IDO1 and neoplasm: To test the tumorigenicity of KPIC Ido-1 KO cells, we subcutaneously transplanted KPIC Ido-1 KO organoids into immunocompetent C57BL/6 mice (n = 7), and found that KPIC Ido-1 KO organoids did not form a subcutaneous tumor in C57BL/6 mice within 25 d after transplantation (Fig. 4f; Supplementary Table S2).