The mCol1a1 environment does not alter tumor PRLR expression, and tumors express progesterone receptors in localized foci. A TC tumors lysates were probed for PRLR. No significant differences were observed between WT and mCol1a1 tumors. Mean ± SEM TC2 tumors: WT n = 7, mCol1a1 n = 6; TC4 tumors: WT n = 7, mCol1a1 n = 8. (Mann-Whitney U test, p > 0.05). B Progesterone receptor immunohistochemical analysis. Progesterone receptor is expressed in localized foci (upper panel). Positive staining of ductal epithelium (lower panel). Original magnifications × 200. Scale bar = 50 μm. (PDF 333 kb)