Activated Steroidogenic Factor 1 Expression Induces Estrogen Synthesis in Benign Prostate Hyperplasia Cell Line BPH-1.

Abstract

Prostate growth in development and disease depends on androgens synthesized by the testis. Thus, treatment of prostate cancer targets androgen production and activity at several fronts. Initially, prostate tumors subject to androgen deprivation therapy regress, but inevitably, rogue cancer cells prevail and an aggressive cancer returns that is unresponsive to this therapy. There are several theories to explain this aggressive resurgence, one of which suggests that prostate adenocarcinoma cells acquire machinery for de novo steroidogenesis. It has long been established that Steroidogenic Factor 1 (NR5A1, ADBP4, SF1) is essential for regulating steroidogenesis in normal endocrine tissues. While normal prostate tissue lacks SF1 expression and is nonsteroidogenic, the presence of SF1 in diseased tissue of the prostate has not been documented, presenting an unexplored potential driver of aberrant steroidogenesis in prostate cancer. We hypothesize then that SF1 is present in prostate cancer and that SF1 is necessary for steroidogenesis to occur in prostate epithelial cells. To test the first part of our hypothesis, we examined SF1 expression in a panel of both benign and cancerous prostate cell lines. All prostate cancer cell lines examined expressed SF1, while a benign prostate hyperplasia cell line did not. We then performed immunohistochemistry on prostate biopsy samples from human patients with benign prostate hyperplasia or recurrent prostate cancer following androgen deprivation therapy. Similar to our results from prostate cell lines, we detected positive nuclear staining for SF1 in prostate adenocarcinoma but not benign prostate hyperplasia specimens. To functionally link SF1 to steroidogenic production in prostate epithelial cells, we tested whether ectopic expression of SF1 was sufficient to induce steroid production in a benign prostate cell line (BPH-1). BPH-1 cells were transfected with expression vectors encoding the mCherry fluorescent protein (negative control), wild type SF1, or a constitutively active mutant of SF1 (SF1ΔLBD). After 48 hours in culture, media was collected and subject to steroid measurement by ELISA. Whereas accumulation of progesterone and testosterone were not detected, estradiol concentrations were increased in BPH-1 cells transfected with wild type SF1 and even more so with transfected SF1ΔLBD. Together, these data indicate that SF1 is induced both in prostate cancer cell lines and in human prostate adenocarcinoma biopsy specimens, and suggest that activated SF1 is sufficient for steroidogenesis in a benign prostate cell line. Our findings present a potential mechanism and target for therapy of androgen deprivation resistant prostate cancers. Future experiments are planned to elucidate the stimulatory signals that induce SF1 within these aggressive prostate tumor cells leading to aberrant steroid production that fuels growth of deadly prostate cancer. This work was supported by The University of Wisconsin-Madison and NIH 5T32-HD041921-07. (platform)