Current strategies and future directions of antiangiogenic tumor therapy.

Neovascularization is a prerequisite for progressive growth of most tumors and their metastases. Therefore, inhibition of angiogenesis could be one of the most promising strategies that might lead to the development of novel anticancer therapy. New blood vessels forming in tumors can be avoided by interfering the process of angiogenesis through suppressing the proangiogenic signal or augmenting the antiangiogenic factors. Concentrated efforts in this area have lead to the discovery of many proangiogenic factors as well as their inhibitors, and antiangiogenic factors. For the established tumor vasculature, tumor vasculature-targeted delivery of antiangiogenic substances and endothelial cell vaccines has been explored. Although some antiangiogenic drugs are currently in clinical development, for future reason, more efficient therapeutic methods, including antiangiogenic gene therapy strategy, targeted drug delivery system, and the combination of antiangiogenic agents with immunotherapy, chemotherapy or radiotherapy are being explored. With the development of tumor model assessment system, clinical use of the above antiangiogenic tumor therapy methods could be achieved.