Kukoamine B Inhibits EMT in Lung Adenocarcinoma Cells by Regulating Intracellular PD-L1-Mediated p65 Nuclear Translocation

Cortex Lycii Radicis, a medicinal plant, has been reported to inhibit epithelial-mesenchymal transition (EMT) and exhibit anti-lung cancer properties. Our previous study identified its major compound, Kukoamine B (KuB), as an inhibitor of membrane PD-1/PD-L1 interaction, thereby restoring T-cell function. However, the effect of KuB on EMT and the underlying mechanism thereof remain unknown. Herein, we show that PD-L1 overexpression enhances the proliferation, migration, and EMT of LUAD cells, upregulating N-cadherin and Vimentin, while downregulating E-cadherin. Mechanistically, PD-L1 directly binds phosphorylated p65 (p-p65) and facilitates p65 nuclear translocation, an interaction confirmed by molecular simulations. We found that KuB disrupts the PD-L1/p65 complex, impedes p65 nuclear translocation, and suppresses EMT, proliferation, and migration in LUAD cells. These inhibitory effects were reversed by PD-L1 overexpression. We therefore conclude that KuB suppresses EMT in LUAD by targeting intracellular PD-L1, blocking PD-L1-p65 interaction and nuclear translocation of p65.