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 CD8α. 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; γδ T cells, IL-17+ T cells and FoxP3+ T cells (Tregs) in relation to the conventional CD3 and CD8α 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 γδ T cells and T cell infiltration in general (CD3), correlated with a good prognosis, while Treg infiltration with a worse. Infiltration of γδ 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 CD8α+ 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.
Keywords: Breast cancer; T lymphocytes; TILs; prognosis; unconventional T cells.