RET and cancer: In light of the role of RAS and RAF as downstream mediators of both the EGFR and VEGFR signals from cell surface, we tested the anti-proliferative effect of sorafenib, a multi-targeted kinase inhibitor, blocking the activation of C-RAF, B-RAF, c-KIT, FLT-3, RET, VEGFR-2, VEGFR-3, and PDGFR-β [8] on the parental WT and TKI-resistant CALU-3 and HCT116 cancer cells.