title: Differences in repair of radiation induced damage in two human tumor cell lines as measured by cell survival and alkaline DNA unwinding.
abstract: We studied the relationship between the repair of radiation induced DNA strand breaks and cellular repair kinetics in two human tumor cell lines, NB-100 (neuroblastoma) and HN-1 (squamous cell carcinoma). Damage was quantified using the fluorometric analysis of DNA unwiding (FADU) for DNA damage, and cell survival was assessed using a clonogenic assay. In plateau phase cells repair of sublethal damage was virtually absent in NB-100 after 4 Gy (recovery ratio 1.0), whereas HN-1 cells did show sublethal damage repair (recovery ratio 1.4). Repair of potentially lethal damage was more pronounced in NB-100 cells (recovery ratio 2.3) than in HN-1 cells (recovery ratio 1.7) after 4 Gy. Graded doses of X-rays induced comparable levels of DNA damage in both tumor cell lines. However, in HN-1 cells more DNA strand breaks were repaired after 4 Gy, leaving about 25% of the initial damage unrepaired, whereas in NB-100 about 50% was unrepaired. This higher fraction of unrepaired DNA damage correlated well with the degree of sublethal damage repair which was lower in NB-100 than in HN-1 cell, but it did not correlate with the repair of potentially lethal damage, which was higher in NB-100 than in HN-1. Since the level of damage remaining post-irradiation may be the critical variable for survival, the FADU technique can contribute in elucidating the relationship between radiosensitivity and DNA damage repair capacity.
authors.affiliation: Department of Radiotherapy, University Hospital, Nijmegen, The Netherlands.
authors.forename: J H
authors.initials: JH
authors.lastname: Schwachöfer
authors.forename: R P
authors.initials: RP
authors.lastname: Crooijmans
authors.forename: H
authors.initials: H
authors.lastname: Hoogenhout
authors.forename: H B
authors.initials: HB
authors.lastname: Kal
authors.forename: R Q
authors.initials: RQ
authors.lastname: Schaapveld
authors.forename: J
authors.initials: J
authors.lastname: Wessels
mesh_terms: D000468:Alkalies; D002294:Carcinoma, Squamous Cell; D002470:Cell Survival / Q000528:radiation effects*; D004249:DNA Damage / Q000528:radiation effects*; D004260:DNA Repair / Q000528:radiation effects*; D004273:DNA, Neoplasm / Q000032:analysis / Q000528:radiation effects*; D004307:Dose-Response Relationship, Radiation; D005470:Fluorometry; D006801:Humans; D009447:Neuroblastoma; D011879:Radiotherapy Dosage; D014407:Tumor Cells, Cultured / Q000528:radiation effects
chemical_list: D000468:Alkalies; D004273:DNA, Neoplasm