Infiltration of γδ T cells, IL-17+ T cells and FoxP3+ T cells in human breast cancer

BACKGROUND: Tumor-infiltrating lymphocytes (TILs) have a strong prognostic value in various forms of cancers. These data often refer to use of the pan-T cell marker CD3, or the cytotoxic T lymphocyte marker CD8 alpha. However, T cells are a heterogeneous group of cells with a wide array of effector mechanisms ranging from immunosuppression to cytotoxicity. OBJECTIVE: In this study we have investigated the prognostic effects of some unconventional T cell subtypes in breast cancer; gamma delta T cells, IL-17(+) T cells and FoxP3(+) T cells (T-regs) in relation to the conventional CD3 and CD8 alpha T cell markers. METHODS: This was done using immunohistochemistry on a human breast cancer tissue microarray consisting of 498 consecutive cases of primary breast cancer. RESULTS: Infiltration of gamma delta T cells and T cell infiltration in general (CD3), correlated with a good prognosis, while T-reg infiltration with a worse. Infiltration of gamma delta T cells was associated with a significantly improved clinical outcome in all breast cancer subtypes except triple negative tumors. Only infiltration of either CD3(+) or CD8 alpha(+) cells was independently associated with better prognosis for all breast cancer patients. CONCLUSIONS: This study sheds further light on the prognostic impact of various T cell subtypes in breast cancer.