Abstract 10: Orthotopic nGEM glioma growth rates in allogenic hosts associate with hypoxia and proximity to host cells
Authors: Baker Angela S. 
Published: April 2023

Abstract
Genomic profiling of glioblastoma uncovers fundamental differences in the driver events of malignant transformation and progression, yet the nuances driving the particular growth rate of glioblastoma in individual patients remain poorly defined. We exploited the availability of fourteen histocompatibility-matched mouse hosts from the collaborative cross (CC) [PMID: 15514660] as hosts for a non-germline, engineered model of murine glioblastoma [PMCID: PMC4210043] to interrogate cell types, functional states and proximity in situ in tumors with varying growth rates. Specifically, Kaplan-Meier survival data was used to determine the rates of Nf1:TP53 null tumor growth in different cc host groups. Spatial transcriptomics and single nucleus RNA seq (sn-seq) analyses were conducted in tumor-bearing brain tissue from C57Bl/6 (syngeneic) and 2 CC histocompatible allogeneic mouse strains with differential survival outcomes. Spatial analysis was conducted using a disease-focused multiplexed mRNA probe set assembled from annotations of GBM/glioma specific genes reported in the literature. Cell segmentation of the data was performed to investigate the spatial pattern of single-cell level expression. The spatial transcriptomic dataset was also analyzed with a segmentation-free pipeline. In addition, to detect cell clusters, the probability of genes detected in close proximity (genes within a cell 5px radius [0.5 um]) was determined using Pdgfra as the tumor marker (anchor). We identified differential levels of spatially correlated expression of cell clusters expressing hypoxia markers such as HIF-1a and PDK1 between hosts with fast and slow growing tumors. Tumors from the 3 hosts were also processed for sn-seq. Integrated analysis of cell clustering was used to determine differences in clusters between the fast growing and slow growing groups. Enrichment of expression of Top2a, a gene associated with proliferation and poor prognosis in glioma, was detected in a unique cluster of cells in the slow-growing tumor when compared to the fast-growing group. This suggests that the host microenvironment may play a role in influencing the decelerated growth of this tumor. These results support the utility of spatial transcriptomics and sn-seq in understanding how differences in tumor:host cell interactions contribute to tumor growth. Future opportunities enabled by histocompatible allogeneic hosts for GEM and nGEM glioma models include unraveling host effects on drug sensitivity, tumor heterogeneity, molecular plasticity, angiogenesis, invasion, and lymphoid and myeloid microenvironmental dependencies, each with profound opportunities for clinical translation.
Citation Format: Angela S. Baker. Orthotopic nGEM glioma growth rates in allogenic hosts associate with hypoxia and proximity to host cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 10.