title: NF-κB regulates radioresistance mediated by β1-integrin in three-dimensional culture of breast cancer cells.
abstract: β1-integrin induction enhances breast cancer cell survival after exposure to ionizing radiation (IR), but the mechanisms of this effect remain unclear. Although NF-κB initiates prosurvival signaling pathways post-IR, the molecular function of NF-κB with other key elements in radioresistance, particularly with respect to extracellular matrix-induced signaling, is not known. We discovered a typical NF-κB-binding site in the β1-integrin promoter region, indicating a possible regulatory role for NF-κB. Using three-dimensional laminin-rich extracellular matrix (3D lrECM) culture, we show that NF-κB is required for β1-integrin transactivation in T4-2 breast cancer cells post-IR. Inhibition of NF-κB reduced clonogenic survival and induced apoptosis and cytostasis in formed tumor colonies. In addition, T4-2 tumors with inhibition of NF-κB activity exhibit decreased growth in athymic mice, which was further reduced by IR with downregulated β1-integrin expression. Direct interactions between β1-integrin and NF-κB p65 were induced in nonmalignant breast epithelial cells, but not in malignant cells, indicating context-specific regulation. As β1-integrin also activates NF-κB, our findings reveal a novel forward feedback pathway that could be targeted to enhance therapy.
authors.affiliation: Department of Cancer and DNA Damage Responses, Life Sciences Division, Lawrence Berkeley National Laboratory, Berkeley.
authors.forename: Kazi Mokim
authors.initials: KM
authors.lastname: Ahmed
authors.forename: Hui
authors.initials: H
authors.lastname: Zhang
authors.forename: Catherine C
authors.initials: CC
authors.lastname: Park
mesh_terms: D000818:Animals; D001665:Binding Sites / Q000235:genetics; D015153:Blotting, Western; D001943:Breast Neoplasms / Q000188:drug therapy / Q000378:metabolism* / Q000473:pathology; D018929:Cell Culture Techniques / Q000379:methods*; D002460:Cell Line; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects / Q000235:genetics / Q000528:radiation effects; D005109:Extracellular Matrix / Q000378:metabolism; D005260:Female; D006801:Humans; D019012:Integrin beta1 / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008819:Mice, Nude; D018613:Microscopy, Confocal; D016328:NF-kappa B / Q000037:antagonists & inhibitors / Q000378:metabolism*; D010655:Phenylenediamines / Q000494:pharmacology; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding / Q000187:drug effects / Q000528:radiation effects; D011836:Radiation Tolerance / Q000235:genetics; D011839:Radiation, Ionizing; D051996:Transcription Factor RelA / Q000037:antagonists & inhibitors / Q000378:metabolism; D047368:Tumor Burden / Q000187:drug effects / Q000528:radiation effects; D023041:Xenograft Model Antitumor Assays
chemical_list: C549066:4-methyl-N1-(3-phenylpropyl)benzene-1,2-diamine; D019012:Integrin beta1; D016328:NF-kappa B; D010655:Phenylenediamines; D051996:Transcription Factor RelA