CD274 and neoplasm: On the one hand, dose-dependently down-regulated PD-L1 expression mediated by PM in CT26 and 4T1 tumor cells was observed, which was about 41.2 ± 11.2% of the basal PD-L1 expression level as 60 μM PM pretreatment in CT26 cells and 24.5 ± 14.7% as 30 μM PM pretreatment in 4T1 cells (Fig. 1A, B, D, E).