The existence of
estrogen receptors in human
meningiomas has long been a controversial issue. This may be explained, in part, by apparent heterogeneity of
estrogen binding sites in
meningioma tissue. In this study,
estrogen receptors were determined in 58
meningiomas with an
enzyme immunoassay using
monoclonal antibodies against human
estrogen receptor protein (
estrophilin) and with a sensitive radioligand binding assay using 125I-labeled
estradiol (125I-estradiol) as radioligand. Low levels of
estrophilin immunoreactivity were found in
tumors from 62% of patients, whereas radioligand binding activity was demonstrated in about 46% of the
meningiomas examined. In eight (14%) tissue samples multiple binding sites for
estradiol were observed. The immunoreactive binding sites correspond to the classical, high affinity
estrogen receptors: the Kd for 125I-estradiol binding to the receptor was approximately 0.2 nM and the binding was specific for
estrogens. The second, low affinity class of binding sites considerably influenced measurement of the classical receptor even at low
ligand concentrations. The epidemiological and clinical data from patients with
meningiomas, and the existence of specific
estrogen receptors confirmed by immunochemical detection, may be important factors in a theory of
oncogenesis.