Platycodin D triggers the extracellular release of programed death Ligand-1 in lung cancer cells.


State Key Laboratory of Quality Research in Chinese Medicine, Institute of Chinese Medical Sciences, University of Macau, Macao, China. Electronic address: [Email]


Programmed death ligand-1 (PD-L1) is an important immune checkpoint for cancer immunotherapy in clinic. In this study, we reported that platycodin D, a natural product isolated from an edible and medicinal plant Platycodon grandiflorus (Jacq.) A. DC., down-regulated the protein level of PD-L1 in lung cancer cells. Flow cytometry and immunofluorescence assay showed a weaker surface PD-L1 signal in NCI-H1975 cells after the incubation with platycodin D (10 μM) for 15 min compared to the control group. Jurkat T cells showed enhancive interleukin-2 secretion when co-cultured with platycodin D-treated NCI-H1975 cells, suggesting that platycodin D-induced PD-L1 reduction increases the activation of Jurkat T cells. An augmentation of PD-L1 protein was detected in the cell culture medium from platycodin D treatment group. Chlorpromazine (60 μM) almost abolished the platycodin D-mediated PD-L1 extracellular release and restored the membrane PD-L1. Finally, hemolysis assay exhibited that platycodin D-triggered PD-L1 extracellular release was independent of the hemolytic mechanism. Taken together, our study demonstrates that platycodin D reduces the protein level of PD-L1 in lung cancer cells via triggering its release into the cell culture medium, which sheds new light for the application of natural products in cancer immunotherapy.


Cancer,Extracellular release,Natural products,Platycodin D,Programmed death ligand-1,