The Genetically Engineered Mouse Cell Line Model: A new tool to improve preclinical glioma research
Preclinical research in glioma requires in vivo tumour models. Many researchers rely on murine transplantation models that fail to fully replicate the complexity of human gliomas, particularly the interactions between the tumour and the immune system. The lack of appropriate models has contributed to the failure of new treatments in the clinic.
To address the limitations, I developed a new genetically engineered mouse cell line model, or the GEM-CLeM. Mutations were introduced into an immortalised C57BL/6 eGFP astrocyte cell line to create a genetic profile that mimics human glioma cells. Two key models were characterised: (1) a high-grade glioma model featuring a knockdown of Pten with RAS V12 overexpression (Pten KD + RAS V12), and (2) an IDH1 mutant low-grade glioma model with a P53 knockdown and IDH1R132H overexpression (P53 KD + IDH1R132H). The aim of this study was to characterise the tumours that develop from these transplanted cells. Histological, immunological, and transcriptional analyses were used to evaluate the tumours.
The Pten KD + RAS V12 model exhibited rapid tumour development, with a median survival of 22 days. Histologically, these tumours displayed dense cell packing, significant invasion into surrounding tissue, and signs of microvascular proliferation. In contrast, the P53 KD + IDH1R132H model produced consistently small tumours, which did not lead to significant tumor-related symptoms. These small tumours were well-vascularised and showed notable macrophage infiltration.
Spectral flow cytometry revealed significant tumor-associated macrophage infiltration in both models. The high-grade glioma model showed reduced functional antigen-presenting cells, particularly dendritic cells. This was indicative of an immunologically “cold” tumour microenvironment. Gene set enrichment analysis of RNA-sequencing data confirmed the immune suppressive phenotype and revealed upregulation of invasion, ECM and angiogenic pathways. In contrast, the P53 KD + IDH1R132H tumours contained a more activated anti-tumour response, exemplified by increased presence of monocyte-derived inflammatory dendritic cells. Gene ontology and gene set enrichment analysis confirmed this myeloid-focussed immune infiltration. This model recapitulated phenotypes associated with earlier stages of IDH1 mutant gliomagenesis.
In conclusion, this new immune-competent glioma models effectively recapitulate key phenotypes of human tumours, including appropriate histological features, immune infiltration profiles, and transcriptional signatures. These models provide a valuable tool for studying glioma biology and testing potential therapies in a representative preclinical setting.
