Prognostic Value of Tumor-Infiltrating Lymphocytes in Triple-Negative Breast Cancer

The adaptive immune system is a crucial component of cancer immunoediting and has emerged, in recent years, as a key foundation on which the success of novel cancer therapeutics have been built, namely the checkpoint inhibitors. Early observational studies have highlighted the importance of tumor-infiltrating lymphocytes (TILs) in patient outcomes across multiple solid tumor types, reflecting its role in cancer immunosurveillance. High TILs in triple-negative breast cancer (TNBC), a poor prognostic subgroup, has been shown to be associated with improved survival. When evaluated in functional TIL subsets, a positive correlation has also been observed with cytotoxic CD8+ TILs but results were conflicting for FOXP3 regulatory T cells. Overexpression of immune response genes corresponded to increased lymphocytic infiltration and improved outcomes in TNBC. Understanding the functional biology of TILs and its interaction with cancer in the immunoediting processes will help guide immunotherapeutic approaches in TNBC. © 2015, Springer Science+Business Media New York.