Pregnenolone stimulates LNCaP prostate cancer cell growth via the mutated androgen receptor

Dmitry N. Grigoryev, Brian J. Long, Vincent C.O. Njar, Angela H.M. Brodie

Research output: Contribution to journalArticle

Abstract

Pregnenolone (P5), a common precursor of many steroids, is present in the blood of normal adult men at concentrations of 1-3 nM. In vitro, P5 was found to stimulate LNCaP-cell proliferation 7-8-fold at a physiological concentration (2 nM), and 3-4-fold at a subphysiological concentration (0.2 nM). Growth stimulation at the 2-nM concentration was comparable with that of the androgen, dihydrotestosterone at its physiological concentration (0.5 nM; 9-10-fold increase in cell number). To determine whether P5 or its metabolites were mediating this growth response, LNCaP cells were incubated with [3H]P5 and high-performance liquid chromatography (HPLC) was performed. After a 48-h exposure, two unidentified metabolites were detected. Although, the P5 metabolites slightly increased LNCaP-cell growth in vitro, their effect was significantly less than P5 alone, suggesting that the growth stimulation was mediated by P5 itself. We further showed that P5 sustained its proliferative activity in vivo and stimulated the growth of LNCaP-tumor xenografts in intact male SCID mice as well as in castrated animals. In order to determine whether P5 was binding to a specific site in LNCaP cells, receptor binding studies were performed. Scatchard analysis predicted for a single class of binding sites with Kd = 1.4 nM. Studies were performed to determine the effects of P5 on transcription mediated by wild-type and LNCaP androgen receptors. P5 was shown to activate transcription through the LNCaP androgen receptor (AR), but not the wild-type AR. This implies that P5 most likely stimulates LNCaP-cell proliferation through binding to the cellular mutated AR present in LNCaP cells. We have also demonstrated that drugs designed to be antagonists of the androgen, progesterone and estrogen receptors, and one of our novel compounds designed to be an inhibitor of androgen synthesis, were potent inhibitors of the AR-mediated transcriptional activity induced by P5, and were able to inhibit LNCaP-cell proliferation. These findings suggest that some prostate cancer patients who appear to become hormone-independent may have tumors which are stimulated by P5 via a mutated AR and that these patients could benefit from treatment with antiestrogens, antiprogestins, or with some of our novel androgen synthesis inhibitors.

Original languageEnglish (US)
Pages (from-to)1-10
Number of pages10
JournalJournal of Steroid Biochemistry and Molecular Biology
Volume75
Issue number1
DOIs
StatePublished - Dec 1 2000

Keywords

  • Androgen receptor
  • Growth inhibition
  • LNCaP prostate cancer cell line
  • Novel androgen synthesis inhibitors
  • Pregnenolone

ASJC Scopus subject areas

  • Endocrinology, Diabetes and Metabolism
  • Biochemistry
  • Molecular Medicine
  • Molecular Biology
  • Endocrinology
  • Clinical Biochemistry
  • Cell Biology

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