Anti-angiogenesis in prostate cancer: knocked down but not out

Angiogenesis is a very complex physiological process, which involves multiple pathways that are dependent on the homeostatic balance between the growth factors (stimulators and inhibitors). This tightly controlled process is stimulated by angiogenic factors, which are present within the tumor and surrounding tumor-associated stromal cells. The dependence of tumor propagation, invasion and metastasis on angiogenesis makes the inhibitors of new blood vessel formation attractive drugs for treating the malignancies. Angiogenesis can be disrupted by several distinct mechanisms: by inhibiting endothelial cells, by interrupting the signaling pathways or by inhibiting other activators of angiogenesis. This strategy has shown therapeutic benefit in several types of solid tumors, leading to Food and Drug Administration (FDA) approval of anti-angiogenic agents in the treatment of kidney, non-small cell lung, colon and brain cancers. Although no angiogenesis inhibitors have been approved for patients with metastatic prostate cancer, therapies that target new blood vessel formation are still an emerging and promising area of prostate cancer research.