Novel Treatment Modalities for High-Risk Neuroblastoma : Studies in Animal Models

Abstract: Neuroblastoma, the most common extracranial solid tumor of childhood, is a heterogeneous tumor. In some patients, the tumor can go into spontaneous regression and disappear whereas other patients have rapidly growing tumors with a poor prognosis. The overall long-term survival rate in patients with high-risk neuroblastoma is less than 30%, indicating the need for new treatment strategies. Angiogenesis inhibition hampers the formation of new blood vessels, thereby limiting the tumors’ metabolic exchange. Neuroblastoma is rapidly growing and high tumor angiogenesis has been associated with poor outcome. Therefore, the aim of this thesis was to investigate the effect of novel treatment modalities for angiogenesis inhibition on high-risk neuroblastoma xenografts. For that purpose, we used subcutaneous mouse models and characterized orthotopic mouse models for high-risk neuroblastoma. We found that xenotransplantation of neuroblastoma cells into the adrenal gland of SCID and SCID beige mice resulted in orthotopic tumors resembling clinical neuroblastoma in respect to tumor site, growth and spread. Using contrast-enhanced ultrasound, we observed that the receptor tyrosine kinase inhibitor SU11248 reduced orthotopic neuroblastoma growth and spread by reducing tumor angiogenesis.In subcutaneous xenografts for high-risk neuroblastoma, valuable for studies requiring continuous assessment of tumor volume, we demonstrated that immune-neutralizing VEGF with the anti-VEGF antibody bevacizumab significantly reduced neuroblastoma growth. Finally, we found that formulations of the chemotherapeutic drug GMX1778 inhibited angiogenesis and induced tumor regression in a dose dependent manner without host toxicity. We showed that relapsing tumors remained responsive to GMX-therapy without accelerated growth or induced drug resistance.In conclusion, SU11248, bevacizumab, and formulations of the active compound GMX1778 may become useful for treating high-risk neuroblastoma.