In fact, IDO1 (i) is a heme-containing enzyme, its catalytic activity is more intense but transient (32) and resides in the cytosol of cells, including DCs and tumor cells; (ii) is a signal transducing molecule that act through phosphorylated ITIMs when anchored to EE, a localization reached from the partnership with, and activation of, class IA PI3K subunits. The gene discussed is IDO1; the disease is neoplasm.