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CancerQuest > Introduction to Patient Information > An Introduction to Cancer Treatments > Targeted Therapy > Angiogenesis Inhibitors

Angiogenesis Inhibitors

Like all cells, cancer cells require a constant supply of nutrients and oxygen in order to grow and divide. Without an adequate blood supply tumors will not grow. Tumors produce factors that stimulate the formation of blood vessels to provide them with the food and oxygen they need.

The process of blood vessel formation is termed angiogenesis. One way to inhibit the development of blood vessels is to block the signals coming from the tumor.  Cancer cells either directly produce signals that cause blood vessels to form or they 'trick' nearby, non-tumor, cells to send out the signals.

One possible benefit of this type of cancer treatment is that they should have less negative effects (side effects) on the patient. Angiogenesis occurs at high levels during fetal development, the menstrual cycle and in wound healing. The treatments might be expected to interfere with these processes but should not harm most normal dividing cells.

Unlike conventional chemotherapy, the cancer cells are not directly killed by the treatment.  The targets of several of these treatments are normal processes controlled by normal cells (such as the cells that form blood vessels), not the tumor cells themselves. Cancer cells are very unstable but the targets of these drugs should be much less likely to change in the presence of the drugs.  This might make the cancer cells less likely to become resistant to these types of treamtent.

There are other approaches to the inhibition of angiogenesis which are actively being investigated:

1. Matrix Metalloproteinases Inhibitors: The degradation of the extracellular matrix that surrounds all cells is an important process in the in the formation of new blood vessels. As described in detail in the section on metastasis, this process is also integral to the spread of tumor cells to distant locations in the body.Growing blood vessel cells secrete enzymes called matrix metalloproteinases (MMPs) that are able to digest the extracellular matrix and allow blood vessels to invade the area and supply the tumor with nutrients. Inhibition of this process is the target of several drugs.
2. Endothelial Cell Inhibitors: Several different drugs are under investigation that inhibit angiogenesis by acting to prevent the growth or activities of the endothelial cells that form the blood vessels.
3. Inhibitors of Angiogenesis Activation: The drugs in this class of angiogenesis inhibitors work by blocking the cascade of events that cause blood vessels to form.

The targeted drugs currently being developed may actually affect more than one target.  Sometimes this is intentional and other times it is an unavoidable side-effect of the drug.

Some FDA approved drugs that work (at least in part) by preventing angiogenesis:

Bevacizumab (Avastin®)

Cetuximab (Erbitux®)

Sorafenib (Nexavar®)

Sunitinib (Sutent®)

Thalidomide (THALOMID®)

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