CD274 and triple-negative breast carcinoma: Notably, a growing number of studies have reported a positive correlation between p53 and PD-L1 expression on the surface of tumor cells.111, 112, 113 In one study, the restoration of p53 activity in p53-deficient triple-negative breast cancer cells resulted in the up-regulation of PD-L1 expression on the surface of tumor cells and sensitized them to anti-PD-1 therapy.114