1325 Toll-Like Receptor 4 (TLR-4) is a Therapeutically Relevant and Specific Pathway to Leptomeningeal Disease Secondary to Glioblastoma

INTRODUCTION: Glioblastoma (GBM) is a devastating primary brain tumor with a poor prognosis. Leptomeningeal disease (LMD) can occur in up to 20%of GBM cases and contributes to a worse prognosis. There is a significant need to develop targeted therapeutics to mitigate the burden of LMD in GBM and improve outcomes. METHODS: We interrogated the TLR-4 pathway using transcriptomic (RNA-seq) and proteomic datasets, as well as isolated RNA and protein from primary GBM tissue and cerebrospinal fluid (CSF) patients with GBM only, GBM with LMD, and other control patients. To understand its role in mediating GBM LMD, we developed a syngeneic murine LMD model and assessed the effect of TLR-4 antagonism in several relevant in vitro and in vivo models. RESULTS: Tissue mRNA from GBM with LMD versus GBM without LMD from our institution showed significant increase in TLR-4 expression (P=0.020). Single-cell RNA sequencing showed significant increase in TLR-4 and its downstream component expressions in CSF of LMD compared to control non-LMD CSF. Additionally, CSF from GBM LMD patients from our institution showed higher expression levels of TLR-4 and downstream components compared to CSF from LMD of other primary tumors and other neurological conditions. TLR-4 antagonism demonstrated favorable anti-tumor effect in multiple GBM cell lines, and significant increase in overall survival in our GBM LMD murine model (median survival 21 days vs. 15 days, P=0.041). CONCLUSIONS: The TLR-4 pathway is a therapeutically relevant pathway specific to LMD secondary to GBM when compared to LMD of other primary tumors, and other neurologic conditions. TLR-4 antagonism results in anti-cancer effect in vitro and prolonged survival in vivo making it a worthy candidate for further translational study.