BSLM-10 Molecular and Histological Characterization of NSCLC Progression to Leptomeningeal Metastasis With Comorbid Intraparenchymal Disease

Abstract Leptomeningeal disease (LMD) is a rare form of central nervous system (CNS) metastasis wherein tumor cells invade the cerebrospinal fluid (CSF) filled space that surrounds the brain and spinal cord. For patients with LMD, prognosis is extremely poor even with aggressive treatment. The mechanisms of progression to LMD and the adaptations tumor cells make to survive in this metabolically sparse microenvironment are poorly understood. As 60% of patients with LMD have concurrent or prior parenchymal metastases, our laboratory examined our established murine models of parenchymal metastases for signs of leptomeningeal infiltration. We identify two xenograft non-small cell lung cancer (NSCLC) models of intraparenchymal metastasis following intra-arterial injection that show progression to LMD in a subset of cases. In the H2030-BrM3 model, this occurs de novo, whereas the EGFR-mutant PC9-R2 model progresses to LMD only following onset of resistance to tyrosine kinase inhibitor treatment. Subsequent in vivo passaging of the H2030-BrM3 line through the cerebral lateral ventricles resulted in the H2030-LMD2 cell line, which has high affinity for leptomeningeal metastases and shows extensive perivascular invasion within the brain parenchyma. In vitro, the H2030-LMD2 line shows altered clustering behavior and increased survival when cultured in suspension. RNA-sequencing of this cell line across adherent and suspension culture conditions shows multiple biological processes upregulated in the LMD-tropic line, including chemotaxis, apical junction formation, and TGF-β signaling. Targetable pathways emerging from this analysis will be functionally investigated for their role in promoting progression to LMD, including through validation in the syngeneic KPN1-BrM line which has been selected for its CNS affinity and shows progression to LMD. Spatial sequencing and multiplexed immunofluorescence will furthermore investigate the tumor microenvironment in the perivascular niche and subarachnoid spaces. These findings will be clinically corroborated with molecular characterization of the CSF of patients with leptomeningeal metastases.