Both Suppressive Effects of Dioxin Toxicity and Antiproliferation of Human Prostate Cancer Cells by Ethanolic Extracts of Brazilian Propolis and its Botanical Origin
Prof. Dr. Yong Kun Park, MD, PhD
State University of Campinas, College of Food Engineering, Department of Food Science, Laboratory of Food Biochemistry, Campinas-SP, Brazil.
Recently numerous biological activities of propolis have been reported such as antitumor, antiradical, antimicrobial, and anti-HIV activities. We have also demonstrated that suppressive effects of ethanolic extracts prepared from Brazilian propolis group 12 and its main botanical origin (leaf bud of Baccharis dracunculifolia) on transformation of the aryl hydrocarbon receptor (AhR), the initial action of dioxin toxicity, were investigated. It was found that suppressive effects of propolis on AhR transformation were relatively higher than those of resins of its botanical origin in cell-free system and in Hepa-1c1c7 cells. When the composition of chemical was measured, propolis contained slightly higher amounts of flavonoids aglycones as compared with its botanical origin with the same characteristics. These results indicate, that not only propolis, but also its botanical origin, contains high amounts of flavonoid aglycones and that both of them are useful dietary sources for flavonoids with a potency to prevent dioxin toxicity.
In the present, we have evaluated the effects of ethanolic extracts of propolis group 12 and its botanical origin (B. dracunculifolia), and propolis group 3 (Populus sp.) on proliferation of metastasis (DU145 and PC-3) and primary malignant tumor (RC58T/h/SA#4)-derived human prostate cancer cells. The strongest inhibition was observed in propolis group 3 extracts whereas moderate growth inhibition was observed in human prostate epithelial cells. In the RC58T/h/SA#4 cells, resins of botanical origin of propolis group 12 and propolis group 12 induced growth inhibition that was associated with S phase arrest whereas propolis group 3 induced growth inhibition that was associated with G2 arrest. The mechanisms of cell cycle effects of propolis were investigated. The resins of botanical origin of propolis group 12 and propolis group 12 showed similar inhibition of cyclin D1, CDK4 and cyclin B1 expression. Propolis group 3 showed higher induction of p21 expression but no inhibition of cyclin D1, CDK4 and cyclin B1 expression. The results obtained here demonstrate that the Brazilian propolis extracts have significant inhibitory effect on proliferation of human prostate cancer cells. Inhibition was achieved regulation of protein expression of cyclin D1, B1 and cyclin dependent kinase (CDK) as well as p21. Our results indicate that the Brazilian propolis extracts show promise as chemotherapeutic agents as well as preventive agents against prostate cancer.