Research Targeting Glucocorticoid Receptor-CCR8 Axis Mediated Bone Marrow T Cell Sequestration to Enhance Anti-tumor T Cell Infiltration in Intracranial Cancer

Background

Brain tumors, especially glioblastomas (GBMs), show significant resistance to immune checkpoint blockade therapy, partly due to limited T cell infiltration into tumors. GBMs account for 50% of adult primary malignant brain tumors, with patients having an average survival time of less than 15 months and a recurrence rate exceeding 90%. Studies have shown that GBM patients have reduced systemic T cell numbers and function, making these tumors respond poorly to immune checkpoint inhibition therapy. Additionally, many T cells are sequestered in the bone marrow of cancer patients, accompanied by tumor-induced disappearance of sphingosine 1 phosphate receptor 1 (S1P1) on T cell surfaces.

Research Source

This study was conducted by Soochow University, The Third Affiliated Hospital of Soochow University, State Key Laboratory of Radiation Medicine and Protection, in collaboration with the University of Rome “Tor Vergata” in Italy. The main authors include Jia Zhang, Yuzhu Shi, Xiaotong Xue, et al., and it was published in “Cellular & Molecular Immunology” in June 2024.

Research Process

Workflow:

1. Experimental Model Establishment: The study established a mouse glioma model by injecting GL261 glioma cells into the brains of C57BL/6 mice. Additionally, AT3 breast cancer cells were injected into the brains of C57BL/6 mice to study the specificity of tumor type effects on the thymus and spleen.
2. T Cell Sequestration Assessment: Flow cytometry analysis and quantification of thymocytes and T cells in the thymus, spleen, and bone marrow (BM) were used to evaluate the impact of tumors on systemic immune suppression.
3. Glucocorticoid Action: Adrenalectomy (ADX) and treatment with the 11beta-hydroxysteroid dehydrogenase inhibitor Metyrapone were used to study the role of glucocorticoids (GC) in T cell redistribution. Glucocorticoid receptor (GR) antagonists RU486 and AL 082D06 were used to assess the mechanism of GC-induced T cell sequestration through GR.
4. GR Action Pathway Study: T cell-specific GR conditional knockout mouse models (GR CKO mice) and CCL1/CCR8 blockade experiments using the chemical inducer antagonist R243 further validated the role of the GR-CCR8 axis in T cell redistribution and anti-tumor immunity.

Detailed Experimental Methods:

1. Modeling and Cell Injection: Under anesthesia, tumor cells were injected into mouse brains using a stereotaxic apparatus, 2mm above the median ridge and 4mm below the skull surface, with 1x10^4 GL261 or AT3 cells injected each time.
2. Bone Marrow and Spleen Cell Analysis: Flow cytometry was used to analyze immune cells in mouse thymus, spleen, and BM, mainly including the number and function of T cells, B cells, monocytes, macrophages, and neutrophils.
3. Drug Treatment: Metyrapone was used to inhibit 11beta-hydroxysteroid dehydrogenase activity, added to drinking water at 800 μg/ml starting one day before tumor transplantation. RU486 and AL 082D06 were used as GR antagonists, injected intraperitoneally at 5mg/kg every two days, starting after tumor transplantation.

Research Results:

1. Systemic Immune Suppression Effect: Mice injected with GL261 and AT3 cells showed thymus and spleen contraction and significant T cell reduction, indicating tumor-induced systemic immune suppression. Notably, a significant increase in CD4+ and CD8+ T cells was observed in the bone marrow, suggesting tumor-induced T cell sequestration.
2. Glucocorticoid-Mediated T Cell Redistribution: Brain tumor mice showed significantly elevated plasma glucocorticoid levels. In adrenalectomized mice, T cells no longer decreased in the spleen or accumulated in the bone marrow, while tumor growth was inhibited and T cell infiltration in tumors increased.
3. Importance of GR Signaling Pathway: T cell-specific GR knockout mice showed no increase in bone marrow T cells after tumor injection, while infiltrating T cells in tumors increased, significantly improving anti-tumor immune responses.
4. Role of CCR8 in T Cell Sequestration: The study found that CCL1 and CCL8 expression was significantly increased in the bone marrow during tumor progression and was inhibited by the chemical inducer R243, which blocked tumor-induced T cell sequestration and tumor growth.

Conclusions and Value

1. Scientific Value: The study reveals the key role of the glucocorticoid-CCR8 axis in bone marrow T cell sequestration and anti-tumor immunity, providing important clues for a deeper understanding of brain tumor immune evasion mechanisms.
2. Application Value: This discovery provides new ideas for immunotherapies targeting the glucocorticoid receptor and CCR8, potentially enhancing anti-brain tumor responses by preventing T cell bone marrow sequestration.