Double-strand break repair deficiency and radiation sensitivity in BRCA2 mutant cancer cells.
BACKGROUND
The protein product of the BRCA2 gene mediates repair of double-strand breaks in DNA. Because a number of cancer therapies exert cytotoxic effects via the initiation of double-strand breaks, cancers comprised of cells carrying BRCA2 gene mutations may be more amenable to treatment with agents that cause such breaks.


METHODS
We identified a human pancreatic adenocarcinoma cell line lacking one copy of the BRCA2 gene and containing a mutation (6174delT) in the remaining copy. In vitro and in vivo experiments were conducted with this cell line and with other carcinoma cell lines matched for similar genetic mutations, similar differentiation status, and/or similar carcinoma type to examine double-strand break repair, sensitivity to drugs that induce double-strand breaks, and radiation sensitivity.


RESULTS
BRCA2-defective cells were unable to repair the double-strand DNA breaks induced by ionizing radiation. These cells were also markedly sensitive to mitoxantrone, amsacrine, and etoposide (drugs that induce double-strand breaks) (two-sided P = .002) and to ionizing radiation (two-sided P = .001). Introduction of antisense BRCA2 deoxyribonucleotides into cells possessing normal BRCA2 function led to increased sensitivity to mitoxantrone (two-sided P = .008). Tumors formed by injection of BRCA2-defective cells into nude mice were highly sensitive (>90% tumor size reduction, two-sided P = .002) to both ionizing radiation and mitoxantrone when compared with tumors exhibiting normal BRCA2 function. Histologic analysis of irradiated BRCA2-defective tumors showed a large degree of necrosis compared with that observed for control tumors possessing normal BRCA2 function.


CONCLUSIONS
BRCA2-defective cancer cells are highly sensitive to agents that cause double-strand breaks in DNA.
Department of Cell Biology and Pathology, Vanderbilt University, Nashville, TN 37232, USA.
D W
DW
Abbott
M L
ML
Freeman
J T
JT
Holt
D000230:Adenocarcinoma / Q000188:drug therapy / Q000235:genetics* / Q000532:radiotherapy; D000970:Antineoplastic Agents / Q000494:pharmacology; D001943:Breast Neoplasms / Q000188:drug therapy / Q000235:genetics* / Q000532:radiotherapy; D002470:Cell Survival / Q000187:drug effects / Q000528:radiation effects; D004249:DNA Damage / Q000528:radiation effects; D017931:DNA Primers; D004260:DNA Repair / Q000528:radiation effects*; D004273:DNA, Neoplasm / Q000528:radiation effects*; D004305:Dose-Response Relationship, Drug; D004307:Dose-Response Relationship, Radiation; D006801:Humans; D009154:Mutation / Q000187:drug effects / Q000528:radiation effects; D009363:Neoplasm Proteins / Q000235:genetics*; D010190:Pancreatic Neoplasms / Q000188:drug therapy / Q000235:genetics* / Q000532:radiotherapy; D016133:Polymerase Chain Reaction; D013997:Time Factors; D014407:Tumor Cells, Cultured / Q000187:drug effects / Q000528:radiation effects
D000970:Antineoplastic Agents; D017931:DNA Primers; D004273:DNA, Neoplasm; D009363:Neoplasm Proteins