Inhibition of NF-kappaB, clonogenicity, and radiosensitivity of human cancer cells.
BACKGROUND
Activation of the transcription factor NF-kappaB is part of the immediate early response of tissues to ionizing irradiation. This pathway has been shown to protect cells from tumor necrosis factor-alpha, chemotherapy, and radiation therapy-induced apoptosis (programmed cell death). However, because the role of NF-kappaB as a modifier of the intrinsic radiosensitivity of cancer cells is less clear, we have studied the impact of NF-kappaB on the intrinsic radiosensitivity of human cancer cells.


METHODS
We used PC3 prostate cancer cells and HD-MyZ Hodgkin's lymphoma cells transduced with an adenovirus vector that contains a gene encoding a form of IkappaB (an inhibitor of NF-kappaB) that cannot be phosphorylated. This form of IkappaB will remain bound to NF-kappaB; thus, NF-kappaB cannot be activated. We monitored NF-kappaB activity with a gel-shift assay and used a colony-forming assay to assess clonogenicity and radiosensitivity.


RESULTS
Constitutive DNA-binding activity of NF-kappaB was dramatically decreased in PC3 cells transduced with the IkappaB super-repressor gene. The clonogenicity of transduced PC3 cells declined to 19.6% of that observed for untreated control cells, a finding similar to one we have previously demonstrated for IkappaB-transduced HD-MyZ cells. However, inhibition of NF-kappaB activity in the surviving PC3 and HD-MyZ cells failed to alter their intrinsic radiosensitivity.


CONCLUSIONS
We conclude that activation of NF-kappaB does not determine the intrinsic radiosensitivity of cancer cells, at least for the cell lines tested in this study.
Pajonk
F
F
Department of Radiation Oncology, Experimental Division, University of California at Los Angeles School of Medicine 10833, USA. fpajonk@ucla.edu
Pajonk
K
K
McBride
W H
WH
D000256:Adenoviridae; D017209:Apoptosis / Q000528:radiation effects*; D004268:DNA-Binding Proteins / Q000378:metabolism*; D004307:Dose-Response Relationship, Radiation; D005822:Genetic Vectors; D006689:Hodgkin Disease / Q000378:metabolism* / Q000532:radiotherapy*; D006801:Humans; D020672:I-kappa B Proteins; D008297:Male; D000072000:NF-KappaB Inhibitor alpha; D016328:NF-kappa B / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000528:radiation effects; D011471:Prostatic Neoplasms / Q000378:metabolism* / Q000532:radiotherapy*; D011836:Radiation Tolerance; D015398:Signal Transduction / Q000528:radiation effects; D014158:Transcription, Genetic / Q000528:radiation effects; D014407:Tumor Cells, Cultured
D004268:DNA-Binding Proteins; D020672:I-kappa B Proteins; D016328:NF-kappa B; C000606204:NFKBIA protein, human; D000072000:NF-KappaB Inhibitor alpha