title: Molecular basis of 'hypoxic' breast cancer cell radio-sensitization: phytochemicals converge on radiation induced Rel signaling.
abstract: BACKGROUND
  Heterogeneously distributed hypoxic areas are a characteristic property of locally advanced breast cancers (BCa) and generally associated with therapeutic resistance, metastases, and poor patient survival. About 50% of locally advanced BCa, where radiotherapy is less effective are suggested to be due to hypoxic regions. In this study, we investigated the potential of bioactive phytochemicals in radio-sensitizing hypoxic BCa cells.
  
  
  METHODS
  Hypoxic (O2-2.5%; N2-92.5%; CO2-5%) MCF-7 cells were exposed to 4 Gy radiation (IR) alone or after pretreatment with Curcumin (CUR), curcumin analog EF24, neem leaf extract (NLE), Genistein (GEN), Resveratrol (RES) or raspberry extract (RSE). The cells were examined for inhibition of NFκB activity, transcriptional modulation of 88 NFκB signaling pathway genes, activation and cellular localization of radio-responsive NFκB related mediators, eNos, Erk1/2, SOD2, Akt1/2/3, p50, p65, pIκBα, TNFα, Birc-1, -2, -5 and associated induction of cell death.
  
  
  RESULTS
  EMSA revealed that cells exposed to phytochemicals showed complete suppression of IR-induced NFκB. Relatively, cells exposed EF24 revealed a robust inhibition of IR-induced NFκB. QPCR profiling showed induced expression of 53 NFκB signaling pathway genes after IR. Conversely, 53, 50, 53, 53, 53 and 53 of IR-induced genes were inhibited with EF24, NLE, CUR, GEN, RES and RSE respectively. In addition, 25, 29, 24, 16, 11 and 21 of 35 IR-suppressed genes were further inhibited with EF24, NLE, CUR, GEN, RES and RSE respectively. Immunoblotting revealed a significant attenuating effect of IR-modulated radio-responsive eNos, Erk1/2, SOD2, Akt1/2/3, p50, p65, pIκBα, TNFα, Birc-1, -2 and -5 with EF24, NLE, CUR, GEN, RES or RSE. Annexin V-FITC staining showed a consistent and significant induction of IR-induced cell death with these phytochemicals. Notably, EF24 robustly conferred IR-induced cell death.
  
  
  CONCLUSIONS
  Together, these data identifies the potential hypoxic cell radio-sensitizers and further implies that the induced radio-sensitization may be exerted by selectively targeting IR-induced NFκB signaling.
authors: Department of Radiation Oncology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA.
authors: Sheeja
authors: S
authors: Aravindan
authors: Mohan
authors: M
authors: Natarajan
authors: Terence S
authors: TS
authors: Herman
authors: Vibhudutta
authors: V
authors: Awasthi
authors: Natarajan
authors: N
authors: Aravindan
mesh_terms: D017209:Apoptosis / Q000187:drug effects / Q000528:radiation effects; D015153:Blotting, Western; D001943:Breast Neoplasms / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology* / Q000532:radiotherapy; D015687:Cell Hypoxia / Q000187:drug effects* / Q000528:radiation effects*; D049109:Cell Proliferation / Q000187:drug effects / Q000528:radiation effects; D003474:Curcumin / Q000494:pharmacology*; D024202:Electrophoretic Mobility Shift Assay; D005260:Female; D005434:Flow Cytometry; D005720:Gamma Rays; D006801:Humans; D012333:RNA, Messenger / Q000235:genetics; D011838:Radiation-Sensitizing Agents / Q000494:pharmacology*; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction; D051996:Transcription Factor RelA / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D014407:Tumor Cells, Cultured
chemical_list: D012333:RNA, Messenger; D011838:Radiation-Sensitizing Agents; D051996:Transcription Factor RelA; D003474:Curcumin