ABSTRACT
Mutations in the androgen receptor (AR), that alter steroid hormone specificity have been identified in a series of androgen-independent prostate cancers. To address the functional properties of these mutant ARs that may have contributed to their selection in vivo, responses to a series of steroid hormones and antiandrogens were assessed. CV-1 cells were cotransfected with wild-type or mutant ARs and a luciferase reporter plasmid regulated by an androgen-responsive element. Dose-response curves were analyzed for 5alpha-dihydrotestosterone, the most active androgen in normal prostate, and androstenedione, a major androgen derived from the adrenals. Although the mutant ARs responded to both of these steroids, the responses were equivalent to or less than the wild-type AR. In contrast, responses to flutamide, a competitive antagonist of the wild-type AR, were markedly increased by three of the mutations. Similar responses were observed with a second antiandrogen, nilutamide. Bicalutamide, another antiandrogen related to flutamide, remained an antagonist for these mutant ARs. Finally, flutamide was observed to be a weak partial agonist of the wild-type AR in this system. These results indicate that flutamide used in conjunction with androgen ablation therapy for prostate cancer may select for tumor cells with flutamide-inducible ARs.
Subject(s)
Androgen Antagonists/pharmacology , Androgens/pharmacology , Imidazolidines , Point Mutation , Prostatic Neoplasms/genetics , Receptors, Androgen/genetics , Amino Acid Substitution , Androstenedione/pharmacology , Animals , Cell Line , Dihydrotestosterone/pharmacology , Estradiol/pharmacology , Flutamide/analogs & derivatives , Flutamide/pharmacology , Genes, Reporter , Imidazoles/pharmacology , Luciferases/genetics , Male , Progesterone/pharmacology , Prostatic Neoplasms/metabolism , Receptors, Androgen/biosynthesis , Receptors, Androgen/physiology , Recombinant Fusion Proteins/biosynthesis , Transfection , beta-Galactosidase/geneticsABSTRACT
A population of mature CD4-CD8-double-negative T cells that expresses an invariant Valpha24-JalphaQ TCR has been identified in humans; the majority of these cells appear to express Vbeta11. A closely related in variant TCRalpha chain is also expressed by a population of NK1+ murine T cells, but these cells may be either CD4+ or double negative. In this report, multiple CD4+ or double-negative Valpha24+Vbeta11+ T-cell clones were isolated, and only the double-negative clones were found to express the invariant TCRalpha chain. Studies of TCRbeta chains expressed by these cells demonstrate that a subset in some donors use Vbeta genes other than Vbeta11. Characterization of Vbeta11 TCRs in one donor by CDR3-length analysis was also carried out. The results indicate that multiple Vbeta11 TCRs of differing CDR3 lengths may associate with the invariant TCRalpha chain.
