The Expression Of Indoleamine 2, 3-dioxygenase In Breast Cancer And Its Significance

Objective:To investigate the expression of indoleamine 2,3-dioxygenase(IDO) and the distribution of Regulatory T cells(Tregs)in breast cancer,tumor draining lymph nodes(TDLNs),benign tumors and normal breast tissues,then to seek the relationship between them.Furthermore,through detecting the expression of IDO and the distribution of Tregs in primary and metastasis 4T1 mouse breast cancer tissues, to discuss the role of IDO in the progress of cancer metastasis and the possible mechanism.Methods:1.The fresh tissues and paraffin blocks of 26 cases of breast cancer and 10 cases of breast benign diseases were collected from Tianjin cancer hospital.RT-PCR was used to detect the mRNA of IDO in breast cancer,TDLNs,benign diseases and normal breast tissues;Immunohistochemistry was used to detect the expression of IDO and Foxp3 proteins in previous tissues,then to seek the relationship between them.2.4T1 mouse breast cancer metastasis model was established,RT-PCR and Immunohistochemistry were used to detect the expression of IDO in primary and metastasis cancer tissues.Flow cytometer was used to detect the percentage of CD4~+CD25~+CD127~-T cells in previous tissues.Results:1.Immunohistochemistry results showed that IDO positive rate and the percentage of IDO~+cells in breast cancer[46.15%(12/26),(13.16±7.82)%]were higher than benign diseases[10.00%(l/10),(3.24±1.30)%]and normal breast tissues [0%(0/26),(2.70±1.53)%](P＜0.05),the metastasis TDLNs[85.00%(17/20), (20.46±6.57)%]were higher than primary cancer and normal TDLNs tissues [33.3%(2/6),(7.55±4.48)%](P＜0.05).RT-PCR results were consistent with Immuno-histochemistry results.The percentage of IDO~+cells in breast cancer was associated with tumor clinical stage and lymph nodes metastasis while had no relationship with tumor diameter,ER,PR and Her-2 status.2.The percentage of Foxp3~+cells in breast cancer[(3.50±1.04)%]was higher than benign diseases[(0.71±0.42)%]and normal breast tissues[(0.55±0.34)%] (P＜0.05),the TDLNs[(6.13±2.31)%]was higher than breast cancer(P＜0.05).3.The percentage of IDO~+cells was positively correlated with the percentage of Foxp3~+cells in breast cancer(r~2=0.449,P＜0.05)and TDLNs(r~2=0.454,P＜0.05), the linear regression equations were Y=0.832+0.140X and Y=2.562+0.167X(Y:The percentage of Foxp3~+cells,X:The percentage of IDO~+cells).The percentage of IDO~+and Foxp3~+cells had no relationship in benign diseases and normal breast tissues(r~2=0.063,r~2=0.113,P＞0.05).4.RT-PCR and Western blot results showed that 4T1 mouse breast cancer cells didn't express IDO andγ-IFN stimulation couldn't upregulate its expression,mouse DC2.4 cells didn't express IDO either,but afterγ-IFN stimulation for 24 or 48h,the expression level of IDO was increased obviously.5.Immunohistochemistry results showed that the percentage of IDO~+cells in primary[(12.40±5.15)%]and secondary[(14.28±6.46)%]cancer tissues of metastasis mouse were all higher than the cancer that didn't have metastasized[(3.16±1.63)%] (P＜0.05).The expression level of IDO in primary and secondary cancer of metastasis mouse had no statistic difference(P＞0.05).6.The Flow cytometer results showed that the percentage of CD4~+CD25~+ CD127~-T cells in primary[(4.70±1.10)%]and secondary[(5.10±1.18)%]cancer tissues of metastasis mouse were all higher than the cancer that didn't have metastasized[(2.27±0.83)%](P＜0.05).The percentage of CD4~+CD25~+CD127~-T cells in primary and secondary cancer of metastasis mouse had no statistic difference (P＞0.05).7.The percentage of IDO~+cells was positively correlated with the percentage of CD4~+CD25~+CD127~-T cells in breast cancer(r~2=0.475,P＜0.05),the linear regression equations was Y=2.318+0.167X(Y:The percentage of CD4~+CD25~+CD127~-T cells,X: The percentage of IDO~+cells).Conclusion:1.The expression level of IDO and the percentage of Tregs in breast cancer were all higher than that in benign diseases and normal breast tissues.The expression level of IDO in metastasis TDLNs was higher than that in breast cancer and normal TDLNs. The percentage of Tregs in TDLNs was higher than that in breast cancer.The percentage of IDO~+cells was positively correlated with Foxp3~+cells in breast cancer and TDLNs.2.The percentage of IDO~+cells and CD4~+CD25~+CD127~-T cells in primary and secondary cancer of metastasis mouse were all higher than the tumor that didn't have metastasized.meanwhile,the percentage of IDO~+cells was positively correlated with the percentage of CD4~+CD25~+CD127~-T cells in breast cancer,which suggested that IDO maybe induced the differentiation of Tregs,then to mediate immune tolerance and promote cancer cells metastasis.