IDO1 and sarcoma: In a different setting, [128] other Authors evaluated the combination of anti-PD-L1 and mCHT in advanced sarcomas; in the correlative study, they found that a strong infiltration of macrophages, most of which expressing the inhibitory enzyme indoleamine 2,3-dioxygenase 1 (IDO1), thus suggesting a potential correlation between immunosuppressive tumor microenvironment, which finally could produce macrophage infiltration and IDO1 pathway activation.