Figure 1

Effect of ovarian hormone on the development of mammary intraepithelial neoplasia outgrowths (MIN-Os) and tumors. (a) Whole-mount images, from intact (top panel) and ovariectomized (bottom panel) murine host mammary fat pads into which 8w-B premalignant MIN-O tissue had been transplanted. MIN-O (dark blue) is significantly larger in the intact host fat pad at 5 weeks after transplantation than in the ovariectomized host fat pad. Lymph node (L) is seen at the left side of the MIN-O. (b) Effect of ovarian ablation on the 8w-B MIN-O line tumor development. Time to palpable tumor was significantly longer in ovariectomized mice (n = 8) than in the intact ones (n = 4). (c) Immunohistochemical staining of the proliferation marker Ki-67 on MIN-O (center and right). The growing edge of the MIN-O is highly proliferative, as seen by intense Ki-67 staining (brown, 10× field, center). A 20× field of the boxed area is shown on the right. The proliferative area (P) is indicated. Corresponding H & E staining is shown on the left. (d) Immunohistochemical staining of estrogen receptor (ER)-α on MIN-O (left) and tumor (right) from 8w-B-line animals at 10 weeks after transplantation. Areas with strong nuclear ER staining as well as cytoplasmic staining were often found in the MIN-O tissue (left). In general, ER staining in tumor tissue was less intense and less frequent (right). ovx, ovariectomized.