Significance of Foxp3 positive regulatory T cell and Tumor infiltrating T lymphocyte in triple negative breast cancer

Background: Triple negative breast cancer (TNBC) is defined as a lack of the expression of estrogen receptor, progesterone receptor and human epidermal growth factor receptor 2 in breast cancer. Many TNBCs show a profound infiltration of tumor infiltrating lymphocytes (TILs). It is still uncertain whether these TILs are protumoral or antitumoral. Regulatory T cells (Tregs) play a role in inducing immune tolerance to antigens, and they may be selectively recruited by cancer cells. This study was conducted to evaluate the significance of TILs with an emphasis on forkhead box p3 (Foxp3), which is a marker for CD25+CD4+ Treg in TNBC. Methods: We investigated the Fox-p3, CD8 and CD4 expressions in 100 cases of TNBC by immunohistochemistry and using a tissue microarray. The Foxp3 expression was divided as the high and low infiltration groups (cut-off value=20). Results: The high infiltration group was correlated with higher histologic and nuclear grades. However, Foxp3+ Tregs were decreased in the T3 and T4 TNBCs as compared to that of the T1 and T2 TNBCs. No significant differences were found for the nodal status, lymphovascular invasion, stage, recurrence and overall survival. Conclusions: High Foxp3+ Treg infiltration in TN-BC is correlated with the nuclear and histologic grades, but there was no relation to recurrence and overall survival.