Characterization of type I 5α-reductase activity in DU145 human prostatic adenocarcinoma cells

• Published in: The Journal of steroid biochemistry and molecular biology Vol. 58; no. 2; pp. 195 - 205
• Main Authors: Kaefer, Martin, Audia, James E., Bruchovsky, Nicholas, Goode, Robin L., Hsiao, Kenneth C., Leibovitch, Ilan Y., Krushinski, Joseph H., Lee, Chung, Steidle, Christopher P., Sutkowski, Debra M., Neubauer, Blake Lee
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01-05-1996; Elsevier Science
• Subjects: 3-Oxo-5-alpha-Steroid 4-Dehydrogenase - genetics; 3-Oxo-5-alpha-Steroid 4-Dehydrogenase - metabolism; 5-alpha Reductase Inhibitors; Adenocarcinoma - drug therapy; Adenocarcinoma - enzymology; Adenocarcinoma - pathology; Androstadienes - pharmacology; Animal tumors. Experimental tumors; Benzoquinones - pharmacology; Biological and medical sciences; Cell Division - drug effects; Enzyme Inhibitors - pharmacology; Experimental renal and urinary tract tumors; Finasteride - pharmacology; Gene Expression Regulation, Neoplastic; Humans; Isoenzymes; Male; Medical sciences; Prostatic Neoplasms - drug therapy; Prostatic Neoplasms - enzymology; Prostatic Neoplasms - pathology; RNA, Messenger - biosynthesis; Selection, Genetic; Skin - drug effects; Skin - metabolism; Testosterone - metabolism; Tumor Cells, Cultured; Tumors; Adenocarcinoma; Human; Urinary system disease; Androgen; Prostate disease; Enzyme; Enzyme inhibitor; Cholestenone 5α-reductase; Gene expression; Metabolism; Testosterone; Cell line; Enzymatic activity; Testicular hormone; Oxidoreductases; Benign neoplasm; Sex steroid hormone; Prostate
• ISSN: 0960-0760; 1879-1220
• DOI: 10.1016/0960-0760(96)00020-9

The conversion of testosterone (T) to dihydrotestosterone (DHT) has been demonstrated to be catalysed by at least two isoforms of human steroid 5α-reductase, designated types I and II. Type II 5α-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 5α-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 5α-reductase II cDNA failed to reveal expression of the type II isoform. The expression of functional type I activity has been confirmed pharmacologically using isoformselective 5α-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 5α-reductase in DU145 cellular homogenates with an apparent Ki value of 4.0 nM. These studies have identified and pharmacologically defined type I 5α-reductase activity in an androgen-insensitive prostatic cancer cell line and provide the basis for additional investigations into the significance of type I 5α-reductase to human prostatic pathophysiology.