Heterogeneity of estrogen binding sites in mammary tumors.

This paper provides a brief summary of our recent work on the heterogeneity of estradiol binding sites in mammary tumors of the mouse and human. Mammary tumors from both species contain the classical estrogen receptor and a second site(s) which we call type II. These type II sites are found in the cytoplasmic and nuclear compartments of both tumors, and can interfere with the measurement of estrogen receptors.

Estrogen binding sites in the nucleus of normal and malignant human tissue: characteristics of the multiple nuclear binding sites.

The studies presented here describe the effects of the nonionic detergent, Tween 80 and the reducing agent, dithiothreitol (5 mM), on the quantitation of specific nuclear estrogen binding sites, both estrogen receptors (ER) and type II estrogen binding sites (EBS), in human breast cancer. Neither of these agents had any significant effect on the apparent Kd of the amount of ER measured; however, both had a dramatic effect on the amount of type II EBS measured. Two antiestrogens, tamoxifen and nafoxidine, were also tested for their ability to bind to ER and type II EBS in human breast tumors.

Estrogen binding sites in the nucleus of normal and malignant human tissue: optimization of an exchange assay for the measurement of specific binding.

An exchange assay has been validated and used to measure the total concentration of estrogen receptors in the nuclei of cells from human breast tumors and myometrium. Tissue homogenates were centrifuged through 1.2 M sucrose pads to separate crude chromatin from soluble ane membranous fractions.

Effects of estradiol and the antiestrogen tamoxifen on steroid hormone receptor concentration and nuclear ribonucleic acid polymerase activities in rat uteri.

The antiestrogen tamoxifen has been used successfully in the treatment of breast cancer. In an attempt to elucidate its mode of action, its effects on steroid hormone receptor concentration and RNA polymerase activities in the uteri of ovariectomized rats have been compared with those of estradiol. A single dose of estradiol and tamoxifen, separately or in combination, produced slight increases in uterine wet weight 12 h after injection.