Tumor Angiogenesis: A Possible Control Point in Tumor Growth

The growth of solid tumors has an avascular phase and vascular phase. These discrete phases each have unique properties; a diffusible tumor angiogenesis factor seems to be responsible for initiating the vascular phase; and when the avascular phase is prolonged, solid tumors in a variety of experimental models fail to grow beyond a few millimetres. This perspective of the manner by which solid tumors grow has become a guide for further experiments to elucidate the nature of tumor angiogenesis factor, to determine whether tumor neovascularization can be inhibited, and to find out whether the neovascularization that sometimes accompanies wound healing, inflammation, or delayed hypersensitivity operates through a different mechanism than tumor angiogenesis.