Study Sheds New Light on Cancer-Fighting Potential of Herbal Supplement for Prostate Cancer

SEATTLE — Nov. 5, 2002 — The research sheds new light on the cancer-fighting mechanisms of PC-SPES, an herbal supplement taken by men with advanced prostate cancer to slow the progression of their disease. "PC" stands for prostate cancer; "SPES" is Latin for hope. Peter Nelson, M.D., an associate member of Fred Hutchinson's Human Biology and Clinical Research divisions and an associate professor of medicine at the University of Washington, led the research. Michael J. Bonham, a graduate student in Nelson's lab, was first author on the paper.

While PC-SPES has long been known to act as an estrogen, blocking male hormones that fuel prostate cancer, the researchers found that it also effectively thwarts cancer growth by inhibiting the assembly of specific structural components within prostate-cancer cells, killing the cells and blocking tumor growth. The researchers also found that the supplement contains compounds that behave much differently from estrogens. More research is needed to identify these compounds and understand how they work.

Just as PC-SPES blocks the assembly of structural components that provide support for a cancer cell, several traditional chemotherapy agents, such as Taxol, work in the opposite way by inhibiting the breakdown of the same components. Either way, the cell dies. The researchers found that while PC-SPES and Taxol effectively kill cancer cells independently, the drugs are less effective when combined. They act against each other, which could decrease the effectiveness of therapy.

Funded by CaP CURE and the National Cancer Institute, the research was laboratory-based; it is unknown whether the results would translate to humans. For the study the researchers analyzed the interaction of PC-SPES extracts and Taxol on human prostate-cancer cells that had been grafted into mice.

PC-SPES, a Chinese dietary supplement consisting of eight herbs, in February was voluntarily recalled by its manufacturer, BotanicLab, due to concerns that it was tainted with undeclared prescription-drug ingredients such as DES (an estrogenic agent) and coumadin, a blood-thinning agent.

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