Hormone steroid receptor variation after tamoxifen administration in endometrial adenocarcinoma from postmenopausal patients.

Cytoplasmic and nuclear variations of estrogen (ER) and progesterone receptors (PgR) induced by tamoxifen (TAM) treatment were investigated in 38 postmenopausal women with endometrial carcinoma. The treatment consisted of a daily oral administration of 40 mg for 7 days. Tumor samples from each patient were withdrawn before TAM administration under hysteroscopy and at the time of hysterectomy. Cytoplasmic and nuclear receptors were respectively determined by the dextran-coated charcoal assay and the hydroxylapatite technique. In the cytoplasmic fraction no significant change in mean ER value was observed, but a statistically significant increase in PgR was found (P less than 0.001). Conversely, in the nuclear fraction PgR did not vary, but a significant increase in ER content (P less than 0.001) was observed. PgR, analyzed by sucrose density gradient after TAM, showed the same sedimentation property (9 S) as the preexisting receptor, but with a single peak profile, indicating a lower heterogeneity. Our data support the hypothesis that the mechanism of PgR synthesis is induced by the ER-TAM complex and suggest the possibility of increasing the PgR content in these patients for sequential endocrine therapy.