Understanding the determinants of individual patient responses to chemotherapeutic drugs is a key component of personalized cancer therapy. These determinants could be regarded as actual drug-response modifiers or as biomarkers for drug response. The NF-kB signaling pathway is linked with cancer initiation and progression. NF-kB signaling has also been suggested to contribute to drug resistance, but the determinants of drug response and resistance after NF-kB activation are not known. For colon cancer cells, we examined the activation of NF-kB activation and its target genes in response to chemotherapeutic drugs.
Materials and Methods: NF-kB reporter stable cells were established by transducing p53-mutant SW480, p53-wild type HCT116, and p53-null HCT116 colon cancer cells with lentiviral constructs containing NF-kB transcriptional response elements (TREs) linked to the luciferase gene. Luciferase expression was quantified as relative luciferase units. To determine which anticancer drugs preferentially activate NF-kB, the reporter cells were treated with 5-fluorouracil (5-FU, DNA/RNA damaging), oxaliplatin (DNA damaging), camptothecin (topoisomerase inhibitor), phleomycin (radiomimetic), or erlotinib (EGFR inhibitor). In addition to luciferase expression, downstream targets of NF-kB activation were evaluated by Western blotting (cIAP2, and Bcl-xL) or ELISA (CXCL8 and IL-6 in culture supernatants).
Results: There were differences in the degrees of activation of NF-kB in response to the drugs. Camptothecin activated NF-kB in SW480 cells, but not in HCT116 cells, which were sensitive to the drug. There was no activation even at drug concentrations that did not diminish viability of HCT116 cells. Phleomycin also activated NF-kB only in SW480 cells, whereas erlotinib activated the pathway only in HCT116 cells. 5-FU failed to activate the NF-kB pathway in any of the three cell lines. Western blotting for the NF-kB targets, cIAP2 and Bcl-xL, showed that activation of NF-kB in SW480 cells by camptothecin was not accompanied by increased expression of these two proteins, which are known mediators of the anti-apoptotic functions of NF-kB. However, there was a robust increase in the expression and release of the cytokine CXCL8 by SW480 cells treated with the drug. IL-6 was not detected in culture supernatants from the cells.
Conclusion: CXCL8, but none the other target genes cIAP2, Bcl-xL nor IL-6, was up-regulated by camptothecin-activated NF-kB. Therefore, the NF-kB-CXCL8 signaling axis appears to be involved in modifying the drug response in colon cancer cells exposed to this topoisomerase inhibitor.
Supported by the Morehouse School of Medicine/Tuskegee University and UAB Comprehensive Cancer Center Partnership grant (NIH U54CA18948-07).
Citation Information: Mol Cancer Ther 2013;12(11 Suppl):B70.
Citation Format: Temesgen Samuel, Khalda Fadlalla, Ramy Elgendy, Balananda-Dhurjati Kumar Putcha, James Posey, Upender Manne. Differential activation of NF-kB signaling and CXCL8 secretion in colon cancer cells treated with chemotherapeutic drugs. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2013 Oct 19-23; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(11 Suppl):Abstract nr B70.