Binding of estradiol to whole prostatic DU‐145 cells in the presence and absence of tamoxifen and acetylsalicylic acid

Abstract

Conflicting results have been obtained with regard to the estradiol receptor (ER) capacity of human prostatic tissue. Human prostatic DU‐145 cells have been found to be ER‐negative with immunohistochemical assays. The object of this investigation was to determine if whole DU‐145 cells, which had been grown in monolayer culture, have ER and, if so, to confirm the finding with antiestrogens. After cells had been lysed, a B_max of 44.7 ± 4.0 fmol/mg (K_d = 0.6 ± 0.6 nM) was obtained. Subcellular localization studies showed that the estrogen receptor level in the cytoplasmic fraction was approximately 10 times higher than in the nuclear fraction. Competitive binding studies showed that tamoxifen, DES, and acetylsalicylic acid decreased estradiol binding. The dissociation constants and relative affinities for tamoxifen, DES, and acetylsalicylic acid were 0.2 nM (281.7%), 0.2 nM (224.0%), and 0.8 nM (78.43%), respectively. However, 5α‐dihydrotestosterone and metabolites of acetylsalicylic acid had no effect in competitive binding studies. These results may contribute to a better understanding of prostatic carcinogenesis, which may in turn lead to more effective treatment.