Mitogen‐activated protein kinase pathway is involved in androgen‐independent PSA gene expression in LNCaP cells

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Abstract
Prostate specific antigen (PSA) is regulated by growth factors and hormones through functional androgen responsive elements in the promoter region of the PSA gene. However, the molecular basis for androgen independent PSA elevation in hormone refractory prostate cancer is unknown. The purpose of this study was to investigate the role of MAP kinase activation in androgen independent regulation of PSA expression. LNCaP cells transfected with MEK1 expression vector with or without the MAP kinase inhibitor U0126 under low androgen conditions were analyzed by luciferase assay and electrophoretic mobility shift assay (EMSA). Transfection experiments of the proximal PSA promoter linked to Luc-reporter identified one region designated as "B" motif centered at -60 bp to be essential for basal activation. Co-transfection with the MEK1 activated vector enhanced PSA expression, while mutation of the "B" motif totally abrogated this induction. EMSA showed a specific DNA-protein complex, but Sp1 family members and AR do not interact with the "B" region by supershift analysis. Our data suggest that enhanced androgen-independent PSA gene expression in MAP kinase-induced LNCaP cells is mediated, at least in part, by the "B" motif of the PSA promoter.