IGF1 and cancer: Strategies to inhibit IGF-IR signaling in human cancers include: (1) monoclonal antibodies that directly block IGF-IR; (2) monoclonal antibodies that function by neutralizing the circulating ligands IGF-I or IGF-II, which prevents IGF-IR from being activated; and (3) small molecule inhibitors that antagonize the kinase activity of IGF-IR [182].