The Paradigm of T Cells in Shaping Tumor Microenvironment

The infiltration of immune cells in the tumor micro-environment is well-documented in cancer patients and the resultant complex interactions are determinants of disease prognosis. Consequently, a proper understanding of this interplay is essential for the development and advancement of therapeutic strategies as well as novel prognostic markers. The co-existence of immune cells with the tumor is often accompanied by an impaired immune response that creates a tumor-promoting micro-environment. T-cell mediated immunity forms the major branch of the immune system that is required to mount an effective response against nascent tumors. Major research in the last few decades indicates that a potent source of immunosuppressive cellular and molecular networks prevailing at the site of tumor is mediated by dysfunctional and defective responses mediated by T cell thereby redirecting and reshaping the destiny of T cell and promoting tumor progression. In this review, we aim to summarize the breakthrough advances in recent years that help us gain a better understanding of the immunosuppressive networks resulting from T-cell anergy, exhaustion, senescence and presence of Treg cells in the tumor micro-environment. We also focus on recent discoveries regarding advance in the Th17 balance, polyfunctionality of T cells as well as T cell stemness that improve our perception of the tumor-immunity interactions. We try to emphasize how such information has an impact on therapeutic development and the clinical outcome of the patients.