1alpha,25-dihydroxyvitamin D3 actions in LNCaP human prostate cancer cells are androgen-dependent.
We and others have recently shown that 1alpha,25-dihydroxyvitamin D3 [1,25-(OH)2D3] significantly inhibits cell proliferation and increases secretion of prostate-specific antigen (PSA) in LNCaP cells, an androgen-responsive human prostate cancer cell line. The present study was designed to investigate the possible interactions between 1,25-(OH)2D3 and androgens in the regulation of LNCaP cellular function. LNCaP cell growth was dose-dependently inhibited by 1,25-(OH)2D3 (60% inhibition at 10 nM) when cells were cultured in medium supplemented with FBS (FBS medium). 1,25-(OH)2D3-treated cells showed a 5-fold increase in PSA secretion, similar to the increase seen in dihydrotestosterone (DHT)-treated cells. In combination, 1,25-(OH)2D3 and DHT synergistically enhanced PSA secretion 22-fold. This synergistic effect was even greater when cells were cultured in medium supplemented with charcoal-stripped serum (CSS medium), where endogenous steroids are substantially depleted. Under these conditions, 1,25-(OH)2D3 and DHT together stimulated PSA secretion up to 50-fold over the untreated control. Radioligand binding assays and Western blot analyses showed that the androgen receptor (AR) content was increased significantly by 1,25-(OH)2D3 at 48 h. Furthermore, the steady-state mRNA level of AR was up-regulated approximately 2-fold by 1,25-(OH)2D3 at 24 h. When cells were grown in CSS medium, 1,25-(OH)2D3 alone no longer inhibited cell growth or induced PSA secretion. Titration experiments revealed that the addition of DHT at 1 nM to the medium restored the antiproliferative activity of 1,25-(OH)2D3. Conversely, an antiandrogen, Casodex, completely blocked 1,25-(OH)2D3 antiproliferative and PSA stimulation activities when cells were cultured in FBS medium. In conclusion, these results demonstrate that the antiproliferative and PSA induction activities of 1,25-(OH)2D3 in LNCaP cells are dependent upon androgen action and that AR up-regulation by 1,25-(OH)2D3 likely contributes to the synergistic actions of 1,25-(OH)2D3 and DHT in these cells.
Zhao
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Department of Medicine, Stanford University School of Medicine, California 94305, USA.
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D000704:Analysis of Variance; D000726:Androgen Antagonists / Q000494:pharmacology; D000728:Androgens / Q000494:pharmacology*; D000813:Anilides / Q000494:pharmacology; D015152:Blotting, Northern; D015153:Blotting, Western; D002117:Calcitriol / Q000494:pharmacology*; D002455:Cell Division / Q000187:drug effects; D013196:Dihydrotestosterone / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004357:Drug Synergism; D006801:Humans; D008297:Male; D009376:Neoplasms, Hormone-Dependent / Q000737:chemistry / Q000378:metabolism / Q000473:pathology*; D009570:Nitriles; D017430:Prostate-Specific Antigen / Q000378:metabolism; D011471:Prostatic Neoplasms / Q000737:chemistry / Q000378:metabolism / Q000473:pathology*; D011944:Receptors, Androgen / Q000032:analysis / Q000187:drug effects / Q000502:physiology; D014105:Tosyl Compounds; D014316:Tritium; D014407:Tumor Cells, Cultured; D015854:Up-Regulation
D000726:Androgen Antagonists; D000728:Androgens; D000813:Anilides; D009570:Nitriles; D011944:Receptors, Androgen; D014105:Tosyl Compounds; D013196:Dihydrotestosterone; D014316:Tritium; C053541:bicalutamide; D017430:Prostate-Specific Antigen; D002117:Calcitriol