Role of IKK and oscillatory NFκB kinetics in MMP-9 gene expression and chemoresistance to 5-fluorouracil in RKO colorectal cancer cells

Nuclear factor kappa B (NF kappa B) is a central participant in the metastasis and chemoresistance of colorectal cancer (CRC). However, it is not fully understood to what extent NF kappa B contributes to induction of the metastasis-associated matrix metalloprotease-9 (MMP-9) gene and sensitivity to the commonly used chemotherapeutic 5-fluorouracil (5-Fu) in CRC. Using the RKO human CRC cell line and two NF kappa B signaling deficient RKO mutants, we investigated NF kappa B's role in the induction of MMP-9 and 5-Fu sensitivity in RKO CRC cells. NF kappa B plays a predominant role in MMP-9 gene induction in RKO cells, as evidenced by the failure of tumor necrosis factor alpha (TNF alpha) to induce MMP-9 in either of the NF kappa B signaling mutants, RKO cells exhibit a robust, oscillatory NF kappa B activity in response to TNF alpha not seen in either of the NF alpha B mutant cell lines, which instead demonstrate diminished, nonoscillatory NF kappa B activation. Analysis of TNF alpha-induced phosphorylati(on and MMP-9 promoter recruitment of the p65 NF kappa B subunit revealed a significant reduction in p65 phosphorylation as well as reduced and altered recruitment of p65 to the MMP-9 gene promoter in the mutants compared to the parental RKO cell line. 5-Fu only activated NF kappa B in the parental RKO cells through induction of I kappa B-kinase (IKK) activity and increased sensitivity to 5-Fu is observed in both NF kappa B mutant lines. Our results suggest that TIN F alpha-dependent induction of MMP-9 gene expression is tightly regulated by oscillatory/ cumulative activation of NF kappa,B and that 5-Fu stimulates NF kappa B and RKO CRC cell survival through induction of IKK activity. (c) 2006 Wiley-Liss, Inc.