Medulloblastoma is the most common malignant brain tumour in children, and while advances in treatment have resulted in up to 80% survival for subsets of patients, the quality of life for survivors is significantly reduced due to the side effects of aggressive treatment. There is a need identify new therapies that improve patient survival, whilst minimising toxicity. Using a high-throughput, cell-based assay to identify compounds that target medulloblastoma, we screened approximately 3,200 compounds and identified several inhibitors that targeted cell cycle regulators and components of the DNA damage response (DDR) pathway. Notably, many of the current therapies used to treat medulloblastoma work by inducing DNA damage, and we confirmed the DDR pathway is active and intact in our medulloblastoma models by immunoblotting and flow cytometry.
We further investigated several inhibitors of the cell cycle checkpoint kinases CHK1 and CHK2. These agents have a demonstrated ability to enhance the cytotoxicity of DNA damaging chemotherapeutics in other cancers, therefore we evaluated their activity in medulloblastoma cells alone and in combination with several agents used in medulloblastoma treatment: cyclophosphamide, gemcitabine and radiation. Immunoblotting and flow cytometry revealed that combined treatment of CHK inhibitors with DNA damaging agents blocked activation of a DDR and markedly increased apoptosis in vitro. These cellular data were confirmed by immunohistochemistry in vivo using mice bearing intracranial medulloblastoma xenografts. Moreover, combination treatment impeded tumour growth rates in vivo and impacted overall survival as measured by bioluminescence imaging and Kaplan-Meier analyses. Our data support the utility of CHK inhibitors in combination with current medulloblastoma treatments as a viable option for clinical trial. Current work will determine which CHK inhibitor is the most effective, and the most optimal method of incorporating these agents into existing clinical treatment protocols.