Abstract 3008: Characterization of a panel of orthotopic bioluminescent patient-derived models for drug discovery

Background: Cancer is a complicated disease featuring geographic, genetic and immunological diversity. The tumor microenvironment (TME) is an essential part of tumor development, influencing tumor growth, metastasis and also therapeutic response. Patient-derived xenografts (PDX) and PDX-derived organoids (PDXO) are widely-used preclinically for drug evaluation with the prominent advantage of largely maintaining the histo- and molecular- pathology of the original tumor. Over decades of studies using PDX models, we found limitations in monitoring the orthotopic and metastatic pattern of cancer. With the development of gene engineering technologies (particularly for luciferase labeling), we now present the transduction of patient-derived models with firefly luciferase, to enable real-time monitoring of tumor burden in mice following orthotopic engraftment of either PDX tumor cells or PDXO in vivo. Methods: A panel of PDX cell slurry or PDXO cultures were transduced with lentiviral vectors carrying both the firefly luciferase gene as well as GFP. Mixed pools or GFP-sorted cells were used for in vivo validation. Bioluminescent PDX or PDXO were orthotopically and subcutaneously engrafted into immunodeficient mice. Real-time tumor growth and metastasis were monitored using the IVIS® Spectrum In Vivo Imaging System. Results: We have established a series of luciferase-labeled PDXO from different cancer types, including liver, ovarian, pancreatic and lung cancer and characterized their growth following orthotopic implantation. We have also established a series of luciferase-labeled PDX models from non-epithelial origin, including brain tumors, osteosarcoma and lymphomas. All of the models were confirmed with GFP signaling in vitro and showed significant luciferase signaling and growth in vivo. A mixed pool of bioluminescent PDXs or PDXOs presented heterogenous luciferase signals in tumors, while single clones or cell sorting by GFP or selected passage in vivo improved the consistency of the bioluminescent signal. Conclusions: PDX models are widely used as preclinical tools for clinical predictivity, however their application in orthotopic/metastatic modeling has been challenging due to the limitation in labelling PDXs for real-time monitoring. With the development of gene engineering technology in vitro and bioluminescent imaging (BLI) in vivo, we have developed and characterized a large panel of bioluminescent PDX and PDXO models from a range of different cancer ty