The Tumor Microenvironment (TME) is a term used to represent the collection of cells, factors, and physiological conditions of the tumor and surrounding tissues. Several reports describe molecular interactions between cancer cells and their microenvironment. In addition, the TME has been shown to have an important role in malignancy5.
The immune system surveils and eliminates tumor cells through the production of inflammatory cytokines, recognition of tumor antigens by dendritic cells, or activation of natural killer cells. Production of cytokines such as TNF-α, IFN-γ, and IL-1β by macrophages and T cells enhances inflammation through additional recruitment of immune cells.
If tumor cells escape immune detection, they can grow and spread to other tissues. This can be done through a variety of mechanisms including the shedding of tumor recognition antigens, tumor associated macrophage (TAM) or myeloid derived suppressor cell (MDSC)-induced immunosuppression, or development of a microenvironment that supports T cell apoptosis6.
Tumor cells can leverage different cellular and non-cellular components of the microenvironment to promote growth and survival under hostile conditions (such as low oxygen and diffusion, and high acid concentration)4,7. These conditions are modulated and maintained by soluble factors such as chemokines, cytokines, growth factors, or exosomes. Endothelial cells (ECs) build up the inner layer of blood vessels in a growing tumor. Tumor endothelial cells (TEC) can benefit tumor cells by promoting angiogenesis, progression, and metastasis. Fibroblasts can also be commandeered by the tumor, changed into carcinoma associated fibroblasts (CAFs), and utilized as a source for growth factors that support angiogenesis6.
Considerable research is ongoing as to the effect of these interactions on the surveillance and treatment of cancer cells8. Understanding how the TME affects cancer progression is expected to make new targets available for cancer cell characterization and cancer treatment5.
Learn more about immune cells and other important cell types in the tumor microenvironment.