Abstract 6902: Development of a stable luciferase expressing PDX-derived cell line for translational in vitro and in vivo testing
Authors: Cold Sigrid , Bøge Rikke N. , Papin Emma , Michler Ida T. , Kristensen Lotte K. , Engel Trine B. , Kjaer Andreas , Nielsen Carsten H. , Gnosa Sebastian 
Published: March 2024

Abstract
Despite much effort invested in developing novel cancer therapies, more than 90% of clinical studies fail due to toxicity or lack of efficacy in patients. This can mainly be ascribed to lack of relevant and translational preclinical models. A common model used in preclinical studies is the xenograft model using immortalized cancer cells. Cell line-based models are cost efficient and can be genetically manipulated but are often criticized for lacking translational value. A murine model with higher clinical relevance is the patient derived xenografts (PDX) model established by implanting patients’ tumor tissue onto immunodeficient mice. Knowledge of patient therapy response, mutational status and tumor heterogeneity makes it a relevant model. However, PDX models are costly, not applicable for in vitro assays or subjective to genetic manipulation. To more closely mimic in vivo tumors we have established a PDX-derived cell line (PDXc) and characterized it extensively in a head-to-head comparison to the parental PDX model. Cells were isolated from a subcutaneous (SC) glioblastoma (GBM) PDX tumor (ST146), processed into single cells and cultivated in vitro. Once the PDXc were stable over several passages the cells were re-implanted into mice. Tumor take and growth rate were evaluated against the parental PDX model and common characteristics of the model such as EFGR and Vimentin expression were determined by IHC. We furthermore generated a stable Luciferase expressing PDXc using 3rd generation lentiviral particles and implanted the cells in an intracranial (IC) model of GBM. Tumor growth was evaluated using bioluminescence imaging (BLI) and MRI. Upon multiple passages and freeze cycles the cell line (ST146c) exhibited a stable in vitro doubling time (2.6 ± 0.2 days) with a morphology like other GBM cell lines with formation of neurospheres. STR analysis confirmed a genetic identical profile to ST146.
ST146c implanted into mice had similar tumor take and growth rates to the parental PDX when injected IC (&gt;90%, Td=3 d) and SC (&gt;75%, Td=6 d). We also showed that ST146c had more homogeneous tumor growth. Ex vivo analysis showed similar expressions of EGFR (-), Vimentin (+++) and Ki67 (++) between the models. The BLI signal obtained from luciferase expressing ST146c implanted orthotopically was correlated to tumor volume obtained by MRI. We developed a PDX cell line that preserved critical in vitro and in vivo characteristics of the PDX model such as doubling time, tumor take rate and marker expression making it feasible to use the PDXc model in future preclinical studies. This will allow in vitro screens with patient derived tumor cells. Furthermore, the expression of luciferase in the PDXc enables intracranial and metastatic implantation with tumor monitoring using BLI. This platform consisting of in vitro and in vivo PDX models could be used as a predictive translational platform for testing new cancer therapies.
Citation Format: Sigrid Cold, Rikke N. Bøge, Emma Papin, Ida T. Michler, Lotte K. Kristensen, Trine B. Engel, Andreas Kjaer, Carsten H. Nielsen, Sebastian Gnosa. Development of a stable luciferase expressing PDX-derived cell line for translational in vitro and in vivo testing [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 6902.