Tea antioxidant has a synergistic effect with a COX-2 inhibitor.

Taking green tea together with low doses of a cyclooxygenase-2 (COX-2) inhibitor slows prostate cancer growth, laboratory tests show.

Tea and a COX-2 inhibitor have a synergistic effect, with each one triggering cellular pathways that, combined, are more powerful than either agent alone, says lead researcher Hasan Mukhtar, PhD. “We hope that a clinical trial could lead to a preventive treatment as simple as tea time.”

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More than 20 clinical trials are currently under way to investigate the cancer-fighting potential of COX-2 inhibitors, but toxic side effects are an issue. COX-2 inhibitors can cause serious cardiovascular problems for people who take high doses for a long time. In earlier research, Dr. Mukhtar and his team at the University of Wisconsin in Madison showed that COX-2 inhibitors and an antioxidant in green tea—a polyphenol called pigallocatechin-3-gallate (EGCG)—individually suppress prostate cancer.

“We believed that COX-2 inhibitors may still prove beneficial [despite the cardiovascular dangers] if used in combination with complementary agents,” Dr. Mukhtar said. “Our studies showed that the additive effect of green tea enables us to use the cancer-fighting abilities of COX-2 inhibitors, but at lower, safer doses.”

They chose green tea for their experiments because it’s an easily accessible beverage. “The idea is that it would be easier to get people to drink green tea than it would be to take an additional dietary supplement,” Dr. Mukhtar said.

His team experimented with EGCG and a COX-2 inhibitor similar to celecoxib in cultured human prostate cancer cells. They found the combination therapy was 15% to 28% more effective in slowing cancer cells’ growth than either agent alone. Repeating the experiment with mice, the team used actual tea and pharmacy-grade celecoxib to simulate real life conditions. The average tumor volume in untreated mice was 1,300 mm3.

Mice given either tea or celecoxib had tumors averaging 835 mm3 and 650 mm3, respectively. But mice that received both the tea and the drug displayed dramatically smaller tumors, with an average volume of 350 mm3. These mice also showed a greater decrease in PSA levels than the other groups. The study was reported in Clinical Cancer Research (2007;13:1611-1619) and funded by the National Cancer Institute.

“Prostate cancer typically arises from more than one defect in the cellular mechanics, which means that a single therapeutic might not work fighting a particular cancer long-term. If tests in human trials replicate these results, we could see a powerful combined therapy that is both simple to administer and relatively cost-effective,” Dr. Mukhtar said.