The androgen derivative 5alpha-androstane-3beta,17beta-diol inhibits prostate cancer cell migration through activation of the estrogen receptor beta subtype.

Prostate cancer growth depends, in its earlier stages, on androgens and is usually pharmacologically modulated with androgen blockade. However, androgen-ablation therapy may generate androgen-independent prostate cancer, often characterized by an increased invasiveness. We have found that the 5alpha-reduced testosterone derivative, dihydrotestosterone (the most potent natural androgen) inhibits cell migration with an androgen receptor-independent mechanism. We have shown that the dihydrotestosterone metabolite 5alpha-androstane-3beta,17beta-diol (3beta-Adiol), a steroid which does not bind androgen receptors, but efficiently binds the estrogen receptor beta (ERbeta), exerts a potent inhibition of prostate cancer cell migration through the activation of the ERbeta signaling. Very surprisingly, estradiol is not active, suggesting the existence of different pathways for ERbeta activation in prostate cancer cells. Moreover, 3beta-Adiol, through ERbeta, induces the expression of E-cadherin, a protein known to be capable of blocking metastasis formation in breast and prostate cancer cells. The inhibitory effects of 3beta-Adiol on prostate cancer cell migration is counteracted by short interfering RNA against E-cadherin. Altogether, the data showed that (a) circulating testosterone may act with estrogenic effects downstream in the catabolic process present in the prostate, and (b) that the estrogenic effect of testosterone derivatives (ERbeta-dependent) results in the inhibition of cell migration, although it is apparently different from that linked to estradiol on the same receptor and may be protective against prostate cancer invasion and metastasis. These results also shed some light on clinical observations suggesting that alterations in genes coding for 3beta-hydroxysteroid dehydrogenases (the enzymes responsible for 3beta-Adiol formation) are strongly correlated with hereditary prostate cancer.

Characterization of prostate cancer DU145 cells expressing the recombinant androgen receptor.

Prostate cancer (PC) develops as a consequence of abnormal androgenic stimulation. Unfortunately, most of the PC cell lines are androgen independent (like DU145), or express mutated forms of androgen receptor (AR). We have produced and characterized a new stably transfected PC line expressing the AR (DU145-AR). Untreated DU145-AR cells showed a lower proliferation rate than mock transfected cells, but responded to testosterone treatment. PSA mRNA, undetectable in mock DU145 cells, was present and upregulated by testosterone in DU145-AR. About 5% of DU 145-AR cells showed modification of morphology and enriched of f-actin after testosterone treatment. Moreover, in DU145-AR plasminogen activator (PA) activity and secreted urokinase type plasminogen activator (uPA) protein were lower than in AR negative cells; again testosterone induced PA activity and uPA protein only in DU145-AR. These results indicate that, in general, the effects of unactivated AR is to suppress function(s) in DU145 cells and the addition of testosterone restores the normal properties associated with the untransfected cells. Some of the effects described may thus be mediated by a ligand-independent activation of AR in DU145 cells.