Targeting of Rad51-dependent homologous recombination: implications for the radiation sensitivity of human lung cancer cell lines.
The aim of the present work was to study the role of Rad51-dependent homologous recombination in the radiation response of non-small-cell lung cancer (NSCLC) cell lines. A dose- and time-dependent increase in the formation of Rad51 and gamma-H2AX foci with a maximum at about 4 and 1 h after irradiation, followed by a decrease, has been found. The relative fraction of cells with persisting Rad51 foci was 20-30% in radioresistant and 60-80% in radiosensitive cell lines. In comparison, a higher fraction of residual Dsb was evident in cell lines with nonfunctional p53. Transfection with As-Rad51 significantly downregulates radiation-induced formation of Rad51 foci and increases apoptosis, but did not influence the rejoining of DNA double-strand breaks. Interestingly, wortmannin, a well-known inhibitor of nonhomologous end-joining, also inhibits Rad51 foci formation. In general, there was no correlation between the clonogenic survival at 2 Gy and the percentage of initial Rad51 or gamma-H2AX foci after ionising radiation (IR). The most reliable predictive factor for radiosensitivity of NSCLC cell lines was the relative fraction of Rad51 foci remaining at 24 h after IR. Although most of the Rad51 foci are co-localised with gamma-H2AX foci, no correlation of the relative fraction of persisting gamma-H2AX foci and SF2 is evident.
Sak
A
A
Department of Radiotherapy, University Hospital Essen, 45122 Essen, Germany. ali.sak@uni-essen.de
Stueben
G
G
Groneberg
M
M
Böcker
W
W
Stuschke
M
M
D002289:Carcinoma, Non-Small-Cell Lung / Q000473:pathology / Q000532:radiotherapy*; D045744:Cell Line, Tumor; D004260:DNA Repair; D004268:DNA-Binding Proteins / Q000502:physiology*; D006801:Humans; D008175:Lung Neoplasms / Q000235:genetics / Q000473:pathology / Q000532:radiotherapy*; D016376:Oligonucleotides, Antisense / Q000494:pharmacology; D051135:Rad51 Recombinase; D011836:Radiation Tolerance; D011995:Recombination, Genetic; D016159:Tumor Suppressor Protein p53 / Q000502:physiology
D004268:DNA-Binding Proteins; D016376:Oligonucleotides, Antisense; D016159:Tumor Suppressor Protein p53; C495153:RAD51 protein, human; D051135:Rad51 Recombinase