NOTCH1 and neoplasm: Upon TNFα stimulation of MDA-MB-231:MSC “Contact” co-cultures, it became evident that down-regulation of p65 in the tumor cells has led to marked inhibition of Notch1 activation (Figures 9A2,C2; lanes 7 vs. 5), and siRNA to p65 in the MSCs also reduced Notch1 activation, although to much lower extent than in the tumor cells (Figures 9A2,C2; lanes 6 vs. 5).