Aberrant Features of Mammary Dysplasias in PRA Transgenic Mice are Unaffected by Mifepristone

The presence of at least two distinct populations of transformed epithelial cells, in mammary glands of PR-A transgenics, was also apparent from their sensitivity to the antiprogestin, mifepristone. While mifepristone abolished BrdU immunostaining in the ducts displaying normal histology, and in those of wild type mice, it did not alter the number of BrdU-positive cells in dysplastic lesions (18). Similarly, in these lesions, mifepristone did not effect the expression ofeither cyclin D1 or ERa. Thus, it appears that deregulation of progesterone action, resulting from an overexpression of PR-A form, may not only trigger transformation of mammary epithelial cells, but may also dictate their phenotype in later stages of transformation.

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