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Targeting the NF‐κB pathway in estrogen receptor negative MDA‐MB‐231 breast cancer cells using small inhibitory RNAs
Author(s) -
Monks Noel R.,
Pardee Arthur B.
Publication year - 2006
Publication title -
journal of cellular biochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.028
H-Index - 165
eISSN - 1097-4644
pISSN - 0730-2312
DOI - 10.1002/jcb.20789
Subject(s) - apoptosis , small interfering rna , estrogen receptor , cancer research , nf κb , biology , iκbα , iκb kinase , estrogen receptor alpha , cancer cell , transcription factor , proteasome inhibitor , inhibitor of apoptosis , cancer , breast cancer , microbiology and biotechnology , programmed cell death , cell culture , transfection , biochemistry , gene , genetics
Cancer cells in order to survive are often mutated to block apoptosis. One chemotherapeutic option is the re‐establishment of apoptosis. An example of such a therapy is the PKC inhibitor Gö6976, which activates apoptosis and shrinks in vivo tumors in estrogen receptor‐negative breast cancers. We proposed as a mechanism blockage of activation of the transcription factor NF‐κB, which is anti‐apoptotic and often elevated in cancers. Over recent years, questions have arisen regarding the specificity of these “small‐molecule inhibitors.” We have therefore explored the role of NF‐κB inhibition in MDA‐MB‐231 breast cancer cells using small inhibitory RNAs (siRNA). siRNAs designed against NF‐κB protein p65 (RelA) and IKKα, IKKβ, and IKKγ, strongly decreased the target proteins. But, unlike Gö6976, they did not decrease basal NF‐κB or cause apoptosis. In particular, the decrease in p65 protein had no effects on apoptosis or cell proliferation, thus questioning the importance of NF‐κB alone in the maintenance of these cells. Furthermore, the proteasome inhibitor MG‐132 caused loss of IκBα, and an increase of it is phosphorylated form, but basal NF‐κB was unchanged, whilst activation of NF‐κB by TNFα was completely inhibited, suggesting that MG‐132 activity is independent of constitutive NF‐κB activation. We ascribe these differences to the specificity of inhibition by siRNAs as compared to the well‐known non‐specificity of small‐molecule inhibitors. We conclude that the mutations in these cancer cells made them resistant to apoptosis, by elevating their NF‐κB and activating other basal pathways that are blocked by Gö6976 but not by IKK and p65 siRNAs. J. Cell. Biochem. 98: 221–233, 2006. © 2006 Wiley‐Liss, Inc.