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The energy metabolic rearrangement of triple‐negative breast cancer (TNBC) from oxidative phosphorylation to aerobic glycolysis is a significant biological feature and can promote the malignant progression. However, there is little knowledge about the functional mechanisms of methyltransferase‐like protein 14 (METTL14) mediated contributes to TNBC malignant progression. Our study found that METTL14 expression was significantly upregulated in TNBC tissues and cell lines. Silencing METTL14 significantly inhibited TNBC cell growth and invasion in vitro, as well as suppressed tumour growth. Mechanically, METTL14 was first found to activate miR‐29c‐3p through m6A and regulate tripartite motif containing 9 (TRIM9) to promote ubiquitination of pyruvate kinase isoform M2 (PKM2) and lead to its transition from tetramer to dimer, resulting in glucose metabolic reprogramming from oxidative phosphorylation to aerobic glycolysis to promote the progress of TNBC. Taken together, these findings reveal important roles of METTL14 in TNBC tumorigenesis and energy metabolism, which might represent a novel potential therapeutic target for TNBC.

In the original text, this work was supported by the following institutes: (1) National Key Research and Development Program of China (2018YFC1004900, 2018YFC1005002); (2) National Natural Science Foundation of China (81672350, 81872225, 81871988, No.82160578, No.81760438). [...]the funding of National Key Research and Development Program of China (2018YFC1004900, 2018YFC1005002) and Natural Science Foundation of China (81672350, 81872225, 81871988) should be deleted. A correction has been made to Materials and Methods, CD34+ Humanized Mouse Models, the description in this section corrected appears below: hPBMC+ Humanized mouse models “hPBMC+ humanized NCG mice were purchased from the Model Animal Research Center of Nanjing University and were constructed as previously reported (25).

Aims: The N6-methyladenosine (m6A) modification plays an important role in various biological processes, but its role in atherosclerosis remains unknown. The aim of this study was to investigate the role and mechanism of m6A modification in endothelial cell inflammation and its influence on atherosclerosis development. Methods: We constructed a stable TNF-α-induced endothelial cell inflammation model and assessed the changes in the expression of m6A modification-related proteins to identify the major factors involved in this process. The m6A-modified mRNAs were identified by methylated RNA immunoprecipitation (RIP) sequencing and forkhead box O1 (FOXO1) was selected as a potential target. Through cytological experiments, we verified whether methyltransferase-like 14 (METTL14) regulates FOXO1 expression by regulating m6A-dependent mRNA and protein interaction. The effect of METTL14 on atherosclerosis development in vivo was verified using METTL14 knockout mice. Results: These findings confirmed that METTL14 plays major roles in TNF-α-induced endothelial cell inflammation. During endothelial inflammation, m6A modification of FOXO1, an important transcription factor, was remarkably increased. Moreover, METTL14 knockdown significantly decreased TNF-α-induced FOXO1 expression. RIP assay confirmed that METTL14 directly binds to FOXO1 mRNA, increases its m6A modification, and enhances its translation through subsequent YTH N6-methyladenosine RNA binding protein 1 recognition. Furthermore, METTL14 was shown to interact with FOXO1 and act directly on the promoter regions of VCAM-1 and ICAM-1 to promote their transcription, thus mediating endothelial cell inflammatory response. In vivo experiments showed that METTL14 gene knockout significantly reduced the development of atherosclerotic plaques. Conclusion: METTL14 promotes FOXO1 expression by enhancing its m6A modification and inducing endothelial cell inflammatory response as well as atherosclerotic plaque formation. Decreased expression of METTL14 can inhibit endothelial inflammation and atherosclerosis development. Therefore, METTL14 may serve as a potential target for the clinical treatment of atherosclerosis.

Spermatogenesis is a differentiation process during which diploid spermatogonial stem cells (SSCs) produce haploid spermatozoa. This highly specialized process is precisely controlled at the transcriptional, posttranscriptional, and translational levels. Here we report that N -methyladenosine (m A), an epitranscriptomic mark regulating gene expression, plays essential roles during spermatogenesis. We present comprehensive m A mRNA methylomes of mouse spermatogenic cells from five developmental stages: undifferentiated spermatogonia, type A spermatogonia, preleptotene spermatocytes, pachytene/diplotene spermatocytes, and round spermatids. Germ cell-specific inactivation of the m A RNA methyltransferase Mettl3 or Mettl14 with Vasa-Cre causes loss of m A and depletion of SSCs. m A depletion dysregulates translation of transcripts that are required for SSC proliferation/differentiation. Combined deletion of Mettl3 and Mettl14 in advanced germ cells with Stra8-GFPCre disrupts spermiogenesis, whereas mice with single deletion of either Mettl3 or Mettl14 in advanced germ cells show normal spermatogenesis. The spermatids from double-mutant mice exhibit impaired translation of haploid-specific genes that are essential for spermiogenesis. This study highlights crucial roles of mRNA m A modification in germline development, potentially ensuring coordinated translation at different stages of spermatogenesis.

The inflammatory response of macrophages has been reported to play a critical role in atherosclerosis. The inflammatory state of macrophages is modified by epigenetic reprogramming. m 6 A RNA methylation is an epigenetic modification of RNAs. However, little is known about the potential roles and underlying mechanisms of m 6 A modification in macrophage inflammation. Herein, we showed that the expression of the m 6 A modification “writer” Mettl14 was increased in coronary heart disease and LPS-stimulated THP-1 cells. Knockdown of Mettl14 promoted M2 polarization of macrophages, inhibited foam cell formation and decreased migration. Mechanistically, the expression of Myd88 and IL-6 was decreased in Mettl14 knockdown cells. Through m 6 A modification, Mettl14 regulated the stability of Myd88 mRNA. Furthermore, Myd88 affected the transcription of IL-6 via the distribution of p65 in nuclei rather than directly regulating the expression of IL-6 through m 6 A modification. In vivo, Mettl14 gene knockout significantly reduced the inflammatory response of macrophages and the development of atherosclerotic plaques. Taken together, our data demonstrate that Mettl14 plays a vital role in macrophage inflammation in atherosclerosis via the NF-κB/IL-6 signaling pathway, suggesting that Mettl14 may be a promising therapeutic target for the clinical treatment of atherosclerosis.

Background N6-methyladenosine (m 6 A) RNA methylation and circular RNAs (circRNAs) have been shown to act vital roles in multiple malignancies including gastric cancer (GC). However, there is little knowledge about how m 6 A modification of circRNAs contributes to GC progression. Methods The association of METTL14 expression with the clinicopathological characteristics and prognosis in patients with GC was assessed by Western blot, Immunohistochemistry and public datasets. In vitro and vivo function experiments were conducted to investigate the role of METTL14 in GC. Furthermore, m 6 A-circRNA epitranscriptomic microarray was utilized to identify METTL14-mediated m 6 A modification of circRNAs, which were validated by methylated RNA immunoprecipitation (Me-RIP), RT-qPCR and rescue experiments in GC cells. The sponge of circORC5 with miR-30c-2-3p was confirmed by luciferase gene report and RNA immunoprecipitation assays. The expression, localization and prognosis of circORC5 in GC were evaluated by fluorescence in situ hybridization. The effects of METTL14 and (or) circORC5 on miR-30c-2-3p-mediated AKT1S1 and EIF4B were estimated by RT-qPCR and Western blot analyses. Results We found that METTL14 was downregulated in GC tissue samples and its low expression acted as a prognostic factor of poor survival in patients with GC. Ectopic expression of METTL14 markedly repressed growth and invasion of GC cells in vitro and in vivo , whereas knockdown of METTL14 harbored the opposite effects. Mechanically, m 6 A-circRNA epitranscriptomic microarray and Me-RIP identified circORC5 as the downstream target of METTL14. Silencing of METTL14 reduced the m 6 A level of circORC5, but increased circORC5 expression. Moreover, circORC5 could sponge miR-30c-2-3p, and reverse METTL14-caused upregulation of miR-30c-2-3p and downregulation of AKT1S1 and EIF4B. In addition, circORC5 possessed a negative correlation with miR-30c-2-3p and indicated a poor survival in GC. Conclusion Our findings demonstrate that METTL14-mediated m 6 A modification of circORC5 suppresses gastric cancer progression by regulating miR-30c-2-3p/AKT1S1 axis.

The transcription factor forkhead box protein O1 (FoxO1) is closely related to the occurrence and development of ovarian cancer (OC), however its role and molecular mechanisms remain unclear. Herein, we found that FoxO1 was highly expressed in clinical samples of OC patients and was significantly correlated with poor prognosis. FoxO1 knockdown inhibited the proliferation of OC cells in vitro and in vivo. ChIP‐seq combined with GEPIA2 and Kaplan–Meier database analysis showed that structural maintenance of chromosome 4 (SMC4) is a downstream target of FoxO1, and FoxO1 promotes SMC4 transcription by binding to its −1400/−1390 bp promoter. The high expression of SMC4 significantly blocked the tumor inhibition effect of FoxO1 knockdown. Furtherly, FoxO1 increased SMC4 mRNA abundance by transcriptionally activating methyltransferase‐like 14 (METTL14) and increasing SMC4 m6A methylation on its coding sequence region. The Cancer Genome Atlas dataset analysis confirmed a significant positive correlation between FoxO1, SMC4, and METTL14 expression in OC. In summary, this study revealed the molecular mechanisms of FoxO1 regulating SMC4 and established a clinical link between the expression of FoxO1/METTL14/SMC4 in the occurrence of OC, thus providing a potential diagnostic target and therapeutic strategy. FoxO1, which is overexpressed in OC, is closely related to poor clinical outcomes. FoxO1 transcriptionally activates SMC4 and promotes OC progression. FoxO1 promotes SMC4 mRNA stability via METTL14‐mediated m6A modification.

Background Pancreatic cancer is one of the most lethal human cancers. N 6 -methyladenosine (m 6 A), a common eukaryotic mRNA modification, plays critical roles in both physiological and pathological processes. However, its role in pancreatic cancer remains elusive. Methods LC/MS was used to profile m 6 A levels in pancreatic cancer and normal tissues. Bioinformatics analysis, real-time PCR, immunohistochemistry, and western blotting were used to identify the role of m 6 A regulators in pancreatic cancer. The biological effects of methyltransferase-like 14 (METTL14), an mRNA methylase, were investigated using in vitro and in vivo models. MeRIP-Seq and RNA-Seq were used to assess the downstream targets of METTL14. Results We found that the m 6 A levels were elevated in approximately 70% of the pancreatic cancer samples. Furthermore, we demonstrated that METTL14 is the major enzyme that modulates m 6 A methylation (frequency and site of methylation). METTL14 overexpression markedly promoted pancreatic cancer cell proliferation and migration both in vitro and in vivo , via direct targeting of the downstream PERP mRNA (p53 effector related to PMP-22) in an m 6 A-dependent manner. Methylation of the target adenosine lead to increased PERP mRNA turnover, thus decreasing PERP (mRNA and protein) levels in pancreatic cancer cells. Conclusions Our data suggest that the upregulation of METTL14 leads to the decrease of PERP levels via m 6 A modification, promoting the growth and metastasis of pancreatic cancer; therefore METTL14 is a potential therapeutic target for its treatment.

Hepatocellular carcinoma (HCC) ranks as the fourth leading cause of cancer-related deaths worldwide. N6-methyladenosine (m6A) RNA methylation is the most common modification of messenger RNAs (mRNAs). The prognosis of HCC patients with metastasis remains poor. Our study aimed to elucidate the regulatory role of m6A on HCC metastasis. All HCC patients were enrolled from The Affiliated Huai'an No. 1 People's Hospital of Nanjing Medical University. The expression levels of gene were tested by quantitative polymerase chain reaction (qPCR), Western blot, or immunohistochemistry (IHC) analysis. Wound healing assay, Transwell invasion assay, and lung metastasis model were implemented to investigate the migration and invasion ability of HCC cells. Candidate targets were selected by a comprehensive analysis of RNA-sequencing and m6A-sequencing of HepG2 cells. In this study, we demonstrated that METTL14 was significantly downregulated in HCC and significantly associated with the prognosis of HCC patients. METTL14 knockdown promoted the migration, invasion, and epithelial-mesenchymal transition (EMT) of HCC cells in vitro and in vivo. In addition, overlapping RNA-sequencing and m6A-sequencing data, we identified EGFR as a direct target of METTL14 in HCC. Mechanistically, METTL14 was found to inhibit HCC cell migration, invasion, and EMT through modulating EGFR/PI3K/AKT signaling pathway in an m6A-dependent manner. Targeting METTL14/EGFR/PI3K/AKT signaling pathway may facilitate the development of a new treatment strategy against the metastasis of HCC.

Background N6-methyladenosine (m6A) is the most prevalent RNA epigenetic regulation in eukaryotic cells. However, understanding of m6A in colorectal cancer (CRC) is very limited. We designed this study to investigate the role of m6A in CRC. Methods Expression level of METTL14 was extracted from public database and tissue array to investigate the clinical relevance of METTL14 in CRC. Next, gain/loss of function experiment was used to define the role of METTL14 in the progression of CRC. Moreover, transcriptomic sequencing (RNA-seq) was applied to screen the potential targets of METTL14. The specific binding between METTL14 and presumed target was verified by RNA pull-down and RNA immunoprecipitation (RIP) assay. Furthermore, rescue experiment and methylated RNA immunoprecipitation (Me-RIP) were performed to uncover the mechanism. Results Clinically, loss of METTL14 correlated with unfavorable prognosis of CRC patients. Functionally, knockdown of METTL14 drastically enhanced proliferative and invasive ability of CRC cells in vitro and promoted tumorigenicity and metastasis in vivo. Mechanically, RNA-seq and Me-RIP identified lncRNA XIST as the downstream target of METTL14. Knockdown of METTL14 substantially abolished m6A level of XIST and augmented XIST expression. Moreover, we found that m6A-methylated XIST was recognized by YTHDF2, a m6A reader protein, to mediate the degradation of XIST . Consistently, XIST expression negatively correlated with METTL14 and YTHDF2 in CRC tissues. Conclusion Our findings highlight the function and prognostic value of METTL14 in CRC and extend the understanding of the importance of RNA epigenetics in cancer biology.