US researchers found that men with prostate cancer who consumed a mix of polyphenols found in green tea experienced a significant reduction in serum markers such as PSA, VGF and VEGF that predict the progression of prostate cancer.

The study was the work of Dr James A Cardelli, professor and director of basic and translational research in the Feist-Weiller Cancer Center, LSU Health Sciences Center in Shreveport, Louisiana, and colleagues and is published in the 19 June issue of Cancer Prevention Research.

Some studies have shown that green tea, the second most popular drink in the world, has many health benefits, and can reduce the incidence of prostate cancer, but trials in humans have been contradictory, said Cardelli, explaining that the few trials done so far have evaluated green tea's clinical efficacy but not its effect on biomarkers of prostate cancer, which indicate cancer progression.

He told the press that:

"The investigational agent used in the trial, Polyphenon E (provided by Polyphenon Pharma) may have the potential to lower the incidence and slow the progression of prostate cancer."

"There is reasonably good evidence that many cancers are preventable, and our studies using plant-derived substances support the idea that plant compounds found in a healthy diet can play a role in preventing cancer development and progression," he added.

For the trial, Cardelli and colleagues recruited 26 men aged 41 to 72 who had been diagnosed with prostate cancer (their biopsies had proved positive) and were scheduled to have a radical prostatectomy.

The patients consumed four capsules of Polyphenon E a day for an average of just over a month (ranging from about 12 to 73 days) until their operation.

Each capsule contained 1.3 g of tea polyphenols, comprising 800 mg of (--)-epigallocatechin-3-gallate (EGCG) and lesser amounts of (--)- epicatechin, (--)-epigallocatechin, and (--)-epicatechin-3-gallate.

Each patient gave a blood sample the day before they started the drug trial and then on the day of their operation.

The researchers looked at changes in 5 biomarkers, including: hepatocyte growth factor (HGF), vascular endothelial growth factor (VEGF), insulin- like growth factor (IGF)-I, IGF binding protein-3 (IGFBP-3), and prostate-specific antigen (PSA).

The results showed that over the period of the study, levels of HGF, VEGF, PSA, IGF-I, IGFBP-3, and the IGF-I/IGFBP-3 ratio decreased significantly, as did 5 of the liver function tests, such as total protein, albumin, aspartate aminotransferase, alkaline phosphatase, and amylase. Other liver function tests also decreased, but not significantly. Thus liver function remained normal.

Some patients showed more than a 30 per cent reduction in HGF, VEGF and PSA levels.

Cardelli and colleagues concluded that:

"Our results show a significant reduction in serum levels of PSA, HGF, and VEGF in men with prostate cancer after brief treatment with EGCG (Polyphenon E), with no elevation of liver enzymes."

This suggests there might be a place for Polyphenon E in the treatment or prevention of prostate cancer, they said.

Researchers in Italy studying the effects of green tea polyphenols found they reduced the risk of developing prostate cancer in men with high-grade prostate intraepithelial neoplasia (HGPIN), said the researchers in a separate statement.

Cardelli said:

"These studies are just the beginning and a lot of work remains to be done, however, we think that the use of tea polyphenols alone or in combination with other compounds currently used for cancer therapy should be explored as an approach to prevent cancer progression and recurrence."

Unfortunately the study was not a randomized trial so we can't rule the possibility that some other factor, such as changes to lifestyle, taking other supplements, improved diet, and so on, may be responsible for the lowering of biomarkers, commented Dr William G Nelson, professor of oncology, urology and pharmacology at the Johns Hopkins Kimmel Cancer Center. However, he added that:

"This trial is provocative enough to consider a more substantial randomized trial."

Cardelli and his team are doing a similar trail with breast cancer patients and plan to carry out further investigations to determine why Polyphenon E had a dramatic effect in some patients and not others.

Cardelli said that controlled clinical trials to see if other combinations of plant phenols might be even more effective than Polyphenon E.

"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."
McLarty, Jerry, Bigelow, Rebecca L.H., Smith, Mylinh, Elmajian, Don, Ankem, Murali, Cardelli, James A.
Cancer Prevention Research, Published Online First on June 19, 2009.
DOI: 10.1158/1940-6207.CAPR-08-0167

Additional sources: American Association for Cancer Research.

Written by: Catharine Paddock, PhD