P01.04.b Transcriptomics of Peripheral and Core Areas of Glioblastoma Reveals Cntn2 as a Potential Therapeutic Target

BACKGROUND Glioblastoma (GB) is an aggressive brain tumor with inevitable recurrence due to the persistence of infiltrative cells in the peritumoral brain. These cells, located in the non-enhancing but FLAIR-hyperintense periphery, are not routinely sampled or molecularly profiled, leaving a gap in our understanding of GB recurrence mechanisms and potential therapeutic targets. METHODS We performed MRI-guided surgical sampling of both the tumor core and periphery in 10 patients with IDH-wildtype GB. Bulk RNA sequencing was conducted on paired samples. To distinguish infiltrated from normal-like peripheral tissues, we developed a 500-gene “tumor-enriched” signature by comparing bulk transcriptomic data from TCGA-GBM (tumor) and GTEx (normal cortex) cohorts. This signature, enriched for cell cycle, DNA replication, and mitosis-related genes, was validated using the Ivy Glioblastoma Atlas dataset. We applied this classifier to our dataset, identifying tumor-enriched and normal-like profiles. Differential expression and gene set enrichment analyses were then performed, and findings were supported by external spatial and single-cell datasets. Functional relevance was assessed through in vitro invasion assays. RESULTS Peripheral samples classified as tumor-enriched showed upregulation of genes involved in invasion, including Rho GTPase signaling and ECM degradation. Gene expression profiles suggested a shift toward an OPC-like phenotype with lower proliferative and higher invasive potential. Among nine underexplored invasion-associated genes, Contactin 2 (CNTN2) emerged as a key candidate. CNTN2 expression was confirmed in the tumor periphery via spatial transcriptomics and immunohistochemistry. Knockdown in 3D tumor models reduced invasiveness. CNTN2-positive cells were enriched in OPC/NPC-like populations and overexpressed in recurrent GB. High CNTN2 levels correlated with shorter survival in two independent GB cohorts (TCGA and Rembrandt et al). CONCLUSION CNTN2 is a promising therapeutic target linked to GB infiltration, recurrence, and poor prognosis. Targeting CNTN2 may help limit tumor invasion beyond the resection margins and represents a potential strategy to improve GB outcomes by focusing on invasive rather than proliferative tumor properties.