CancerQuest >> Cancer Treatments >> Targeted Therapies

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. More details on this process.

The process of blood vessel formation is termed angiogenesis.This process is a very active area of research in cancer treatment for several reasons. 1. The treatments should have low toxicity. 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. 2.The treatments are not designed to directly attack the cancer cells. 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. The high mutation rates of cancer cells that often render chemotherapy ineffective will not interfere with these drugs.

There are also three other approaches to the inhibition of angiogenesis:

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.
   See the Current Research chapter for information on experimental treatments of this type.


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.
   See the Current Research chapter for information on experimental treatments of this type.


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.
   
   One drug is currently approved in this category: Avastin®.