Although overexpression of NCOA1 in the mouse mammary gland is not oncogenic by itself and is also incapable of promoting oncogene-induced tumor growth, it significantly increased lung metastasis in Tg(MMTV-PyMT) (transgenic mouse mammary tumor virus-polyoma middle T) and Tg(MMTV-Neu) breast cancer mouse models [19]. This evidence concerns the gene ERBB2 and breast carcinoma.