The Regulation of Progesterone Receptor by 17b Estradiol and Tamoxifen in the ZR-751 Human Breast Cancer Cell Line in Defined Medium

Allegra, J C.; Korat, O; Do, H M.T.; Lippman, M

Journal of Receptor and Signal Transduction Research 2(1): 17-27


ISSN/ISBN: 1079-9893
DOI: 10.3109/10799898109038795
Accession: 061646558

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The regulation of progesterone receptor by 17 beta estradiol and tamoxifen in the ZR-75-1 human breast cancer cell line in defined medium is described. ZR-75-1 cells maintained in serum free hormone supplemented medium minus estradiol lack progesterone receptor activity. Readdition of estradiol to these cells leads to a marked stimulation of progesterone receptor activity (0 to greater than 100 fmols of specifically bound progesterone per million cells). Tamoxifen (10(-6)M-10(-8)M) does not stimulate progesterone receptor activity in this cell line. The presence of progesterone receptor activity is not directly related to growth. Withdrawal of insulin in the continued presence of estradiol has no effect on progesterone receptor concentration although net cell growth ceases. Conversely, withdrawal of estradiol in the continued presence of insulin induces a cessation of net cell growth accompanied by a loss of all progesterone receptor activity within 3-5 days.