Csig-24. Cancer Cell Intrinsic Immune Signaling Mediates Leptomeningeal Metastasis

Leptomeningeal metastasis (LM) is an aggressive and advanced stage of cancer in which cancer cells disseminate to the leptomeninges surrounding the central nervous system (CNS). The leptomeninges, filled with cerebrospinal fluid (CSF), are a hypoxic, nutrient-deprived environment, which is marked by profound inflammatory changes in LM. Despite this hostile environment, certain cancer cells thrive, ultimately leading to neurological deficits and death in patients. To investigate signaling pathways specific to LM-associated cancer cells, we analyzed multiple patient-derived single-cell RNA sequencing datasets. By comparing LM-positive and LM-negative patients, we find robust immune responses in LM. This is mirrored in single-cell transcriptomic analysis of LM mouse models. We identified two distinct clusters of LM tumor cells, annotated as proliferative and non-proliferative cancer cells. Interestingly, we found that proliferative cancer cells cluster exhibited significant enrichment of immune response-related gene signatures compared to non-proliferative cancer cells. Furthermore, bulk RNA sequencing of LM-derived cancer cell lines revealed upregulation of immune-related gene signatures compared to their parental cell lines. Functional validation using CRISPR-Cas9-mediated knockout of NFΚB p65 (Rela), a key immune signaling molecule, demonstrated markedly reduced leptomeningeal growth and significantly improved survival in mouse models implanted with the knockout cells. Collectively, our findings suggest that intrinsic immune signaling within cancer cells enables cancer cells to flourish within the inflammatory milieu of the leptomeningeal space. Moreover, it suggests novel therapeutic targets to arrest cancer growth in the space.