metribolone and 4-(3-4-4-trimethyl-5-oxo-2-thioxo-1-imidazolidinyl)-2-(trifluoromethyl)benzonitrile

Natural and pharmacological androgen receptor (AR) ligands were tested for their ability to induce the AR NH2-terminal and carboxyl-terminal (N/C) interaction in a two-hybrid protein assay to determine whether N/C complex formation distinguishes in vivo AR agonists from antagonists. High-affinity agonists such as dihydrotestosterone, mibolerone, testosterone, and methyltrienolone at concentrations between 0.1 and 1 nM induce the N/C interaction more than 40-fold. The lower affinity anabolic steroids, oxandrolone and fluoxymesterone, require concentrations of 10-100 nM for up to 23-fold induction of the N/C interaction. However no N/C interaction was detected in the presence of the antagonists, hydroxyflutamide, cyproterone acetate, or RU56187, at concentrations up to 1 microM, or with 1 microM estradiol, progesterone, or medroxyprogesterone acetate; each of these steroids at 1-500 nM inhibited the dihydrotestosterone-induced N/C interaction, with medroxyprogesterone acetate being the most effective. In transient and stable cotransfection assays using the mouse mammary tumor virus reporter vector, all ligands displayed concentration-dependent AR agonist activity that paralleled induction of the N/C interaction, with antagonists and weaker agonists failing to induce the N/C interaction. AR dimerization and DNA binding in mobility shift assays and AR stabilization reflected, but were not dependent on, the N/C interaction. The results indicate that the N/C interaction facilitates agonist potency at low physiological ligand concentrations as detected in transcription, dimerization/DNA binding, and stabilization assays. However the N/C interaction is not required for agonist activity at sufficiently high ligand concentrations, nor does its inhibition imply antagonist activity.

Topics: Androgen Antagonists; Androgen Receptor Antagonists; Androgens; Animals; COS Cells; Dihydrotestosterone; Dimerization; DNA; Dose-Response Relationship, Drug; Imidazoles; Luciferases; Mammary Tumor Virus, Mouse; Medroxyprogesterone Acetate; Metribolone; Mice; Nandrolone; Nitriles; Peptide Fragments; Progesterone Congeners; Receptors, Androgen; Recombinant Proteins; Testosterone Congeners; Transcription, Genetic; Transfection

The responses, in terms of cell proliferation and c-myc messenger RNA content, of human prostate cancer cells to androgen-receptor ligands were investigated. Experiments were performed with three types of cells (LNCaP, R2 and MOP) and three compounds (the androgen R 1881 and two anti-androgens: cyproterone acetate, CYPA, and RU 56187). MOP cells were established in the laboratory and the effects of RU 56187 had not been studied in culture. In terms of proliferation, LNCaP was stimulated by the three compounds, R2 was inhibited by R 1881 and RU 56187 but was stimulated by CYPA while MOP was inhibited by the three compounds. In the three types of cells, c-myc messenger RNAs were down regulated by R 1881 and RU 56187 but not by CYPA. The conclusions are: (1) the sets of responses of cell proliferation to three androgen-receptor ligands are cell specific; (2) the control of c-myc messenger RNA by R 1881 and RU 56187 may be related to the inhibition of cell proliferation by these compounds but not to their stimulatory effect on cell proliferation; (3) if prostate tumor cells would respond in vivo to androgens and antiandrogens like in culture, patients with prostate cancer could take benefits of reversible medical castration and sequential prescription of various antiandrogens.

Topics: Androgen Antagonists; Cell Division; Cyproterone Acetate; Genes, myc; Humans; Imidazoles; Kinetics; Male; Metribolone; Nitriles; Prostatic Neoplasms; Proto-Oncogene Proteins c-myc; RNA, Messenger; Testosterone Congeners; Transcription, Genetic; Tumor Cells, Cultured