Ginsenoside Rg3 activates the immune function of CD8+ T cells via circFOXP1-miR-4477a-PD-L1 axis to induce ferroptosis in gallbladder cancer.

Gallbladder cancer (GBC) is the most common and leading cause of cancer-associated mortality among biliary tract carcinomas worldwide and there is no specific drug for treatment. Activation of CD8+ T cell immune activity is one of the strategies to improve GBC treatment. This study is aimed to investigate the role of Ginsenoside Rg3 on CD8+ T cell activation and pathogenesis of GBC. In GBC cells, Rg3 administration led to the significant reduction of circFOXP1 and PD-L1 as measured by Quantitative real-time polymerase chain reaction (RT-qPCR) and Western blotting. Mechanistically, circFOXP1 acted as the sponge of miR-4477a to regulate PD-L1 expression as demonstrated by RNA pull-down assay and dual luciferase reporter assay. Rg3 treatment enhanced the activity of CD8+ T cells by inhibiting the circFOXP1/miR-4477a/PD-L1 signaling axis. Besides, Rg3 administration induced lipid oxidation and ROS reduction as detected by Flow cytometry, resulting in ferroptosis via the inactivation of circFOXP1/miR-4477a/PD-L1 axis. Ferroptosis inhibitor Fer-1 administration could reverse the beneficial effects caused by Rg3 treatment while ferroptosis inducer Erastin treatment enhanced the effects. Moreover, Rg3 gavage alleviated tumor growth and elevated ferroptosis and apoptosis in tumor tissues, which were prevented by PD-L1 overexpression. Furthermore, Rg3 was demonstrated to activate the function of CD8+ T cells via regulating the circFOXP1-miR-4477a-PD-L1 signaling axis in vivo. Rg3 inactivated the circFOXP1-miR-4477a-PD-L1 signaling axis to activate the immune function of CD8+ T cells, thereby inducing ferroptosis and apoptosis in GBC cells. This research recognizes the mechanism of Rg3-mediated anti-cancer effect and offers evidence for the potentiality of Rg3 in clinical application for GBC therapy.