Almost everyone has some cancer cells in their body. However, for most of us the cancer is idle or dormant, and described medically as cancer in situ. It remains dormant, or in situ, because it lacks a blood supply to grow.
If blood vessels emerge to feed the cancer cells, they grow. The process of blood vessel emergence is called angiogenesis. If angiogenesis can be stopped, the cancer will stop growing.
There are many substances that can induce angiogenesis. These are called vascular endothelial growth factors (VEGF). To date, 14 of these factors have been discovered. Science has developed several drugs which can inhibit the action of some of these factors.
Substances which inhibit angiogenesis are called anti-angiogenesis factors. The first anti-angiogenesis factor to be discovered was Inteferon in 1980. Since then many others have been identified. A recently approved anti-angiogenesis factor, Avastin, has received a great deal of acclaim. Erbitux, an epidermal growth factor receptor inhibitor, has also received much attention in the press. In addition, the sedative drug, thalidomide, (which is well-known for causing birth defects) has been discovered to have anti-angiogenic effects; as have cox-2 inbitors, such as Celebrex.
In addition to growing blood vessels to feed cancer cells, angiogenesis also grows the blood vessels which feed the normal cells needed for normal living. Therefore, a delivery system which targets cancer cells, and spares angiogenesis in normal cells, is important to anti-angiogenic therapy. Direct injection (intratumoral injection) of anti-angiogenesis factors may be the key to such percision.
With intratumoral injection, image guidance (CT scan, for example) is used to place a hollow needle into the tumor. The anti-angiogenic chemotherapy, mixed with oil, is injected directly into the tumor. The oil helps to bind the chemo to the tumor so that it stays there to do its work. Intratumoral injection runs about $5,000 per treatment.
This same delivery system can also be used for gene therapy. Instead of injecting chemo, an adenovirus containing p53 can be injected into the area of the tumor. This could correct the genetic error causing the cancer.
