Tumor-Infiltrating Lymphocytes and Their Role in Solid Tumor Progression

Abstract

Tumor-infiltrating lymphocytes (TIL) are an important component of the tumor environment. Their role in tumor growth and progression has been debated for decades, with the current emphasis on survival benefits TIL appear to bestow on the host when present in situ as large aggregates of activated T and B cells. Gene signatures and protein profiling of TIL provide clues about their potential functions in the tumor, and correlations with clinicopathological tumor characteristics, clinical outcome, and patients’ survival data indicate that TIL exert influence on the disease progression, especially in colorectal carcinomas and breast cancer. At the same time, the recognition that TIL signatures vary in composition and with time, and that TIL interactions with the tumor cells are complex, calls for a more careful assessment of their prognostic significance. The mechanisms tumors utilize to subvert the host immune system are well-known. The balance between pro- and anti-tumor responses of TIL might be orchestrated by the tumor serving as a measure of its aggressiveness and potentially providing a key to selecting therapeutic strategies and to prognosis.