LITTLE FALLS, N.J., June 19 — Certain compounds in green tea may slow the progression of prostate cancer, researchers say.

Men with prostate cancer who consumed polyphenon E — a polyphenol found in green tea — had a significant reduction in biomarkers of cancer progression, James A. Cardelli, PhD, of Louisiana State University, and colleagues reported in the July issue of Cancer Prevention Research.

“These findings support a potential role for polyphenon E in the treatment or prevention of prostate cancer,” the researchers said.

Some studies have shown that green tea may be tied to a reduced incidence of prostate cancer, and its polyphenols have been regarded as a potential cancer therapy.

• Explain that men in a small phase II study who consumed a polyphenol found in green tea had a significant reduction in biomarkers of cancer progression, including VEGF and HGF.

But epidemiological data on green tea consumption are still inconclusive: some studies show possible benefits and others find no effects on risk ratios for cancer, the researchers said.

Last year said FDA announced that the evidence for green tea benefits was inconclusive, because people consume relatively small quantities.

So the researchers conducted an open-label, single-arm phase II clinical trial to determine the effects of short-term supplementation with active compounds in green tea on serum biomarkers in patients with prostate cancer.

The biomarkers included hepatocyte growth factor (HGF), vascular endothelial growth factor (VEGF), and prostate specific antigen (PSA).

They assessed 26 men, ages 41 to 68, who had been diagnosed with prostate cancer and were scheduled for radical prostatectomy.

The men consumed four capsules containing polyphenon E every day until the day before surgery. Four capsules are equivalent to about 12 cups of green tea, the researchers said.

They found a significant reduction in serum levels of the three biomarkers (P<0.03).

A total of 10 of 25 patients had more than a 25% decrease in HGF levels, and six of 25 had a greater than 25% decrease in their VEGF levels.

The researchers said that in vitro, EGCG (the main catechin in polyphenon E) rapidly blocked the production of HGF, and the block “seems to be at the level of transcription.”

EGCG also blocked the production of VEGF, which plays a critical role in the angiogenic process in cancer-associated fibroblasts, they said.

And age, race, and time on drug did not have a significant effect on the changes in serum biomarkers.

Some case studies have suggested that high doses of EGCG may have adverse effects on liver function.

But this study found that all markers of liver dysfunction decreased, five of them significantly: total protein, albumin, aspartate aminotransferase, alkaline phosphatase, and amylase.

“The doses that we used seem to be safe,” Dr. Cardelli said.

This raises a strictly practical question. The patients got results from taking concentrated active ingredients equal to 12 cups of tea daily.

“Does that translate to ‘If I drink 12 cups of green tea a day, will that work?’” Dr. Cardelli asked. “You can speculate, but I don’t know.”

Still, the researchers concluded that the data “support a potential role for polyphenon E in the treatment or prevention of prostate cancer.”

They said that the findings need to be “verified by larger, placebo-controlled clinical trials. The effects of different doses, long-term administration, and combination with other drugs remain to be seen.”

Polyphenon Pharma supplied the polyphenon E used in the trial. The researchers reported no conflicts of interest.

Primary source: Cancer Prevention Research

Source reference:
McLarty J, et al “Tea polyphenols decrease serum levels of prostate-specific antigen, hepatocyte growth factor, and vascular endothelial growth factor in prostate cancer patients and inhibit production of hepatocyte growth factor and vascular endothelial growth factor in vitro” Cancer Prev Res 2009; 2(7).

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