In conclusion, our study for the first time proved that intra-arterial chemotherapy with sequential anti-PD-1 antibody is a safe and effective conversion treatment strategy for unresectable GC, and preliminarily revealed that TIME transformation induced by intra-arterial chemotherapy including the formation of TLSs, infiltration of CD8+ T cells and phenotype transition of TAM might possibly mediate the additive and synergistic effect of the combination regimen. This evidence concerns the gene PDCD1 and gastric cancer.