Modeling Principle

The Mouse GL261 Model is a syngeneic xenograft tumor model established by subcutaneous or orthotopic intracranial inoculation of the GL261 mouse glioma cell line into immunocompetent C57BL/6 mice, serving as the most widely applied standardized in-vivo model in glioma immunotherapy, tumor immune microenvironment, immune checkpoint blockade (anti-PD-1/PD-L1, anti-CTLA-4), CAR-T/tumor vaccine, radio-immunotherapy combination and tumor immunopharmacology research. The GL261 cell line is derived from methylcholanthrene (MCA) chemically induced glioblastoma in C57BL/6 mice, carrying characteristic mutations including K-Ras and p53, and shares partial similarity with human glioblastoma in molecular features and immune infiltration phenotypes. Its core advantage lies in the immunocompetent background—GL261 and C57BL/6 mice are of syngeneic origin, so transplanted cells are not rejected by the immune system, and tumors grow within a complete immune microenvironment (T cells, NK cells, macrophages, dendritic cells, myeloid-derived suppressor cells, etc.), faithfully recapitulating the immunosuppressive microenvironment and immune evasion mechanisms of human glioma—a key function unachievable in immunodeficient mouse models such as U87MG and LN229. After orthotopic intracranial inoculation, tumors grow invasively within the brain parenchyma, forming poorly demarcated, highly infiltrative malignant glioma accompanied by intracranial hypertension, neurological deficits and eventual death, enabling stable survival evaluation. The subcutaneous model facilitates tumor measurement and administration, suitable for efficacy screening. The GL261 model is widely applied in pharmacodynamic evaluation of immune checkpoint inhibitors, analysis of immune cell infiltration in tumor microenvironment, optimization of combination strategies (radiotherapy+immunotherapy, chemotherapy+immunotherapy), and development of tumor vaccines and cell therapies, serving as the in-vivo gold-standard model for glioma translational research under immunocompetent background.

Model Validation Criteria

Quantitative Criteria for Tumor Formation and Growth

1. Tumor take rate: subcutaneous model achieves ≥90% take rate within 2–3 weeks after inoculation (tumor volume >50 mm³ judged as successful tumor formation), orthotopic model confirmed by pathological evidence of intracranial tumor; 2. Tumor growth: vehicle control group shows stable, sustained and reproducible growth, with average tumor volume reaching 500–1200 mm³ at weeks 3–4 after inoculation; 3. Inter-group consistency: coefficient of variation (CV) of tumor volume in vehicle control group <30%, confirming excellent inoculation operation and model reproducibility; 4. Immune system validation: anti-PD-1 positive control group or TMZ positive control group achieves TGI ≥40% or significantly prolonged median survival (P<0.05), confirming sensitive and effective efficacy/immune evaluation system, and the model is judged successfully established for stable efficacy and immune evaluation.

Histopathological and Immune Microenvironment Gold-Standard Indexes

1. HE staining: orthotopic xenografts present high cellular density, nuclear atypia, microvascular proliferation, pseudopalisading necrosis and invasive growth within brain parenchyma; 2. Ki-67 proliferation index: Ki-67 positive rate of treatment group significantly decreased compared with vehicle group (P<0.05), indicating proliferation suppression; 3. TUNEL apoptosis: significantly increased apoptotic cells in treatment group, confirming pro-apoptotic effect; 4. Immune microenvironment: immunotherapeutic group shows significantly increased intratumoral CD8⁺ T cell infiltration, decreased FoxP3⁺ regulatory T cell proportion and elevated CD8/Treg ratio, indicating activated antitumor immunity; 5. Molecular indexes: down-regulation of PD-L1 expression and proliferation/invasion-related proteins and up-regulation of apoptotic proteins in treatment group, cross-validated with flow cytometry and in-vitro mechanism results, confirming closed-loop efficacy and immune mechanism.

Academic Evidence for Model Validity

Core validation evidence for GL261 model: ① immunocompetent C57BL/6 mice successfully tolerate syngeneic GL261 transplantation with high take rate and stable tumor phenotype; ② syngeneic immune background preserves a complete tumor immune microenvironment, enabling evaluation of immunotherapy mechanisms including immune checkpoints and T cell responses—a core function irreplaceable by immunodeficient xenograft models; ③ orthotopic xenograft histology and immune infiltration features share partial similarity with human GBM; ④ reproducible tumor growth with controllable individual variation meeting pharmacodynamic and survival statistical requirements; ⑤ positive immune/chemotherapy control system validated effective, confirming model sensitivity to intervention. Combined verification of above indexes confirms model reliability and reproducibility, serving as the gold-standard model carrier for in-vivo glioma efficacy and immune mechanism research under immunocompetent background.

Model Advantages

The GL261 model is the most widely applied glioma in-vivo model under immunocompetent background. Its core advantage lies in the complete immune microenvironment—syngeneic transplantation preserves full-spectrum immune cells including T cells, NK cells, macrophages and MDSC, enabling authentic evaluation of immunotherapeutic strategies such as immune checkpoint blockade, CAR-T and tumor vaccines, a key function unachievable in immunodeficient models such as U87MG and LN229. The orthotopic intracranial model closely mimics the anatomical location and immune infiltration features of human glioma, enabling stable survival evaluation. GL261 features mature cell culture, high take rate, rapid growth and short experimental cycle. Multi-dimensional evaluation including immune microenvironment flow cytometry, immunohistochemistry, survival analysis and imaging monitoring is supported. Complete detection system (tumor growth + survival + immune microenvironment + pathology + molecular mechanism + toxicological safety) forms closed-loop evidence chain, and results are readily accepted by neuro-oncology and tumor immunology SCI journals, suitable for NSFC projects, postgraduate dissertations and research proposals.

Research Applications

The Mouse GL261 Model is mainly applied to evaluate in-vivo antitumor efficacy and immune activation effects of immune checkpoint inhibitors (anti-PD-1/PD-L1, anti-CTLA-4), CAR-T cell therapy, tumor vaccines, oncolytic viruses and radio/chemo-immunotherapy combination strategies; to dissect glioma immunosuppressive microenvironment, immune evasion mechanisms and T cell response regulatory networks; to analyze immune cell infiltration in tumor microenvironment (TILs flow cytometry, immunohistochemistry) and dynamically monitor immune-related cytokines and chemokines; to optimize combination treatment strategies and translational medical validation. It extensively serves basic and clinical translational research on glioma immunotherapy, tumor immunology new drug development, NSFC projects, postgraduate dissertations and SCI manuscript methodology construction, acting as the most widely applied standardized in-vivo gold-standard model in glioma immunotherapy research under immunocompetent background.

GL261 mouse syngeneic glioma model, C57BL/6 intracranial glioma model, immunocompetent tumor microenvironment, glioma immunotherapy, immune checkpoint blockade, orthotopic brain glioma, survival analysis, tumor immunopharmacology