Down-regulation of Notch-1 Inhibits Invasion by Inactivation of Nuclear Factor-κB, Vascular Endothelial Growth Factor, and Matrix Metalloproteinase-9 in Pancreatic Cancer Cells

Abstract

Notch signaling plays a critical role in the pathogenesis and progression of human malignancies but the precise role and mechanism of Notch-1 for tumor invasion remains unclear. In our earlier report, we showed that down-regulation of Notch-1 reduced nuclear factor-κB (NF-κB) DNA-binding activity and matrix metalloproteinase-9 (MMP-9) expression. Because NF-κB, VEGF, and MMPs are critically involved in the processes of tumor cell invasion and metastasis, we investigated the role and mechanism(s) by which Notch-1 down-regulation (using molecular approaches) may lead to the down-regulation of NF-κB, vascular endothelial growth factor (VEGF), and MMP-9, thereby inhibiting invasion of pancreatic cancer cells through Matrigel. We found that the down-regulation of Notch-1 by small interfering RNA decreased cell invasion, whereas Notch-1 overexpression by cDNA transfection led to increased tumor cell invasion. Consistent with these results, we found that the down-regulation of Notch-1 reduced NF-κB DNA-binding activity and VEGF expression. Down-regulation of Notch-1 also decreased not only MMP-9 mRNA and its protein expression but also inactivated the pro-MMP-9 protein to its active form. Taken together, we conclude that the down-regulation of Notch-1 could be an effective approach for the down-regulation and inactivation of NF-κB and its target genes, such as MMP-9 and VEGF expression, resulting in the inhibition of invasion and metastasis. (Cancer Res 2006; 66(5): 2778-84)