Abstract: Indoleamine 2,3-dioxygenase 1 (IDO1) metabolizes L-tryptophan to kynurenines (KYN), inducing T-cell suppression either directly or by altering antigen-presenting-cell function. Cyclooxygenase (COX)-2, the rate-limiting enzyme in the synthesis of prostaglandins, is over-expressed by several tumours. We aimed at determining whether COX-2 inhibitors down-regulate the IFN-g-induced expression of IDO1 in acute myeloid leukaemia (AML) cells. IFN-γ at 100 ng/mL up-regulated COX-2 and IDO1 in HL-60 AML cells, both at mRNA and protein level. The increased COX-2 and IDO1 expression correlated with heightened production of prostaglandin (PG)E2 and kynurenines, respectively. Nimesulide, a preferential COX-2 inhibitor, down-regulated IDO1 mRNA/protein and attenuated kynurenine synthesis, suggesting that overall IDO inhibition resulted both from reduced IDO1 gene transcription and from inhibited IDO1 catalytic activity. From a functional standpoint, IFN-g-challenged HL-60 cells promoted the in vitro conversion of allogeneic CD4+CD25− T cells into bona fide CD4+CD25+FoxP3+ regulatory T cells, an effect that was significantly reduced by treatment of IFN-γ-activated HL-60 cells with nimesulide. Overall, these data point to COX-2 inhibition as a potential strategy to be pursued with the aim at circumventing leukaemia-induced, IDO-mediated immune dysfunction.
Keywords: indoleamine 2-3-dioxygenase; immune tolerance; acute leukaemia; regulatory T cells; immunotherapy; interferon-γ
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Iachininoto, M.G.; Nuzzolo, E.R.; Bonanno, G.; Mariotti, A.; Procoli, A.; Locatelli, F.; Cristofaro, R.D.; Rutella, S. Cyclooxygenase-2 (COX-2) Inhibition Constrains Indoleamine 2,3-Dioxygenase 1 (IDO1) Activity in Acute Myeloid Leukaemia Cells. Molecules 2013, 18, 10132-10145.
Iachininoto MG, Nuzzolo ER, Bonanno G, Mariotti A, Procoli A, Locatelli F, Cristofaro RD, Rutella S. Cyclooxygenase-2 (COX-2) Inhibition Constrains Indoleamine 2,3-Dioxygenase 1 (IDO1) Activity in Acute Myeloid Leukaemia Cells. Molecules. 2013; 18(9):10132-10145.
Iachininoto, Maria G.; Nuzzolo, Eugenia R.; Bonanno, Giuseppina; Mariotti, Andrea; Procoli, Annabella; Locatelli, Franco; Cristofaro, Raimondo D.; Rutella, Sergio. 2013. "Cyclooxygenase-2 (COX-2) Inhibition Constrains Indoleamine 2,3-Dioxygenase 1 (IDO1) Activity in Acute Myeloid Leukaemia Cells." Molecules 18, no. 9: 10132-10145.