Nuclear factor-κB p65 inhibits mitogen-activated protein kinase signaling pathway in radioresistant breast cancer cells

Kazi M. Ahmed, Shaozhong Dong, Ming Fan, Jian-Jian Li

Research output: Contribution to journalArticlepeer-review

69 Scopus citations


The molecular mechanism by which tumor cells increase their resistance to therapeutic radiation remains to be elucidated. We have previously reported that activation of nuclear factor-κB (NF-κB) is causally associated with the enhanced cell survival of MCF+FIR cells derived from breast cancer MCF-7 cells after chronic exposure to fractionated ionizing radiation. The aim of the present study was to reveal the context of NF-κB pathways in the adaptive radioresistance. Using cell lines isolated from MCF+FIR populations, we found that the elevated NF-κB activity was correlated with enhanced clonogenic survival, and increased NF-κB subunit p65 levels were associated with a decrease in phosphorylation of mitogen-activated protein kinase/extracellular signal-regulated kinase (ERK) kinase (MEK)/ERK in all radioresistant MCF+FIR cell lines. Further irradiation with 30 fractions of radiation also inhibited MEK/ERK phosphorylation in paired cell lines of MCF+FIR and parental MCF-7 cells. Activation of ataxia-telangiectasia mutated (ATM) protein, a sensor to radiation-induced DNA damage, was elevated with increased interaction with NF-κB subunits p65 and p50. The interaction between p65 and MEK was also enhanced in the presence of activated ATM. In contrast, both interaction and nuclear translocation of p65/ERK were reduced. Inhibition of NF-κB by overexpression of mutant IκB increased ERK phosphorylation. In addition, MEK/ERK inhibitor (PD98059) reduced the interaction between p65 and ERK. Taken together, these results suggest that NF-κB inhibits ERK activation to enhance cell survival during the development of tumor adaptive radioresistance.

Original languageEnglish (US)
Pages (from-to)945-955
Number of pages11
JournalMolecular Cancer Research
Issue number12
StatePublished - Dec 2006
Externally publishedYes

ASJC Scopus subject areas

  • Molecular Biology
  • Cancer Research


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