Article révisé par les pairs
Résumé : The transplantable MXT mouse mammary carcinoma is characterized by a marked sensitivity to ovarian hormones. It grows slowly in ovariectomized mice; administration of estradiol and medroxyprogesterone acetate abolishes this effect. Estrogen receptor (ER) concentrations were measured in the cystosol of MXT tumors from 3 groups of mice: intact (A), ovariectomized (B) and ovariectomized treated with estradiol and medroxyprogesterone acetate (C). ER were found in all tumors from groups A and C. In both groups, their concentration varied from tumor to tumor (range in fmoles/mg prot.; A = 11-52, C = 13-95). In contrast, no ER was found in group B. Tumors of group A displayed a histological morphology typical for adenocarcinomas (numerous epithelial cells arranged in ducts; very little connective tissue). Pattern of the tumors of group B was consistent with a sarcoma type (a few epithelial ducts surrounded by dense collagen fibers). Tumors from group C gave an intermediate pattern. Mitoses were observed in all groups. These data show that the suppression of ovarian hormone secretion favours the growth of MXT mammary tumors characterized by the absence of ER. These tumors are of the sarcoma type.