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Double-strand break repair deficiency and radiation sensitivity in BRCA2 mutant cancer cells
D W Abbott1, M L Freeman, J T Holt
1Department of Cell Biology and Pathology, Vanderbilt University, Nashville, TN 37232, USA.
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.
Conclusion:
BRCA2-defective cancer cells are highly sensitive to agents that cause double-strand breaks in DNA.
Insights
BRCA2-defective cancer cells show heightened sensitivity to DNA-damaging agents. These findings suggest potential therapeutic strategies targeting BRCA2 mutations in cancer treatment.
Area of Science:
- Genetics
- Oncology
- Molecular Biology
Background:
- The BRCA2 gene is crucial for DNA double-strand break repair.
- Cancers with BRCA2 mutations may respond better to therapies inducing DNA breaks.
Purpose of the Study:
- To investigate the DNA repair capacity and drug sensitivity of BRCA2-defective cancer cells.
- To evaluate the efficacy of double-strand break-inducing agents in BRCA2-mutated cancers.
Main Methods:
- Utilized a human pancreatic adenocarcinoma cell line with BRCA2 deficiency.
- Conducted in vitro and in vivo experiments assessing double-strand break repair and sensitivity to radiation and specific drugs.
- Introduced antisense BRCA2 deoxyribonucleotides into normal cells to assess impact.
Main Results:
- BRCA2-defective cells exhibited impaired double-strand DNA break repair.
- These cells showed significant sensitivity to ionizing radiation, mitoxantrone, amsacrine, and etoposide.
- In vivo studies demonstrated marked tumor reduction in BRCA2-defective xenografts treated with radiation and mitoxantrone.
Conclusions:
- BRCA2-defective cancer cells are highly sensitive to DNA double-strand break-inducing agents.
- This sensitivity presents a potential therapeutic vulnerability for targeted cancer treatments.