Normal but Not Carcinomatous Primary Rat Mammary Epithelium: Readily Transplanted to and Maintained in the Athymic Nude Mouse<xref ref-type="fn" rid="FN2">2</xref>

Abstract

Transplantation success rates of primary 7,12-dimethylbenz(a)anthracene [(DMBA) CAS: 57-97-6]-induced rat mammary carcinomas and normal rat mammary glandular epithelium into female athymic mice were compared. The rat mammary carcinomas obtained from female Sprague-Dawley rats were transplanted into host athymic mice (6-8 wk of age) as 1 x 1-cm slices xenografted sc (2 slices/mouse) or as enzymatically dissociated cells inoculated into the gland-free mammary fat pad. Normal rat mammary glands (No. 4 glands and 3- to 5-mo-old virgin rats) were transplanted into host athymic mice as whole, intact mammary glands sc (1 gland/mouse) or as enzymatically dissociated cells inoculated into the gland-free mammary fat pad. All (100%) of the normal rat mammary glands were readily accepted and maintained in the athymic mice when transplanted either sc as whole glands or as dispersed cells inoculated into the gland-free fat pad. In contrast, only 13-14% of the DMBA-induced rat mammary carcinomas were accepted and maintained in the athymic mice (transplanted as slices sc or as dispersed cells inoculated into the gland-free fat pad). Treatment of host athymic nude mice with an intense mammotropic hormonal stimulus (prolactin and/or ovarian steroids) markedly enhanced the developmental growth of the transplanted normal rat mammae (subcutaneous slices and fat-pad inoculates); such a hormonal stimulus did not influence the transplantation success rate of the DMBA-induced rat mammary carcinomas. Thus female athymic nude mice can readily accept and maintain transplants of normal rat mammae but not carcinogen-induced carcinomatous rat mammae; the meager acceptance rate of the carcinomatous rat mammae by the athymic nude mouse was not enhanced by providing the host mice with a potent mammotropic hormonal growth stimulant.