Based on the KEGG pathway analysis, the differentially expressed FRGs were mainly enriched in the HIF-1 signaling pathway, ferroptosis, microRNA in cancer, the PPAR signaling pathway, bladder cancer, autophagy, programmed death ligand 1 (PD-L1) expression, and the PD-1 checkpoint pathway (Fig. 1C). This evidence concerns the gene PDCD1 and cancer.