Using melanoma cell lines bearing wild-type (wt) p53, p53 knock-out derivatives, and p53-null cell lines cells bearing mutant p53, we investigated the impact of an MDM2 inhibitor on CD274 mRNA levels, total PD-L1, and membrane PD-L1 protein, and performed natural killer (NK)-cell mediated killing assays to evaluate the effect on the tumor immune response. Here, TP53 is linked to neoplasm.