Angiogenesis and cancer.

Tumor development, growth and progression depends on an adequate vascular supply, which derives from the host vasculature. This process involves complex interactions between tumor cells and nonneoplastic vasculature, the immune system, and the connective tissues. Tumor angiogenesis refers to the development of new vessels within the tumor. An imbalance between angiogenic growth factors and inhibitors released by the tumor cells and/or endothelial and inflammatory cells is necessary to produce tumor neovascularization. In the last two decades, several studies have clarified the main aspects of this phenomenon, although further analysis will be necessary to understand if tumoral neoangiogenesis can play a pivotal role as a potential target for innovative anticancer therapies. Here, I review and update the basic aspects of tumor angiogenesis, as well as the role of the quantitative analysis of tumor vasculature as an independent prognostic indicator in human cancers.