The screening of compounds regulating PD-L1 transcriptional activity in a cell functional high-throughput manner.

Immune checkpoints are protein molecules expressed on the immune cell membrane, which regulate the immune system to kill tumor cells. As an essential immune checkpoint, overexpressed PD-1 on tumor cells could inhibit T-cell activation after being bonded to PD-1. Due to this inhibitory effect, T-cell proliferation and cytokine secretion are suppressed, leading to immune escape of tumor cells. Here, we established a high-throughput method based on cell function screening technology to screen drugs regulating PD-L1 expression in tumor cells at the transcriptional level. After two screening rounds, 12 compounds that enhanced PD-L1 transcription while seven weakened were sorted out among 1018 FDA-approved drugs. Finally, a tumor cell line was used to verify the upregulation of endogenous PD-L1 expression for a drug named "vorinostat," a histone deacetylation inhibitor, after the two rounds of optional selection. Therefore, our research provides another perspective for using "vorinostat" in treating tumors and offers a convenient method to detect the transcriptional expression of other intracellular proteins besides PD-L1.