Identification of a novel functional androgen response element withinhPar1promoter: implications to prostate cancer progression

Abstract

Human protease-activated receptor-1 (hPar1) plays a role in malignant and physiological invasion processes. We have identified a functional androgen response element (ARE) located in the hPar1 promoter upstream of the transcription start site at -1791 to -1777. Dihydrotestosterone treatment of the prostate cancer cell line LNCaP increased endogenous hPar1 mRNA levels, consistent with the threefold increase in promoter activity of hPar1-luciferase reporter construct. Specific binding of the hPar1-derived ARE to LNCaP nuclear extracts was demonstrated by electrophoretic mobility shift assay. This binding was abrogated by antiandrogen receptor (anti-AR) antibodies or excess cold oligonucleotide but not by a mutated oligonucleotide. Moreover, using chromatin immunoprecipitation assays, we confirm the in vivo interaction between the AR and ARE domain of the hPar1 promoter. In parallel, we show that hormone ablation therapy markedly reduces the otherwise high hPar1 expression levels in prostate cancer biopsy specimens. We suggest that the hPar1 gene is regulated transcriptionally by androgens, representing one of several target genes effectively reduced during hormone ablation therapy. A major limitation of hormonal deprivation is that it causes only a temporary remission, and the cancer eventually reappears in a more malignant, androgen-independent form. hPar1 is also overexpressed in CL1 cells, an aggressively metastasizing, hormone-independent subclone of LNCaP, and in PC3 prostate adenocarcinoma lacking AR in a mechanism yet to be fully elucidated. These data may imply that hPar1 expression correlates with prostate cancer progression in androgen-dependent and -independent phases and therefore, provides an instrumental, therapeutic target for treatment in prostate cancer.