ABSTRACT
Angiogenesis is controlled by a number of pro-angiogenic and anti-angiogenic factors, which can also be regulated by the oxygen-tension of the microenvironment. This phenomenon has been termed the “angiogenic switch” (Hanahan and Folkman 1996). These classical angiogenesis regulation pathways have been well-described
in numerous studies. Equally, it is well-established that tumors express and secrete several factors that stimulate angiogenesis, including the classical growth factors (VEGF and bFGF), thrombospondin and angiopoetin. However, tumors produce a number of non-classical factors capable of modulating the angiogenesis process. These factors can be classified as 1) peptides or proteins (e.g., Cox-2, galectins, iNOS), 2) lipids and steroids (e.g., steroid hormones and retinoic acid), and 3) other small molecules (e.g., nitric oxide). This chapter will describe these factors, provide the latest research findings concerning the roles they play in angiogenesis, and explore possible mechanisms for the effects of these factors.
