Study On 1-methyl-tryptophan Enhanced Potency Of Dendritic Cells Pulsed With Tumor Cell Lysate By Inhibition Of Indoleamine2, 3-Dioxygenase

OBJECTIVE:1. In order to determine whether indoleamine 2,3-dioxygenase(IDO)expression was induced in the mouse pancreas adenocarcinoma cell line Pan02 by interferon-y (IFN-y), and IDO activity was inhibited by 1-methyl tryptophan (1-MT).2. To investigate the expression of indoleamine 2,3-dioxygenase(IDO) and the prevalence of regulatory T cells(Treg) in tumor draining lymph nodes(TDLNs) and spleen in a murine pancreas adenocarcinoma model.3. In order to determine the IDO expression relevant to the anti-tumor immune response provoked by DC vaccine.4. In order to determine whether 1-MT might reduce CD4+CD25+ Treg proliferation and improve the anti-tumor efficacy of dendritic cells pulsed with tumor cell lysate in the murine pancreas adenocarcinoma model.METHORDS:1. The mouse pancreas adenocarcinoma cell line Panc02 was treated by IFN-y and the levels of IDO expression was analyzed by Western blotting and reverse phase high-performance liquid chromatography (HPLC).2. Tumor models were established in C57BL/6 mice by s.c. injection of Pan02 cells. Both the expression of indoleamine 2,3-dioxygenase(IDO) and the prevalence of regulatory T cells(Treg) were investigated in tumor draining lymph nodes(TDLNs) and spleen in a murine pancreas adenocarcinoma model.1-MT was administered to pancreas adenocarcinoma mice and investigated the effect on the prevalence of regulatory T cells(Treg) in tumor draining lymph nodes(TDLNs) and spleen.3. To prepare the DC vaccine,dendritic cells were pulsed with tumor cell lysate. This DC vaccine, as a single agent or in combination with 1-MT, was administered to pancreas adenocarcinoma mice. Both the expression of indoleamine 2,3-dioxygenase(IDO) and the prevalence of regulatory T cells(Treg) were investigated in tumor draining lymph nodes(TDLNs) and spleen in mice. The anti-tumor efficacy in different treatment was determined by regular observation of tumor development.RESULTS:1. IDO expression was acutely induced in the mouse pancreas adenocarcinoma cell line Pan02 by IFN-y. and IDO activity is completely abrogated by the IDO inhibitor,1-methyl tryptophan (1-MT).2. The level of IDO protein in tumor-bearing mice were significantly higher than control mice.3. The percentage of CD25+CD4+ T lymphocytes is higer in tumor-bearing group than in normal control group and tumor-bearing administration of 1-MT group(P <0.05).4. After 1-MT appling, the percentage of CD25+CD4+ T lymphocytes and Foxp3 expression were considerably lower in TDLN and spleen than in control LN and spleen.5. After DC vaccine appling, both the expression of IDO and the prevalence of Treg were were considerably higer in TDLN and spleen than in other group LN and spleen.6. In the group of 1-MT+ DC vaccine,the tumor growth rate was much slower than the group of DC vaccine,1-MT and PBS in day 36 after tumor challenge..CONCLUSIONS:1. IDO expression was acutely induced in the mouse pancreas adenocarcinoma cell line Pan02 by IFN-y.2. The up-modulation expression of IDO in TDLN and increased prevalence of Treg in TDLN and TS is induced by pancreas adenocarcinoma.3.1-MT might be enhance anti-tumor efficacy of dendritic cells pulsed with tumor cell lysate by downregulation of CD4+CD25+Treg.