Sorafenib inhibits FIP1L1-PDGFRα and FIP1L1-PDGFRα(T674I). (A) Initial screen of different PDGFR inhibitors (100 nM) using Ba/F3 cells expressing FIP1L1-PDGFRA(T674I). The inhibition by K252a was shown to be due to nonspecific toxicity. (B) Structure of sorafenib. (C) Dose-response curves showed inhibition of the growth of Ba/F3 cells expressing FIP1L1-PDGFRA or FIP1L1-PDGFRA(T674I) by sorafenib. Error bars show standard deviation. (D) Western blot analysis confirmed that sorafenib directly inhibits FIP1L1-PDGFRα and FIP1L1-PDGFRα(T674I). Phosphorylation of ERK1/2 was also decreased upon sorafenib treatment.