The formation of new blood vessels, or angiogenesis, is an Achilles’ heel of tumor growth, because tumors depend on the supply of oxygen and nutrients for survival. Therefore, for some years now substances called angiogenesis inhibitors have been used in cancer treatment to suppress this process.

The two vascular systems in mammals develop sequentially during embryonic life. The blood vascular system, which is essential for the delivery of oxygen and nutrients to the tissues, develops first. This is followed by the lymphatic vascular system that returns extracellular fluid and proteins back to the blood vascular system from the spaces between the tissues.