[Analysis of indoleamine 2, 3-dioxygenase expression in breast cancer patients with bone metastasis].

We evaluated the clinical significance of indoleamine 2, 3-dioxygenase (IDO) expression in breast cancer patients with bone metastasis. IDO activity can be measured by the tryptophan(Trp)/kynurenine(Kyn) ratio. Trp and Kyn levels were measured by high-performance liquid chromatography (HPLC). The serum IDO levels of postoperative breast cancer patients with a high number of bone metastases were lower than those of patients with a single metastasis lesion. In addition, IDO activity increased in the cases in which the number of metastatic lesions to the bone increased. These results suggest that the expression of IDO in breast cancer patients with bone metastasis may play a critical role in immunosuppression in these patients.