Intracellular Fusobacterium nucleatum infection increases METTL3-mediated m6A methylation to promote the metastasis of esophageal squamous cell carcinoma

The tumor-associated microbiota plays a vital role in cancer development. Accumulating evidence shows that Fusobacterium nucleatum (Fn) participates in the progression of multiple tumor types. However, the underlying mechanisms remain unclear. This study examined the expression of methyltransferase-like protein 3 (METTL3) during Fn infection and elucidated the function and pathway of Fn-induced m6A methylation in esophageal squamous cell carcinoma (ESCC). The abundance of Fn in patient tissues was determined by qPCR. Western blot, qRT-PCR, and immunohistochemistry were performed to measure METTL3 expression in cells and tissues. METTL3 function was evaluated in vitro by colony formation and cell migration assays. MeRIP-qPCR was performed to determine the relationship between METTL3 and c-Myc. In addition, the half-lives of genes that are downstream of METTL3 were determined with RNA stability assays. Fn was enriched in hepatocellular carcinoma (HCC), breast cancer (BRCA), ESCC, and colorectal cancer (CRC) tumor tissues. METTL3 expression was positively associated with Fn abundance in ESCC tissues. Fn could survive and proliferation as well as increase METTL3 expression in ESCC, HCC, CRC, and BRCA cells. Moreover, METTL3 overexpression promoted ESCC cells proliferation, migration in vivo and in vitro. Mechanistically, Intracellular Fn infection increases METTL3 transcription. METTL3 promoted c-Myc mRNA methylation in the 3'-untranslated Region (3'-UTR) and enhanced its mRNA stability in a YTH N6-Methyladenosine RNA binding protein 1(YTHDF1)-dependent manner, which contributes to Fn induced ESCC proliferation and metastasis. This study indicates that intracellular Fn infection promotes ESCC development and metastasis, and eradicating Fn infection may be a promising strategy for treating ESCC.