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Irradiation-Induced Activated Microglia Affect Brain Metastatic Colonization of NSCLC Cells via miR-9/CDH1 Axis
Yu Jin1, Yalin Kang1, Xiaohong Peng1
1Department of Oncology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei Province, People's Republic of China.
Background And Purpose:
Brain metastasis is among the leading causes of death in patients with non-small-cell lung cancer (NSCLC). Through yet unknown mechanisms, prophylactic cranial irradiation (PCI) can significantly decrease the incidence of brain metastases. Given that PCI probably exerts indirect anti-tumoral effects by turning cerebral "soil" unfavorable for the colonization of metastatic tumor "seeds". This study aims to reveal how PCI regulates the brain microenvironment conducing to a reduction in brain metastases.
Materials And Methods:
Key markers of M1/M2 microglia types and mesenchymal-to-epithelial transition (MET) were analyzed by qRT-PCR and Western Blot in vitro. The target miR-9 was obtained by miRNA array analysis and confirmed by qRT-PCR in microglia. We used miRTarBase and TargetScan to analyze the target genes of miR-9 and confirmed by luciferase activity assay. Anti-metastatic effects of irradiation on the brain were evaluated by intravital imaging using a brain metastatic A549-F3 cell line in a nude mouse model.
Results:
Irradiation induced M1 microglia activation, which inhibited the MET process of A549 cell lines. Furthermore, levels of miR-9 secreted by irradiated M1 microglia significantly increased and played a vital role in the inhibition of the A549 MET process by directly targeting CDH1, concurrently decreasing cell capacity for localization in the brain, thus reducing brain metastases.
Conclusion:
We demonstrated that miR-9 secreted by irradiated M1-type microglia played an important role in modulating A549 cell lines into mesenchymal phenotype and further decreased their localization capabilities in the brain. Our findings signify the modulating effect of irradiation on metastatic soil and the cross-talk between tumour cells and the metastatic microenvironment; importantly, they provide new opportunities for effective anti-metastasis therapies, especially for brain metastasis patients.
Insights
Prophylactic cranial irradiation (PCI) activates M1 microglia, which release miR-9. This microRNA inhibits lung cancer cell metastasis to the brain by targeting CDH1 and reducing their ability to colonize.
Area of Science:
- Oncology
- Neuroscience
- Molecular Biology
Background:
- Brain metastasis is a major cause of death in non-small-cell lung cancer (NSCLC) patients.
- Prophylactic cranial irradiation (PCI) reduces brain metastases incidence through unknown mechanisms.
- PCI likely alters the brain microenvironment to prevent tumor cell colonization.
Purpose of the Study:
- To elucidate how PCI regulates the brain microenvironment to reduce brain metastases.
- To identify the molecular mechanisms underlying PCI's anti-metastatic effects in the brain.
Main Methods:
- Analyzed M1/M2 microglia markers and mesenchymal-to-epithelial transition (MET) using qRT-PCR and Western Blot.
- Identified and confirmed miR-9 as a key microRNA involved in microglia response to irradiation.
- Validated miR-9 targets and evaluated anti-metastatic effects in a mouse model using intravital imaging.
Main Results:
- Irradiation promoted M1 microglia activation, inhibiting A549 lung cancer cell MET.
- Irradiated M1 microglia secreted increased levels of miR-9.
- miR-9 directly targeted CDH1, inhibiting A549 cell MET and brain localization, thus reducing brain metastases.
Conclusions:
- Irradiated M1 microglia-secreted miR-9 inhibits lung cancer cell MET and brain colonization.
- PCI modulates the metastatic microenvironment, highlighting the crosstalk between tumor cells and the brain.
- Findings offer novel therapeutic strategies for preventing brain metastasis in NSCLC patients.
