PDCD1 and neoplasm: The mechanism of anti PD-1 antibody resistance is still unclear, which may be related to TYRO3 (118), KRAS (119) and other gene mutations, and the mutation rate of the tumor itself (117), β-catenin related immune escape (120), the expression level of PD-1 in the tumor itself (117) and IFN-γ related to the disruption of tumor signal pathways.