The cytoplasmic estrogen receptor was measured in 9 intracranial meningiomas and 8 thymomas. The binding affinities of the estrogen receptor derived from the tumors to various estrogens and antiestrogens were compared with that observed for the receptor from rat normal uterus. The cytoplasmic progesterone receptor was measured concomitantly.
The estrogen receptor was positive in 4 and 3 cases of meningioma and thymoma, respectively. The positive rates of estrogen receptor in those tumors did not differ from each other, however, rather low than that in breast cancer in Japan. The numbers of hormone binding sites were almost equal to those of estrogen receptor in breast cancer from pre-menopausal patients.
The binding affinities of estrogen receptor derived from those tumors to estrogens and antiestrogens were equivalent with that observed for rat uterine receptor. Namely, diethylstilbestrol inhibited the protein binding of tritiated 17β-estradiol to 50% by the same amount addition with the latter. Tamoxifen and epithiostanol caused 50% inhibition with 250 and 100 fold amounts, respectively. 17α-Estradiol showed median affinity. Again no differences were observed between the receptors derived from both tumors.
The progesterone receptor was not detected in all of the assayed cases. Therefore, the positive rates of this receptor seemed very low in those kinds of tumors.
These results suggest that the cytoplasmic estrogen receptor found in diverse human tumors other than meningioma or thymoma may have same biological characteristics.
Therefore, as observed in human breast cancer, so neither the positiveness of estrogen receptor nor the binding affinity to estrogens and antiestrogens will coincide directly with the hormone dependency of those tumors.