RU-486 can abolish glucocorticoid-induced increases in CSF-1 receptor expression in primary human breast carcinoma specimens

OBJECTIVE: We present the results of the application of organ culture techn iques previously described in this journal to the study of steroid hormone responsiveness of primary breast carcinoma specimens. METHODS AND RESULTS: Nearly all breast carcinomas that express macrophage c olony-stimulating factor-1R (CSF-1R) at tissue harvest (15 of 18) had level s of CSF-1R expression lowered after incubation in steroid-free media. The decrease in CSF-1R expression was reversed by treatment with glucocorticoid s; this glucocorticoid-induced increase in CSF-1R expression can be blocked by mifepristone (RU-486), a competitive inhibitor of glucocorticoid action . CONCLUSION: These results demonstrate that steroid hormone responsiveness o f primary breast carcinomas can be assayed in vitro, a result which can not only be employed to better predict the responsiveness of breast carcinomas to therapies with steroid hormone agonists and antagonists, but also sugge sts that the therapeutic utility of mifepristone in breast cancer deserved further study. Copyright (C) 2001 by the Society for Gynecologic Investigat ion.