IDO1 and cancer: In addition to the IDO1 expression by tumor cells, the picture of the intrinsic pro-tumorigenic IDO1-mediated pathway could contribute to a better selection and stratification of cancer patients for future clinical trials; iii) notably, the signaling conformation of IDO1 in tumor cells seems to be more stable than the physiological turnover of the protein, which is reminiscent of an oncogenic property.