Interactions between the estradiolreceptor and the progesteronereceptor are known to exist in the uterus. The "priming effect" of estradiol is likely to exist also in human and rat mammary tumors. In detecting also the progesteronereceptors along with the estrogenreceptors, one cannot only demonstrate the presence but also the activity of the estrogenreceptor. This finding should improve the response rate of hormonesensitivity to receptorpositivity. However preoperative irradiation possibly induces negative progesteronereceptortiters in human breast tumors.
PIP: Interactions between the estradiolreceptor and the progesteronereceptor have been demonstrated in many laboratories. The priming effect of estradiol is likely to exist in human and rat mammary tumors. The presence and activity of the estrogenreceptor can be demonstrated in detecting the progesteronereceptors along with the estrogenreceptors. This finding should improve the response rate of hormonesensitivity to receptorpositivity. Nearly 80% of estrogen, and progesterone, receptorpositive human breast tumors are likely to be hormonedependent; only 50% of the estrogenpositive tumors are. 500 mg tissue samples were analyzed for estradiol and progesteronereceptors. The receptor titers for the receptorpositive samples were not affected by irradiation. The amount of progesteronereceptor-positive tumors decreased from 76% for the controls to 25% and 37% for those who received 7 and 20 Gy respectively. Irradiation may reduce progesteronereceptors in human breast tumors.