To test this hypothesis, we initially used 11C-l-1MTrp to evaluate therapeutic efficacy in B16F10 tumor-bearing immunocompetent mice, a commonly used preclinical tumor model with successful immunotherapies, receiving one of two clinically relevant IDO1 blockade-containing combinatorial therapy regimens, l-1MTrp (5 g/kg) plus cyclophosphamide (CPA, 150 mg/kg, an immunomodulatory chemical toxin21 or l-1MTrp plus paclitaxel (PTX, 13.3 mg/kg) (figure 2A). This evidence concerns the gene IDO1 and neoplasm.