Relationship between DNA double-strand breaks, cell killing, and fibrosis studied in confluent skin fibroblasts derived from breast cancer patients.
OBJECTIVE
To investigate the relationship between DNA double-strand breaks (dsbs), cell killing, and fibrosis using skin fibroblasts derived from breast cancer patients who received postmastectomy radiotherapy.


METHODS
Experiments were performed with 12 lines of normal skin fibroblasts derived from recurrence-free breast cancer patients. Cells were irradiated in confluence and cell survival was determined either after immediate or delayed (14 h) plating using a colony-forming assay. Dsbs were measured by constant-field gel electrophoresis. The "excess risk of fibrosis" was previously scored by Johansen et al. (IJRB 1994;66:407-412).


RESULTS
The 12 cell lines showed a typical spectrum of radiosensitivity. The mean value of surviving fraction after 3.5 Gy (SF3.5) was 0.063 for immediate and 0.174 for delayed plating with a coefficient of variation (CV) of 44 and 39%, respectively. There was also a broad variation in the extent of recovery from potentially lethal damage (RPLD), which was not correlated with the immediate sensitivity. The number of initial dsbs as well as the half-times of dsb repair showed little variation, whereas there were considerable differences in the number of residual dsbs (CV = 29%). The number of residual dsbs after 100 Gy was correlated significantly only with SF3.5 after delayed (r2 = O.59; p = 0.006) but not after immediate plating (r2 = 0.21, p = 0.16). There was also no significant relationship between residual dsbs and the "excess risk of fibrosis" determined for the respective patients.


CONCLUSIONS
It is shown that the number of residual dsbs measured in confluent human fibroblast lines can be used to predict the cellular radiosensitivity after delayed but not after immediate plating and also not to predict the excess risk of fibrosis of the respective breast cancer patients.
Dikomey
E
E
Institute of Biophysics and Radiobiology, University of Hamburg, Germany. dikomey@uke.uni-hamburg.de
Brammer
I
I
Johansen
J
J
Bentzen
S M
SM
Overgaard
J
J
D001943:Breast Neoplasms / Q000473:pathology / Q000532:radiotherapy; D002460:Cell Line; D002470:Cell Survival / Q000528:radiation effects*; D004249:DNA Damage; D004260:DNA Repair / Q000528:radiation effects*; D004273:DNA, Neoplasm / Q000528:radiation effects*; D005260:Female; D005347:Fibroblasts / Q000502:physiology / Q000528:radiation effects*; D005355:Fibrosis; D006801:Humans; D011829:Radiation Dosage; D011836:Radiation Tolerance; D011853:Radiobiology; D012867:Skin / Q000166:cytology / Q000528:radiation effects*
D004273:DNA, Neoplasm