Angiogenesis is a biological phenomenon, where new blood capillaries in adults are developed from preexisting primary blood vessels by sprouting and branching, responding directly to tissue demands .<br />Angiogenesis is required for invasive tumor growth and metastasis and constitutes an important point in the control of cancer progression and is an essential component of the metastatic pathway.<br />Chronic and sustained angiogenesis, a hallmark of cancer, is vital for continued tumor mass development, and is functionally essential for multistage tumorigenesis .Its inhibition may be a valuable new approach to cancer therapy. <br />Avascular tumors are severely restricted in their growth potential because of the lack of a blood supply. <br />For tumors to develop in size and metastatic potential they must make an angiogenic switch through perturbing the local balance of proangiogenic and antiangiogenic factors. <br />Frequently, tumors overexpress proangiogenic factors, such as vascular endothelial growth factor, allowing them to make this angiogenic switch. <br /> <br />For many tumors, the vascular density can provide a prognostic indicator of metastatic potential, with the highly vascular primary tumors having a higher incidence of metastasis than poorly vascular tumors. <br /><br />Angiogenesis is generally initiated from capillaries and its regulation exhibits a significant role in tumor progression and metastasis .<br /><br /> Malignant cells need consistent access of the circulatory system, hence tumor growth is accompanied by blood vessels ingrowth, either via new blood vessels formation or through co-optation of the preexistent vasculature. <br /><br />Tumor angiogenesis is regulated by the production of angiogenic stimulators including members of the fibroblast growth factor and vascular endothelial growth factor families.<br /> In addition, tumors may activate angiogenic inhibitors such as angiostatin and endostatin that can modulate angiogenesis both at the primary site and at downstream sites of metastasis. <br />Targeting angiogenic biomarkers could reduce tumor mass and promote tumor regression, providing a rationale for antiangiogenic therapy for tumors. <br />The potential use of these and other natural and synthetic angiogenic inhibitors as anticancer drugs is currently under intense investigation. <br /><br />Such agents may have reduced toxicity and be less likely to generate drug resistance than conventional cytotoxic drugs. <br />To date, several antiangiogenic treatments have been approved by the Food and Drug Administration (FDA), that target proangiogenic growth factors and their receptors.<br />Many pharmaceutical companies have expended massive efforts over angiogenesis therapies involving angiogenesis inhibition in oncology and ophthalmology, as well as angiogenesis stimulation in tissue engineering and wound healing.<br />