Immune cells within the tumor microenvironment

A plethora of intrinsic and extrinsic factors, including communication between tumorigenic cells and infiltrating immune cells, fibroblasts, epithelial cells, vascular and lymphatic endothelial cells, cytokines and chemokines, constitute the tumor microenvironment. Although cancer cells can be immunogenic, tumor progression is associated with the evasion of immune surveillance, the promotion of tumor tolerance, and even the production of pro-tumorigenic factors by tumor-infiltrating immune cells. Here we will review the different types of immune cells within the tumors, with a focus on their fundamental role in tumor growth and immune escape, namely cancer immunoediting. Unraveling their roles and the molecular mechanisms of action represents today an important issue for the development of new therapeutic approaches to fighting cancer.