The objective of this study was to investigate the expression and function of indoleamine 2, 3-dioxygenase (IDO) in
leukemia. The IDO expressions in human acute monocyte
leukemia (M(5)) and acute lymphocyte
leukemia (ALL) were detected by immunofluorescence staining. Constructed
leukemia mouse model was used to observe whether the IDO inhibitor, 1-methyl
tryptophan (1-MT), has any effect in treating
leukemia. The experimental group were fed with 1-MT
solution every day while the mice in control group had no further treatment. The results showed that the average ratios of IDO expression were 29.4 +/- 11.2% in M(5) patients and 24.7 +/- 7.96% in ALL patients respectively. After statistical test, IDO expression level in
leukemia cells was significantly higher than that of normal mononuclear cells. The
tumor decreased gradually in mice treated with 1-MT. At the terminal point of the experiment (88 days after vaccination), the average survival time in the experimental group was 42.3 days while the mice in control group only lived 15.1 days in average, which difference was statistically significant (P < 0.05). Some of the
leukemia mice in the experimental group long-term survived without
tumor (more than three months after vaccination). It is concluded that human acute monocyte
leukemia (M(5)) and acute lymphocyte
leukemia (ALL) express IDO, and both can be treated by 1-MT in mice.