Regions of prostate-specific antigen (PSA) promoter confer androgen-independent expression of PSA in prostate cancer cells

Prostate-specific antigen (PSA) is expressed primarily by both normal prost ate epithelium and the vast majority of prostate cancers. Increases in seru m PSA during endocrine therapy are generally considered as evidence for pro state cancer recurrence or progression to androgen independence. The mechan isms by which PSA upregulation occurs in androgen-refractory prostate cance r cells are unknown. In this study, by using LNCaP and its lineage-derived androgen-independent PSA-producing subline, C4-2, we identified two cis-ele ments within the 5.8-bilobase pair PSA promoter that are essential for the androgen-independent activity of PSA promoter in prostate cancer cells. Fir st, a previously reported 440-bp androgen-responsive Element enhancer core (AREc) was found to be important for the high basal PSA promoter activity i n C4-2 cells. Both mutation analysis and supershift experiments demonstrate d that androgen receptor (AR) binds to the AREs within the AREc and activat e the basal PSA promoter activity in C4-2 cells under androgen-deprived con ditions. Second, a 150-bp pN/H region was demonstrated to be a strong AR-in dependent positive-regulatory element of the PSA promoter in both LNCaP and C4-2 cells. Through DNase I footprinting and linker scan mutagenesis, a 17 -bp RI site was identified as the key cis-element within the pN/H region. D ata from electrophoretic mobility shift analysis and UV cross-linking exper iments further indicated that a 45-kDa (p45) cell-specific transcription fa ctor associates with RI in prostate cancer cells and may be responsible for driving the PSA promoter activity independent of androgen and AR. Furtherm ore, by juxtaposing AREc and pN/H, we produced a chimeric PSA promoter (sup ra-PSA) that exhibits 2-3-fold higher activity than the wild type PSA promo ter in both LNCaP and C4-2 cells.