AbstractBACKGROUNDSteroid receptor coactivators p300 and CBP are highly expressed in advanced prostate cancer. They potentiate activation of androgen receptor by androgens and anti‐androgens. In the present study, we have addressed the question whether these coactivators enhance activity of estrogen receptor‐beta (ER‐β), which is variably expressed in prostate cancers.METHODSExpression levels of the coactivators p300 and CBP were manipulated by plasmid or siRNA transfections and activity of ER‐β was measured by luciferase assays. Viability was measured by MTT assays and cellular migration was determined by wound‐healing and Boyden chamber assays.RESULTSHigh expression of ER‐β was found in PC3 cells which were used for the experiments. p300 or CBP enhanced activation of ER‐β by genistein. Antiestrogens did not acquire agonistic properties in the presence of increased concentrations of either coactivator. Inhibition of p300 or CBP decreased genistein stimulation of ER‐β. Genistein reduced migration of PC3 prostate cancer cells and down‐regulation of p300 potentiated this effect.CONCLUSIONSp300 and CBP are implicated in regulation of ER‐β activity and cellular migration in prostate cancer. These findings are important for understanding of action of ER‐β in carcinoma of the prostate. Prostate 77:431–437, 2011. © 2010 Wiley‐Liss, Inc.