Effect of citrus bioflavonoids naringenin and hesperetin on hormone-insensitive human prostate cancer DU145 cells

Flavonoids were primarily recognized as pigments responsible for the autumnal burst of the hues and many shades of yellow, orange and red in flowers and food. They are abundantly found in fruits, vegetables, nuts, seeds, herbs, spices, stems, flowers as well as tea and red wine. In plants, flavonoids are bound to sugars as glycosides and are heat stable. Flavonoids are a class of polyphenolic compounds and the functional groups attached to this polyphenolic backbone alter biological properties of the specific flavonoids. Naringenin and hesperitin belong to a class of flavonoids known as flavonones and are reported to have various pharmacological activities including inhibitory effects on the growth and proliferation of tumor cells. However, very few studies have been undertaken to see the effects of naringenin and hesperitin on the human prostate cancer cell lines. Therefore, we investigated the effects of these flavonoids on the DU145 human prostate cancer cell line.; We conducted experiments to see the effects of naringenin and hesperitin on the proliferation of DU145 cells. Cells treated with bioflavonoids for up to 72 hours showed a 6-fold decrease in the number of the cells when compared with untreated cultures. Using an MTT assay we also observed decrease viability of cells treated with bioflavonoids. Our data show that the overall number of viable cells in treated cultures was lower than controls. We observed a tremendous drop in the number of viable cells after 24 hours of treatment with both naringenin and hesperitin. The MTT assay also showed that the number of viable cells was generally lower in treated cultures when compared with control samples for up to 96 hours.; To determine whether the decreased viability and cell proliferation was due to cell death by apoptosis or necrosis, we performed western blot analysis using antibodies raised against the pro-apoptotic and anti-apoptotic proteins Bad and Bcl2 respectively. We observed a time-dependent increase in the expression of pro-apoptotic Bad gene after 48 hours of treatment with hesperitin and a decrease in the anti-apoptotic Bcl-2 expression over a period of 72 hours. This effect was minimal when cells were treated with naringenin under the same experimental conditions.; Finally, to confirm the occurrence of apoptosis, we performed DNA fragmentation studies on control and treated cells. The results show that DNA fragmentation began at 48 hours in the presence of hesperitin and naringenin and appeared to peak at 72 hours. However, DNA fragmentation was more prominent when cells were treated with 40 muM hesperitin for up to 72 hours. These results suggest that the flavonoids naringenin and hesperitin have an inhibitory effect on the viability and proliferation of DU 145 cells and that the decrease in proliferation especially for hesperitin is due to programmed cell death. Further studies are required to investigate the detailed mechanism of apoptosis in response to treatment of DUI45 cells with these and other flavonoids, and whether there may be synergistic or antagonist effects when cells are treated with mixtures of flavonoids.