Similarly, Arandi et al. reported the highest IDO expression in patients with AML compared with that in the normal group, suggesting that high IDO expression, along with increased FoxP3 expression levels (indicating an increase in the Treg phenotype), contributed to the poor immune response of patients with AML, disease progression to later stages, and poor prognosis [12]. This evidence concerns the gene IDO1 and acute myeloid leukemia.