Fusobacterium nucleatum promotes colorectal cancer metastasis by excretion of miR-122-5p from cells via exosomes

Fusobacterium nucleatum (Fn) infection and microRNAs (miRNAs) are closely associated with colorectal cancer (CRC) development, but the mechanism by which Fn regulates tumor-suppressive miRNAs via exosomes and facilitates CRC metastasis remains unclear. Here, we identified that Fn infection significantly increased exosomal miR-122-5p levels in the serum of CRC patients and CRC cell culture supernatants through two miRNA panels of high-throughput sequencing and RT-qPCR analysis. In Fn-infected patients, the serum exosomal levels of miR-122-5p were negatively associated with their expression levels of tissues. Downregulated miR-122-5p was demonstrated to enhance the migration, invasion, and metastasis abilities of CRC cells in vivo and in vitro. Secretion of miR-122-5p into exosomes is mediated by hnRNPA2B1. Mechanistically, Fn activated the TGF-β1/Smads signaling pathway to promote EMT by regulation of the miR-122-5p/FUT8 axis. In conclusion, Fn infection may stimulate CRC cells to excrete exosome-wrapped miR-122-5p, and activate the FUT8/TGF-β1/Smads axis to promote metastasis.