Triptolide inhibits interferon-γ-induced programmed death-1-ligand 1 surface expression in breast cancer cells

Triptolide, a natural compound purified from the Chinese herb Tripterygium wilfordii, has been reported to inhibit the growth and metastasis of tumors in vivo. However, the effects of triptolide on the immune responses of cancer cells remain unknown. Up-regulation of programmed death-1-ligand 1 (PD-L1) in cancer cells is an important mechanism of tumor immune evasion. In the present study, we demonstrated that triptolide was able to inhibit interferon-γ-induced PD-L1 surface expression in human breast cancer cells. Therefore, by down-regulating PD-1/PD-L1 pathway, triptolide may also serve as a modulator to promote cancer cell-reactive immune responses.