It has been hypothesized that previous administration of cancer vaccines can drive immune cells to the TME and upregulate PD-L1 expression in the tumor cells due to cytokine release in the TME, thus giving a chance for anti-PD-L1/PD-1 drugs in patients who may not have otherwise benefited from such immunotherapies (36, 37). This evidence concerns the gene PDCD1 and neoplasm.