Also, and despite the studies about the role of IDO1 in supporting tumor vessel formation (33, 34), the ability of activated GCN2K to induce p53 expression, and possibly cell cycle arrest or apoptosis, in endothelial cells (30), raises questions about the effect of IDO1 inhibition on the required for the tumor progression neoangiogenesis. Here, IDO1 is linked to neoplasm.