To induce Notch signaling we co-cultured mouse embryonic fibroblast 3T3-L1 cells transiently transfected with human DLL4 plasmid (3T3-L1DLL4) or GFP plasmid (3T3-L1GFP) as control, with human breast adenocarcinoma MDA-MB-231 cells, which express robust levels of the Notch1 receptor [31, 50] (schematically depicted in Fig. 2a). This evidence concerns the gene DLL4 and breast adenocarcinoma.