Abstract
The ovarian steroid hormones progesterone and estrogen play vital roles in the development of normal mammary gland and are likewise linked to mammary carcinogenesis via their receptors. Progesterone receptor (PR) is expressed as two isoforms, PR-A and PR-B. In human breast tumors the PR-A/PR-B expression ratio is altered, with the PR-A isoform predominating. Transgenic mice carrying an ad…