Angiogenesis is an important natural process for generation of new vasculature during embryonic development and in tissue or wound repair. Angiogenic growth factors, including numerous cytokines, chemokines and growth factors, activate cells present in existing blood vessels to proliferate and form new vessels, as well as to release additional factors into the microenvironment.
While research around this process is important for diseases characterized by poor vascularisation, there is ever-increasing research on angiogenic processes in the development and support of tumorigenesis. Oncogenes can induce the release of angiogenic factors that recruit and reprogram other cells, induce cell differentiation, and establish a tumor microenvironment. Consequently, tumor tissues contain a large number of endothelial cells, fibroblasts and tumor-infiltrating-lymphocytes (TILs) that modulate the immune response in the microenvironment.