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"Tumor angiogenesis" is a medical term for the way tumors create new blood vessels in the body. These new blood vessels channel nutrients and oxygen directly to the tumor, allowing it to grow. Chemical signals are produced by the tumor to trick the body into making these vessels.
Tumors are made up of cells that multiply abnormally and cause disease. These cells need the same type of nutrients as normal cells. Regular cells of the body are supplied by blood vessels, which carrying oxygen, essential micro-nutrients such as iron and energy sources such as glucose.
The nutrients enter the body through the gastrointestinal system and the lungs. There they are broken down if necessary and are transported into the circulatory system. The blood system then carries them through the major blood vessels, into smaller capillaries and across the vessel wall into the spaces between the cells. Then the cells can take up the nutrients they need. The body can create new networks of these vessels if necessary.
As tumors grow, the existing blood vessels might not be able to meet all of the needs of the new tumor cells. Cells that are located too far from a blood vessel become starved of oxygen and nutrients, so they die. Tumor angiogenesis typically begins when tumor cells at a certain critical distance from a blood supply sense that they are becoming starved.
A tumor takes advantage of the body's capability for angiogenesis. To do this, the tumor releases chemical signals known as growth factors. These growth factors signal the body to create new vessels.
Growth factors include a chemical known as vascular endothelial derived growth factor (VEGF). Expression of these growth factors might also be increased by the presence of genetic mutations. These mutations either block proteins that could control the growth factors or produce signals that actively increase the amount of growth factors produced.
VEGF and other growth factors usually are beneficial to the body under normal circumstances, but the tumor uses them to help itself. Tumor angiogenesis does not always trick the body into creating new blood vessels of a good quality. Sometimes the new vessels leak more often than a regular vessel and are less organized than they otherwise would be.
Tumor angiogenesis is so important to the survival and growth of a tumor that it is a potential target for cancer treatments. If researchers can identify a way of effectively preventing these new vessels from growing, it would starve the tumor and stop it from growing. If a tumor could not induce angiogenesis, tumors would be able to grow only to a point of less than 1 inch (2.54 cm) in diameter.