OBJECTIVETo investigate the expression and activity regulation of indoleamine 2,3-dioxygenase(IDO) in acute myeloid leukemia cells.

METHODSExpression of IDO and TLR9 in HL-60 and K562 cells cocultured with or without IFN-γ,Tα1,IFN-γ+Tα1 and chloroquine were determined by reverse transcription-polymerase chain reaction(RT-PCR). Then, the IDO activity in HL-60 and K562 cells cocultured with or without IFN-γ,Tα1,IFN-γ+ Tα1 was assayed by coomassie brilliant blue staining and modified colorimetric method.

RESULTSBoth IDO and TLR9 mRNA were expressed in HL-60 and K562 cells; IFN-γ increased the expression and activity of IDO in a concentration-dependent manner; Tα1 decreased the expression and activity of IDO in a concentration-dependent manner; the up-regulation of IFN-γ on IDO induced expression and activity had been weakened by Tα1(P<0.01); Chloroquine had no effect on the expression of IDO. The expression of TLR9 in HL-60 cells and K562 cells cocultured with IFN-γ,Tα1,IFN-γ+Tα1 and chloroquine was not significantly changed.

CONCLUSIONIDO can be expressed in acute myeloid leukemia cells and possesses the activity. IDO may play an important role in immune tolerance induced by leukemia cells, and become a new predictor of AML prognosis. Tα1 decreases the expression and activity of IDO, which can weaken the induction of IFN-γ on IDO expression and activity, thus Tα1 as an immune modulator may be a new agent for AML immunotherapy.