BackgroundBrain metastasis (BM) is one of the principal causes of mortality for lung cancer patients. While the molecular events that govern BM of lung cancer remain frustrating cloudy.MethodsThe miRNA expression profiles are checked in the paired human BM and primary lung cancer tissues. The effect of miR-143-3p on BM of lung cancer cells and its related mechanisms are investigated.ResultsmiR-143-3p is upregulated in the paired BM tissues as compared with that in primary cancer tissues. It can increase the invasion capability of in vitro blood brain barrier (BBB) model and angiogenesis of lung cancer by targeting the three binding sites of 3’UTR of vasohibin-1 (VASH1) to inhibit its expression. Mechanistically, VASH1 can increase the ubiquitylation of VEGFA to trigger the proteasome mediated degradation, further, it can endow the tubulin depolymerization through detyrosination to increase the cell motility. m6A methyltransferase Mettl3 can increase the splicing of precursor miR-143-3p to facilitate its biogenesis. Moreover, miR-143-3p/VASH1 axis acts as adverse prognosis factors for in vivo progression and overall survival (OS) rate of lung cancer.ConclusionsOur work implicates a causal role of the miR-143-3p/VASH1 axis in BM of lung cancers and suggests their critical roles in lung cancer pathogenesis.

N6-methyladenosine (m 6 A) is the most abundant modification on eukaryotic mRNA, which regulates all steps of the mRNA life cycle. An increasing number of studies have shown that m 6 A methylation plays essential roles in tumor development. However, the relationship between m 6 A and the progression of cancers remains to be explored. Here, we reported that transforming growth factor-β (TGFβ1)-induced epithelial-mesenchymal transition (EMT) was inhibited in methyltransferase-like 3 (METTL3) knockdown (Mettl3 Mut/− ) cells. The expression of TGFβ1 was up-regulated, while self-stimulated expression of TGFβ1 was suppressed in Mettl3 Mut/− cells. We further revealed that m 6 A promoted TGFB1 mRNA decay, but impaired TGFB1 translation progress. Besides this, the autocrine of TGFβ1 was disrupted in Mettl3 Mut/− cells via interrupting TGFβ1 dimer formation. Lastly, we found that Snail, which was down-regulated in Mettl3 Mut/− cells, was a key factor responding to TGFβ1-induced EMT. Together, our research demonstrated that m 6 A performed multi-functional roles in TGFβ1 expression and EMT modulation, suggesting the critical roles of m 6 A in cancer progression regulation.structural supports for METTL3 [15][16][17]. Acting as the executor of m 6 A modification, METTL3 plays crucial roles in various biological processes, including tumor development [18,19]. For instance, METTL3 is necessary for the development and maintenance of mouse and human myeloid leukemia [20]. Our recent study indicated that METTL3 regulated the epithelial-mesenchymal transition (EMT) of cancer cells via Snail translation [21]. Although associations between m 6 A methylation and tumorigenesis, especially EMT process, have arisen for the last decade, the detailed mechanisms remained to be elucidated.EMT of cancer can be induced by a plethora of signaling pathways, and transforming growth factor β (TGFβ) is the prominent EMT inducer in cancer cells [22]. TGFβ, which contains three isoforms, TGFβ1, TGFβ2, and TGFβ3, is synthesized as a pro-protein monomer. During the maturation, the TGFβ dimer forms a complex with latent TGFβ binding proteins (LTBPs), called a latent complex [23,24], which is crucial for the secretion of TGFβ and the activation of TGFβ receptor (TGFR)-mediated cell signaling [25,26]. TGFβ induces the expression of many other growth factors and cytokines to initiate EMT, while also cooperating with the initial stimulus of TGFβ to stimulate self-expression, which is necessary for sustained signaling, which continually supports the long process of EMT [22,27].In this study, we investigate the potential effects of m 6 A on the TGFβ1-induced EMT of cancer cells. Our data reveal that TGFβ1-induced EMT is suppressed in METTL3 knockdown cells (Mettl3 Mut/− ). However, the expression of TGFβ1 is enhanced in Mettl3 Mut/− cells but decreased in TGFβ1-treated Mettl3 Mut/− cells. We demonstrate that m 6 A regulates the stability and translation of TGFB1 mRNA. In addition, METTL3 modulates the secretion and activation of TGFβ1. Besides this, we furth...

Angiogenesis is hijacked by cancer to support tumor growth. RNA modifications such as N6-methyladenosine (m6A) can regulate several aspects of cancer, including angiogenesis. Here, we find that m6A triggers angiogenesis in lung cancer by upregulating vascular endothelial growth factor-A (VEGFA), a central regulator of neovasculature and blood vessel growth. m6A-sequencing and functional studies confirmed that m6A modification of the 5’UTR of VEGFA positively regulates its translation. Specifically, methylation of a 5’UTR internal ribosome entry site (IRES) recruited the YTHDC2/eIF4GI complex to trigger cap-independent translation initiation. Intriguingly, the m6A methylation site A856 of the 5’UTR was located within the conserved upstream open reading frame (uORF) of VEGFA IRES-A, which overcomes uORF-mediated translation suppression while facilitating G-quadruplex-induced translation of VEGFA. Targeted specific demethylation of VEGFA m6A significantly decreased expression of VEGFA and reduced lung cancer cell-driven angiogenesis. In vivo and clinical data confirmed the positive effects of m6A modification of VEGFA on angiogenesis and tumor growth of lung cancer. This study not only reveals that the m6A/VEGFA axis is a potential target for lung cancer therapy but also expands our understanding of the impact of m6A modification of IRES in the 5’UTR of mRNA on translation regulation.

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