中国生物工程杂志

This study was aimed to investigate the mechanism of indoleamine 2,3-dioxygenase(IDO) in HepG2 cells contributing to tumor immune escape. Methods T-lymphocyte and HepG2 cell were cocultured, and 1-methyl-tryptophan(1-MT) was added to make an intervening experiment. The expression of IDO mRNA in HepG2 cell cocultured with T-lymphocyte was detected by RT-PCR ;the apoptosis rate of HepG2 cell cocultured with T-lymphocyte was analyzed by flow cytometer; The cytotoxicity of T-lymphocyte against HepG2 cell was examined by MTT assay. Results In combine reaction system , the expression of IDO mRNA was strongly induced in HepG2 cell cocultured with T-lymphocyte and faintly induced when cultured with 1-MT ; the earlier apoptosis rate of HepG2 cell in control group and experiment group(1-MT:1.25 mmol/l，2.5 mmol/l，5mmol/l) was respectively（3.48±0.34）%，（7.82±0.41）%，（18.62±0.42）%，（25.32±0.40）%（P<0.01），The cytotoxicity of T-lymphocyte against HepG2 cell was respectively（17.36±1.24）%，（25.48±1.48）%，（32.89±1.73）%，（42.04±2.16）%（P<0.01）. Conclusion These results suggest that IDO from HepG2 cell can suppress the tumor immunity of T-lymphocyte to kill hepatoma carcinoma cell, which may be contributing to hepatoma immune escape