Transient exposure to tamoxifen inhibits mammary ductal side-branching, proliferation, PR and ERα in the p53 null mammary gland.

<p>(A) Mammary epithelium from p53 null mice was transplanted into the cleared fat pad of syngeneic WT Balb/c mice. At 8 weeks after transplantation, mice received a tamoxifen (TAM) (5mg) or sham (control) pellet (SC) for 13 weeks. Four weeks after tamoxifen removal, all mice were treated with E₂ (100ug) for 8 h and whole-mount images of carmine-stained p53 null mammary glands. Scale bars correspond to 500μm. A total of 6 mice per treatment group were used. (B-E) Representative immunohistochemical staining for Ki67, cyclin D1, PR and ERα on paraffin-embedded p53 null transplanted mammary gland sections from sham and tamoxifen treated mice. Scale bars correspond to 50 μm. A total of 5 mice were used per treatment group. Graphs representing the ratio of Ki67, cyclin D1, PR and ERα positive cells in p53 null mammary epithelium. Data are mean ± SEM of 5 mice. *, <i>P</i> < 0.05; **, <i>P</i> < 0.01.