Sorafenib inhibited Raf/MEK/ERK signaling involved in NK activation.

(A) NK cells were cultured with K562 cells (E:T = 30∶1) in the presence of sorafenib (10 µM) and the indicated specific inhibitors (10 µM). (B) NK cells were cultured with K562 tumor cells in the presence of sorafenib (10 µM) and the indicated specific inhibitors (10 µM). After 24 h, IFN-γ levels in cell culture supernatants were determined by ELISA. (C) Isolated human NK cells were treated with sorafenib and the indicated specific inhibitors for 30 min and exposed to IL-2 for 10 min. Subsequently, cell lysates were analyzed for phosphorylated ERK (pERK1/2) and whole (panERK) ERK1/2 protein. (D, E) NK92-MI cells were treated with different concentrations of sorafenib for 30 min and exposed to IL-2 for 10 min or fixed Raji cells for 15 min. Subsequently, cell lysates were analyzed as described in C. (F, G) Isolated human NK cells were treated with different concentrations of sorafenib for 30 min and exposed to IL-2 for 10 min or fixed Raji cells for 15 min.