BackgroundN6-methyladenosine (m6A) emerges as one of the most important modification of RNA. Bladder cancer is a common cancer type in developed countries, and hundreds of thousands of bladder cancer patients die every year.Materials and methodsThere are various cells in bladder tumor bulk, and a small population cells defined as tumor initiating cells (TIC) have self-renewal and differentiation capacities. Bladder TICs drive bladder tumorigenesis and metastasis, and their activities are fine regulated. However, the role of N6-methyladenosine in bladder TIC self-renewal is unknown.ResultsHere, we found a decrease of N6-methyladenosine in bladder tumors and bladder TICs. N6-methyladenosine levels are related to clinical severity and outcome. Mettl14 is lowly expressed in bladder cancer and bladder TICs. Mettl14 knockout promotes the proliferation, self-renewal, metastasis and tumor initiating capacity of bladder TICs, and Mettl14 overexpression exerts an opposite role. Mettl14 and m6A modification participate in the RNA stability of Notch1 mRNA. Notch1 m6A modification inhibits its RNA stability. Notch1 plays an essential role in bladder tumorigenesis and bladder TIC self-renewal.ConclusionThis work reveals a novel role of Mettl14 and N6-methyladenosine in bladder tumorigenesis and bladder TICs, adding new layers for bladder TIC regulation and N6-methyladenosine function.

Bladder cancer is a serious cancer in the world, especially in advanced countries. Bladder cancer stem cells (CSCs) drive bladder tumorigenesis and metastasis. Circular RNAs (circRNAs) are involved in many biological processes, but their roles in bladder oncogenesis and bladder CSCs are unclear. Here, we identified that circGprc5a is upregulated in bladder tumors and CSCs. circGpr5a knockdown impairs the self-renewal and metastasis of bladder CSCs, and its overexpression exerts an opposite role. circGpr5a has peptide-coding potential and functions through a peptide-dependent manner. circGprc5a-peptide binds to Gprc5a, a surface protein highly expressed in bladder CSCs. Gprc5a knockout inhibits the bladder CSC self-renewal and metastasis. circGprc5a-peptide-Gprc5a can be utilized to target bladder cancer and bladder CSCs.

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Background Silicosis is one of the most common occupational pulmonary fibrosis caused by respirable silica-based particle exposure, with no ideal drugs at present. Metformin, a commonly used biguanide antidiabetic agent, could activate AMP-activated protein kinase (AMPK) to exert its pharmacological action. Therefore, we sought to investigate the role of metformin in silica-induced lung fibrosis. Methods The anti-fibrotic role of metformin was assessed in 50 mg/kg silica-induced lung fibrosis model. Silicon dioxide (SiO2)-stimulated lung epithelial cells/macrophages and transforming growth factor-beta 1 (TGF-β1)-induced differentiated lung fibroblasts were used for in vitro models. Results At the concentration of 300 mg/kg in the mouse model, metformin significantly reduced lung inflammation and fibrosis in SiO2-instilled mice at the early and late fibrotic stages. Besides, metformin (range 2–10 mM) reversed SiO2-induced cell toxicity, oxidative stress, and epithelial-mesenchymal transition process in epithelial cells (A549 and HBE), inhibited inflammation response in macrophages (THP-1), and alleviated TGF-β1-stimulated fibroblast activation in lung fibroblasts (MRC-5) via an AMPK-dependent pathway. Conclusions In this study, we identified that metformin might be a potential drug for silicosis treatment.

Background N6-methyladenosine (m6A) is the most common and abundant internal modification of RNA. Its critical functions in multiple physiological and pathological processes have been reported. However, the role of m6A in silica-induced pulmonary fibrosis has not been fully elucidated. AlkB homolog 5 (ALKBH5), a well-known m6A demethylase, is upregulated in the silica-induced mouse pulmonary fibrosis model. Here, we sought to investigate the function of ALKBH5 in pulmonary fibrosis triggered by silica inhalation. Methods We performed studies with fibroblast cell lines and silica-induced mouse pulmonary fibrosis models. The expression of ALKBH5, miR-320a-3p, and forkhead box protein M1 (FOXM1) was determined by quantitative real-time polymerase chain reaction (qRT-PCR) analysis. RNA immunoprecipitation (RIP) assays and m6A RNA immunoprecipitation assays (MeRIP), western bolt, immunofluorescence assays, and 5-ethynyl-2'-deoxyuridine (EdU) fluorescence staining were performed to explore the roles of ALKBH5, miR-320a-3p, and FOXM1 in fibroblast activation. Results ALKBH5 expression was increased in silica-inhaled mouse lung tissues and transforming growth factor (TGF)-β1-stimulated fibroblasts. Moreover, ALKBH5 knockdown exerted antifibrotic effects in vitro. Simultaneously, downregulation of ALKBH5 elevated miR-320a-3p but decreased pri-miR-320a-3p. Mechanically, ALKBH5 demethylated pri-miR-320a-3p, thus blocking the microprocessor protein DGCR8 from interacting with pri-miR-320a-3p and leading to mature process blockage of pri-miR-320a-3p. We further demonstrated that miR-320a-3p could regulate fibrosis by targeting FOXM1 messenger RNA (mRNA) 3′-untranslated region (UTR). Notably, our study also verified that ALKBH5 could also directly regulate FOXM1 in an m6A-dependent manner. Conclusions Our findings suggest that ALKBH5 promotes silica-induced lung fibrosis via the miR-320a-3p/FOXM1 axis or targeting FOXM1 directly. Approaches aimed at ALKBH5 may be efficacious in treating lung fibrosis.