Expression and role of functional glucocorticoid receptors in the human androgen-independent prostate cancer cell line, DU145

Abstract

We investigated the presence of glucocorticoid receptors (GR) as well as the role of glucocorticoids (Gc) in the control of proliferation of the androgen-independent prostate cancer cell line, DU145. We detected the presence of a specific high affinity binding site (K(d) 2.3 nM) for [(3)H]dexamethasone ([(3)H]Dex) in the cytosolic preparations of DU145 cells; the density of these binding sites is significantly higher than that detected in HA22T/VGH and in HepG2, two hepatoma cell lines classically considered models for the study of GR. Immunocytochemistry studies confirmed the presence of GR in the cytosolic compartment of DU145 cells; GR undergo translocation to the nucleus following exposure to dexamethasone (Dex). The functional activity of GR present in DU145 cells was also studied by analyzing the potency of Dex in inducing chloramphenicol acyltransferase (CAT) activity in DU145 cells transfected with a glucocorticoid/progesterone response element (GRE/PRE) tkCAT plasmid (GRE/PREtkCAT plasmid). The results have shown that Dex stimulates the transcriptional activity of GR in transfected DU145 cells with an EC(50) of 9.65 nM and a maximal induction of sevenfold above basal levels. Finally, a dose-dependent (IC(50) 3.14 nM) decrease of DU145 cell numbers was observed after their exposure to Dex for 4 days; this effect was counteracted by the presence of the steroid antagonist, RU486. In conclusion, the present data suggest a possible role of corticoids in the control of the growth of androgen-independent prostate cancer.