Expression and function analysis of indoleamine 2 and 3-dioxygenase in bladder urothelial carcinoma

Indoleamine 2, 3-dioxygenase (IDO) is a rate-limiting enzyme for tryptophan metabolism inducing immune tolerance of tumors. The purpose of this study is to investigate IDO expression and its prognostic significance in bladder urothelial carcinoma (BUC). In this study, immunohistochemical staining for IDO expression in BUC tissues (n = 84) and normal bladder tissues (n = 22) was performed. The mRNA expression levels of IDO in BUC and normal bladder were analyzed by quantitative RT-PCR. Survival analysis was performed for the correlation of IDO expression and clinicopathological factors with disease-free survival. Positive expression of IDO was found in 48 of 84 cases in BUC tissues and was significantly correlated with histological classification, histological grade and TNM stage. While IDO expression in normal bladder tissues was expressed in only 4 of 22 (18.2%) cases. Moreover, IDO mRNA levels of BUC were significantly higher than that of normal bladder. We also found that IDO, histological grade and TNM stage were closely associated with DFS. These results indicated that IDO was related to the progression of BUC and might be one of the crucial prognostic factors for BUC.