The Prostate Cancer Protection Plan : The Foods, Supplements, and Drugs that Can Combat Prostate Cancer
By Robert Arnot, M.D.
Although the final verdict on soy and prostate cancer is still out, soy looks like a true wonder food because of its myriad effects. The most powerful component of soy in protecting you against prostate cancer appears to be genistein. What is genistein? Genistein is secreted in the roots of the soybean. Its role is to attract to the soybean the bacteria that fix nitrogen in the soil. Technically, genistein is a plant estrogen. You needn't be alarmed that you're taking a female hormone, since genistein has only l/1000th the power of full-strength estrogen. Genistein's real strength is that it acts in nearly a half dozen quite different ways as an anticancer agent. Listed below are the most important mechanisms known to date. Experts emphasize that these different mechanisms don't work independently of one another but are interconnected. The big picture is that genistein can slow cell growth and even the spread of tumors.
Stops New Blood Vessel Growth
Just as an army travels on its stomach, a cancer needs new blood vessels to grow, spread, and metastasize. The tumor's blood supply growth is called angiogenesis. There are two distinct stages of blood vessel growth, or angiogenesis, in prostate cancer development. The first is a "prevascular" phase, in which there is a limited amount of growth but the tumor hasn't completed all the steps necessary to become a full-blown cancer. When the next stage kicks in, there is substantial development of new blood vessels. This finally allows the cancer to grow freely, to spread, and even to metastasize after years of lying in wait. That's why so many preventive medicine experts so strongly favor taking chemoprevention agents that inhibit this blood vessel growth. Dr. Adlercreutz showed that genistein inhibits metastasis by inhibiting the tumor's blood vessel growth.
Slows the Prostate Cancer Cell Cycle
The speed at which cells grow and divide is regulated by the speed of the cell cycle. One powerful substance that controls the prostate cancer cell cycle is P-27, which acts as a brake. The more P-27 the better. When P-27 is increased, researchers see a decrease in speed of progression through the cell cycle. Healthy men have an abundance of P-27 in their prostate cells, which keeps the cell cycle in check. Where does genistein fit in? Dr. Qingyi Wei of M. D. Anderson found that the intake of genistein increases the P-27 expression. In theory, the more genistein, the more P-27. Steven Hursting, Ph.D., of M. D. Anderson found that genistein, even at fairly low concentrations, slows down the rate at which the human prostate cancer cells progress through the cell cycle.
Certain compounds signal the cell to increase cell growth. They do so by attaching to receptors that act as on-off switches. Genistein can interfere with the cell signaling by blocking the receptors at two levels. Think of a room with a lighting system that has both a wall switch that if flicked can turn on several lights in the room and a master switch that if off will not permit the wall switch to turn on the lights. Genistein can block both the wall switch and the master switch.
Here's an example of how it can block the wall switch. Epidermal growth factor (EGF) locks onto the receptor in the cell and causes the cell to grow. A group of Japanese researchers led by Dr. T. Akiyama found that genistein is a superb inhibitor of the epidermal growth factor receptor. Genistein blocks the EGF receptor so the cell nucleus does not get this signal to continue growing.
Genistein also blocks the master switch, which Allan Wells, M.D., Ph.D., of the University of Pittsburgh says is the adhesion switch. For the wall switch to work in the first place, the adhesion or stickiness among cells has to be lessened. Responsible for the decrease in stickiness is a class of enzymes called the tyrosine kinases. And genistein blocks the tyrosine kinase receptors so that they can't cause a decrease in stickiness.
Maintains Cell Stickiness
In their normal state cells are tightly linked to other cells. For a cancer to grow, one of the things required is to loosen these adhesions to other cells. In fact, a change in stickiness is one of the differences between tumor cells and normal cells. Cancer cells usually have a decrease in stickiness that allows the cells to grow and travel. Cell migration is important for the cancer growth, because it allows tumor invasion and metastasis. And by blocking the tyrosine-kinase receptors, genistein blocks the tyrosine-kinase pathway that causes less cell stickiness.