Low content of estrogen receptors in human giant cell tumors of bone

We tried to identify estrogen receptors (ERs) in human giant cell tumors of bone. Samples from eight patients were used for biochemical and immunohistochemical studies using [¹²⁵I]17-estradiol and monoclonal antibody against the human ER. Estradiol binding sites were detected in seven cases out of eight. The dissociation constant of the higher affinity binding site was 0.5 nM. Nonlabeled 17-estradiol and synthetic estrogen, diethylstilbestrol, inhibited the binding of labeled 17-estradiol to the tumor cytosol, while dexamethasone did not inhibit the binding. Using a monoclonal antibody, Western blotting identified bands ofMr 68000 and 59000. No ERs were observed in any case examined immunohistochemically. These results suggest that human giant cell tumors of bone have a low level of ERs that cannot be detected immunohistochemically.