Dr. Shuyuan Yeh, professor and researcher at the University of Rochester’s Department of Urology and Pathology, came a step closer to cracking the code of cancer last month in her discovery of how a particular protein allows Vitamin E tocopherol to fight prostate cancer. This study provides the closest look ever into the mechanism of action of alpha tocopherol protein, or TAP. It’s a bodily protein that is produced within the liver, as well as other cells within the body.
Yeh’s research is vitally important because prostate cancer is the most common cancer in U.S. men. Around one out of every six men in the U.S. gets prostate cancer. A predicted 232,000 new cases of prostate cancer will be diagnosed this year alone, and there will be a predicted 30,000 deaths from the disease.
Yeh is intent on discovering the power Vitamin E contains—a power that can work in the battle against cancer. “Vitamin E can influence the mortality of the cancer rate,” says Yeh. Enough studies have been done to prove that Vitamin E has a modifying effect on prostate cancer. Yeh and her team at the University of Rochester are among the many scientists studying the exact modes of action of Vitamin E in order to use it most effectively.
With continued research into TAP, levels of the protein could be used by doctors to predict both a cancer’s aggressiveness, as well as a patient’s potential responsiveness to treatment.
Yeh says that she decided to pursue her research into Vitamin E’s chemical makeup and how it can prevent cancer after a significant research study was published in 1995. Interestingly, says Yeh, “The original goal of that study was to try to prevent lung cancer. It was actually surprising to observe that it (Vitamin E) was very good for prostate cancer and colon cancer.”
Since the publication of the research studies, Yeh and her team at the University of Rochester have made themselves an important part of the cancer research scene. A 2002 study spearheaded by Yeh paved the way to the current one. “My 2002 study,” says Yeh, “shows the reason for the cell proliferation increases in cancer. A lot of people don’t understand how cancer works—they think that cancer grows ‘all out of control.’ In my 2002 study, we found the reason for cell proliferation increases. Vitamin E can slow down the cancer cell growth cycle.”
Doctors and scientists are still not sure why, but although prostate cancer “invariably” goes away after treatment, it seems to always return. Advanced- stage prostate cancer treatments focus on reducing testosterone levels, because the male hormones—known as androgens— are known to have a causative relationship with prostate cancer. That's why many studies focus on trying to block the development of any chemicals which might serve to stimulate androgen production and thus feed the growth rate of the cancer.
The protein identified by Yeh’s team, TAP, disrupts a signaling pathway in prostate cancer cells, thus suppressing the growth of cancer. The TAP also allows beneficial Vitamin E to be held in the cancer cells longer, further halting growth of the cancer.
High levels of TAP were found in normal, healthy prostate tissue epithelial cells. The recent study proved for the first time that TAP, a protein found in the body, supports the retention of Vitamin E. In addition, the team found the way in which Vitamin E accesses cells—with the assistance of TAP. The TAP increases Vitamin E’s ability to slow the growth of cancer cells.
This was not the first time Yeh has sought to look behind the curtain of Vitamin E’s power over cancer. In a 2002 study released in Proceedings of the National Academy of Sciences, Yeh and her team showed the scientific community how the vitamin disrupts cancer-causing proteins in the prostate.
“My 2002 study shows how Vitamin E effectively controls androgen receptors,” the scientist explained. Yeh’s 2002 study revealed the exact way in which Vitamin E disrupts the workings of proteins playing a role in causing the cancer. It was discovered that Vitamin E inhibits prostate cancer cells from producing prostate-specific antigen (PSA) and the androgen receptor. In disrupting these components of the cancer cycle, progression of the disease can be slowed.
One finding was that, in prostate cancer, expression levels of TAP are much lower than in a normal prostate. Because of this, TAP may become a valuable warning signal for those at risk for prostate cancer. High levels of TAP protein in prostate cells might have a protective function due, in part, to its relationship to Vitamin E. Possible future uses of TAP include treatment for the disease itself.
Says Yeh, “We tested various forms of vitamin E, and found that an analog form is actually more effective.” Now, Yeh and the rest of the research team at the University of Rochester are trying to find an even more effective analog form of Vitamin E than what is currently available, as well as investigating whether TAP levels can be increased within the prostate. The team is also studying why and how cells can lose their ability to produce the protective TAP protein.
Maximum Vitality contains all the tocopherol and tocotrienol forms of Vitamin E.
Yeh S. Chemopreventive roles of vitamin E in prostate cancer. Cancer Research 2005; Nov 1;Vol 65, issue 21, pp 9807-16. http://www.urmc.rochester.edu/path/fac/shuyuan_yeh.htm