Angiogenesis is fundamental to reproduction, development, and repair. All these processes depend on the tightly regulated growth of blood vessels that can “turn on” and “turn off” within a brief period. When blood vessels grow unabated, angiogenesis becomes pathologic and sustains the progression of many neoplastic and non-neoplastic diseases. The realization that tumor growth requires new blood vessels and the identification of chemical factors that mediate angiogenesis have broadened our understanding of pathologic processes and opened new avenues to the diagnosis and treatment of these diseases.

Tumor hypervascularity was initially thought to reflect inflammatory vasodilation of preexisting host vessels, a . . .