Abstract Pediatric-type high-grade gliomas (HGGs) are aggressive brain tumors characterized by rapid growth, infiltrative behavior, and significant therapy resistance. One major challenge in treating HGGs involves the interplay of tumor cells to their microenvironment; allowing for creation of the blood-tumor barrier (BTB). Our studies combined histologic and transcriptomic evaluations of immune-deficient rodent injected with H3K27M mutant pediatric-type glioma cells. Multiplex staining provided temporospatial analysis of known cellular markers involved in BBB formation, including known pericyte, tight-junction, and immune markers. Regions of interest were classified as tumor core, peritumor (+250µM), or distal (250µM). Analysis was conducted with the use of QuPath and cell segmentation performed using Mesmer, with expression proportions quantified for each cell/protein marker. Utilization of vessel isolation and nuclei extraction for sc-RNAseq (VINE-seq) explored the molecular landscape of vasculature within the tumor microenvironment. All rodent models were untreated, evaluated early to late post-intracranial injection (D20-50). Preliminary results revealed elevated endothelial tight junctions within distal regions compared to the core (p 0.0001), demonstrating an intact BTB furthest from tumor bulk. Within the tumor core, high Iba1+ macrophage (46%) and low neuronal (1%) expression was present (p 0.0001), while highest localized expression of glioma cells, and PDGFRβ+ pericytes were present among intratumoral core vasculature; all at late disease progression (p 0.0001). Initial VINE-seq studies identified varied cell-types in early disease models and ongoing studies will identify regional and temporal expression changes. These findings offer cellular and molecular HGG microenvironment changes over time; which underscores the importance of neuronal-immune interactions related to the restrictive BTB. Future studies are aimed at identifying genomic and proteomic expression patterns, to gain a better understanding of pediatric-type HGG progression for predictions of improved treatment timing.
Mills et al. (Fri,) studied this question.