As expression of MenaINV is essential for induction of an intravasation- and extravasation-competent phenotype in breast cancer cells which endows tumor cells the ability to metastasize, it is critical to determine if Notch1 signaling, caused by a juxtacrine, macrophage–tumor cell interaction, can promote NF-κB signaling and subsequently contribute to increased MenaINV expression in vivo. This evidence concerns the gene NFKB1 and breast carcinoma.