title: Cytotoxicity of restriction enzyme-induced DNA strand breaks in radiosensitive and radioresistant human tumor cell lines.
abstract: OBJECTIVE
  To examine the role of sensitivity to specific types of DNA double strand breaks in human tumor cell response.
  
  
  METHODS
  The X ray-sensitive human squamous carcinoma cell line SCC-61 and the X ray-resistant line SQ-20B were exposed to the restriction enzymes HaeIII, HinfI, PvuII, BamHI by electroporation. Cytotoxicity of these restriction endonucleases was measured by a colony formation assay.
  
  
  RESULTS
  Cell killing by each enzyme occurred in a concentration-dependent manner. The radiosensitive cell line was more sensitive to all four restriction enzymes than the radioresistant line, paralleling the response to ionizing radiation. However, the magnitude of the difference was smaller than for radiation. The 5-base sticky ended cutter HinfI and 6-base blunt ended cutter PvuII were much more effective in killing cells from both lines than BamHI, a 6-base sticky ended cutter, whereas the 4-base blunt ended cutter HaeIII was intermediate in its effectiveness. Thus, enzyme sensitivity could not be related to the type of cutter or the distance between cutting sites.
authors.affiliation: Harvard School of Public Health, Laboratory of Radiobiology, Boston, MA 02115.
authors.forename: Y
authors.initials: Y
authors.lastname: Kinashi
authors.forename: H
authors.initials: H
authors.lastname: Nagasawa
authors.forename: J B
authors.initials: JB
authors.lastname: Little
mesh_terms: D002294:Carcinoma, Squamous Cell / Q000532:radiotherapy*; D002470:Cell Survival; D004262:DNA Restriction Enzymes / Q000494:pharmacology*; D004273:DNA, Neoplasm / Q000187:drug effects*; D006258:Head and Neck Neoplasms / Q000532:radiotherapy*; D006801:Humans; D014407:Tumor Cells, Cultured / Q000528:radiation effects
chemical_list: D004273:DNA, Neoplasm; D004262:DNA Restriction Enzymes