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Abstract 53:Ex vivomodels of glioblastoma: a comparison of 3D tissues and patient-derived xenografts to clinical response

Standard first-line treatment of newly diagnosed Glioblastoma (GBM) is primarily radiotherapy and Temozolomide (TMZ) with a strong NCCN recommendation of enrollment in clinical trials. The only biomarker that can currently provide a stratification of strong and poor responders to standard of care is methylation of MGMT which indicates a median PFS of 10.3 months for methylated patients and 5.3 months for unmethylated patients. Development of patient-specific in vitro models of GBM for rapid testing of therapeutic options may yield more efficacious therapies and faster, more accurate assignation of therapies to each patient. To that end, we have developed a multi-faceted, patient-based 3D GBM model with modularity that facilitates increasing levels of model complexity such as the inclusion of immune cell components. Stable populations of glioma stem cells (GSC) from 24 of 41 patient samples have been successfully established, verified for stemness through limited dilution in in vitro and in vivo studies, and cultured long-term with minimal molecular changes, as determined from genetic analyses including RT-PCR arrays and MGMT methylation status, flow cytometry, and IHC. These cell populations have been used to establish and validate our 3D model system as well as generate comparable patient-derived xenografts (PDX). KIYATEC’s 3D microtumor in our 3DKUBE™ perfusion system provides a moderate throughput, dynamic system that is easily controlled to establish complex microtumors. GSC cell populations were cultured in monoculture only, co-cultured with human brain endothelial cells (HBEC), and tri-cultured with HBEC and CD14+ peripheral blood mononuclear cells (PBMC). Three microtumors were characterized by drug response to TMZ and axitinib, IHC, and molecular profiling including RNA expression and MGMT methylation status. Interestingly, increasing the complexity of the microtumor was capable of reestablishing the primary tumor MGMT methylation status if it were lost during culturing. We also generated PDX models from the same 3 patient tumor tissues as the above 3D models. PDX are a low throughput, time consuming, and expensive model that are still utilized for many systemic drug response studies and therefore a good comparator to the 3D tissue models we established. In vitro drug response in the 3D tissue models has been compared to both the matched PDX in vivo drug response and the patient’s clinical response to TMZ and MGMT methylation. Our data supports that KIYATEC’s complex patient-derived GBM model can be successfully used to identify, screen, and characterize novel treatments of GBM. Citation Format: Ashley M. Smith, Lillia Holmes, Lacey E. Dobrolecki, Charles Kanos, Stephen Gardner, Philip Hodge, Michael Lynn, Jeff Edenfield, Michael T. Lewis, Howland E. Crosswell, Teresa M. DesRochers. Ex vivo models of glioblastoma: a comparison of 3D tissues and patient-derived xenografts to clinical response [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 53.