IDO1 and neoplasm: In the context of cancer, using B16-F10 mouse melanoma cells transfected with either the wild-type Ido1 gene (Ido1WT) or a mutated variant lacking the catalytic, but not signaling activity (Ido1H350A), Orecchini and colleagues demonstrated that IDO1 promote tumor growth by increasing SHP-2-mediated activation of Ras and Erk signaling in vitro and in vivo.