Abstract 52: PDX-derived 3D InSightTM tumor microtissues as ex-vivo human experimental models for evaluating therapeutic responses

Background The selection of appropriate preclinical models 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. With our in vitro 3D InSightTMTumor Microtissues derived from PDX lines, we provide a relevant physiological environment and a strategy 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. After careful removal of mouse cell contaminants in each PDX sample, 3D PDX cell cultures were supplied with exogenous normal human dermal fibroblasts (nHDF). Furthermore, to provide a more physiological cancer niche, PDX cells were also co-cultured with tumor-matched cancer-associated fibroblasts (CAFs). 3D in vitro tumors were analyzed histologically and cancer phenotypic alterations were evaluated through the analysis of epithelial-to-mesenchymal transition (EMT) markers. The morphology, viability and growth rate of PDX-derived microtumors were assessed by size analysis (cell scanner) and ATP assay. 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. Immunohistochemistry assessment of 3D microtumors validated the resemblance with their respective PDX tumor models. 3D tumor growth rate and cell behavior observations reflected the diversity of disease progression in vivo. Conclusion Further efforts will focus on employing this platform to establish more complex co-cultures with integra