RET and neoplasm: REG, an orally bioavailable MKI, blocks the activity of several protein kinases, including KIT, BRAF, RAF-1, RET, VEGFR-1, VEGFR-2, VEGFR-3, PDGFR and FGFR, which are associated with tumor microenvironment signaling, tumor angiogenesis, and cell proliferation (28,29).