title: Variable NF-κB pathway responses in colon cancer cells treated with chemotherapeutic drugs.
abstract: BACKGROUND
  The nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) signaling pathway is activated in cells exposed to various stimuli, including those originating on the cell surface or in the nucleus. Activated NF-κB signaling is thought to enhance cell survival in response to these stimuli, which include chemotherapy and radiation. In the present effort, we determined which anticancer drugs preferentially activate NF-κB in colon cancer cells.
  
  
  METHODS
  NF-κB reporter cells were established and treated with 5-fluorouracil (5-FU, DNA/RNA damaging), oxaliplatin (DNA damaging), camptothecin (CTP, topoisomerase inhibitor), phleomycin (radiomimetic), or erlotinib (EGFR inhibitor). The activation of NF-κB was assessed by immunofluorescence for p65 translocation, luciferase assays, and downstream targets of NF-κB activation (cIAP2, and Bcl-XL) were evaluated by immunoblotting, by ELISA (CXCL8 and IL-6 in culture supernatants), or by gene expression analysis.
  
  
  RESULTS
  Colon cancer cells responded variably to different classes of therapeutic agents, and these agents initiated variable responses among different cell types. CPT activated NF-κB in SW480 colon cancer cells in a dose-dependent manner, but not in HCT116 cells that were either wild-type or deficient for p53. In SW480 colon cancer cells, NF-κB activation by CPT was accompanied by secretion of the cytokine CXCL8, but not by up-regulation of the anti-apoptotic genes, cIAP2 or Bcl-XL. On the contrary, treatment of HCT116 cells with CPT resulted in up-regulation of CXCR2, a receptor for CXCL8, without an increase in cytokine levels. In SW480 cells, NF-κB reporter activity, but not cytokine secretion, was inhibited by SM-7368, an NF-κB inhibitor.
  
  
  CONCLUSIONS
  The results show that, in response to cancer therapeutic agents, NF-κB activation varies with the cellular make up and that drug-induced NF-κB activation may be functionally uncoupled from anti-apoptotic outcomes found for other stimuli. Some cancer cells in a heterogeneous tumor tissue may, under therapeutic pressure, release soluble factors that have paracrine activity on neighboring cells that express the cognate receptors.
authors.affiliation: School of Veterinary Medicine, Pathobiology Department and TU Center for Cancer Research, Tuskegee University, Tuskegee, AL 36088, USA. tsamuel@mytu.tuskegee.edu.
authors.forename: Temesgen
authors.initials: T
authors.lastname: Samuel
authors.forename: Khalda
authors.initials: K
authors.lastname: Fadlalla
authors.forename: Dominique N
authors.initials: DN
authors.lastname: Gales
authors.forename: Balananda D K
authors.initials: BD
authors.lastname: Putcha
authors.forename: Upender
authors.initials: U
authors.lastname: Manne
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology* / Q000627:therapeutic use; D002166:Camptothecin / Q000494:pharmacology / Q000627:therapeutic use; D045744:Cell Line, Tumor; D003110:Colonic Neoplasms / Q000188:drug therapy* / Q000378:metabolism; D000069347:Erlotinib Hydrochloride; D005472:Fluorouracil / Q000494:pharmacology / Q000627:therapeutic use; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D045325:HCT116 Cells; D006801:Humans; D016328:NF-kappa B / Q000378:metabolism*; D009944:Organoplatinum Compounds / Q000494:pharmacology / Q000627:therapeutic use; D000077150:Oxaliplatin; D010692:Phleomycins / Q000494:pharmacology / Q000627:therapeutic use; D011799:Quinazolines / Q000494:pharmacology / Q000627:therapeutic use; D015398:Signal Transduction / Q000187:drug effects*
chemical_list: D000970:Antineoplastic Agents; D016328:NF-kappa B; D009944:Organoplatinum Compounds; D010692:Phleomycins; D011799:Quinazolines; D000077150:Oxaliplatin; D000069347:Erlotinib Hydrochloride; D005472:Fluorouracil; D002166:Camptothecin