IDO1 and breast cancer: For instance, Xing et al. constructed a fluorinated polymeric nanoparticle loaded with Ce6 and NLG919 (an IDO inhibitor) for synergistic tumor PDIT, which could induce stronger PDT efficacy by fluorinated polymers directly carrying high concentrations of oxygen and suppress immune escape of tumors by blocking IDO, thereby enhancing suppressive ability against breast cancer cells of PDIT (Figure 2F)132.