[14]), conditional overexpression of oncogenes in the mammary gland (MMTV-rtTA/TetO-NeuNT [15], MTB/TWNT [16]), nonfunctional or conditional loss of tumor-suppressor genes (Stat1−/−, MMTV-Cre/BRCA1fl/fl) [14], or overexpression of exogenous transforming oncoproteins (MMTV-PyMT [17...