One of the keys to finding a cure for cancer is to understand how cancer grows and spreads within the body. Angiogenesis is our body's ability to form new blood vessels. This is important and needed for the body to help heal wounds and is also a part of a woman's menstruation each month. Its function in our bodies is a positive thing most of the time.
Angiogenesis also has a role in how cancer cells grow to become tumors. Cancer cells need a blood supply to live and grow. The cancerous tumor actually develops its own blood supply by sending messages to nearby blood vessels. These vessels then have the ability to grow toward the tumor. The tumor then has its own blood vessels to thrive, survive and grow.
This was not taken seriously back in 1961 when Dr. Judith Folkman came up with the theory of angiogenesis. He felt strongly that tumors could not grow bigger than a head of a pin without blood supply. He thought that an entirely new way to treat cancer would be to block this blood vessel growth to the tumor. Decades of work has proven this theory to be correct. What changed a lot of people's minds was an experiment that was done at the end of the 1970's at Dr. Folkman's lab. Tumor cells were put into a rabbit's eye, a place in the eye where there are no blood vessels. Blood vessels did grow toward and into the eye where the cancerous cells lived.
Our bodies can make chemicals that prevent angiogenesis from occurring when it isn't needed. Something goes wrong when the cancer cells are able to make this process happen on it own. Angiogenesis inhibitors can inhibit blood vessel growth. This is not a new concept and there are many clinical trials in process and being developed to use and find new inhibitors to stop the cancer from getting its supply of nutrients.
In the future they hope to use the angiogenesis inhibitors along with chemotherapy to completely stop cancer from growing.
1. Angiogenesis is essential for the growth and metastasis (spread) of cancer. A growing tumor requires nutrients and oxygen, which helps it grow, invade nearby tissue, and metastasize. To reach these nutrients, the tumor builds new blood vessels. In fact, growing tumors can become inactive if they can't find a new supply of nutrients.
Because angiogenesis is necessary in the growth and spread of cancer, each part of the angiogenesis process is a potential target for new cancer therapies. The assumption is that if a drug can stop the tumor from receiving the supply of nutrients, the tumor will "starve" and die.
However, there are multiple ways by which tumors can evolve that are independent of angiogenesis. There are some scientists that believe the realization of Dr. Judah Folkman's brilliant dream of inhibition of angiogenesis, or new blood vessel formation, and starving tumors by shutting off their blood flow, is not sufficient to consistently control cancer.
Tumors can acquire a blood supply by angiogenesis, but some say also by co-option of existing blood vessels, and vasculogenic mimicry. All must be inhibited to consistently starve tumors of oxygen.
Vascular co-option is the invasion of malignant cells along blood vessels. Instead of growing new blood vessels, tumor cells can just grow along existing blood vessels. This process cannot be stopped with drugs that inhibit new blood vessel formation.
Vasculogeneic mimicry is where some types of cancers form channels that carry blood, but are not actual blood vessels. Drugs that target new blood vessel formation also cannot stop this process.
All three of these processes involve the use of normal cellular machinery to carry out proliferation and invasiveness.
The consistent and specific control of cancer requires therapy that can target the set of "all" malignant cells that could evolve. It is critical that each drug be given at a dose sufficient to kill "all" cells that express the pattern targeted by the individual drug. That requires that all three mechanisms be addressed.
These new targeted drugs mostly need to be combined with active chemotherapy to provide any benefit and the need for predictive tests allowing for a rational and economical use of them for individualized therapy selection has increased.
Posted at 1:32AM on Jul 23rd 2006 by Gregory D. Pawelski