Share This Article:

The PARP-1 Inhibitor Olaparib Causes Retention of γ-H2AX Foci in BRCA1 Heterozygote Cells Following Exposure to Gamma Radiation

Abstract Full-Text HTML Download Download as PDF (Size:449KB) PP. 44-52
DOI: 10.4236/jct.2013.411A006    4,133 Downloads   6,164 Views   Citations


A novel treatment for cancer patients with homozygous deletions of BRCA1 and BRCA2 is to use drugs that inhibit the enzyme poly(ADP-ribose) polymerase (PARP). Specific inhibition of PARP-1 can induce synthetic lethality in irradiated cancer cells while theoretically leaving normal tissue unaffected. We recently demonstrated in a cell survival assay that lymphoblastoid cells with mono-allelic mutations of BRCA1 were hypersensitive to gamma radiation in the presence of the PARP-1 inhibitor Olaparib compared to normal cells and mono-allelic BRCA2 cells. To determine if the enhanced radiation sensitivity was due to a persistence of DNA strand breaks, we performed γ-H2AX foci analysis in cells derived from two normal individuals, three heterozygous BRCA1 and three heterozygous BRCA2 cell lines. Cells were exposed to 2 Gy gamma radiation in the presence or absence of 5 μM Olaparib. Using immunofluorescence and imaging flow cytometry, foci were measured in untreated cells and at 0.5, 3, 5 and 24 hours post-irradiation. In all lymphoblastoid cells treated with 2 Gy gamma radiation, there was a predictable induction of DNA strand breaks, with a modest but significant retention of foci over 24 hours in irradiated cells treated with Olaparib (ANOVA P < 0.05). However, in mono-allelic BRCA1 cells, there was a failure to fully repair DNA double-strand breaks (DSB) in the presence of Olaparib, evidenced by a significant retention of foci at 24 hours post irradiation (t-Test P < 0.05). These data show that the cellular hypersensitivity of mono-allelic BRCA1 lymphoblastoid cells to gamma radiation in the presence of the Olaparib is due to the retention of DNA DSB. These data may indicate that patients with inherited mutations in the BRCA1 gene treated with radiotherapy and PARP-1 inhibitors may experience elevated radiation-associated normal tissue toxicity.

Conflicts of Interest

The authors declare no conflicts of interest.

Cite this paper

E. Bourton, P. Plowman, A. Harvey, S. Zahir and C. Parris, "The PARP-1 Inhibitor Olaparib Causes Retention of γ-H2AX Foci in BRCA1 Heterozygote Cells Following Exposure to Gamma Radiation," Journal of Cancer Therapy, Vol. 4 No. 11A, 2013, pp. 44-52. doi: 10.4236/jct.2013.411A006.


[1] K. Yoshida and Y. Miki, “Role of BRCA1 and BRCA2 as Regulators of DNA Repair, Transcription, and Cell Cycle in Response to DNA Damage,” Cancer Science, Vol. 95, No. 11, 2004, pp. 866-871.
[2] R. Roy, J. Chun and S. N. Powell, “BRCA1 and BRCA2: Different Roles in a Common Pathway of Genome Protection,” Nature Reviews. Cancer, Vol. 12, No. 1, 2011, pp. 68-78. 10.1038/nrc3181
[3] A. R. Venkitaraman, “Functions of BRCA1 and BRCA2 in the Biological Response to DNA Damage,” Journal of Cell Science, Vol. 114, No. 20, 2001, pp. 3591-3598.
[4] A. Bhattacharyya, U. S. Ear, B. H. Koller, R. R. Weichselbaum and D. K. Bishop, “The Breast Cancer Susceptibility Gene BRCA1 is Required for Subnuclear Assembly of Rad51 and Survival Following Treatment with the DNA Cross-Linking Agent Cisplatin,” The Journal of Biological Chemistry, Vol. 275, No. 31, 2000, pp. 23899-23903.
[5] R. A. Weinberg, “The Rational Treatment of Cancer,” In: R. A. Weinberg, Ed., The Biology of Cancer, 2nd Edition, Garland Science, New York, 2013, pp. 797-876.
[6] J. Bernier, E. J. Hall and A. Giaccia, “Radiation Oncology: A Century of Achievements,” Nature Reviews. Cancer, Vol. 4, No. 9, 2004, pp. 737-747.
[7] S. L. Tucker, F. B. Geara, L. J. Peters and W. A. Brock, “How Much Could the Radiotherapy Dose Be Altered for Individual Patients Based on a Predictive Assay of Normal-Tissue Radiosensitivity?” Radiotherapy and Oncology: Journal of the European Society for Therapeutic Radiology and Oncology, Vol. 38, No. 2, 1996, pp. 103-113.
[8] U. Hoeller, S. Tribius, A. Kuhlmey, K. Grader, F. Fehlauer and W. Alberti, “Increasing the Rate of Late Toxicity by Changing the Score? A Comparison of RTOG/EORTC and LENTA/SOMA Scores,” International Journal of Radiation Oncology, Biology, Physics, Vol. 55, No. 4, 2003, pp. 1013-1018.
[9] M. F. Lavin and Y. Shiloh, “The Genetic Defect in Ataxia-Telangiectasia,” Annual Review of Immunology, Vol. 15, 1997, pp. 177-202.
[10] F. Abbaszadeh, P. H. Clingen, C. F. Arlett, P. N. Plowman, E. C. Bourton, M. Themis, E. M. Makarov, R. F. Newbold, M. H. L. Green and C. N. Parris, “A Novel Splice Variant of the DNA-PKcs Gene Is Associated with Clinical and Cellular Radiosensitivity in a Patient with Xeroderma Pigmentosum,” Journal of Medical Genetics, Vol. 47, No. 3, 2010, pp. 176-181. jmg.2009.068866
[11] D. Moshous, I. Callebaut, R. de Chasseval, B. Corneo, M. Cavazzana-Calvo, F. Le Deist, I. Tezcan, O. Sanal, Y. Bertrand, N. Philippe, A. Fischer and J.-P. de Villartay, “Artemis, A Novel DNA Double-Strand Break Repair/ V(D)J Recombination Protein, Is Mutated in Human Severe Combined Immune Deficiency,” Cell, Vol. 105, No. 2, 2001, pp. 177-186. 00309-9
[12] T. A. Buchholz, X. Wu, A. Hussain, S. L. Tucker, G. B. Mills, B. Haffty, S. Bergh, M. Story, F. B. Geara and W. A. Brock, “Evidence of Haplotype Insufficiency in Human Cells Containing a Germline Mutation in BRCA1 or BRCA2,” International Journal of Cancer, Vol. 97, No. 5, 2002, pp. 557-561.
[13] T. Leong, J. Whitty, M. Keilar, S. Mifsud, J. Ramsey, G. Birrell, D. Venter, M. Southey and M. McKay, “Mutation Analysis of BRCA1 and BRCA2 Cancer Predisposition Genes in Radiation Hypersensitive Cancer Patients,” International Journal of Radiation Oncology, Biology, Physics, Vol. 48, No. 4, 2000, pp. 959-965.
[14] E. R. Plummer, “Inhibition of Poly(ADP-ribose) Polymerase in Cancer,” Current Opinion in Pharmacology, Vol. 6, No. 4, 2006, pp. 364-368.
[15] N. J. Curtin, “PARP Inhibitors for Cancer Therapy,” Expert Reviews in Molecular Medicine, Vol. 7, No. 4, 2005, pp. 1-20.
[16] D. Davar, J. H. Beumer, L. Hamieh and H. Tawbi, “Role of PARP Inhibitors in Cancer Biology and Therapy,” Current Medicinal Chemistry, Vol. 19, No. 23, 2012, pp. 3907-3921.
[17] E. C. Bourton, H. A. Foster, P. N. Plowman, A. J. Harvey and C. N. Parris, “Hypersensitivity of BRCA1 Heterozygote Lymphoblastoid Cells to Gamma Radiation and PARP Inhibitors,” Journal of Genetic Syndrome & Gene Therapy, Vol. 4, No. 5, 2013, pp. 146-151.
[18] E. C. Bourton, P. N. Plowman, D. Smith, C. F. Arlett and C. N. Parris, “Prolonged Expression of the γ-H2AX DNA Repair Biomarker Correlates with Excess Acute and Chronic Toxicity from Radiotherapy Treatment,” International Journal of Cancer, Vol. 129, No. 12, 2011, pp. 2928-2934.
[19] E. C. Bourton, P. N. Plowman, S. Adam Zahir, G. Ulus Senguloglu, H. Serrai, G. Bottley and C. N. Parris, “Multispectral Imaging Flow Cytometry Reveals Distinct Frequencies of γ-H2AX Foci Induction in DNA Double Strand Break Repair Defective Human Cell Lines,” Cytometry A, Vol. 81A, No. 2, 2012, pp. 130-137.
[20] H. Farmer, N. McCabe, C. J. Lord, A. N. J. Tutt, D. A. Johnson, T. B. Richardson, M. Santarosa, K. J. Dillon, I. Hickson, C. Knights, N. M. B. Martin, S. P. Jackson, G. C. M. Smith and A. Ashworth, “Targeting the DNA Repair Defect in BRCA Mutant Cells as a Therapeutic Strategy,” Nature, Vol. 434, No. 7035, 2005, pp. 917-921.
[21] O. Fernandez-Capetillo, A. Lee, M. Nussenzweig and A. Nussenzweig, “H2AX: The Histone Guardian of the Genome,” DNA Repair, Vol. 3, No. 8-9, 2004, pp. 959-967. j.dnarep.2004.03.024

comments powered by Disqus

Copyright © 2018 by authors and Scientific Research Publishing Inc.

Creative Commons License

This work and the related PDF file are licensed under a Creative Commons Attribution 4.0 International License.