Characterization of type I 5 alpha-reductase activity in DU145 human prostatic adenocarcinoma cells.
The conversion of testosterone (T) to dihydrotestosterone (DHT) has been demonstrated to be catalysed by at least two isoforms of human steroid 5 alpha-reductase, designated types I and II. Type II 5 alpha-reductase expression predominates in human accessory sex tissues, localized to the fibromuscular stromal compartment. The type I isoform predominates in skin, prostatic epithelia and, to a lesser extent, in prostatic fibromuscular stroma. The significance of the type I isoform to prostatic cellular growth and function remains undefined. In cultured DU145 cells, we evaluated the metabolism of [14C]-T and demonstrated the time-dependent formation of [14C]-DHT. Oxidative metabolism (conversion of [14C]-T to [14C]-androstenedione) and the formation of conjugated androgen metabolites occurred at a relatively low rate in the DU145 cells. Using human type I 5 alpha-reductase cDNA, Northern blot analysis of DU145 cell mRNA revealed high levels of type I isoform expression. Analogous probing of the DU145 cells with a human 5 alpha-reductase II cDNA failed to reveal expression of the type II isoform. The expression of functional type I activity has been confirmed pharmacologically using isoform-selective 5 alpha-reductase inhibitors. Reductive metabolism of [3H]-T in the DU145 cells was inhibited in a concentration-dependent manner by LY306089, a potent non-steroidal type I-selective inhibitor (IC50 = 10.0 nM). SKF105657, a steroidal type II-specific inhibitor was distinctly less active at inhibiting [3H]-DHT formation. LY306089 was a non-competitive inhibitor of type I 5 alpha-reductase in DU145 cellular homogenates with an apparent Ki value of 4.0 nM. These studies have identified and pharmacologically defined type I 5 alpha-reductase activity in an androgen-insensitive prostatic cancer cell line and provide the basis for additional investigations into the significance of type I 5 alpha-reductase to human prostatic pathophysiology.
Kaefer
M
M
Lilly Research Laboratories, Division of Eli Lilly and Company, Lilly Corporate Center, Indianapolis, IN 46285, USA.
Audia
J E
JE
Bruchovsky
N
N
Goode
R L
RL
Hsiao
K C
KC
Leibovitch
I Y
IY
Krushinski
J H
JH
Lee
C
C
Steidle
C P
CP
Sutkowski
D M
DM
Neubauer
B L
BL
D013741:3-Oxo-5-alpha-Steroid 4-Dehydrogenase / Q000235:genetics / Q000378:metabolism*; D058891:5-alpha Reductase Inhibitors; D000230:Adenocarcinoma / Q000188:drug therapy / Q000201:enzymology* / Q000473:pathology; D000730:Androstadienes / Q000494:pharmacology; D016227:Benzoquinones / Q000494:pharmacology; D002455:Cell Division / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D018120:Finasteride / Q000494:pharmacology; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D007527:Isoenzymes; D008297:Male; D011471:Prostatic Neoplasms / Q000188:drug therapy / Q000201:enzymology* / Q000473:pathology; D012333:RNA, Messenger / Q000096:biosynthesis; D012641:Selection, Genetic; D012867:Skin / Q000187:drug effects / Q000378:metabolism; D013739:Testosterone / Q000378:metabolism; D014407:Tumor Cells, Cultured
D058891:5-alpha Reductase Inhibitors; D000730:Androstadienes; D016227:Benzoquinones; D004791:Enzyme Inhibitors; D007527:Isoenzymes; C101585:LY 306089; D012333:RNA, Messenger; C072547:epristeride; D013739:Testosterone; D018120:Finasteride; D013741:3-Oxo-5-alpha-Steroid 4-Dehydrogenase