The Study of Protein Expression and Activity of Indoleamine 2,3-Dioxygenase in Breast Cancer

• Main Authors: Chun-Yu Fu, 傅軍毓
• Other Authors: Li-Yu Tsai
• Format: Others
• Language: en_US
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/56pxxy

碩士 === 高雄醫學大學 === 醫學檢驗生物技術學研究所 === 102 === Backgrounds: Breast cancer is the most frequently diagnosed cancer in woman. In present study, the new breast cancer classification which based on molecular features divides breast cancer into five groups. Indoleamine 2,3-dioxygenase (IDO1) and the new enzyme, IDO2, are the enzymes of tryptophan along the kynurenine pathway. Kynurenine, a tryptophan metabolite, will affect the growth cycle of T lymphocytes to make tumor cells enhance the immune tolerance to escape from immune surveillance. Through this mechanism, IDO mediates immune escape of tumor. A simple small molecule chemically inhibitor, 1-mehtyl-tryptophan (1MT) has been discovered and been used widely to inhibit the activity of IDO in cancer and in other immune diseases. There are two stereoisomer of 1MT that remains the question of which isomer would be more suitable one in immune therapy. In this study, we measured the status of IDO1 and IDO2 in patients with breast cancer and in the four breast cancer cell lines. Also, the cells were treated with 1MT to estimate the changes of the IDO1 and IDO2 status. Materials and Methods: To investigate the correlation between the expression of IDO1 and IDO2 and the expression of HER2 in breast cancer patients, we enrolled 115 tissue sections to perform their immunohistochemical staining (IHC) for the expression of IDO1 and IDO2. In addition, to explore the alteration of the activity of IDO in the patients with breast cancer, we measure the levels of tryptophan and kynurenine in the serum of the patients (N=122) and the controls (N=62) by the capillary electrophoresis. Moreover, four breast cancer cells (MDAMB231, MCF7, SKBR3, and BT474) were treat with different concentration of 1MT and estimated the change of IDO1 and IDO2 in mRNA level and in protein level. Results: There were strong positive relationships between the expression of IDO1 and HER2 and between the expression of IDO2 and HER2 in the patients. Compared with the healthy women, patients with breast cancer showed increased kynurenine levels but lower tryptophan levels. In addition, the Kyn/Trp ratios in healthy women were lower than those in the patients. Moreover, the Kyn/Trp ratios in the HER2 positive breast cancer patients were significantly higher than those in the HER2 negative breast cancers. In cell experiment, without any treatment, BT474 cell line has the highest expression of IDO2 and the lowest is the MDAMB231. When treated with IFN-γ, both IDO1 and IDO2 can be induced. However, the increased percentage of IDO1 expression is much more than the increased percentage of IDO2 expression. The last, when cells treated with different concentrations of 1MT, Luminal A subtype (MCF7) and Luminal B subtype (BT474) showed the similar consequences which can be inhibited by L-1MT only or combined both stereoisomer. In HER2 subtype and basal like subtype, the best treatment to inhibit the expression of IDO2 is with D-1MT. Conclusion There is a positive relationship between IDOs and the HER2 protein in breast cancer patients. Also the levels of kynurenine, tryptophan, and the Kyn/Trp ratio in serum indicated the same results. In cell experiment, the expressions of IDOs in each breast cancer cell lines are different. In addition, they have different response to the treatment with L-1MT, D-1MT, or combined with both stereoisomers. Different from the results of the first experiment, it showed that the Luminal subtypes of breast cancer demonstrated similar responses to the different treatments.