI = 0.874–1.006) and HK2 (AUC = 0.911, 95 %CI = 0.843–0.980) expression levels showed excellent diagnostic accuracy for UC, METTL3 showed excellent diagnostic accuracy for CD (AUC = 0.91, 95 %CI = 0.828–0.992), meanwhile, WTAP showed excellent discriminative power between the two diseases (AUC = 0.91, 95 %CI = 0.849–0.979). Multivariate logistic analysis unveiled the association of METTL3 and UBE2L3 expression with the risk of CD and UC diagnosis, respectively, controlled by age and sex as confounders. Remarkable correlations were recorded between the gene expression of studied m6A regulators and targets in both diseases. Among UC patients, serum METTL3 and WTAP were correlated with UC extent/type, while WTAP was correlated with IL-6. Among CD patients, serum METTL3 and HK2 were correlated with CD activity index (CDAI) and CD location. In conclusion, m6A regulators and target genes are distinctly expressed in UC and CD clinical samples, correlate with disease activity and extent/location, and could serve as a novel approach to empower the diagnosis and stratification of IBD subtypes.

METTL3 regulates M6A methylation-modified EBV-pri-miR-BART3-3p to promote NK/T cell lymphoma growth

OBJECTIVEN6-methyladenosine (M6A) is the most prevalent epigenetic alteration. Methyltransferase-like 3 (METTL3) is a key player in the control of M6A modification. Methyltransferase promote the processing of mature miRNA in an M6A-dependent manner, thereby participating in disease occurrence and development. However, the regulatory mechanism of M6A in NK/T cell lymphoma (NKTCL) remains unclear. PATIENTS AND METHODSWe determined the expression of METTL3 and its correlation with clinicopathological features using qRT-PCR and immunohistochemistry. We evaluated the effects of METTL3 on NKTCL cells using dot blot assay, CCK8 assay and subcutaneous xenograft experiment. We then applied M6A sequencing combined with gene expression omnibus data to screen candidate targets of METTL3. Finally, we investigated the regulatory mechanism of METTL3 in NKTCL by methylated RNA immunoprecipitation and RNA immunoprecipitation (RIP) assays. RESULTSWe demonstrated that METTL3 was highly expressed in NKTCL cells and tissues and indicated poor prognosis. The METTL3 expression was associated with NKTCL survival. Functionally, METTL3 promoted the proliferation capability of NKTCL cells in vitro and in vivo. Furthermore, EBV-miR-BART3-3p was identified as the downstream effector of METTL3, and silencing EBV-miR-BART3-3p inhibited the proliferation of NKTCL. Finally, we confirmed that PLCG2 as a target gene of EBVmiR-BART3-3p by relative assays. CONCLUSIONSWe identified that METTL3 is significantly up-regulated in NKTCL and promotes NKTCL development. M6A modification contributes to the progression of NKTCL via the METTL3/EBV-miR-BART3-3p/PLCG2 axis. Our study is the first to report that M6A methylation has a critical role in NKTCL oncogenesis, and could be a potential target for NKTCL treatment.

METTL3 promotes the osteogenic differentiation of human periodontal ligament cells by increasing YAP activity via IGF2BP1 and YTHDF1-mediated m6A modification.

N6-Methyladenosine (m6A) has been confirmed to play a dynamic role in osteoporosis and bone metabolism. However, whether m6A is involved in the osteogenic differentiation of human periodontal ligament cells (hPDLCs) remains unclear. The present study aimed to verify the role of methyltransferase-like 3 (METTL3)-mediated m6A modification in the osteogenic differentiation of hPDLCs. The METTL3, Runx2, Osx, and YAP mRNA expression was determined by qPCR. METTL3, RUNX2, OSX, YTHDF1, YAP, IGF2BP1, and eIF3a protein expression was measured by Western blotting and immunofluorescence assays. The levels of m6A modification were evaluated by methylated RNA immunoprecipitation (MeRIP) and dot blot analyses. MeRIP-seq and RNA-seq were used to screen potential candidate genes. Nucleic acid and protein interactions were detected by immunoprecipitation. Alizarin red staining was used to evaluate the osteogenic differentiation of hPDLCs. Gene transcription and promoter activities were assessed by luciferase reporter assays (n ≥ 3). The expression of METTL3 and m6A modifications increased synchronously with the osteogenic differentiation of hPDLCs (p = .0016). YAP was a candidate gene identified by MeRIP-seq and RNA-seq, and its mRNA and protein expression levels were simultaneously increased. METTL3 increased the m6A methylated IGF2BP1-mediated stability of YAP mRNA (p = .0037), which in turn promoted osteogenic differentiation (p = .0147). Furthermore, METTL3 increased the translation efficiency of YAP by recruiting YTHDF1 and eIF3a to the translation initiation complex (p = .0154), thereby promoting the osteogenic differentiation of hPDLCs (p = .0012). Our study revealed that METTL3-initiated m6A mRNA methylation promotes osteogenic differentiation of hPDLCs by increasing IGF2BP1-mediated YAP mRNA stability and recruiting YTHDF1 and eIF3a to the translation initiation complex to increase YAP mRNA translation. Our findings reveal the mechanism of METTL3-mediated m6A modification during hPDLC osteogenesis, providing a potential therapeutic target for periodontitis and alveolar bone defects.

METTL3 as a potential predictive biomarker for immunotherapy response in metastatic head and neck cancer.

e18019 Background: Head and neck squamous cell carcinoma (HNSCC) that has metastasized presents a significant challenge for cancer treatment, requiring innovative approaches to predict immunotherapy response. Methyltransferase-like 3 (METTL3), a key component of the m6A RNA methylation machinery, has been shown to have various roles in cancer, including its potential impact on immunotherapy responses. In this study, we aim to explore the expression and related function of METTL3 in metastatic HNSCC. Methods: We investigated the expression level and its clinicopathological significance of METTL3 using The Cancer Genome Atlas Head-Neck Squamous Cell Carcinoma (TCGA-HNSC) datasets. Further validation of the METTL3 mRNA and protein expression were carried out with real-time PCR and Western blot on tissues from 112 cases of HNSCC patients. In addition, the functional role of METTL3 was investigated in vitro studies. The treatment response prediction values of METTL3 in metastatic HNSCC were calculated using ROC-plotter. Results: Our investigation revealed a significant overexpression of METTL3 in HNSCC tissue samples than in normal tissues ( p &lt; 0.001). The high expression of METTL3 was significantly correlated with nodal metastasis, advanced cancer stages, and higher tumor grades in HNSCC samples, indicating that METTL3 plays an important role in driving HNSCC progression and aggressiveness. The functional study revealed intricate connections between METTL3 and immune regulatory genes expression, highlighting its potential to influence the tumor immune microenvironment. Silencing or pharmacological inhibition of METTL3 by METTL3 inhibitor STM2457 reduced tumorigenic activity through decreasing PD-L1 expression. ROC-plotter calculations showed that the high METTL3 expression predicted powerful immunotherapy (AUC=0.588, p=6.3e-06) in metastatic HNSCC patients. Conclusions: In conclusion, METTL3 appears to be a promising predictive biomarker for the response to immunotherapy in patients with metastatic HNSCC. This research provides valuable insights into the multifaceted role of METTL3 and promising therapeutic response predictor in metastatic HNSCC.

Synergistic antitumor activity of METTL3 peptide degrader and immune checkpoint inhibitor in advanced urothelial cancer.

e14623 Background: In patients afflicted with advanced urothelial carcinoma (aUC), the durable response rate to immune checkpoint inhibitor (ICI) is approximately 20%. Recent study showed the pivotal role of N6-methyladenosine (m6A) methyltransferase-like 3 (METTL3) in immune escape and the progression of aUC. This study aimed to develop a novel METTL3 peptide degrader RKL and investigate its synergistic effects and underlying mechanisms in combination with ICI for aUC. Methods: Methyltransferase expression profiles were scrutinized using The Cancer Genome Atlas database; while the prognostic implications of METTL3 expression in response to ICI were analyzed in the IMvigor210 cohort study. Single-cell RNA sequencing (scRNA-seq) was employed to elucidate the mechanistic insights. The METTL3 peptide degrader RKL was synthesized using Fmoc solid-phase peptide synthesis and purified with high-performance liquid chromatography. In vivo and in vitro experiments were conducted to assess the impact of RKL, ICI, and their combination on aUC inhibition. Results: In aUC, METTL3 exhibited the most significant up-regulation among m6A methyltransferases, while METTL14 and WTAP showed down-regulated expression. In the IMvigor210 cohort study, aUC patients with elevated METTL3 expression and treated with ICI demonstrated a poorer prognosis. scRNA-seq revealed that METTL3 upregulation promoted the expression of genes regulating cancer-associated fibroblast proliferation, contributing to enhanced tumor resistance to immunotherapy. RKL demonstrated high toxicity to urothelial carcinoma cell lines, inhibiting their proliferative, migratory, and invasive capacities in vitro. The combined treatment of RKL and ICI significantly reduced tumor volume (P&lt;0.001), with a complete response achieved in 87.5% (7/8) of mice in the combination group, 12.5% (1/8) in the RKL group, and 25.0% (2/8) in the ICI group. Conclusions: METTL3 overexpression in aUC is associated with immune escape and resistance to ICI therapy. The METTL3 peptide degrader RKL, when combined with ICI, demonstrates synergistic antitumor effects in aUC, warranting further exploration in clinical research.

METTL3's role in cervical cancer development through m6A modification.

N6-methylated adenosine (m6A) is a crucial RNA modification in eukaryotes, particularly in cancer. However, its role in cervical cancer (CC) is unclear. We aimed to elucidate the part of m6A in CC by analyzing methyltransferase-like 3 (METTL3) expression, identifying downstream targets, and exploring the underlying mechanism. We assessed METTL3 expression in CC using western blotting, quantitative polymerase chain reaction (qPCR), and immunohistochemistry. Invitro and invivo experiments examined METTL3's role in CC. We employed RNA sequencing, methylated RNA immunoprecipitation sequencing, qPCR, and RNA immunoprecipitation qPCR to explore METTL3's mechanism in CC. METTL3 expression was upregulated in CC, promoting cell proliferation and metastasis. METTL3 knockdown inhibited human cervical cancer by inactivating AKT/mTOR signaling pathway. METTL3-mediated m6A modification was observed in CC cells, targeting phosphodiesterase 3A (PDE3A). METTL3 catalyzed m6A modification on PDE3A mRNA through YTH domain family protein 3 (YTHDF3). Our study indicated the mechanism of m6A modification in CC and suggested the METTL3/YTHDF3/PDE3A axis as a potential clinical target for CC treatment.

METTL3 inhibits BMSC apoptosis and facilitates osteonecrosis repair via an m6A-IGF2BP2-dependent mechanism

Hypoxia-induced apoptosis of bone marrow mesenchymal stem cells (BMSCs) limits the efficacy of their transplantation for steroid-induced osteonecrosis of the femoral head (SONFH). As apoptosis and RNA methylation are closely related, exploring the role and mechanism of RNA methylation in hypoxic apoptosis of BMSCs is expected to identify new targets for transplantation of BMSCs for SONFH and enhance transplantation efficacy. We performed methylated RNA immunoprecipitation sequencing (MeRIP-seq) combined with RNA-seq on a hypoxia-induced apoptosis BMSC model and found that the RNA methyltransferase-like 3 (METTL3) is involved in hypoxia-induced BMSC apoptosis. The expression of METTL3 was downregulated in BMSCs after hypoxia and in BMSCs implanted in osteonecrosis areas. Knockdown of METLL3 under normoxic conditions promoted apoptosis of BMSCs. In contrast, overexpression of METTL3 promoted the survival of BMSCs under hypoxic conditions, and overexpression of METTL3 promoted the survival of BMSCs in the osteonecrosis area and the repair of the osteonecrosis area. Regarding the mechanism, the m6A levels of the mRNAs of anti-apoptotic genes Bcl-2, Mcl-1, and BIRC5 were significantly increased upon the overexpression of METTL3 under hypoxic conditions, which promoted the binding of Bcl-2, Mcl-1, and BIRC5 mRNAs to IGF2BP2, enhanced the mRNA stability, and increased the protein expression of the three anti-apoptotic genes. In conclusion, overexpression of METTL3 promoted m6A modification of mRNAs of Bcl-2, Mcl-1, and BIRC5, promoted the binding of IGF2BP2 to the above-mentioned mRNAs, enhanced mRNA stability, inhibited hypoxia-induced BMSC apoptosis, and promoted repair of SONFH, thereby providing novel targets for transplantation of BMSCs for SONFH.

METTL3 mediates SOX5 m6A methylation in bronchial epithelial cells to attenuate Th2 cell differentiation in T2 asthma

ObjectiveAsthma, a chronic inflammatory disease in which type 2 T helper cells (Th2) play a causative role in the development of T2 asthma. N6-methyladenosine (m6A) modification, an mRNA modification, and methyltransferase-like 3 (METTL3) is involved in the development of T2 asthma by inhibiting Th2 cell differentiation. Sex determining region Y-box protein 5 (SOX5) is involved in regulating T cell differentiation, but its role in T2 asthma was unclear. The objective of this study was to explore the role of METTL3 and SOX5 in T2 asthma and whether there is an interaction between the two. Materials and methodsAdults diagnosed with T2 asthma (n = 14) underwent clinical information collection and pulmonary function tests. In vivo and in vitro T2 asthma models were established using female C57BL/6 mice and human bronchial epithelial cells (HBE). The expressions of METTL3 and SOX5 were detected by Western blot and qRT-PCR and Western blot. Th2 cell differentiation was determined by flow cytometry and IL-4 level was detected by ELISA. m6A methylation level was determined by m6A quantitative assay. The relationship between METTL3 expression and clinical parameters was determined by Spearman rank correlation analysis. The function of METTL3 and SOX5 genes in asthma was investigated in vitro and in vivo. The RNA immunoprecipitation assay detected the specific interaction between METTL3 and SOX5. ResultsPatients with T2 asthma displayed lower METTL3 levels compared to healthy controls. Within this group, a negative correlation was observed between METTL3 and Th2 cells, while a positive correlation was noted between METTL3 and clinical parameters as well as Th1 cells. In both in vitro and in vivo models representing T2 asthma, METTL3 levels decreased significantly, while SOX5 levels showed the opposite trend. Overexpression of METTL3 gene in HBE cells significantly inhibited Th2 cell differentiation and increased m6A methylation activity. From a mechanism perspective, low METTL3 negatively regulates SOX5 expression through m6A modification dependence, while high SOX5 expression is positively associated with T2 asthma severity. Cell transfection experiments confirmed that METTL3 regulates Th2 cell differentiation and IL-4 release through SOX5. ConclusionsOverall, our results indicate that METTL3 alleviates Th2 cell differentiation in T2 asthma by modulating the m6A methylation activity of SOX5 in bronchial epithelial cells. This mechanism could potentially serve as a target for the prevention and management of T2 asthma.

Circ_0027791 contributes to the growth and immune evasion of hepatocellular carcinoma via the miR-496/programmed cell death ligand 1 axis in an m6A-dependent manner.

Emerging evidence indicates the critical roles of circular RNAs in the development of multiple cancers, containing hepatocellular carcinoma (HCC). Herein, our present research reported the biological function and mechanism of circ_0027791 in HCC progression. Circ_0027791, microRNA-496 (miR-496), programmed cell death ligand 1 (PDL1), and methyltransferase-like 3 (METTL3) levels were detected by real-time quantitative polymerase chain reaction (RT-qPCR). Cell viability, proliferation, invasion, and sphere formation ability were detected using 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide, 5-ethynyl-2'-deoxyuridine, transwell, and sphere formation assays. Macrophage polarization was detected using flow cytometry assay. To understand the role of circ_0027791 during the immune escape, HCC cells were cocultured with peripheral blood mononuclear cells or cytokine-induced killer (CIK) cells in vitro. A xenograft mouse model was applied to assess the function of circ_0027791 in vivo. After prediction using circinteractome and miRDB, the binding between miR-496 and circ_0027791 or PDL1 was validated based on a dual-luciferase reporter assay. Interaction between METTL3 and circ_0027791 was determined using methylated RNA immunoprecipitation (MeRIP)-qPCR, RIP-qPCR, and RNA pull-down assays. Circ_0027791, PDL1, and METTL3 expression were upregulated, and miR-496 was decreased in HCC patients and cells. Moreover, circ_0027791 knockdown might repress proliferation, invasion, sphere formation, M2 macrophage polarization, and antitumor immune response. Circ_0027791 knockdown repressed HCC tumor growth in vivo. In mechanism, circ_0027791 functioned as a sponge for miR-496 to increase PDL1 expression. In addition, METTL3 mediated the m6A methylation of circ_0027791 and stabilized its expression. METTL3-induced circ_0027791 facilitated HCC cell progression partly regulating the miR-496/PDL1 axis, which provided a new prognostic and therapeutic marker for HCC.

Intestinal Epithelial Cell-specific Knockout of METTL3 Aggravates Intestinal Inflammation in CLP Mice by Weakening the Intestinal Barrier.

Many studies have demonstrated that the expression of methyltransferase- like 3 (METTL3) is altered in various inflammatory diseases. Its specific mechanistic role in the intestinal inflammatory response during sepsis remains limited and requires further investigation. Explore the potential mechanism of METTL3 in the intestinal inflammatory response during sepsis. Immunohistochemical analysis was utilized to detect the expression of METTL3 in the necrotic intestine of patients with intestinal necrosis and the small intestine of cecal ligation and puncture (CLP) mice. Mice were subjected to the CLP and Sham surgeries, intestine tissue was harvested and performed HE staining, and ELISA to examine intestinal inflammatory responses, while TUNEL staining was applied to detect intestinal cell apoptosis. Additionally, ELISA was used to detect diamine oxidase (DAO) and intestinal fatty acid binding protein (I-FABP) levels in intestinal tissue. Immunohistochemistry and RT-qPCR were also employed to examine the mRNA and protein expression levels of Zona Occludens 1 (ZO-1) and Claudin-1. Finally, transcriptomic sequencing was performed on the small intestine tissues of METTL3 Knock-out (KO) and Wild-type (WT) mice in response to sepsis. METTL3 exhibited lower expression level in the necrotic intestine of patients and the small intestine of CLP mice. Loss of METTL3 in CLP mice triggered significantly higher expression of TNF-α and IL-18, down-regulated expression of ZO-1 and claudin-1, and decreased expression of DAO and I-FABP in the intestinal tissue. KEGG enrichment analysis showed that the differential genes were significantly enriched in immune-related pathways. This study reveals a novel mechanism responsible for exacerbated intestinal inflammation orchestrated by METTL3. Particularly, METTL3 null mice displayed decreased ZO- 1 and Claudin-1 expression, which largely hampered intestinal epithelial barrier function, resulting in bacterial and toxin translocation and intestinal immune activation and inflammation against sepsis.

METTL3-mediated the m6A modification of SF3B4 facilitates the development of non-small cell lung cancer by enhancing LSM4 expression.

Splicing factor B subunit 4 (SF3B4) has been confirmed to participate in the progression of many cancers and is considered to be a potential target for non-small cell lung cancer (NSCLC). Thus, the role and molecular mechanism of SF3B4 in NSCLC progression deserves further study. Quantitative real-time PCR and western blot were employed to detect the mRNA and protein levels of SF3B4, Sm-like protein 4 (LSM4) and methyltransferase-like 3 (METTL3). Cell proliferation, apoptosis, invasion, migration and stemness were tested by cell counting kit-8, colony formation, flow cytometry, transwell, wound healing, and sphere formation assays. The interaction between SF3B4 and METTL3 or LSM4 was confirmed by MeRIP, RIP and Co-IP assays. Mice xenograft models were constructed to assess the effects of METTL3 and SF3B4 on NSCLC tumorigenesis. SF3B4 had high expression in NSCLC tissues and was associated with the shorter overall survival of NSCLC patients. Knockdown of SF3B4 suppressed NSCLC cell proliferation, invasion, migration and stemness, while inducing apoptosis. METTL3 promoted SF3B4 mRNA stability by m6A modification, and its knockdown inhibited NSCLC cell growth, metastasis and stemness by downregulating SF3B4. SF3B4 could interact with LSM4, and sh-SF3B4-mediated the inhibition on NSCLC cell functions could be reversed by LSM4 overexpression. In addition, reduced METTL3 expression restrained NSCLC tumor growth, and this effect was reversed by SF3B4 overexpression. METTL3-stablized SF3B4 promoted NSCLC cell growth, metastasis and stemness via positively regulating LSM4.