Hormone dependency of a serially transplantable human breast cancer (Br-10) in nude mice

The human breast cancer (Br-10) serially transplanted to nude mice (BALB/c-nu/nu) grew well in female mice but very slowly or not at all in untreated male mice and female mice treated with 1 mg of testosterone i.m. twice a week. The growth in female mice was arrested by ovariectomy, and that in male mice was accelerated by 0.1 mg of estradiol i.m. once a week. Tumors in female and estrogenized male mice retained the original histology of duct carcinoma. Tumors in ovariectomized female, androgenized female, and male mice consisted of cells with smaller and more uniform nuclei, forming markedly dilated lumina in the first group and arranged in lobular patterns in the latter two groups. High-affinity 8 S and 4 S estrogen receptors were present in tumors transplanted to female nude mice, but no progesterone receptors were detected. These results provide experimental evidence for the hormone dependency of a human breast cancer in vivo and strongly suggest the important role of estrogen and androgen in the growth regulation of some estrogen receptor-positive human breast cancers.