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


CONCLUSIONS
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.
Machuca
Catalina
C
Facultad de Estudios Superiores, ZARAGOZA, UNAM, CP 09230, Mexico D.F., Mexico. cmachuca@ifc.unam.mx
Mendoza-Milla
Criselda
C
Córdova
Emilio
E
Mejía
Salvador
S
Covarrubias
Luis
L
Ventura
José
J
Zentella
Alejandro
A
D017209:Apoptosis / Q000187:drug effects*; D015153:Blotting, Western; D001943:Breast Neoplasms / Q000235:genetics / Q000473:pathology / Q000503:physiopathology; D018797:Cell Cycle Proteins / Q000235:genetics / Q000502:physiology; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects / Q000235:genetics; D003907:Dexamethasone / Q000494:pharmacology*; D054638:Dual Specificity Phosphatase 1; D024202:Electrophoretic Mobility Shift Assay; D005260:Female; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D017874:Immediate-Early Proteins / Q000235:genetics / Q000502:physiology; D051034:Inhibitor of Apoptosis Proteins / Q000235:genetics / Q000502:physiology; D016328:NF-kappa B / Q000235:genetics / Q000502:physiology*; D051058:Oncogene Protein v-akt / Q000235:genetics / Q000502:physiology*; D010749:Phosphoprotein Phosphatases / Q000235:genetics / Q000502:physiology; D054645:Protein Phosphatase 1; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000502:physiology; D017027:Protein Tyrosine Phosphatases / Q000235:genetics / Q000502:physiology; D011965:Receptors, Glucocorticoid / Q000235:genetics / Q000502:physiology; D014162:Transfection; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*; D051636:X-Linked Inhibitor of Apoptosis Protein / Q000235:genetics / Q000502:physiology; D000099184:Serum-Glucocorticoid Regulated Kinases
D018797:Cell Cycle Proteins; D003907:Dexamethasone; D054638:Dual Specificity Phosphatase 1; D017874:Immediate-Early Proteins; D051034:Inhibitor of Apoptosis Proteins; D016328:NF-kappa B; D051058:Oncogene Protein v-akt; D010749:Phosphoprotein Phosphatases; D054645:Protein Phosphatase 1; D017346:Protein Serine-Threonine Kinases; D017027:Protein Tyrosine Phosphatases; D011965:Receptors, Glucocorticoid; D014409:Tumor Necrosis Factor-alpha; D051636:X-Linked Inhibitor of Apoptosis Protein; D000099184:Serum-Glucocorticoid Regulated Kinases; C496866:XIAP protein, human; C517019:DUSP1 protein, human