5alpha-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 aim of the present study was: 1) to evaluate the pattern of androgen metabolism (relative production of 5alpha-reduced vs. 17-keto androgens); and 2) to analyze whether one or both the two known 5alpha-reductase isoforms (5alpha-R1 and 5alpha-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 androgen-independent human CaP. In these cells, the expression of the two 5alpha-Rs and of Aro were evaluated by reverse transcription-polymerase chain reaction (RT-PCR) and Southern blot, using specific sets of oligoprimers and of [(32)P]-labeled oligoprobes; the enzymatic activities of 5alpha-R and of Aro were evaluated by radioenzymatic methods. The pH optimum for the activity of the two 5alpha-Rs was assessed in cell homogenates at different pH (from 3.5-8), using substrate concentrations similar either to 5alpha-R1 or to 5alpha-R2 Kms.


RESULTS
The two CaP cell lines DU145 and PC3, although unresponsive to androgens, possess the enzymatic machinery involved in the metabolism of this class of hormonal steroids: 5alpha-Rs, which allow their transformation into 5alpha-reduced steroids (5alpha-dihydrotestosterone, DHT, and 5alpha-androstandione, 5alpha-A), and 17beta-hydroxysteroid-oxidoreductase (17beta-HSD), which interconverts testosterone (T) and androstenedione (ADIONE); however, the two cell lines show differences in the rate of formation of these metabolites. Furthermore, two cell lines expressed the type 1 isoform of 5alpha-R, but only DU145 cells also possess 5alpha-R2. Aro is expressed 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 estrogens by the action of Aro; the biological role played by the two 5alpha-Rs in androgen-independent CaP deserves further investigation.
Negri-Cesi
P
P
Center for Endocrinological Oncology, Department of Endocrinology, University of Milan, Milan, Italy. pnc@mialserver.unimi.it
Colciago
A
A
Poletti
A
A
Motta
M
M
D013741:3-Oxo-5-alpha-Steroid 4-Dehydrogenase / Q000096:biosynthesis* / Q000737:chemistry / Q000378:metabolism; D000077384:Anastrozole; D000728:Androgens / Q000378:metabolism*; D000735:Androstenedione / Q000378:metabolism; D001141:Aromatase / Q000096:biosynthesis* / Q000378:metabolism; D047072:Aromatase Inhibitors; D015139:Blotting, Southern; D013196:Dihydrotestosterone / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005043:Etiocholanolone / Q000031:analogs & derivatives / Q000378:metabolism; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007527:Isoenzymes / Q000096:biosynthesis / Q000378:metabolism; D008297:Male; D008861:Microsomes / Q000201:enzymology; D009570:Nitriles / Q000494:pharmacology; D011470:Prostatic Hyperplasia / Q000201:enzymology / Q000378:metabolism; D011471:Prostatic Neoplasms / Q000201:enzymology* / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013739:Testosterone / Q000378:metabolism; D014230:Triazoles / Q000494:pharmacology; D014407:Tumor Cells, Cultured
D000728:Androgens; D047072:Aromatase Inhibitors; D004791:Enzyme Inhibitors; D007527:Isoenzymes; D009570:Nitriles; D012333:RNA, Messenger; D014230:Triazoles; D013196:Dihydrotestosterone; D000077384:Anastrozole; D013739:Testosterone; D000735:Androstenedione; C006576:androstane-3,17-dione; D005043:Etiocholanolone; D001141:Aromatase; D013741:3-Oxo-5-alpha-Steroid 4-Dehydrogenase