Inhibition of constitutive NF-kappa B activity by I kappa B alpha M suppresses tumorigenesis.

We have demonstrated that nuclear factor-kappa B (NF-kappa B) is constitutively activated in human pancreatic adenocarcinoma and human pancreatic cancer cell lines but not in normal pancreatic tissues or in immortalized, nontumorigenic pancreatic epithelial cells, suggesting that NF-kappa B plays a critical role in the development of pancreatic adenocarcinoma. To elucidate the role of constitutive NF-kappa B activity in human pancreatic cancer cells, we generated pancreatic tumor cell lines that express a phosphorylation defective I kappa B alpha (S32, 36A) (I kappa B alpha M) that blocks NF-kappa B activity. In this study, we showed that inhibiting constitutive NF-kappa B activity by expressing I kappa B alpha M suppressed the tumorigenicity of a nonmetastatic human pancreatic cancer cell line, PANC-1, in an orthotopic nude mouse model. Immunohistochemical analysis showed that PANC-1-derived tumors expressed vascular endothelial growth factor (VEGF) and induced angiogenesis. Inhibiting NF-kappa B signaling by expressing I kappa B alpha M significantly reduced expression of Bcl-x(L) and Bcl-2. The cytokine-induced expression of VEGF and Interleukin-8 in PANC-1 cells is also decreased. Taken together, these results suggest that the inhibition of NF-kappa B signaling can suppress tumorigenesis of pancreatic cancer cells and that the NF-kappa B signaling pathway is a potential target for anticancer agents.