[Hormone independent murine carcinoma BX-1 spontaneously arising from nude mouse bearing Br-10, a hormone dependent human breast carcinoma strain].

BX-1, an adenocarcinoma spontaneously arising from nude mouse bearing Br-10, a human breast carcinoma strain was characterized. And the purification of a hormone independent murine carcinoma strain, BX-1 was found in August 1986 in three institutes where a hormone dependent transplantable human breast carcinoma cell line Br-10 has been serially passaged. The histological features of BX-1 were different from any other strains which were maintained in these three institutes. Estrogen receptor of BX-1 was negative and no estrogen dependency was observed while Br-10 was the receptor positive and the growth of Br-10 was dependent on estrogen. Although the graft of BX-1 into the thymus intact littermates was rejected, the chromosomal analysis revealed only murine chromosomes for BX-1, while both of human and murine chromosomes were detected in Br-10 tumor. By incubating Br-10 tumor in untreated female nude mice for 2 months and stimulating the growth of the tumor by exogenous estradiol, the purification of Br-10 from BX-1 could be achieved. Whereas the stability of human tumor xenografts in nude mice is confirmed, the spontaneously arising murine tumor from nude mice bearing human tumor xenografts should be considered for the experiments.