Inhibition of the activity of 'basic' 5 alpha-reductase (type 1) detected in DU 145 cells and expressed in insect cells.
The purpose of this study was 2-fold: (1) to identify the 5 alpha-reductase (5 alpha-R) isozyme(s) present in DU 145 cells, a human cell-line of low androgen sensitivity derived from a cerebral metastasis of an epithelial prostate cancer; and (2) to compare the inhibitory potencies of three compounds on the 'basic' 5 alpha-R isozyme expressed in a baculovirus-directed insect cell system. Conversion of testosterone (T) into 5 alpha-dihydrotestosterone (DHT) in DU 145 cells was measured by HPLC coupled to a Flo-one HP radioactivity detector. DU 145 cells exhibited 5 alpha-R activity (21 pmol DHT/min/mg protein) at pH 7.4 which disappeared at pH 5.5 suggesting that, of the two genomically distinct human isozymes identified so far, type 1 5 alpha-R is expressed in DU 145 cells. This was confirmed by at least two observations: first, 5 alpha-R activity in DU 145 cells was inhibited with much higher potency by 4-MA than by finasteride which is known to be a very poor competitor of the 'basic' enzyme (IC50s = 2.8 +/- 0.2 and 264 +/- 55 nM, respectively). Second, only the type 1 5 alpha-R cDNA and not type 2 5 alpha-R cDNA hybridized with DU 145 RNA. A high potency differential was also recorded for the inhibition of 'basic' type 1 5 alpha-R expressed in a baculovirus-directed-insect cell system by these two compounds, 4-MA being considerably more active than finasteride (Ki = 8.4 +/- 2.3 and 330 +/- 9 nM, respectively). This inhibition was competitive. On the other hand, inhibition by an n-hexane lipid/sterol extract of Serenoa repens (LSESr) was non-competitive and, when expressed in terms of recommended therapeutic doses, was 3-fold greater for LSESr than for finasteride. These studies suggest that LSESr might exert a regulatory inhibitory activity due to its specific lipid/sterol composition.
Délos
S
S
Laboratoire de Cancérologie Expérimentale, Faculté de Medecine, Secteur Nord, Marseille, France.
Iehlé
C
C
Martin
P M
PM
Raynaud
J P
JP
D013741:3-Oxo-5-alpha-Steroid 4-Dehydrogenase / Q000032:analysis / Q000235:genetics; D058891:5-alpha Reductase Inhibitors; D000818:Animals; D001378:Azasteroids / Q000494:pharmacology; D016367:Baculoviridae / Q000235:genetics; D001932:Brain Neoplasms / Q000201:enzymology / Q000556:secondary*; D002851:Chromatography, High Pressure Liquid; D013196:Dihydrotestosterone / Q000031:analogs & derivatives / Q000378:metabolism / Q000494:pharmacology; D018120:Finasteride / Q000494:pharmacology; D015870:Gene Expression; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007527:Isoenzymes / Q000032:analysis / Q000037:antagonists & inhibitors* / Q000235:genetics; D007700:Kinetics; D008297:Male; D009036:Moths; D011471:Prostatic Neoplasms / Q000201:enzymology*; D011994:Recombinant Proteins / Q000037:antagonists & inhibitors; D013739:Testosterone / Q000378:metabolism; D014407:Tumor Cells, Cultured
D058891:5-alpha Reductase Inhibitors; D001378:Azasteroids; D007527:Isoenzymes; D011994:Recombinant Proteins; D013196:Dihydrotestosterone; D013739:Testosterone; D018120:Finasteride; C031563:17-N,N-diethylcarbamoyl-4-methyl-4-azaandrostane-3-one; D013741:3-Oxo-5-alpha-Steroid 4-Dehydrogenase