TGFB1 and neoplasm: Metastatic spread of tumor cells in the MMTV-PyMT model is driven by TGF-β.26 Co-staining for E-cadherin and C/EBPβ in tumor sections from 10- and 14-week-old MMTV-PyMT mice revealed significant loss of C/EBPβ expression in E-cadherin-negative areas compared with E-cadherin-positive tumor areas of adenocarcinomas (Figures 1d and e).