Lymphoblastoid cell lines (LCL) with a heterozygous mutation in the breast 
cancer susceptibility gene BRCA1 have been repeatedly used to elucidate the 
biological consequences of such a mutation with respect to radiation sensitivity 
and DNA repair deficiency. Our previous results indicated that LCL with a BRCA1 
mutation do not generally show the same chromosomal mutagen sensitivity in the 
micronucleus test as lymphocytes with the same BRCA1 mutation. To further study 
the radiosensitivity of LCL with a BRCA1 mutation, we now performed comparative 
investigations with the alkaline (pH 13) and the neutral (pH 8.3) comet assay 
and pulsed field gel electrophoresis (PFGE). These tests are commonly used to 
determine the repair capacity for DNA double strand breaks (DNA-DSB). Six LCL 
(three established from women with a heterozygous BRCA1 mutation and three from 
healthy controls) were investigated. Induction (2 and 5 Gy) of gamma-ray-induced 
DNA damage and its repair (during 60 min after irradiation) was measured with 
the alkaline and neutral comet assay. Comparative experiments were performed 
with PFGE determining the induction of DNA-DSB by 10-50 Gy gamma-irradiation and 
their repair during 6 h. There was no significant difference between LCL with 
and without BRCA1 mutation in any of these experiments. Therefore, using these 
methods, no indication for a delayed repair of DNA-DSB in LCL with a BRCA1 
mutation was found. However, these results do not generally exclude DNA-DSB 
repair deficiency in these cell lines because the methods applied have limited 
sensitivity and only measure the speed but not the fidelity of the repair 
process.