Hormonal regulation of β2-adrenergic receptor level in prostate cancer

Abstract

BACKGROUND. Androgen deprivation is the only effective systemic therapy available for patients with prostatic carcinoma, but is associated with a gradual transition to a hormone-refractory prostate cancer (HRCAP) in which ligand-independent activation of the androgen receptor has been implicated. The β2-adrenergic receptor (β2-AR) is a well-known activator of the androgen receptor. METHODS. Prostatic cell lines were analyzed using cDNA micro-array, real time RT-PCR, radioligand binding assay, cAMP measurements, transfection and thymidine incorporation assay. Clinical specimens were studied by immunohistochemistry and Affymetrix microarrays. RESULTS. Here, we show that β2-AR was transiently down-regulated both at mRNA- and protein levels when hormone-sensitive prostate cancer cells, LNCaP, were cultured in steroid stripped medium (charcoal-stripped fetal calf serum) or when the cells were treated with the anti-androgen, bicalutamide (Casodex). The number of β-adrenergic receptors was modestly up-regulated in androgen independent cell lines (LNCaP-C4, LNCaP-C4-2 and DU145) compared to LNCaP. Triiodothyronine (T3) increased the level of β2-AR and the effect of T3 was inhibited by bicalutamide. Immunohistochemical staining of human prostate specimens showed high expression of β2-AR in glandular, epithelial cells and increased expression in malignant cells compared to benign hyperplasia and normal tissue. Interestingly, β2-AR mRNA was strongly down-regulated by androgen ablation therapy of prostate cancer patients. CONCLUSION. The level of β2-AR was increased by T3 in prostatic adenocarcinoma cells and reduced in prostate cancer patients who had received androgen ablation therapy for 3 months. © 2008 Wiley-Liss, Inc.