MODL-01. TRACTABLE PATIENT-DERIVED MODELS FOR PRECLINICAL THERAPEUTIC STUDIES OF CNS METASTASES

Abstract INTRODUCTION Brain metastases are the most common brain tumors and occur in 10-30% of cancer patients, whereas leptomeningeal disease (LMD) occurs in approximately 5% of adults with systemic malignancies. Tractable preclinical disease models that faithfully represent metastasis to the brain and recapitulate LMD are needed to improve our understanding of the biological basis of CNS disease as well developing effective therapeutic strategies. Our goal in this study was to generate representative preclinical disease models using two methods. METHODS We isolated tumor cells from CSF of 16 patients with cytologically proven LMD (9 NSCLC, 1 melanoma, 1 ovarian cancer, 1 endometrial cancer, and 4 breast cancer) and implanted the cells subcutaneously into the flank of immunocompromised mice. Cell lines were also generated from PDX tissues. Models were characterized by next-generation sequencing (NGS). We also generated a model of CNS metastasis of kinase-driven sarcoma by intracardiac (IC) injection of human mesenchymal stem cells (HMSC) expressing a SPECC1L::RET fusion (CRISPR-Cas9 gene editing). The cells (HMSC-RET) were also labeled with a luciferase construct to allow non-invasive bioluminescence imaging. RESULTS We established three PDX models (2 lung, 1 ovarian) from CSF (19% success rate compared to approximately 33% for solid tumors) and matched cell lines from the resulting PDX tissues. Intracardiac injection of HMSC-RET cells resulted in tumors establishing in several peripheral organs and the brain. SUMMARY AND CONCLUSIONS We have established disease models of CNS metastasis and LMD. Translational studies where patients with clinical suspicion of LMD undergo CSF sampling, NGS/ctDNA analysis, and PDX modeling are crucial in improving our understanding of this metastatic compartment and investigating novel treatment paradigms. Future studies will be focused on examining the biochemical and genetic nature of these tumors as well as developing effective therapeutic strategies.