Acquisition of stable inducible up-regulation of nuclear factor-kappaB by tumor necrosis factor exposure confers increased radiation resistance without increased transformation in breast cancer cells.
High-grade breast cancers are better adapted to hypoxia and more resistant to chemotherapy and radiotherapy. Constitutive activation of the transcription factor nuclear factor-kappaB (NF-kappaB) increases in breast tumors and in breast cancer cell lines, where it promotes chemoradiation resistance, in part by activation of antiapoptotic genes. The role for up-regulation of NF-kappaB in breast cancer progression is less clear. Here, we first show that whereas the constitutive activity of NF-kappaB is incrementally elevated from immortalized breast epithelial to frank transformed invasive ductal breast cancer cell lines (~3-fold, +/-0.1-fold, P < 0.05), inflammatory cytokine-inducible activity is further increased (up to 9-fold, +/-0.9-fold, P < 0.05). We then show that inhibition of NF-kappaB activity selectively sensitizes transformed but not immortalized cells to killing by ionizing radiation or low levels of tumor necrosis factor (TNF) by up to 10-fold (+/-1-fold, P < 0.05) but has little effect on hypoxia-mediated cell death. Prolonged cultivation of immortalized and partially transformed cells in TNF selected for cells displaying stable constitutive and strongly inducible overexpression of NF-kappaB even in the absence of TNF. Stable acquisition of increased NF-kappaB activity conferred resistance to ionizing radiation or inflammatory cytokines, which was dependent on elevated NF-kappaB activity, but had no effect on transformation potential measured by in vitro and in vivo parameters. Thus, TNF and possibly other inflammatory cytokines in the tumor-stroma matrix likely select for breast cancer cells that stably overexpress NF-kappaB, leading to greater cancer cell survival. Greater cell survival despite increased genomic injury may permit increased acquisition of malignant genetic alterations as well as resistance to chemoradiation therapy.
Braunstein
Steve
S
Department of Microbiology, New York University School of Medicine, New York, NY 10016, USA.
Formenti
Silvia C
SC
Schneider
Robert J
RJ
D000818:Animals; D001943:Breast Neoplasms / Q000473:pathology*; D016923:Cell Death / Q000187:drug effects / Q000528:radiation effects; D015687:Cell Hypoxia / Q000187:drug effects / Q000528:radiation effects; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects / Q000528:radiation effects; D002471:Cell Transformation, Neoplastic / Q000187:drug effects* / Q000528:radiation effects; D016207:Cytokines / Q000494:pharmacology; D005260:Female; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects / Q000528:radiation effects; D006801:Humans; D051379:Mice; D008819:Mice, Nude; D016328:NF-kappa B / Q000037:antagonists & inhibitors; D011836:Radiation Tolerance / Q000187:drug effects* / Q000528:radiation effects; D011839:Radiation, Ionizing; D048069:Tumor Necrosis Factors / Q000494:pharmacology*; D014410:Tumor Stem Cell Assay; D015854:Up-Regulation / Q000187:drug effects / Q000235:genetics* / Q000528:radiation effects
D016207:Cytokines; D016328:NF-kappa B; D048069:Tumor Necrosis Factors