Secretion of cytokines and growth factors as a general cause of constitutive NFκB activation in cancer

Tao Lu, Swati S. Sathe, Shannon M. Swiatkowski, Chetan V. Hampole, George R. Stark

Research output: Contribution to journalArticle

61 Scopus citations

Abstract

The constitutive activation of nuclear factor κB (NFκB) helps a variety of tumors to resist apoptosis and desensitizes them to chemotherapy, but the causes are still largely unknown. We have analysed this phenomenon in eight mutant cell lines derived from human 293 cells, selected for NFκB-dependent expression of a marker gene, and also in seven tumor-derived cell lines. Conditioned media from all of these cells stimulated the activation of NFκB (up to 30-fold) in indicator cells carrying an NFκB-responsive reporter. Therefore, secretion of extracellular factors as the cause of constitutive activation seems to be general. The mRNAs encoding several different cytokines and growth factors were greatly overexpressed in the tumor and mutant cells. The pattern of overexpression was distinct in each cell line, indicating that the phenomenon is complex. Two secreted factors whose roles in the constitutive activation of NFκB are not well defined were investigated further as pure proteins: transforming growth factor β2 (TGFβ2) and fibroblast growth factor 5 (FGF5) were both highly expressed in some mutant clones and tumor cell lines, each activated NFκB alone, and the combination was synergistic. Our data indicate that a group of different factors, expressed at abnormally high levels, can contribute singly and synergistically to the constitutive activation of NFκB in all of the mutant and tumor cell lines we studied. Since several NFκB target genes encode secreted proteins that induce NFκB, autocrine loops are likely to be ubiquitously important in the constitutive activation of NFκB in cancer. We provide the first evidence of the general, complex, and synergistic activation of NFκB in tumor and mutant cell lines through the action of secreted factors and suggest that the same explanation is likely for the constitutive activation of NFκB in cancers.

Original languageEnglish (US)
Pages (from-to)2138-2145
Number of pages8
JournalOncogene
Volume23
Issue number12
DOIs
StatePublished - Mar 18 2004
Externally publishedYes

Keywords

  • ELISA
  • FGF5
  • Microarrays
  • Mutant 293 cells
  • TGFβ2

ASJC Scopus subject areas

  • Molecular Biology
  • Genetics
  • Cancer Research

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