Construction of the PD-L1 promoter-luciferase reporter expressing vector for small molecule inhibitors screening

Abstract

Majority of cancer cells up-regulate co-inhibitory molecule PD-L1 which inhibits T cell activation and proliferation, and allows cancers to escape from host immune surveillance, suggesting that it is a potential cancer therapeutic target in drug discovery. To screen the small molecule inhibitors down-regulating the transcriptional activity of PD-L1 promoter, the luciferase reporter expressing vector containing PD-L1 promoter was constructed, then the activity of promoter was detected in the HeLa cells. Moreover, the screening model of small molecule inhibitors suppressing the transcriptional activity of PD-L1 promoter using the luciferase reporter assay system was established, and we identified a small molecule chemical Fludarabine Phosphate which inhibited the activity of PD-L1 promoter with the inhibitory rate of 0.6. Furthermore, Fludarabine Phosphate inhibited the expression of PD-L1 at both mRNA and protein levels in MGC-803 cells. Our study provides a useful tool for screening small molecules efficiently inhibiting PD-L1 expression.