Complementary DNAs (cDNAs) encoding androgen receptors were obtained from human testis and rat ventral prostate cDNA libraries. The amino acid sequence deduced from the nucleotide sequences of the cDNAs indicated the presence of a cysteine-rich DNA-binding domain that is highly conserved in all steroid receptors. The human cDNA was transcribed and the RNA product was translated in cell-free systems to yield a 76-kilodalton protein. The protein was immunoprecipitable by human autoimmune antibodies to the androgen receptor. The protein bound androgens specifically and with high affinity.

Green tea polyphenols, especially the catechin, (-)-epigallocatechin gallate (EGCG), have been proposed as a cancer chemopreventative based on a variety of laboratory studies. For clear assessment of the possible physiological effects of green tea consumption, we injected pure green tea catechins ip into rats and studied their acute effects on endocrine systems. We found that EGCG, but not related catechins, significantly reduced food intake; body weight; blood levels of testosterone, estradiol, leptin, insulin, insulin-like growth factor I, LH, glucose, cholesterol, and triglyceride; as well as growth of the prostate, uterus, and ovary. Similar effects were observed in lean and obese male Zucker rats, suggesting that the effect of EGCG was independent of an intact leptin receptor. EGCG may interact specifically with a component of a leptin-independent appetite control pathway. Endocrine changes induced by parenteral administration of EGCG may relate to the observed growth inhibition and regression of human prostate and breast tumors in athymic mice treated with EGCG as well as play a role in the mechanism by which EGCG inhibits cancer initiation and promotion in various animal models of cancer.

Structural analysis of cDNAs for human and rat androgen receptors (ARs) indicates that the amino-terminal regions of ARs are rich in oligo-and poly(amino acid) motifs as in some homeotic genes. The human AR has a long stretch of repeated glycines, whereas rat AR has a long stretch of glutamines. There is a considerable sequence similarity among ARs and the receptors for glucocorticoids, progestins, and mineralocorticoids within the steroid-binding domains. The cysteine-rich DNA-binding domains are well conserved. Translation of mRNA transcribed from AR cDNAs yielded 94-and 76-kDa proteins and smaller forms that bind to DNA and have high affinity toward androgens. These rat or human ARs were recognized by human autoantibodies to natural ARs. Molecular hybridization studies, using AR cDNAs as probes, indicated that the ventral prostate and other male accessory organs are rich in AR mRNA and that the production of AR mRNA in the target organs may be autoregulated by androgens.

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When the human prostate cancer cell line, LNCaP 104-S, the growth of which is stimulated by physiological levels of androgen, is cultured in androgen-depleted medium for >100 and androgen-independent LNCaP 104-R2t sublines were isolated as described (6). The characteristics of these cells in vitro were confirmed before injection into nude mice. Briefly, proliferation of LNCaP 104-S cells increased 10-to 13-fold in medium containing charcoal-treated fetal bovine serum (FBS) and 0.1 nM synthetic androgen R1881, compared with cells cultured in medium containing charcoal-treated FBS without added androgen. LNCaP 104-R2 cells grew in medium supplemented with charcoal-treated FBS without additional androgen. Their proliferation was not stimulated but was repressed by 0.1 nM R1881. LNCaP 104-S cells were maintained in DMEM (GIBCO) supplemented with 1 nM S5t-dihydrotestosterone and 10% FBS (Summit Biotechnology, Ft. Collins, CO), and LNCaP 104-R2 cells were maintained in DMEM supplemented with 10% FBS treated with charcoal to remove steroid (6). PC-3 and MCF-7 cell lines were obtained from the American Type Culture Collection (Rockville, MD) and were maintained in DMEM supplemented with 10% FBS.Animals. BALB/c athymic (nude) male (LNCaP, PC-3 cell lines) and female (MCF-7 cell line) mice (Taconic, Germantown, NY), 5 to 7 weeks old, were used. Mice were housed in a pathogen-free environment, four to five mice per cage. Cages (filter top), bedding, and water were autoclaved before use. Feed was irradiated Pico Lab Mouse Chow 20 5058 (Purina).Abbreviations: AR, androgen receptor; FBS, fetal bovine serum; PSA, prostate-specific antigen; TP, testosterone propionate.