Effects of sex steroid hormones on the human endometrial carcinoma transplanted endometrial carcinoma transplanted into nude mice. Estrogen priming aimed at the enhancement of tumor tissue-sensitivity to progesterone.

A study aimed at the enhancement of endometrial carcinoma tissue-sensitivity to progesterone by estrogen priming involved the serial transplantation of human moderately-differentiated endometrial carcinoma into nude mice in which estradiol receptors were detectable but progesterone receptors undetectable. Quantitative induction of cytosol progesterone receptors occurred in the groups receiving a small dose of estradiol concomitantly with progesterone but not in the groups receiving estradiol alone and progesterone alone. Ultrastructurally, the effects of progesterone tended to be more conspicuous in these concomitantly treated groups than in the progesterone-treated group in respect of an increase in the number of lysosomes and lipid droplets and appearance of secretory granules and other vesicles. Suppression of tumor growth was evident in the progesterone-treated group and in the concomitantly treated groups as compared with the control group, and the effect was somewhat more pronounced in the latter groups. The present data suggest that the administration of a small dose of estradiol concomitantly with progesterone is more effective than that of progesterone alone in gestagen therapy for endometrial carcinoma, when it is assumed that the progesterone effects on endometrial carcinoma are mediated primarily by progesterone receptors.