Antibody-recognized [125I]estradiol-receptor complex in ovarian epithelial carcinoma

Monoclonal antibody against human breast cancer estrogen receptor was used to demonstrate binding of a gamma- and Auger electron-emitting estrogen to the estrogen receptor in ovarian epithelial carcinomas. When cytosols of estrogen receptor-rich ovarian adenocarcinomas were analyzed on sucrose gradients containing 0.4 M KCl, the presence of monoclonal antibody against breast cancer estrogen receptor caused a binding peak for [125I]- and [3H]estradiol to shift from the 4S to the 8-9S region, indicating antibody complex formation with ovarian adenocarcinoma estrogen receptor. The antibody-shifted peak of 8-9S [125I]- and [3H]estradiol binding was totally inhibited by a 100-fold molar excess of diethylstilbestrol (DES), but not by testosterone or progesterone, indicating a preference for estrogen binding by the antibody-shifted estrogen receptor. When estrogen receptor from the nuclear fraction of ovarian adenocarcinomas was incubated with [125I]estradiol at 1C, in the presence of 0.4 M NaSCN to facilitate exchange with endogenous ligand, binding occurred that was inhibitable by DES and restricted to the 4S region. Under these conditions the nuclear estrogen receptor was also shifted to the 8-9S region by the presence of the monoclonal antibody against estrogen receptor.