Insulin-like growth factor 1 signaling in human gastrointestinal carcinoid tumor cells.

Background Insulin-like growth factor 1 (IGF-1) is an autocrine regulator of carcinoid tumors. Blockade of IGF-1 signaling has been proposed as a therapeutic target in the treatment of patients with carcinoid syndrome. We hypothesized that the induction of parallel raf-1/MEK1 pathways will block IGF-1-mediated chromogranin A (CgA) maintenance.