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Updated: Nov 5, 2025
Evaluating In Vitro DNA Damage Using Comet Assay
Published on: October 11, 2017
Veliparib Is an Effective Radiosensitizing Agent in a Preclinical Model of Medulloblastoma
Jessica Buck1,2, Patrick J C Dyer1, Hilary Hii1
1Brain Tumour Research Program, Telethon Kids Cancer Centre, Telethon Kids Institute, Perth, WA, Australia.
Abstract:
Medulloblastoma is the most common malignant childhood brain tumor, and 5-year overall survival rates are as low as 40% depending on molecular subtype, with new therapies critically important. As radiotherapy and chemotherapy act through the induction of DNA damage, the sensitization of cancer cells through the inhibition of DNA damage repair pathways is a potential therapeutic strategy. The poly-(ADP-ribose) polymerase (PARP) inhibitor veliparib was assessed for its ability to augment the cellular response to radiation-induced DNA damage in human medulloblastoma cells. DNA repair following irradiation was assessed using the alkaline comet assay, with veliparib inhibiting the rate of DNA repair. Veliparib treatment also increased the number of γH2AX foci in cells treated with radiation, and analysis of downstream pathways indicated persistent activation of the DNA damage response pathway. Clonogenicity assays demonstrated that veliparib effectively inhibited the colony-forming capacity of medulloblastoma cells, both as a single agent and in combination with irradiation. These data were then validated in vivo using an orthotopic implant model of medulloblastoma. Mice harboring intracranial D425 medulloblastoma xenografts were treated with vehicle, veliparib, 18 Gy multifractionated craniospinal irradiation (CSI), or veliparib combined with 18 Gy CSI. Animals treated with combination therapy exhibited reduced tumor growth rates concomitant with increased intra-tumoral apoptosis observed by immunohistochemistry. Kaplan-Meier analyses revealed a statistically significant increase in survival with combination therapy compared to CSI alone. In summary, PARP inhibition enhanced radiation-induced cytotoxicity of medulloblastoma cells; thus, veliparib or other brain-penetrant PARP inhibitors are potential radiosensitizing agents for the treatment of medulloblastoma.
Insights
Poly-(ADP-ribose) polymerase (PARP) inhibitor veliparib enhances radiation therapy effectiveness in childhood medulloblastoma. This combination therapy significantly improves survival rates by inhibiting DNA repair and increasing cancer cell death.
Area of Science:
- Oncology
- Cancer Therapeutics
- Molecular Biology
Background:
- Medulloblastoma, a common pediatric brain tumor, has limited survival rates, necessitating novel therapeutic strategies.
- Radiotherapy and chemotherapy induce DNA damage, making DNA repair inhibition a promising approach to sensitize cancer cells.
Purpose of the Study:
- To evaluate the efficacy of veliparib, a poly-(ADP-ribose) polymerase (PARP) inhibitor, in sensitizing human medulloblastoma cells to radiation-induced DNA damage.
- To validate the combination therapy's effectiveness in an in vivo medulloblastoma model.
Main Methods:
- Alkaline comet assay and gamma-H2AX foci analysis to assess DNA repair inhibition and DNA damage response.
- Clonogenicity assays to evaluate the impact of veliparib and irradiation on medulloblastoma cell survival.
- In vivo studies using intracranial medulloblastoma xenografts treated with veliparib, irradiation, or combination therapy.
Main Results:
- Veliparib inhibited DNA repair rates and increased DNA damage markers (γH2AX foci) in irradiated medulloblastoma cells.
- Veliparib demonstrated potent inhibition of medulloblastoma cell colony formation, both alone and with irradiation.
- Combination therapy in vivo significantly reduced tumor growth, increased apoptosis, and improved survival compared to irradiation alone.
Conclusions:
- Poly-(ADP-ribose) polymerase (PARP) inhibition potentiates the cytotoxic effects of radiotherapy in medulloblastoma.
- Veliparib, as a brain-penetrant PARP inhibitor, shows potential as a radiosensitizing agent for medulloblastoma treatment.
