Effects of the flavonoid baicalin and its metabolite baicalein on androgenreceptor expression, cell cycle progression and apoptosis of prostate cancer cell lines

Recent studies on the Chinese herbal medicine PC SPES showed biological act ivities against prostate cancer in vitro, in vivo and in patients with adva nced stages of the disease. In investigating its mode of action, we have is olated a few of the active compounds. Among them, baicalin was the most abu ndant (about 6%) in the ethanol extract of PC SPES, as determined by HPLC. Baicalin is known to be converted in vivo to baicalein by the cleavage of t he glycoside moiety. Therefore, it is useful to compare their activities in vitro. The effects of baicalin and baicalein were studied in androgen-posi tive and -negative human prostate cancer lines LNCaP and JCA-1, respectivel y. Inhibition of cell growth by 50% (ED50) in LNCaP cells was seen at conce ntrations of 60.8 +/- 3.2 and 29.8 +/- 2.2 muM baicalin and baicalein, resp ectively. More potent growth inhibitory effects were observed in androgen-n egative JCA-1 cells, for which the ED50 values for baicalin and baicalein w ere 46.8 +/- 0.7 and 17.7 +/- 3.4, respectively. Thus, it appears that cell growth inhibition by these flavonoids is independent of androgen receptor status. Both agents (1) caused an apparent accumulation of cells in G(1) at the ED50 concentration, (2) induced apoptosis at higher concentrations, an d (3) decreased expression of the androgen receptor in LNCaP cells.