【Objective】To study the molecular mechanism of TSA-induced indoleamine 2

3-dioxygenase (IDO) down-regulation in human lung adenocarcinoma cell line A549. 【Methods】The roles of TSA on the IFN-γ induced IDO expression in A549 cell

the phosphorylation of signal transducer and activator of transcription 1 (STAT1) and the activation of interferon regulatory factor 1 (IRF-1) were examined by western blotting. Effect of TSA on STAT1 nuclear translocation was observed by a confocal laser-scanning scanning microscope. The luciferase activity of the activation of γ-interferon activated sites (GAS)

interferon stimulated response element (ISRE) and nuclear factor-κB (NF-κB) was measured by dual luciferase reporter assay system. 【Results】TSA concentration-dependently reduced IFN-γ induced IDO expression

inhibited STAT1 phosphorylation at Tyr-701 and nuclear translocation in A549 cell. Dual luciferase reporter assay and Western blotting results showed that TSA blocked IFN-γ -induced activation of GAS

ISRE

and IRF-1

but not NF-κB. 【Conclusions】TSA can down-regulate IFN-γ induced IDO expression in A549 cell

which may be associated with the repression of phosphorylation and nuclear translocation of STAT1 and its binding to GAS.