Green Tea Reduced Inflammation, May Inhibit Prostate Cancer Tumor Growth
Embargo expired: 18-Oct-2012 10:30 AM EDT
Source Newsroom: American Association for Cancer Research (AACR)
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Newswise — ANAHEIM, Calif. — Men with prostate cancer who consumed green tea prior to undergoing prostatectomy had reductions in markers of inflammation, according to data presented at the 11th Annual AACR International Conference on Frontiers in Cancer Prevention Research, held here Oct. 16-19, 2012.
“Our study showed that drinking six cups of green tea affected biomarkers in prostate tissue at the time of surgery,” said Susanne M. Henning, Ph.D., R.D., adjunct professor at the David Geffen School of Medicine at the University of California Los Angeles. “This research offers new insights into the mechanisms by which green tea consumption may reduce the risk for prostate cancer by opposing processes such as inflammation, which are associated with prostate cancer growth.”
Prior epidemiological data have been inconclusive about the relationship between green tea and prostate cancer. However, one recent intervention study conducted in Italy revealed that men with a precursor to prostate cancer called prostatic intraepithelial neoplasia who consumed a green tea extract reduced their risk for progression to prostate cancer.
Henning and colleagues examined potential mechanisms by which green tea may have beneficial effects among 67 men with prostate cancer scheduled to undergo prostatectomy. The researchers randomly assigned the men to either six cups of brewed green tea or water daily for three to eight weeks, depending on the timing of their surgery. They collected blood and urine samples before and after the green tea or water consumption and collected prostate tissue following the pathology exam.
The data showed that serum prostate-specific antigen (PSA) concentrations were significantly lower at the end of the study compared with baseline levels in men consuming green tea. In addition, prostate tissue PSA protein expression was lower in men assigned to green tea consumption compared with the control group at the end of the study.
Further, immunostaining analysis revealed that nuclear factor kappa B, a marker of inflammation, was significantly reduced in those men assigned to green tea compared with those in the control group. A urinary marker of oxidative DNA damage was significantly decreased in urine from men consuming green tea compared with controls.
The researchers found no differences in markers of tumor cell proliferation between the two treatment groups.
Henning and her colleagues are further evaluating the association between green tea and prostate cancer by trying to enhance its activity. Currently, they are exploring the possibility of combining green tea with other natural products in mouse studies.
Funding for this study was provided by the National Institutes of Health.
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B67 Inhibition of NFκB and proapoptotic Effect of Green Tea in Prostate Tumor Tissue: A Phase II clinical Trial in Men with Prostate Cancer. Susanne M. Henning, Piwen Wang, William J. Aronson, Catherine L. Carpenter, David Heber. University of California Los Angeles, Los Angeles, CA.
Background: Green tea polyphenols (GTPs) have been shown to play a role in the regulation of cell proliferation, apoptosis and inflammation in prostate cancer cells in vitro and in animal models using human prostate cancer cell xenografts. While there is extensive epidemiological and basic scientific evidence for these effects of GTPs, data from human intervention studies is much more limited.
Objective: We conducted a phase II intervention study to evaluate the anticarcinogenic effects of green tea in prostate cancer by administering green tea in men prior to prostatectomy.
Design: 79 men, diagnosed with prostate cancer and scheduled for prostatectomy, were randomized to either 6 cups of brewed green tea or water daily for 3-8 weeks prior to surgery. 67 men (GT group, N=34; control group, N=33) completed the intervention. Blood and urine samples were collected before and after the intervention and sections of prostate tissue were frozen as OCT blocks following the pathology evaluation. Serum prostate specific antigen (PSA) concentration was determined by ELISA assay and prostate tissue PSA protein concentration was measured by Western blot. The prostate concentration of GTPs and their metabolites was measured using high-performance liquid chromatography (HPLC) with CoulArray electrochemical detection. The protein expression of Ki67 (proliferation), Bcl2, Bax (apoptosis) and nuclear factor kappa B (NFκB) (inflammation) were determined by immunostaining in prostate tissue of confirmed tumor areas.
Results: Statistical analysis within each treatment arm showed that the serum PSA concentration was significantly decreased in the GT group (final vs. baseline blood) (P<0.01), while no change was observed in the control group. Prostate tissue PSA protein expression was lower in men consuming GT compared to water control (p=0.06). Bioactive GTPs including epigallocatechin gallate (EGCG) and its methyl metabolite 4″-O-methyl EGCG and epicatechin gallate (ECG) were detected in prostate tissue from 31 of 34 men consuming GT but were absent in prostates in the control group. Intranuclear NFκB staining was decreased significantly while there was no change in cytoplasmic NFκB staining in prostate tumors from men drinking GT by comparison to tumors from the control group. The ratio of cytoplasmic staining of pro-apoptotic Bax to Bcl-2 was increased significantly while cytoplasmic Bcl2 and Bax staining were not changed. Nuclear Ki67 staining was not changed with GT consumption.
Conclusion: Green tea consumption may contribute to the inhibition of prostate tumor growth through reducing inflammation and stimulating apoptosis. Analyses of additional markers are needed to confirm these findings.