title: DNA double-strand break rejoining rates, inherent radiation sensitivity and human tumour response to radiotherapy.
abstract: The relationship between DNA double-strand break rejoining rates, inherent radiation sensitivity and tumour response to radiation therapy was determined for a group of 25 squamous cell carcinoma (SCC) and eight sarcoma (SAR) tumours. DNA double-strand break frequencies were measured by neutral filter elution in first passage following explant tumour samples after in vitro exposure to 100 Gy of 60Co gamma-rays. There was no significant difference between SCC and SAR tumour cells in their sensitivity to break induction, but in a 1 h time period SAR tumour cells rejoined significantly fewer breaks than SCC tumour cells, consistent with the greater sensitivity of SAR and suggesting that differences in rates of break rejoining account for the different distributions of radiosensitivities seen when different tumour types are compared. The percentage of breaks rejoined in 1 h in these tumour samples correlated well with D(o) and with the beta component of the survival curve, measured in vitro by clonogenic assay in tumour cell lines established from the tumour samples, but not with SF2 or the alpha component of the survival curve. The rates of DNA double-strand break rejoining therefore appear to influence the exponential portion of survival curves and probably the interactions between breaks. The percentage of breaks rejoined in 1 h was higher in SCC tumours that subsequently failed radiotherapy and, although the differences were not significant, they suggest that rates of break rejoining are an important component of tumour response to radiation therapy.
authors.affiliation: Center for Mechanistic Biology and Biotechnology, Argonne National Laboratory, Illinois 60439-4833, USA.
authors.forename: J L
authors.initials: JL
authors.lastname: Schwartz
authors.forename: R
authors.initials: R
authors.lastname: Mustafi
authors.forename: M A
authors.initials: MA
authors.lastname: Beckett
authors.forename: R R
authors.initials: RR
authors.lastname: Weichselbaum
mesh_terms: D016475:3T3 Cells / Q000528:radiation effects; D000818:Animals; D002294:Carcinoma, Squamous Cell / Q000378:metabolism / Q000532:radiotherapy*; D002470:Cell Survival / Q000528:radiation effects; D004249:DNA Damage; D004260:DNA Repair; D004273:DNA, Neoplasm / Q000378:metabolism / Q000528:radiation effects*; D006258:Head and Neck Neoplasms / Q000378:metabolism / Q000532:radiotherapy*; D006801:Humans; D051379:Mice; D011237:Predictive Value of Tests; D011836:Radiation Tolerance / Q000502:physiology*; D012509:Sarcoma / Q000378:metabolism / Q000532:radiotherapy*; D014407:Tumor Cells, Cultured / Q000528:radiation effects
chemical_list: D004273:DNA, Neoplasm