Abstract A039: Characterization of the heterogeneous nature of the peritumoral zone of glioblastomas and its relevance for the clinical progression of the disease
Authors: de Dios Olaya , Ramírez-González María de los Ángeles , Herranz Beatriz , Romero Juan , Ramos Ana , Sepúlveda-Sánchez Juan Manuel , Gargini Ricardo , Hernández-Laín Aurelio , González Pedro , Jiménez-Roldán Luis , García-Posadas Guillermo , Pérez-Núñez Ángel , Sánchez-Gómez Pilar 
Published: November 2024

Abstract
Glioblastoma (GBM) is one of the most aggressive forms of cancer, with a recurrence rate of nearly 100% within 12 months of diagnosis. This is attributable to the persistence of residual tumor cells following surgical resection, which can repopulate the tumor even after the administration of aggressive chemoradiotherapy. These cells are embedded in a specific microenvironment in the peritumoral zone (PTZ), which is formed by their interaction with the brain parenchyma. The PTZ can be classified radiologically into two distinct categories: areas of clear tumor infiltration (non-contrast-enhancing (non-CE) tumor) and areas of vascular edema. Recent data suggest that the extent of surgical resection to non-CE regions may confer substantial benefits to patients with GBM. However, while the tumor core niche has been the subject of extensive study, there is a paucity of knowledge regarding the nature of the PTZ. In this study, we prospectively collected a large cohort of radiologically guided biopsies from GBM patients and performed a comprehensive cellular analysis. To this end, we initially integrated publicly available single-cell RNA sequencing (scRNA-seq) datasets from non-pathogenic human brains and gliomas, resulting in an integrated atlas representing the major cell types: immune (myeloid cells and T cells), astrocytic, oligodendroglial, and vascular. By means of a meticulous multi-stage examination of differentially expressed genes in glioma and cell type-specific markers, we were able to identify several genes that could serve to characterize the cellular content of the biopsies obtained from the tumor core and the periphery, comprising non-CE tumor, edema, and what was deemed "normal" tissue. The application of unsupervised clustering enabled the separation of the most pathogenic samples (including CE and non-CE tumor biopsies) based on the enrichment of proliferative markers and the pronounced absence of normal endothelial and oligodendrocyte expression. The tumorigenic samples were clustered into two main groups: one group that was enriched in astrocytic and proliferative markers and another one that was enriched in myeloid cells. Furthermore, our findings indicate the existence of inter- and intra-tumor heterogeneity in the cellular composition of the PTZ in GBM, with observed differences associated with the degree of tumor infiltration, but also patient age and gender. In particular, a distinct pathological pattern was discerned in select edema and normal biopsies from multiple patients, particularly those of an advanced age. Moreover, several markers of neural and immune cells associated with a favorable prognosis were identified, though only when expressed in the periphery. In conclusion, our study offers a comprehensive scRNA-seq resource for investigating the involvement of diverse cell types in the pathobiology of GBM. Additionally, it highlights the heterogeneous nature of the glioma periphery, which could explain the gender and age-related prognostic differences that have been observed among patients with GBM.
Citation Format: Olaya de Dios, María de los Ángeles Ramírez-González, Beatriz Herranz, Juan Romero, Ana Ramos, Juan Manuel Sepúlveda-Sánchez, Ricardo Gargini, Aurelio Hernández-Laín, Pedro González, Luis Jiménez-Roldán, Guillermo García-Posadas, Ángel Pérez-Núñez, Pilar Sánchez-Gómez. Characterization of the heterogeneous nature of the peritumoral zone of glioblastomas and its relevance for the clinical progression of the disease [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Tumor-body Interactions: The Roles of Micro- and Macroenvironment in Cancer; 2024 Nov 17-20; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2024;84(22_Suppl):Abstract nr A039.