Os05.2.a Deciphering the Longitudinal Trajectories of Glioblastoma Ecosystems by Integrative Single-Cell Genomics

Abstract BACKGROUND The mechanisms governing the progression of IDH-wildtype glioblastoma (GBM) following standard-of-care therapy remain incompletely understood. While recurrence is nearly universal, the cellular and molecular trajectories that underpin this process - particularly the dynamics of tumor and microenvironmental compartments - have yet to be fully resolved. MATERIAL AND METHODS To dissect the longitudinal evolution of the GBM ecosystem, we analyzed paired primary and recurrent tumor specimens from 59 patients. We employed single-nucleus RNA sequencing to profile transcriptomic states at single-cell resolution and integrated these data with bulk DNA sequencing to assess genomic alterations. This approach enabled a comprehensive interrogation of cellular heterogeneity and malignant state transitions over time. RESULTS Across the cohort, the most consistent feature at recurrence was a decreased proportion of malignant cells, accompanied by a reciprocal expansion of non-malignant glial and neuronal cell populations within the tumor microenvironment (TME). While the dominant malignant cell state often differed between primary and recurrent samples, no state was uniquely associated with a specific disease stage. Moreover, no singular evolutionary trajectory characterized the cohort as a whole. Instead, subsets of patients exhibited enriched and partially convergent state transitions. Notably, shifts in malignant cell states were mirrored by concurrent remodeling of the TME, implicating a tightly interwoven pattern of tumor-microenvironment co-evolution. CONCLUSION These findings reveal diverse and patient-specific evolutionary trajectories in IDH-wildtype GBM, shaped by both therapeutic pressure and microenvironmental context. Our study provides a reference framework for understanding longitudinal GBM dynamics and highlights the importance of ecosystem-level interactions in driving recurrence.