5 alpha-reductase isozymes and aromatase are differentially expressed and active in the androgen-independent human prostate cancer cell lines DU145 and PC3

BACKGROUND. The presence and possible role of androgen-metabolizing enzymes in androgen-independent prostate carcinoma (CaP) are still unclear. The ai m of the present study was: 1) to evaluate the pattern of androgen metaboli sm (relative production of 5 alpha-reduced vs. 17-keto androgens); and 2) t o analyze whether one or both the two known Sa-reductase isoforms (5 alpha- R1 and 5 alpha-R2) and the aromatase (Aro) are expressed and active in this pathology. METHODS. Two different cell lines (DU145 and PC3) were used as a model of a ndrogen-independent human CaP. Ln these cells, the expression of the two 5 alpha-Rs and of Aro were evaluated by reverse transcription-polymerase chai n reaction (RT-PCR) and Southern blot, using specific sets of oligoprimers and of [P-32]-labeled oligoprobes; the enzymatic activities of 5 alpha-R an d of Aro were evaluated by radioenzymatic methods. The pH optimum for the a ctivity of We two 5 alpha-Rs was assessed in cell hamogenates at different pH (from 3.5-8), using substrate concentrations similar either to 5 alpha-R 1 or to 5 alpha-R2 Kms. RESULTS. The two CaP cell lines DU145 and PC3, although unresponsive to and rogens, possess the enzymatic machinery involved in the metabolism of this class of hormonal steroids: 5 alpha-Rs, which allow their transformation in to 5 alpha-reduced steroids (5 alpha-dihydrotestosterone, DHT, and 5 alpha- androstandione, 5 alpha-A), and 17 beta-hydroxysteroid-oxidoreductase (17 b eta-HSD), which interconverts testosterone (T) and androstenedione (ADIONE) ; however, the two cell. lines show differences in the rate;rate of formati on of these metabolites. Furthermore, two cell lines expressed the type 1 i soform of 5 alpha-R, but only DU145 cells also possess 5 alpha-R2. Aro is e xpressed and active in DU145 as well as in PC3 cells. CONCLUSIONS. The present findings suggest that T might still be indirectly active in androgen-unresponsive CaP through its local conversion into estro gens by the action of Are; the biological role played by the two 5 alpha-Rs in androgen-independent Cap deserves further investigation. (C) 1999 Wiley -Liss, Inc.