['While cardiac glycosides are the mainstay of congestive heart failure treatment, early studies showed that pharmacological doses of cardiac glycosides inhibited prostate cancer cell line proliferation. We evaluated the mechanisms of cardiac glycosides, including digoxin, digitoxin and ouabain (Sigma®), on prostate specific antigen gene expression in vitro.', 'We cultured LNCaP cells (ATCC®) and used them to determine the effect of cardiac glycosides on prostate derived Ets factor and prostate specific antigen expression. We determined prostate derived Ets factor and prostate specific antigen expression by reverse transcription-polymerase chain reaction, immunoblot, transient gene expression assay or enzyme-linked immunosorbent assay.', 'Noncytotoxic doses (100 nM) of cardiac glycosides for 24 hours inhibited prostate specific antigen secretion by LNCaP cells. Reverse transcriptase-polymerase chain reaction and immunoblot revealed that cardiac glycosides significantly down-regulated prostate specific antigen and prostate derived Ets factor expression. Transient gene expression assays showed that prostate derived Ets factor over expression enhanced prostate specific antigen promoter activity. However, prostate specific antigen and prostate derived Ets factor gene promoter activity was attenuated when LNCaP cells were treated with 100 nM cardiac glycosides. When LNCaP cells were treated with 25 nM digitoxin or digoxin for 60 hours, prostate specific antigen secretion decreased by 30%.'] Do cardiac glycosides decrease prostate specific antigen expression by down-regulation of prostate derived Ets factor?