Angiogenesis is an essential process in tumor growth. The concept of angiogenesis, when proposed by Folksman in 1971, had a great impact on cancer research and therapy, as the survival and proliferation of cancer depend on angiogenesis, which could be a target of cancer therapy. In subsequent decades, numerous antiangiogenic agents were developed, and some of them have been applied clinically. However, angiogenesis includes a complex and multistep process that has not been sufficiently elucidated. In this review, we focus on signaling pathways related with tumor angiogenesis and several antiangiogenic agents approved by the United States Food and Drug Administration or under investigation
