Indoleamine2,3-dioxygenase Up Regulates The Expression Of Human Leucocyte Antigen-G In Hepatocellular Carcinoma Cells

Objects:Indoleamine 2,3 - dioxygenase (IDO) and human leukocyte antigen-G (HLA-G) areboth immunosuppressive molecules can induce immune tolerance state.They display commonproperties in term of expression ,function and regulation.Both in the expression.some studieshave confirmed that IDO could affect the expression of HLA-G in antigen-presenting cells andmelanoma cells .This study was aim to discuss whether IDO can affect the expression of HLA-Gin SMMC-7721 and its possible regulation mechanism .Method:The hepatocellular carcinoma cells SMMC-7721 were transfected withpcDNA3.1-IDO recombinant plasmid by lipofectamineTM2000 reagent(pcDNA3.1-IDO group),SMMC-7721 transfected with blank plasmid( pcDNA3.1 group) and blankSMMC-7721(non-transfected group) were used as control groups. The expression of IDO weretested by RT-PCR and Western blot, the expression of HLA-G mRNA and protein molecules incells were tested by real time fluorescence quantitative PCR and Western blot ; thenpcDNA3.1-IDO group cells were respectively given IDO competitiveinhibitior( 1-methyl-D-trypophan) and its substrate(L-tryptophan) intervention to investigate theeffect of drugs on the expression of HLA-G.Results: 1.The IDO was highly expressed in pcDNA3.1-IDO group cells shown by RT-PCR andWestern blot.2.the expression of HLA-G mRNA in each group cells were tested by RTFQ-PCR: the level of HLA-G mRNA in pcDNA3.1-IDO group significantly compared with the pcDNA3.1 groupand non-transfected group up-regulated(pcDNA3.1-IDO group, pcDNA3.1 group andnon-transfected group were 0.9135±0.0033,0.0037±0.0004,0.0048±0.0005),it was consideredstatistically significant comparing the former with the latter two (P<0.05),the latter two was nosignificant difference (P> 0.05). The expression of HLA-G mRNA I group cells with 1-D-MTand L-tryptophan intervention(the 1- D-MT group and L-tryptophan group were 0.0053±0.0005and 0.0046±.0009 ) than non-intervention (0.9135±0.0033) were significantly decreased, thelatter with the former two have statistically significant differences (P <0.05).3. The level of HLA-G protein in each group cells were tested by Western blot:pcDNA3.1-IDO group express HLA-G protein was significantly upregulated compared with thepcDNA3.1 group and non-transfected group(pcDNA3.1-IDO group, pcDNA3.1 group andnon-transfected group were 0.9314±0.0252,0.4743±0.0140,0.5019±.0339), it was consideredstatistically significant comparing the former with the latter two (P<0.05),the latter two was nosignificant difference (P> 0.05).The expression of HLA-G protein in I group cells with 1-D-MTand L-tryptophan intervention(1-D-the MT group and L-tryptophan group were 0.6078±0.0025and 0.4960±.0167 ) were significantly decreased than non-intervention (0.9314±.0252) , thelatter with the former two have statistically significant differences (P <0.05).Conclusions: SMMC-7721 cells stably transfected with the IDO gene were highlyexpressed IDO mRNA and IDO protein. IDO can up regulates the expression of HLA-G inSMMC-7721 cells,IDO-mediated regulation of HLA-G expression is transcriptional andtranslational level,1-D-MT can reverse this process. Tryptophan degradation pathway involved inIDO regulation of HLA-G.We consider that IDO may induce immune escape in hepatocellularcarcinom though upregulate HLA-G.