What is Angiogenesis?


Angiogenesis is the formation of new blood vessels. This process involves the migration, growth, and differentiation of endothelial cells, which line the inside wall of blood vessels. It is necessary in the development of a baby, and "good" in the setting of tissue repair, but bad in the setting of cancer.

Angiogenesis is a complex process of coordination between proangiogenic factors and inhibitors. Under normal circumstances, the two factors are in a state of balance. Once the balance is broken, the vascular system will be activated, resulting in excessive angiogenesis or the vascular system will be inhibited and the blood vessels will degenerate.





Fig.1 Angiogenesis morphology (Picture from


The Process of Angiogenesis


The process of angiogenesis involves several steps involving endothelial cells (the cells that line the vessels). The process is shown in Figure 2:

Fig.2 The process of angiogenesis


Angiogenesis and Cancer


Angiogenesis plays an important role in the growth and progression of cancer. Tumors require a rich blood supply to grow and continue to divide rapidly. Angiogenesis is essential for further tumor growth, is therefore a key step in the transformation of a benign tumor into a malignant one. For this reason, inhibition of angiogenesis is a key target of anti-tumor cancer therapies. The most important clinical implication of tumor angiogenesis is the development of a novel strategy of anticancer therapy targeting tumor vessels instead of cancer cells. Antiangiogenic therapy aims to inhibit the growth of tumors, and current evidence suggests that it works best in combination with conventional cytotoxic chemotherapy.


Fig.3 Illustration of the progression of angiogenesis (Image credit: Dr. Jon Heras)

Angiogenesis is regulated by both activator and inhibitor molecules. More than a dozen different proteins have been identified as activators and inhibitors of angiogenesis. The expression levels of angiogenic factors reflect the aggressiveness of tumor cells. For example, VEGF is a potent stimulator of angiogenesis because, in the presence of this growth factor, plated endothelial cells will proliferate and migrate, eventually forming tubular structures resembling capillaries. Other chemical signals, called angiogenesis inhibitors, interfere with the formation of blood vessels.

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