ERBB2 and breast cancer: Moreover, quantitative RT-PCR (QPCR) analysis revealed that the relative expression levels of CD31 mRNA is significantly reduced in Ncoa1−/− × Tg(MMTV-PyMT) mouse mammary tumors with Ncoa1 knockout, but significantly increased in Tg(MMTV-NCOA1) × Tg(MMTV-TVA/RCAS-PyMT) and Tg(MMTV-NCOA1) × Tg(MMTV-Neu) mouse mammary tumors with NCOA1 overexpression when compared with their respective control tumors described above (Figure 1c).