When PD-L1 expression was compared between the PD-1 antibody treatment group and the treatment group with the addition of intrapleural and continuous subcutaneous administration of HVJ-E, the PD-L1 expression was significantly elevated in the combination group, suggesting that treatment with PD-1 antibodies activates the resistance mechanism of the tumor to PD-1 antibodies, resulting in a weakening of PD-L1 expression, which may lead to PD-1 antibody ineffectiveness. This evidence concerns the gene PDCD1 and neoplasm.