Radiosensitivity and double-strand break rejoining in tumorigenic and non-tumorigenic human epithelial cell lines.
Radiosensitivity and repair of DNA damage induced by ionizing radiation and restriction enzymes were investigated in three human epithelial cell lines: two tumorigenic squamous carcinoma cell lines (SCC-4 and SCC-25), and a non-tumorigenic epidermal keratinocyte cell line (RHEK-1). Sensitivity to ionizing radiation was determined using a clonogenic cell survival assay, which showed SCC-4 to be more radiosensitive than SCC-25 and RHEK-1, which in turn displayed about equal sensitivity. Using DNA precipitation under alkaline conditions for the analysis of induction and repair of DNA single-strand breaks (ssb), an increased level of ssb induction was found for SCC-4 while the efficiency of ssb repair was about equal in all three cell lines. Using pulsed-field gel electrophoresis (PFGE) for the measurement of induction and repair of DNA double-strand breaks (dsb), no consistent differences were detected between the three cell lines. A plasmid reconstitution assay was used to determine the capacity to rejoin restriction enzyme-induced dsb in whole-cell extracts prepared from the three cell lines. In these experiments, dsb rejoining was shown to be significantly reduced in the most radiosensitive SCC-4 cell line while it was about equal in RHEK-1 and SCC-25. The results indicate that plasmid reconstitution in cell-free extracts is a sufficiently sensitive assay to detect differences in repair capacity among tumour cell lines of different radiosensitivity which remain undetectable by DNA precipitation and PFGE.
Daza
P
P
Department of Cell Biology, University of Seville, Spain.
Schübler
H
H
McMillan
T J
TJ
Girod
S C
SC
Pfeiffer
P
P
D000595:Amino Acid Sequence; D002294:Carcinoma, Squamous Cell / Q000378:metabolism / Q000532:radiotherapy; D002460:Cell Line; D002470:Cell Survival / Q000528:radiation effects; D002474:Cell-Free System; D004247:DNA / Q000187:drug effects / Q000378:metabolism / Q000528:radiation effects; D004249:DNA Damage; D004260:DNA Repair / Q000502:physiology*; D004262:DNA Restriction Enzymes / Q000378:metabolism / Q000494:pharmacology; D004273:DNA, Neoplasm / Q000187:drug effects / Q000378:metabolism / Q000528:radiation effects; D004847:Epithelial Cells; D004848:Epithelium / Q000502:physiology / Q000528:radiation effects; D006801:Humans; D015603:Keratinocytes / Q000166:cytology / Q000502:physiology / Q000528:radiation effects; D008969:Molecular Sequence Data; D011836:Radiation Tolerance / Q000502:physiology*; D014062:Tongue Neoplasms / Q000378:metabolism / Q000532:radiotherapy; D014407:Tumor Cells, Cultured / Q000528:radiation effects
D004273:DNA, Neoplasm; D004247:DNA; D004262:DNA Restriction Enzymes