Estrogen receptor immunoreactivity in meningiomas. Comparison with the binding activity of estrogen, progesterone, and androgen receptors.

Estrogen receptor (ER) analysis was performed in 70 meningioma samples by means of two assays: an enzyme immunoassay that used monoclonal antibodies against human ER protein (estrophilin), and a sensitive radioligand binding assay that used iodine-125-labeled estradiol as the radioligand. Low levels of ER immunoreactivity were found in tumors from 51% of patients, whereas ER binding activity was demonstrated in 40% of the meningiomas examined. In eight (11%) of the tissue samples, multiple binding sites for estradiol were observed. The immunoreactive binding sites corresponded to those of the classic high-affinity ER. In ligand binding studies, however, measurement of classic ER was considerably influenced by a second low-affinity high-capacity estrogen binding component, even at low ligand concentrations. Binding activity of the progesterone receptor (PR) and androgen receptor (AR) was determined concurrently using 17 alpha-methyl-3H-promegestone (3H-R 5020) and 17 alpha-methyl-3H-trienolone (3H-R 1881), a synthetic gestagen and androgen, respectively. High concentrations of PR were detected in 53 (76%) of the tumors, whereas a moderate number of AR binding sites were demonstrated in 33 (47%) of the tumors. A positive correlation between ER immunoreactivity and AR binding activity is suggestive of estrogen regulation of AR via the ER system. The presence of gonadal steroid receptors in a large proportion of meningiomas and the tendency toward a dependence of receptor concentrations on the histological subtype of the meningioma could have implications for tumor therapy.