The androgen receptor (AR) is a ligand-responsive transcription factor known to play a central role in the pathogenesis of prostate cancer. However, the regulation of AR gene expression in the normal and pathological prostate remains poorly understood. This study focuses on the effect of the phosphoinositide 3-kinase (PI 3-kinase)/Akt axis on AR expression in vas deferens epithelial cells (VDEC), a suitable model to study androgen regulation of gene expression, and LNCaP cells (derived from a metastasis at the left supraclavicular lymph node from a 50-year-old patient with a confirmed diagnosis of metastatic prostate carcinoma). Taken together, our data show for the first time that the PI 3-kinase/Akt pathway is required for basal and dihydrotestosterone-induced AR protein expression in both VDEC and LNCaP. Inhibition of the PI 3-kinase/Akt pathway reduced AR expression and the decline in AR protein level correlated with a decrease in AR mRNA in VDEC but not in LNCaP. Since PI 3-kinase/Akt axis is active in prostate cancer, cross-talk between PI 3-kinase/Akt and AR signalling pathways may have implications for endocrine therapy.
Abbreviations used: DHT, dihydrotestosterone; EGF, epidermal growth factor; ERK, extracellular-signal-related kinase; GAPDH, glyceraldehyde-3-phosphate dehydrogenase; HA, haemagglutinin; (h)AR, (human) androgen receptor; IGF-I, insulin-like growth factor I; luc, luciferase; MAPK, mitogen-activated protein kinase; MVDP, mouse vas deferens protein; PARP, poly(ADP-ribose) polymerase; PI 3-kinase, phosphoinositide 3-kinase ('phosphatidylinositol 3-kinase'); PKC, protein kinase C; PSA, prostate-specific antigen; VDEC, vas deferens epithelial cells.