P01.36.B MODELING SPINAL DISSEMINATION IN GLIOBLASTOMA USING POST-MORTEM AND EX VIVO APPROACHES

Abstract BACKGROUND Glioblastoma (GB) is the most aggressive malignant primary brain tumor in adults, characterized by rapid growth and local invasion. Leptomeningeal dissemination occurs in up to 2/3 of cases within two years of diagnosis, with over 90% being diagnosed at the time of progression or recurrence. The clinical presentation can be diverse, ranging from very subtle or asymptomatic to symptomatic in 2% of cases. No known efficient treatment regimen for this condition exists and the prognosis remains poor. Understanding the molecular relationship between the primary tumors and their spinal leptomeningeal metastasis (LM) is critical for facilitating early diagnosis and exploiting new therapeutic strategies. MATERIAL AND METHODS We evaluated a case of methylated temporooccipital GB with radiologically suspect leptomeningeal dissemination, occurring after repeat seizures 14 months post-initial diagnosis and completion of multimodal standard treatment. Radiological follow-up showed marginal signs of progression at the original tumor site. Histological examination and comprehensive molecular profiling with next-generation sequencing of the primary tumor and spinal metastatic nodule were conducted. Subsequently, we cultivated patient-derived tumor cells (PDCs) of the primary tumor ex vivo and performed automated high-throughput drug screening with selected drugs used for treating solid tumors and hematological malignancies. Based on their cytotoxic activity, relative viability based on adenosine triphosphate levels was calculated to suggest the best personalized treatment. In parallel, we also cultivated tumor cells of the LM removed 2 days post-mortem and characterized them in detail. To further investigate the biological behavior of these metastatic cells, we established an in vivo model by injecting them into mice, resulting in a disseminating glioblastoma phenotype. RESULTS Molecular analysis demonstrated a high degree of concordance of copy number variations between primary tumor and the spinal LM. Primary tumor and cell culture of the spinal lesion shared identical IDH-Wildtype status and MGMT promoter methylation pattern, with novel mutations PTCH1 and TP53 detected in the spinal LM cells. Using these cells, we successfully established a disseminating glioblastoma model in a mouse and, importantly, detected metastasis, highlighting a persistent aggressive phenotype. Carfizomib, Lurbinectedin, Panobinostat, Ixazomib, Idasanutlin, Cobimetinib and Trametinib all showed good cytotoxic activity ex- vivo. CONCLUSION Our study highlights that the molecular pathology of spinal LM cells closely mirrors the primary tumor, and the dissemination might occur with some degree of genetic evolution. Novel treatment approaches for this aggressive tumor cell phenotype could include a personalized treatment based on the drug-screening platform results.