Upregulation of prostate-derived Ets factor by luteolin causes inhibition of cell proliferation and cell invasion in prostate carcinoma cells

Luteolin is a polyphenolic flavone and has antitumor activity for many cancers. The prostate-derived Ets factor (PDEF), a novel epithelium-specific Ets transcription factor, acts as an androgen-independent transcriptional activator of the prostate-specific antigen (PSA) promoter. We determined the antitumor function of luteolin via upregulation of PDEF gene expression in human prostate carcinoma LNCaP cells. Results from flow cytometry and 3H-thymidine incorporation assays revealed that luteolin treatments attenuated cell proliferation and arrested the cell cycle at the G1/S phase. High concentration of luteolin (30 mu M) induced cell apoptosis. Immunoblot assays and enzyme linked immunosorbent assay revealed that luteolin treatment upregulated PDEF but downregulated androgen receptor (AR) gene expression, which decreased PSA gene expression in LNCaP cells. Results of immunoblot and transient gene expression assays revealed that luteolin treatments at proapoptosis dosage, enhanced gene expression of PDEF, B-cell translocation gene 2 (BTG2), N-myc downstream regulated gene 1 (NDRG1) and Maspin. Transient gene expression assays indicated that cotransfection of the PDEF expression vector enhanced the promoter activities of the BTG2, NDRG1 and Maspin genes. Stable overexpression of PDEF significantly induced BTG2, NDRG1 and Maspin gene expression, which markedly attenuated in vitro cell proliferation and invasion of LNCaP cells. The modulatory effect of luteolin on BTG2, NDRG1 and Maspin gene expression were attenuated when PDEF was knocked-down. These results suggest that luteolin blocks PSA gene expression by downregulation of AR expression. The enhancement of PDEF expression, which induced BTG2, NDRG1 and Maspin gene expression, could account for the function of luteolin for antiproliferation and anti-invasion in LNCaP cells.