Abstract 1684: PDX-derived 3D InSightTM immune-competent tumor microtissues as ex-vivo human model for evaluating therapeutic responses
Authors: Wardwell Judi , Chiovaro Francesca , Buschmann Nicole , Strebel Silvan , Wolf Armin , Agarkova Irina 
Published: September 2020

Abstract
Background: Current in vitro preclinical models to assess the efficacy of drug candidates only poorly recapitulate the complex features of human tumors. The development of better screening models and platforms comes always with the major question on how accurately and robustly they can represent the complexity of human disease. Patient-derived xenograft (PDX) models faithfully preserve the biological features and the genetic expression profile of human tumor specimens. However, one limiting aspect of patient-derived models is the replacement of the human host microenvironment by murine stroma within the tumor. Lack of cross-species compatibility compromises the induction of a broad range of signaling pathways that cannot be entirely recapitulated. In that respect, our in vitro 3D InSightTM Tumor Microtissues derived from PDX lines retain key properties of the parental human tumors and provide a relevant physiological tumor microenvironment (TME) to assess candidate drugs for novel therapeutic approaches.
Aim: Development of in vitro 3D InSightTM Tumor Microtissues from PDX lines aimed to retain the cellular heterogeneity found in the original human tumor tissue.
Material & Methods and Results: PDX cell suspensions of lung, breast and melanoma origin were successfully used to assess 3D aggregation in 96-well format and characterized over 10 days in culture. 3D PDX cell cultures were supplied with exogenous normal human dermal fibroblasts (nHDF) and to provide a more physiological cancer niche, PDX cells were also co-cultured with tumor-matched cancer-associated fibroblasts (CAFs). 3D InSight™ Tumor Microtissue from Melanoma PDX were labeled with CellTracker to monitor for tumor cell viability once exposed to peripheral blood mononuclear cells (PBMCs). PBMCs were stimulated with cytokines or anti-CD3/CD28 to generate a pro-inflammatory tumor microenvironment with the subsequent immune-cell mediated tumor attack. To assess the distribution of various cell populations within the tumor, 3D PDX samples were screened for standard stromal vs. epithelial-tumor cells markers (e.g. FAP, pan-CK, E-Cadherin), and diagnostic cancer type-specific biomarkers. 3D PDX samples were also employed to investigate the efficacy of specific targeted therapies based on distinct molecular signatures of PDX tumor models. The gradual modulation of PBMCs mediated either by antibodies or cytokines had a defined impact of the tumor cell killing effect with higher cell death in presence of CD3/CD28 antibodies. Conclusion PDX-derived 3D InSightTM tumor microtissues faithfully model the features and heterogeneity of original human tumor specimens. The successful integration of immune cells (PBMCs) will provide reliable preclinical translational research of tumor/immune cell interactions. We suggest that in vitro 3D PDX models offer a more relevant and robust approach to assess the efficacy of immunomodulators and their combinations to create the new strategies for cancer therapy.
Citation Format: Judi Wardwell, Francesca Chiovaro, Nicole Buschmann, Silvan Strebel, Armin Wolf, Irina Agarkova. PDX-derived 3D InSightTM immune-competent tumor microtissues as ex-vivo human model for evaluating therapeutic responses [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 1684.