Overexpression of indoleamine 2,3-dioxygenase correlates with regulatory T cell phenotype in acute myeloid leukemia patients with normal karyotype

BACKGROUND: Production of immunosuppressive enzymes such as indoleamine 2,3-dioxygenase (IDO) is one of the strategies employed by hematologic malignancies, including acute myeloid leukemia (AML), to circumvent immune surveillance. Moreover, IDO has the ability to convert CD4(+)CD25(−) conventional T cells into regulatory T cells (Tregs). In this study, we evaluated the expression of IDO in cytogenetically normal acute myeloid leukemia (CN-AML) patients and its correlation with the Treg marker, FOXP3, as well as clinical and laboratory parameters. METHODS: Thirty-seven newly diagnosed CN-AML patients were enrolled in our study along with 22 healthy individuals. The expression of the IDO and FOXP3 genes was analyzed by SYBR Green real-time PCR. RESULTS: Both IDO and FOXP3 were highly upregulated in CN-AML patients compared to control groups (P=0.004 and P=0.031, respectively). A positive correlation was observed between IDO and FOXP3 expression among AML patients (r=0.512, P=0.001). Expression of IDO and FOXP3 showed no significant correlation with laboratory parameters such as white blood cell and platelet counts, hemoglobin levels, bone marrow blast percentage, gender, and FLT3 mutation status (P>0.05). CONCLUSION: Higher IDO expression in CN-AML patients may be associated with an increased Treg phenotype which may promote disease progression and lead to poor prognosis of CN-AML patients.