Fusobacterium nucleatum stimulates cell proliferation and promotes PD-L1 expression via IFIT1-related signal in colorectal cancer
Yaqi Gao, Tianhui Zou, Pingping Xu, Yingchao Wang, Yi Jiang, Yingxuan Chen, Haoyan Chen, Jie Hong, Jing‐Yuan Fang
Abstract
Fusobacterium nucleatum (F. nucleatum) is enriched in colorectal cancer (CRC) tissues and a high amount of F. nucleatum was associated with an immunosuppressive tumor environment. PD-L1 is an important immune checkpoint expressed on tumor cells and promotes tumor immune escape. Whether PD-L1 is regulated by F. nucleatum is still unclear. We demonstrated that F. nucleatum promoted CRC progression and upregulated PD-L1 protein expression in CRC cell lines. Combined m6A-seq and RNA-seq identified m6A-modified IFIT1 mediating F. nucleatum induced PD-L1 upregulation. IFIT1 mRNA was modified with m6A modifications in 3’UTR and the m6A levels were altered by F. nucleatum treatment. Our results also indicated that IFIT1 served as a potential oncogene in CRC and regulated PD-L1 protein levels through altering PD-L1 ubiquitination. Clinical CRC data confirmed the correlation among F. nucleatum abundance, IFIT1 and PD-L1 expressions. Our work highlighted the function of F. nucleatum in stimulating PD-L1 expression through m6A-modified IFIT1 and provided new aspects for understanding F. nucleatum mediated immune escape.