Replication-dependent radiosensitization of human glioma cells by inhibition of poly(ADP-Ribose) polymerase: mechanisms and therapeutic potential

Dungey, Fiona, Loser, Dana and Chalmers, Anthony (2008) Replication-dependent radiosensitization of human glioma cells by inhibition of poly(ADP-Ribose) polymerase: mechanisms and therapeutic potential. International Journal of Radiation Oncology • Biology • Physics, 72 (4). pp. 1188-1197. ISSN 0360-3016

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Abstract

Purpose
Current treatments for glioblastoma multiforme are inadequate and limited by the radiation sensitivity of normal brain. Because glioblastoma multiforme are rapidly proliferating tumors within nondividing normal tissue, the therapeutic ratio might be enhanced by combining radiotherapy with a replication-specific radiosensitizer. KU-0059436 (AZD2281) is a potent and nontoxic inhibitor of poly(ADP-ribose) polymerase-1 (PARP-1) undergoing a Phase II clinical trial as a single agent.
Methods and Materials
Based on previous observations that the radiosensitizing effects of PARP inhibition are more pronounced in dividing cells, we investigated the mechanisms underlying radiosensitization of human glioma cells by KU-0059436, evaluating the replication dependence of this effect and its therapeutic potential.
Results
KU-0059436 increased the radiosensitivity of four human glioma cell lines (T98G, U373-MG, UVW, and U87-MG). Radiosensitization was enhanced in populations synchronized in S phase and abrogated by concomitant exposure to aphidicolin. Sensitization was further enhanced when the inhibitor was combined with a fractionated radiation schedule. KU-0059436 delayed repair of radiation-induced DNA breaks and was associated with a replication-dependent increase in γH2AX and Rad51 foci.
Conclusion
The results of our study have shown that KU-0059436 increases radiosensitivity in a replication-dependent manner that is enhanced by fractionation. A mechanism is proposed whereby PARP inhibition increases the incidence of collapsed replication forks after ionizing radiation, generating persistent DNA double-strand breaks. These observations indicate that KU-0059436 is likely to enhance the therapeutic ratio achieved by radiotherapy in the treatment of glioblastoma multiforme. A Phase I clinical trial is in development.

Item Type: Article
Keywords: Glioblastoma multiforme, Radiotherapy, Poly(ADP-ribose) polymerase, KU-0059436, Radiosensitizer
Schools and Departments: Brighton and Sussex Medical School > Clinical Medicine
Brighton and Sussex Medical School > Brighton and Sussex Medical School
Subjects: R Medicine > R Medicine (General)
R Medicine > RC Internal medicine > RC0254 Neoplasms. Tumors. Oncology Including cancer and carcinogens
Depositing User: Lisa Costick
Date Deposited: 01 Sep 2010
Last Modified: 29 Aug 2012 22:56
URI: http://sro.sussex.ac.uk/id/eprint/2468
Google Scholar:37 Citations
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