Angiogenesis:
Tumor Blood Supply

As discussed earlier, angiogenesis (the development of new blood vessels) is a normal process in growth and development, as well as in wound healing. However, this is also a fundamental step in the transition of a tumor from a dormant state to a malignant state.

A great deal of research has led to the understanding that cancer cells send out signals to create adequate blood supplies.

Image courtesy of the National Cancer Institute

The success of this angiogenesis process is necessary to sustain cancer growth.

Angiogenesis is also required for the spread of a tumor, or metastasis, as well.

Single cancer cells can break away from an established solid tumor, enter the blood vessel, and travel to a distant site, where they can implant and begin the growth of a secondary tumor.

Therapeutic anti-angiogenesis uses synthetic compounds that may inhibit the creation of new blood vessels in the body in order to impede the growth of cancerous tumors. Almost two dozen angiogenesis inhibitors are currently being tested in cancer patients.

 

Angiogenesis Inhibitors:

These inhibitors fall into several different categories, depending on their mechanism of action:

• Some inhibit endothelial cells that line the blood vessels:

• Endostatin

• Combretastatin A4

• Thalidomide

• Others inhibit the angiogenesis signaling cascade:

• Bevacizumab (Avastin)

• Interferon-alpha

• Some block the ability of endothelial cells to break down the extracellular matrix:

• Marimistat

• Neovastat

CISN Summary

• Tumors cannot grow beyond a certain size, generally 1-2 mm³, due to a lack of oxygen and other essential nutrients.




• To maintain their needed oxygen supply, tumors induce blood vessel growth (angiogenesis) by secreting various growth factors (e.g. Vascular Endothelial Growth Factor or VEGF).




• Angiogenesis inhibitors attempt to stop or slow tumor blood vessel growth, limiting cancer's ability to grow.