FN1 and cancer: Although Fn has been reported to enhance the effect of anti-programmed cell death protein (PD-L1) monoclonal antibody (mAb) in CRC, thus exerting an anti-tumor effect (9), most studies report the pro-cancer effect of Fn in CRC, namely Fn plays the role of “driver” in CRC (10), and several human samples currently investigating Fn include tissue, mucosa, stool, serum, and oral samples.