BackgroundAccumulating evidence has revealed the critical roles of N6-methyladenosine (m6A) modification of mRNA in various cancers. However, the biological function and regulation of m6A in bladder cancer (BC) are not yet fully understood.MethodsWe performed cell phenotype analysis and established in vivo mouse xenograft models to assess the effects of m6A-modified ITGA6 on BC growth and progression. Methylated RNA immunoprecipitation (MeRIP), RNA immunoprecipitation and luciferase reporter and mutagenesis assays were used to define the mechanism of m6A-modified ITGA6. Immunohistochemical analysis was performed to assess the correlation between METTL3 and ITGA6 expression in bladder cancer patients.FindingsWe show that the m6A writer METTL3 and eraser ALKBH5 altered cell adhesion by regulating ITGA6 expression in bladder cancer cells. Moreover, upregulation of ITGA6 is correlated with the increase in METTL3 expression in human BC tissues, and higher expression of ITGA6 in patients indicates a lower survival rate. Mechanistically, m6A is highly enriched within the ITGA6 transcripts, and increased m6A methylations of the ITGA6 mRNA 3’UTR promotes the translation of ITGA6 mRNA via binding of the m6A readers YTHDF1 and YTHDF3. Inhibition of ITGA6 results in decreased growth and progression of bladder cancer cells in vitro and in vivo. Furthermore, overexpression of ITGA6 in METTL3-depleted cells partially restores the BC adhesion, migration and invasion phenotypes.InterpretationOur results demonstrate an oncogenic role of m6A-modified ITGA6 and show its regulatory mechanisms in BC development and progression, thus identifying a potential therapeutic target for BC.FundThis work was supported by National Natural Science Foundation of China (81772699, 81472999).

N6-methyladenosine (m6A) is the most abundant internal modification in mammalian mRNAs. Despite its functional importance in various physiological events, the role of m6A in chemical carcinogenesis remains largely unknown. Here we profiled the dynamic m6A mRNA modification during cellular transformation induced by chemical carcinogens and identified a subset of cell transformation-related, concordantly modulated m6A sites. Notably, the increased m6A in 3′-UTR mRNA of oncogene CDCP1 was found in malignant transformed cells. Mechanistically, the m6A methyltransferase METTL3 and demethylases ALKBH5 mediate the m6A modification in 3′-UTR of CDCP1 mRNA. METTL3 and m6A reader YTHDF1 preferentially recognize m6A residues on CPCP1 3′-UTR and promote CDCP1 translation. We further showed that METTL3 and CDCP1 are upregulated in the bladder cancer patient samples and the expression of METTL3 and CDCP1 is correlated with the progression status of the bladder cancers. Inhibition of the METTL3-m6A-CDCP1 axis resulted in decreased growth and progression of chemical-transformed cells and bladder cancer cells. Most importantly, METTL3-m6A-CDCP1 axis has synergistic effect with chemical carcinogens in promoting malignant transformation of uroepithelial cells and bladder cancer tumorigenesis in vitro and in vivo. Taken together, our results identify dynamic m6A modification in chemical-induced malignant transformation and provide insight into critical roles of the METTL3-m6A-CDCP1 axis in chemical carcinogenesis.

Background The posttranscriptional modifications of transfer RNA (tRNA) are critical for all aspects of the tRNA function and have been implicated in the tumourigenesis and progression of many human cancers. By contrast, the biological functions of methyltransferase‐like 1 (METTL1)‐regulated m 7 G tRNA modification in bladder cancer (BC) remain obscure. Results In this research, we show that METTL1 was highly expressed in BC, and its level was correlated with poor patient prognosis. Silencing METTL1 suppresses the proliferation, migration and invasion of BC cells in vitro and in vivo. Multi‐omics analysis reveals that METTL1‐mediated m 7 G tRNA modification altered expression of certain target genes, including EGFR/EFEMP1. Mechanistically, METTL1 regulates the translation of EGFR/EFEMP1 via modifying certain tRNAs. Furthermore, forced expression of EGFR/EFEMP1 partially rescues the effect of METTL1 deletion on BC cells. Conclusions Our findings demonstrate the oncogenic role of METTL1 and the pathological significance of the METTL1‐m 7 G‐EGFR/EFEMP1 axis in the BC development, thus providing potential therapeutic targets for the BC treatment.

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