Fig. 4.

Quercetin mediated inhibition of Hsp90 stimulates apoptosis of prostate cancer cells. A: Increase in annexin V−positive cells (assayed by flow cytometry) following treatment of LNCaP and PC-3 prostate cancer cells with varying concentrations of quercetin for 24 hr. Incubation with dihydroquercetin or 0.2% DMSO did not induce apoptosis. B: Increased apoptosis of PC-3 cells treated with varying doses of quercetin for 24 hr as determined by in situ TUNEL staining as described in the text. C: Increased caspase-3 and -9 activities in prostate cancer cells, LNCaP and PC-3. Cells were incubated with or without varying concentrations of quercetin or dihydroquercetin for 24 hr. Caspase activities were measured by a colorimetric assay as described in the text. DMSO (0.2%) did not have any effect on caspase activation. Values are mean ± SE from six experiments; *P < 0.05 and **P < 0.001 compared to treatment with dihydroquercetin. [Color figure can be viewed in the online issue, which is available at http://www.interscience.wiley.com.]