title: Role of IKK and oscillatory NFkappaB kinetics in MMP-9 gene expression and chemoresistance to 5-fluorouracil in RKO colorectal cancer cells.
abstract: Nuclear factor kappa B (NFkappaB) is a central participant in the metastasis and chemoresistance of colorectal cancer (CRC). However, it is not fully understood to what extent NFkappaB 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 NFkappaB signaling deficient RKO mutants, we investigated NFkappaB's role in the induction of MMP-9 and 5-Fu sensitivity in RKO CRC cells. NFkappaB plays a predominant role in MMP-9 gene induction in RKO cells, as evidenced by the failure of tumor necrosis factor alpha (TNFalpha) to induce MMP-9 in either of the NFkappaB signaling mutants. RKO cells exhibit a robust, oscillatory NFkappaB activity in response to TNFalpha not seen in either of the NFkappaB mutant cell lines, which instead demonstrate diminished, nonoscillatory NFkappaB activation. Analysis of TNFalpha-induced phosphorylation and MMP-9 promoter recruitment of the p65 NFkappaB 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 NFkappaB in the parental RKO cells through induction of IkappaB-kinase (IKK) activity and increased sensitivity to 5-Fu is observed in both NFkappaB mutant lines. Our results suggest that TNFalpha-dependent induction of MMP-9 gene expression is tightly regulated by oscillatory/cumulative activation of NFkappaB and that 5-Fu stimulates NFkappaB and RKO CRC cell survival through induction of IKK activity.
authors.affiliation: Department of Cancer Biology, Cleveland Clinic, Cleveland, Ohio 44195, and School of Biomedical Sciences, Kent State University, USA.
authors.forename: Ryuichi
authors.initials: R
authors.lastname: Fukuyama
authors.forename: Kwok Peng
authors.initials: KP
authors.lastname: Ng
authors.forename: Muzaffer
authors.initials: M
authors.lastname: Cicek
authors.forename: Clare
authors.initials: C
authors.lastname: Kelleher
authors.forename: Roxana
authors.initials: R
authors.lastname: Niculaita
authors.forename: Graham
authors.initials: G
authors.lastname: Casey
authors.forename: Nywana
authors.initials: N
authors.lastname: Sizemore
mesh_terms: D000970:Antineoplastic Agents / Q000633:toxicity; D045744:Cell Line, Tumor; D015179:Colorectal Neoplasms / Q000201:enzymology / Q000503:physiopathology*; D019008:Drug Resistance, Neoplasm; D005472:Fluorouracil / Q000633:toxicity*; D015971:Gene Expression Regulation, Enzymologic; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D051550:I-kappa B Kinase / Q000502:physiology*; D007700:Kinetics; D020780:Matrix Metalloproteinase 9 / Q000235:genetics*; D016328:NF-kappa B / Q000502:physiology*; D015533:Transcriptional Activation
chemical_list: D000970:Antineoplastic Agents; D016328:NF-kappa B; D051550:I-kappa B Kinase; D020780:Matrix Metalloproteinase 9; D005472:Fluorouracil