Popular Herbal Compound Causes Prostate Cancer Cells to Die, Study Finds

      A Chinese herbal mixture taken by a growing number prostate cancer patients appears to work in part by inducing tumor cells to die, laboratory studies reveal.

      In the October issue of the Journal of Urology, researchers from Columbia University in New York and Henry Mondor Hospital in France measured the effects of PC-SPES, a compound consisting of eight herbs, on three different human prostate cancer cell lines, on human tumors implanted in mice and in a group of 69 men with prostate cancer.

      Since it first became commercially available in 1996, scientists have been studying PC-SPES, which as an herbal remedy is not regulated by the Food and Drug Administration. While there is a broad consensus that the mixture appears to mimic the actions of estrogens--and therefore counters the impact of tumor-fueling male hormones--investigators haven''t been able to determine exactly how PC-SPES works against prostate cancer (see a related story ).

      "Each herb individually seems to have some anti-tumoral effect," lead researcher Aaron Katz, M.D., of Columbia University wrote in the study.

      In this study, scientists took a three-pronged approach. First, they tested the actions of the compound on human prostate cancer cell lines that included both hormone-sensitive and resistant. After exposure to PC-SPES for five days, the scientists saw that it caused cell death, called apoptosis, in all three cell lines.

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      Next, they gave PC-SPES to mice injected with hormone-resistant human prostate cancer cells. They found that PC-SPES did not suppress tumor growth when injected into mice one week after tumor injection. But if PC-SPES therapy began the same day as tumor injection, it led to smaller tumors, compared to those in animals not receiving PC-SPES.

      Though this difference did not reach statistical significance, the tumor shrinkage, combined with shrinkage of the testes and prostates of treated mice, led Katz to conclude that PC-SPES has estrogen-like effects.

      "There was also an increased apoptotic rate in these sexual accessory tissues in PC-SPES-treated versus untreated mice, which would support the estrogenic effect of PC-SPES," he wrote.

      The third facet of the study examined the effects of PC-SPES in men with prostate cancer. The 69 men were split into three groups: 43 men who had received prior therapy and were considered to have hormone-sensitive disease; 22 men who had received prior hormone therapy but were experiencing a recurrence and classified as having hormone-resistant cancer; and four men who were receiving PC-SPES as primary therapy.

      All patients took capsules of 320 milligrams of PC-SPES orally three times a day. Of the four patients receiving PC-SPES as primary therapy, two had a decline in levels of the tumor marker prostate-specific antigen (PSA) of greater than 50 percent after two months. Of the 22 men with hormone-resistant disease, PSA decreased in 90 percent after two months, and remained lower at six months in 74 percent. Of the 43 men considered to have hormone-sensitive disease, decreased PSA was observed in 82 percent at two months, 78 percent at six months and 82 percent at 12 months.

      In terms of side effects, 42 percent of all the men reported swollen, tender breasts, 7 percent had hot flashes and 2 percent had clots in their veins.

      Katz concluded that "the observation that this agent has a clinical effect on patients with hormone-resistant prostate cancer suggests that estrogen-like activity is not its sole mechanism of action."

      In an accompanying editorial, Ian Thompson, Jr., M.D., of the University of Texas Health Science Center in San Antonio called the findings of the study both "exciting and disturbing."

      "The prospect of lives saved in an otherwise incurable disease is an electrifying development," he wrote.

      But he cautioned that strokes and heart attacks attributable to PC-SPES could occur as the popularity of this untested and unregulated compound grows.

      "The efficacy and toxicity of PC-SPES should be a call to action for elected officials to demand testing of agents, such as these, that by any other definition are truly pharmaceuticals," he wrote. "We cannot allow any less for our patients."

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