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Updated: Jul 5, 2025
Visualization, Quantification, and Mapping of Immune Cell Populations in the Tumor Microenvironment
Published on: March 25, 2020
Spatial and temporal heterogeneity of tumor immune microenvironment between primary tumor and brain metastases in
Jin-Sheng Liu1, Yu-Xiang Cai2, Yong-Ze He1
1Department of Neurosurgery, Zhongnan Hospital of Wuhan University, 430062, Wuhan, China.
Background:
Brain metastasis is a common outcome in non-small cell lung cancer, and despite aggressive treatment, its clinical outcome is still frustrating. In recent years, immunotherapy has been developing rapidly, however, its therapeutic outcomes for primary lung cancer and brain metastases are not the same, suggesting that there may be differences in the immune microenvironment of primary lung cancer and brain metastases, however, we currently know little about these differences.
Methods:
Seventeen paired samples of NSCLC and their brain metastases and 45 other unpaired brain metastases samples were collected for the current study. Immunohistochemical staining was performed on all samples for the following markers: immune checkpoints CTLA-4, PD-1, PD-L1, B7-H3, B7-H4, IDO1, and EphA2; tumor-infiltrating lymphocytes (TILs) CD3, CD4, CD8, and CD20; tumor-associated microglia/macrophages (TAMs) CD68 and CD163; and tumor proliferation index Ki-67. The differences in expression of these markers were compared in 17 paired samples, and the effect of the expression level of these markers on the prognosis of patients was analyzed in lung adenocarcinoma brain metastases samples. Subsequently, multiplex immunofluorescence staining was performed in a typical lung-brain paired sample based on the aforementioned results. The multiplex immunofluorescence staining results revealed the difference in tumor immune microenvironment between primary NSCLC and brain metastases.
Results:
In 17 paired lesions, the infiltration of CTLA-4+ (P = 0.461), PD-1+ (P = 0.106), CD3+ (P = 0.045), CD4+ (P = 0.037), CD8+ (P = 0.008), and CD20+ (P = 0.029) TILs in brain metastases were significantly decreased compared with primary tumors. No statistically significant difference was observed in the CD68 (P = 0.954) and CD163 (P = 0.654) TAM infiltration between primary NSCLC and paired brain metastases. In all the brain metastases lesions, the expression of PD-L1 is related to the time interval of brain metastases in NSCLC. In addition, the Cox proportional hazards regression models showed high expression of B7-H4 (hazard ratio [HR] = 3.276, 95% confidence interval [CI] 1.335-8.041, P = 0.010) and CD68 TAM infiltration (HR = 3.775, 95% CI 1.419-10.044, P = 0.008) were independent prognosis factors for lung adenocarcinoma brain metastases patients.
Conclusions:
Both temporal and spatial heterogeneity is present between the primary tumor and brain metastases of NCSLC. Brain metastases lesions exhibit a more immunosuppressive tumor immune microenvironment. B7-H4 and CD68+ TAMs may have potential therapeutic value for lung adenocarcinoma brain metastases patients.
Insights
Non-small cell lung cancer brain metastases show a more immunosuppressive tumor microenvironment compared to primary tumors. High B7-H4 and CD68+ TAMs indicate poor prognosis, suggesting potential therapeutic targets.
Area of Science:
- Oncology
- Immunology
- Cancer Research
Background:
- Brain metastasis is a frequent and challenging complication of non-small cell lung cancer (NSCLC).
- Despite advancements in immunotherapy, treatment outcomes for primary NSCLC and its brain metastases differ, hinting at distinct tumor immune microenvironments.
- Current understanding of these immune microenvironmental differences remains limited.
Purpose of the Study:
- To investigate the spatial and temporal heterogeneity of the tumor immune microenvironment between primary NSCLC and its corresponding brain metastases.
- To identify potential immune markers associated with prognosis in NSCLC brain metastases.
Main Methods:
- Analysis of 17 paired NSCLC and brain metastasis samples, along with 45 unpaired brain metastases.
- Immunohistochemical staining for immune checkpoints (CTLA-4, PD-1, PD-L1, B7-H3, B7-H4, IDO1, EphA2), tumor-infiltrating lymphocytes (TILs: CD3, CD4, CD8, CD20), tumor-associated macrophages (TAMs: CD68, CD163), and proliferation (Ki-67).
- Comparison of marker expression in paired samples, prognostic analysis in lung adenocarcinoma brain metastases, and multiplex immunofluorescence staining.
Main Results:
- Brain metastases showed significantly decreased infiltration of CD3+, CD4+, CD8+, and CD20+ TILs compared to primary tumors.
- No significant difference in CD68+ and CD163+ TAM infiltration was observed between primary NSCLC and brain metastases.
- High expression of B7-H4 and CD68+ TAMs were identified as independent negative prognostic factors for lung adenocarcinoma brain metastases.
Conclusions:
- NSCLC brain metastases exhibit temporal and spatial heterogeneity, presenting a more immunosuppressive tumor immune microenvironment.
- B7-H4 and CD68+ TAMs represent potential therapeutic targets for improving outcomes in lung adenocarcinoma brain metastases.
