Abstract B23: Neuroblastoma patient-derived orthotopic xenografts: Clinically relevant models for drug testing

Background: We previously established neuroblastoma patient-derived orthotopic xenografts (PDXs) by implanting patient neuroblastoma fragments into immunodeficient NSG mice. SNP array analysis confirmed that PDXs maintain patient-specific chromosomal aberrations 1p del, MYCN amp and 17q gain. Immunohistochemistry showed that PDXs retain neuroblastoma markers and a highly infiltrative growth pattern. Importantly, we found spontaneous distant metastasis to lungs, liver and bone marrow. In vitro cultures established from the PDXs express neuroblastoma markers and retain their tumorigenic and metastatic ability in vivo after orthotopic injection. Methods and Results: Given the important role of the tumor stroma for tumor progression and treatment response, we examined PDX stroma by immunohistochemistry. PDXs were highly vascularized with mouse endothelial cells and two PDX models also formed tumor vasculature by co-engrafted human tumor endothelial cells. Tumors contained pericytes, cancer-associated fibroblasts, macrophages and extracellular components resembling the patient disease. PDXs established in athymic nude mice additionally developed intratumoral lymphatic vessels and contained mouse-derived CD45+ lymphoid cells. Thus, PDXs reflect important tumor microenvironment hallmarks for high-stage neuroblastoma. Furthermore, we demonstrate the feasibility of using short-term in vitro cultured PDX-derived cells as a drug-testing model, and show that the HIF2A oncogene is transcriptionally regulated at hypoxia via the PI3K/mTORC2 pathway in these cells. The results establish the PI3K and mTORC2 pathways as potential therapeutic targets of aggressive neuroblastoma. Conclusion: Neuroblastoma orthotopic PDXs reflect clinical aspects of high-risk disease including spontaneous metastasis, copy number changes and microenvironmental hallmarks. Neuroblastoma PDXs are relevant models for in vitro and in vivo preclinical drug testing. Citation Format: Daniel Bexell, Noemie Braekeveldt, Sofie Mohlin, Caroline Wigerup, David Gisselsson, Irene Tadeo, Ana P. Berbegall, Sam Navarro, Rosa Noguera, Sven Pahlman. Neuroblastoma patient-derived orthotopic xenografts: Clinically relevant models for drug testing. [abstract]. In: Proceedings of the AACR Special Conference: Patient-Derived Cancer Models: Present and Future Applications from Basic Science to the Clinic; Feb 11-14, 2016; New Orleans, LA. Philadelphia (PA): AACR; Clin Cancer Res 2016;22(16_Suppl):Abstract nr B23.