P02.19.B NEW MURINE MODEL OF GLIOBLASTOMA SHOWS SUPPRESSIVE IMMUNE INFILTRATION
Creators: name: Forsythe, DR
name: Burn, OK
name: Small, SJ
name: Hermans, IF
name: McConnell, Melanie-Jane
Publisher: name: Open Access Te Herenga Waka-Victoria University of Wellington
Year: 2025
Subjects: classificationCode: 32
subject: Biomedical and clinical sciences
classificationCode: 3204
subject: Immunology
subject: FOS: Clinical medicine
classificationCode: 3211
subject: Oncology and carcinogenesis

description: Abstract
 
 BACKGROUND
 Glioblastoma (GBM) research urgently requires a new murine model for preclinical research. The highly used cell line, GL261, reliably forms glioma-like tumours when transplanted intracranially, yet these tumours do not recapitulate human GBM, particularly when applied as a model for immune therapy. The tumour immune microenvironment (TIME) of a GL261 tumour consistently responds to immune checkpoint inhibitors, such as αPD-1 and αCTLA-4, which have shown no significance in multiple clinical trials.
 
 
 MATERIAL AND METHODS
 We have developed a novel murine model of GBM which has been designed to address the shortcomings of GL261. Into an immortalised eGFP astrocyte C57BL/6 cell line mutations were introduced to create genetic profile similar to human GBM cells. One version of these astrocytes models a classical GBM cell, with a Pten knockdown and RAS V12 stable transfection. Pten/RAS V12 and GL261 cells were separately transplanted intracranially into C57BL/6 mice and developed for either two weeks (spectral flowcytometry) or until ethical endpoint (survival and histological analysis).
 
 
 RESULTS
 Intracranial tumours reliably formed in both GL261 and Pten/RAS V12 models, with median survivals of 19.50 and 20.00 days, respectively. However, key histological differences were seen in H&amp;E sections. The GL261 tumours were highly vascularised and showed clear borders with the healthy tissue. The Pten/RAS V12 tumours had very densely packed cell mass with more invasion into the surrounding tissue. Spectral flow cytometry indicated that macrophages and monocytes contributed predominately to the tumour immune infiltration of both models. Despite similar abundance of these cells, key inflammatory markers showed significant differences. The GL261 tumours myeloid compartment was largely comprised of classical monocytes (cMo). While the populations were heterogeneous, these cMo cells were characterised by high expression of Ly6C and MHCII, both markers associated with a proinflammatory, anti-tumour responses. Conversely, Pten/RAS V12 tumours showed significantly less of Ly6C+ MHCII+ cells, indicative of an immune suppressive environment comprised of anti-inflammatory TAMs and non-classical monocytes (ncMo). Additionally, GL261 tumours contained higher numbers of dendritic cells suggesting increased antigen presentation and greater potential for anti-tumour immune responses. Higher PDL1 expression was seen on infiltrating leukocytes in GL261 tumours, consistent with literature on GL261 demonstrating response to PD1 inhibitors. However, Pten/RAS V12 tumours showed minimal expression of PDL1, consistent with poor responses in GBM patients to immune checkpoint inhibitors.
 
 
 CONCLUSION
 Together, these data indicate that this novel model will be a more appropriate tool for GBM research to help understand how to better implement immune therapy.