Dexamethasone protection from TNF-alpha-induced cell death in MCF-7 cells requires NF-kappaB and is independent from AKT

BMC Cell Biol. 2006 Feb 21;7:9. doi: 10.1186/1471-2121-7-9.

Abstract

Background: The biochemical bases for hormone dependence in breast cancer have been recognized as an important element in tumor resistance, proliferation and metastasis. On this respect, dexamethasone (Dex) dependent protection against TNF-alpha-mediated cell death in the MCF-7 cell line has been demonstrated to be a useful model for the study of this type of cancer. Recently, cytoplasmic signaling induced by steroid receptors has been described, such as the activation of the PI3K/Akt and NF-kappaB pathways. We evaluated their possible participation in the Dex-dependent protection against TNF-alpha-mediated cell death.

Results: Cellular cultures of the MCF-7 cell line were exposed to either, TNF-alpha or TNF-alpha and Dex, and cell viability was evaluated. Next, negative dominants of PI3K and IkappaB-alpha, designed to block the PI3K/Akt and NF-kappaB pathways, respectively, were transfected and selection and evaluation of several clones overexpressing the mutants were examined. Also, correlation with inhibitor of apoptosis proteins (IAPs) expression was examined. Independent inhibition of these two pathways allowed us to test their participation in Dex-dependent protection against TNF-alpha-cytotoxicity in MCF-7 cells. Expression of the PI3K dominant negative mutant did not alter the protection conferred by Dex against TNF-alpha mediated cell death. Contrariwise, clones expressing the IkappaB-alpha dominant negative mutant lost the Dex-conferred protection against TNF-alpha. In these clones degradation of c-IAP was accelerated, while that of XIAP was remained unaffected.

Conclusion: NF-kappaB, but not PI3K/Akt activation, is required for the Dex protective effect against TNF-alpha-mediated cell death, and correlates with lack of degradation of the anti-apoptotic protein c-IAP1.

MeSH terms

  • Apoptosis / drug effects*
  • Blotting, Western
  • Breast Neoplasms / genetics
  • Breast Neoplasms / pathology
  • Breast Neoplasms / physiopathology
  • Cell Cycle Proteins / genetics
  • Cell Cycle Proteins / physiology
  • Cell Line, Tumor
  • Cell Survival / drug effects
  • Cell Survival / genetics
  • Dexamethasone / pharmacology*
  • Dual Specificity Phosphatase 1
  • Electrophoretic Mobility Shift Assay
  • Female
  • Gene Expression Regulation / drug effects
  • Humans
  • Immediate-Early Proteins / genetics
  • Immediate-Early Proteins / physiology
  • Inhibitor of Apoptosis Proteins / genetics
  • Inhibitor of Apoptosis Proteins / physiology
  • NF-kappa B / genetics
  • NF-kappa B / physiology*
  • Oncogene Protein v-akt / genetics
  • Oncogene Protein v-akt / physiology*
  • Phosphoprotein Phosphatases / genetics
  • Phosphoprotein Phosphatases / physiology
  • Protein Phosphatase 1
  • Protein Tyrosine Phosphatases / genetics
  • Protein Tyrosine Phosphatases / physiology
  • Protein-Serine-Threonine Kinases / genetics
  • Protein-Serine-Threonine Kinases / physiology
  • Receptors, Glucocorticoid / genetics
  • Receptors, Glucocorticoid / physiology
  • Transfection
  • Tumor Necrosis Factor-alpha / pharmacology*
  • X-Linked Inhibitor of Apoptosis Protein / genetics
  • X-Linked Inhibitor of Apoptosis Protein / physiology

Substances

  • Cell Cycle Proteins
  • Immediate-Early Proteins
  • Inhibitor of Apoptosis Proteins
  • NF-kappa B
  • Receptors, Glucocorticoid
  • Tumor Necrosis Factor-alpha
  • X-Linked Inhibitor of Apoptosis Protein
  • XIAP protein, human
  • Dexamethasone
  • Oncogene Protein v-akt
  • Protein-Serine-Threonine Kinases
  • serum-glucocorticoid regulated kinase
  • Phosphoprotein Phosphatases
  • Protein Phosphatase 1
  • DUSP1 protein, human
  • Dual Specificity Phosphatase 1
  • Protein Tyrosine Phosphatases