The Angiogenesis Foundation educates patients about the role of angiogenesis in cancer development and progression, and about antiangiogenic therapies that are both approved and being developed for their cancer type. Our information comes from the Foundation's comprehensive databases, as well as from our network of leading oncologists, cancer researchers, biopharmaceutical companies, governmental resources, and patient advocacy groups.

The Patient Help Center is made possible by unrestricted educational grants.

Disclaimer:

The materials provided on this site are of an educational nature only, and are not meant to be interpreted as medical advice. If you are a cancer patient, you must seek the care of an experienced oncologist.

Basic Facts on Angiogenesis

• Angiogenesis, the growth of new blood vessels, is an important natural process used by the body for reproduction and for healing injured tissues
  
  
• Blood vessels bring oxygen and nutrients via the circulation to nourish all tissues in the body

• The cells comprising blood vessels are called endothelial cells

• The endothelial cells of a blood vessel also produce molecules that support the growth of tissues

• In females, angiogenesis also occurs each month in the ovaries and in the uterus as part of the reproductive menstrual cycle

• In virtually all other situations, angiogenesis only occurs if there is disease present

• In healthy adults, angiogenesis is kept in check by a tightly regulated balance of angiogenesis growth factors and inhibitors produced in the body
  
  
• Cancer cells take over the body's control of angiogenesis by producing high amounts of angiogenic growth factors to recruit their own private blood supply

Angiogenesis in Cancer

Every cancer begins its existence as a tiny cluster of abnormal tumor cells growing in an organ. Without its own blood supply to bring in oxygen and nutrients, the tumor cannot grow larger than 1-2 millimeters in diameter (about the size of a small pea). While this early stage of tumor growth can last for month or even years, eventually a few cancer cells gain the ability to produce proteins known as angiogenic growth factors. These growth factors are released by the tumor into nearby tissues, and stimulate new blood vessels to sprout vigorously from existing healthy blood vessels toward and into the tumor.

Once new blood vessels enter the tumor:

• The tumor can rapidly expand in size
• The tumor can invade local tissues and organs
• Cancer cells can escape through the new blood vessels into the circulation
• Escaped cancer cells lodge in other organs to form new tumors (metastases)

Antiangiogenic Therapy

Antiangiogenic therapy is a new form of cancer treatment involving drugs called 'angiogenesis inhibitors' that specifically halt new blood vessel growth and starve a tumor by cutting off its blood supply.

More than 300 angiogenesis inhibitor molecules have been discovered so far:

• Some angiogenesis inhibitors are naturally present in the human body — healthy tissues appear to resist cancer growth by containing these antiangiogenic compounds.

• Other angiogenesis inhibitors occur naturally in substances found in green tea, soy beans, fungi, mushrooms, tree bark, shark tissues, snake venom and many other plants and animals.

• Still other angiogenesis inhibitors have been manufactured synthetically in the laboratory.

• Some FDA-approved medicines have also been "re-discovered" to have antiangiogenic properties.

Currently, there are eight different angiogenesis inhibitors approved in the U.S. to treat cancers of the breast, lung, liver, kidney, colon and bone marriow. More than 40 antiangiogenic drugs are being tested in human cancer patients in clinical trials sponsored by biotechnology and pharmaceutical companies, medical centers and by the U.S. National Cancer Institute. These clinical trials are taking place in the United States, Canada, Australia, and throughout Europe.

• Conventional chemotherapy preferentially targets rapidly dividing cancer cells. However, certain normally dividing cells (hair cells, intestinal cells, mucous membranes, bone marrow cells) are also destroyed, which causes the well-known severe chemotherapy side effects of hair loss, diarrhea, mouth ulcer, infection, and low blood counts. Some chemotherapy regimens work very well at treating cancers that are diagnosed early.

• Most antiangiogenic therapies attack only growing new blood vessel (endothelial) cells. Since blood vessels do not grow in normal, healthy tissues, the side effects of antiangiogenic therapy are concentrated primarily at the cancer site. Most antiangiogenic drugs do not kill cancer cells directly and are therefore better tolerated compared to chemotherapy, with fewer and less severe side effects. To keep cancers from regrowing, it is possible that some patients may need to take antiangiogenic drugs as a chronic therapy, although this hypothesis is still being tested in clinical studies.

Three Major Types of Antiangiogenic Therapies

There are three main types of antiangiogenic drugs:

1. Drugs that stop new blood vessels from sprouting (true angiogenesis inhibitors)

2. Drugs that attack a tumor's established blood supply (vascular targeting agents)

3. Drugs that attack both the cancer cells as well as blood vessel cells (the double-barreled approach).

How effective are antiangiogenic therapies for cancer? As mentioned, eight different antiangiogenic drugs have been FDA approved in the U.S. to treat several common, deadly cancer types. In the case of advanced liver and kidney cancer, angiogenesis inhibitors are the first drugs to show any real benefit for these tumor types.  Many other antiangiogenic drugs are still experimental and undergoing clinical trials, the gold standard for determining the safety effectiveness of a new drug. The Angiogenesis Foundation estimates that more than 6,500 patients have received some form of antiangiogenic therapy through a clinical trial.

The majority of cancer patients who are ‘responders’ to antiangiogenic therapy have experienced stabilization of their disease, meaning that their tumors have stopped growing. A smaller percentage of patients have experienced reduction in the size of their tumors, and in a few cases the tumors have disappeared altogether. Clinical trials are underway to determine why some patients respond better to these drugs than others, and which angiogenesis inhibitors work best for specific cancer types.

Clinical studies in different cancer types have shown that antiangiogenic therapy generally works best when used in combination with cytotoxic chemotherapy or radiation. Most experts believe that such combinations will ultimately provide cancer patients with the greatest benefit.