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The PD-1/B7-H1 pathway modulates the natural killer cells versus mouse glioma stem cells
Bo Yuan Huang1, Yi Ping Zhan1, Wen Jing Zong2
1Department of Neurosurgery, Beijing San Bo Brain Hospital, Capital Medical University, Beijing, China.
Purpose:
Glioblastoma multiforme (GBM) is the most malignant primary type of brain tumor in adults. There has been increased focus on the immunotherapies to treat GBM patients, the therapeutic value of natural killer (NK) cells is still unknown. Programmed death-1 (PD-1) is a major immunological checkpoint that can negatively regulate the T-cell-mediated immune response. We tested the combination of the inhibiting the PD-1/B7H1 pathway with a NK-cell mediated immune response in an orthotopic mouse model of GBM.
Methods And Materials:
Mouse glioma stem cells (GL261GSCs) and mouse NK cells were isolated and identified. A lactate dehydrogenase (LDH) assay was perfomed to detect the cytotoxicity of NK cells against GL261GSCs. GL261GSCs were intracranially implanted into mice, and the mice were stratified into 3 treatment groups: 1) control, 2) NK cells treatment, and 3) PD-1 inhibited NK cells treatment group. Overall survival was quantified, and animal magnetic resonance imaging (MRI) was performed to determine tumor growth. The brains were harvested after the mice were euthanized, and immunohistochemistry against CD45 and PCNA was performed.
Results:
The mouse NK cells were identified as 90% CD3- NK1.1+CD335+ by flow cytometric analysis. In the LDH assay, the ratios of the damaged GL261GSCs, with the E:T ratios of 2.5:1, 5:1, and 10:1, were as follows: 1) non-inhibited group: 7.42%, 11.31%, and 15.1%, 2) B7H1 inhibited group: 14.75%, 18.25% and 29.1%, 3) PD-1 inhibited group: 15.53%, 19.21% and 29.93%, 4) double inhibited group: 33.24%, 42.86% and 54.91%. In the in vivo experiments, the mice in the PD-1 inhibited NK cells treatment group and IL-2-stimulated-NK cells treatment group displayed a slowest tumor growth (F = 308.5, P<0.01) and a slower tumor growth compared with control group (F = 118.9, P<0.01), respectively. The median survival of the mice in the three groups were as follows: 1) conrol group: 29 days, 2) NK cells treatment group: 35 days (P = 0.0012), 3) PD-1 inhibited NK cells treatment group: 44 days (P = 0.0024). Immunologic data of PCNA-positive cell ratios and CD45-positive cell ratios of the tumor specimens in the three groups were as follows: 1) control group: 65.72% (PCNA) and 0.92% (CD45), 2) NK treatment group: 27.66% (PCNA) and 13.46% (CD45), and 3) PD-1 inhibited NK cells treatment group: 13.66% (PCNA) and 23.66% (CD45) (P<0.001).
Conclusion:
The results demonstrated that blockade of PD-1/B7H1 pathway could promote mouse NK cells to kill the GL261GSCs, and the PD-1-inhibited NK cells could be a feasible immune therapeutic approach against GBM.
Insights
Blocking the programmed death-1 (PD-1)/B7H1 pathway enhances natural killer (NK) cells to target glioblastoma multiforme (GBM). This PD-1 inhibited NK cell therapy shows promise for treating this aggressive brain cancer.
Area of Science:
- Immunology
- Oncology
- Neuroscience
Background:
- Glioblastoma multiforme (GBM) is a highly aggressive primary brain tumor in adults.
- Immunotherapies are increasingly explored for GBM, but the role of natural killer (NK) cells remains unclear.
- Programmed death-1 (PD-1) is a key immune checkpoint inhibiting T-cell responses.
Purpose of the Study:
- To investigate the efficacy of combining PD-1/B7H1 pathway inhibition with NK cell immunotherapy in an orthotopic GBM mouse model.
- To evaluate the impact of PD-1 blockade on NK cell-mediated cytotoxicity against glioma stem cells.
Main Methods:
- Isolated and identified mouse glioma stem cells (GL261GSCs) and NK cells.
- Assessed NK cell cytotoxicity against GL261GSCs using a lactate dehydrogenase (LDH) assay.
- Administered control, NK cells, or PD-1 inhibited NK cells to mice with intracranial GL261GSC tumors.
- Monitored tumor growth via MRI and quantified overall survival.
- Analyzed tumor tissues for CD45 and PCNA expression.
Main Results:
- PD-1/B7H1 inhibition significantly enhanced NK cell cytotoxicity against GL261GSCs in vitro.
- Mice treated with PD-1 inhibited NK cells exhibited significantly slower tumor growth and prolonged median survival (44 days) compared to control (29 days) and NK cell groups (35 days).
- Immunohistochemistry revealed reduced PCNA-positive cells and increased CD45-positive cells in tumors treated with PD-1 inhibited NK cells, indicating decreased proliferation and increased immune infiltration.
Conclusions:
- Blockade of the PD-1/B7H1 pathway potentiates NK cell activity against GBM.
- PD-1 inhibited NK cells represent a viable immunotherapeutic strategy for GBM treatment.
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