scRNA‐seq and proteomics reveal the distinction of M2‐like macrophages between primary and recurrent malignant glioma and its critical role in the recurrence

AIMS: Tumor‐associated macrophages (TAMs) in the immune microenvironment play an important role in the increased drug resistance and recurrence of malignant glioma, but the mechanism remains incompletely inventoried. The focus of this study was to investigate the distinctions of M2‐like TAMs in the immune microenvironment between primary and recurrent malignant glioma and its influence in the recurrence. METHODS: We employed single‐cell RNA sequencing to construct a single‐cell atlas for a total of 23,010 individual cells from 6 patients with primary or recurrent malignant glioma and identified 5 cell types, including TAMs and malignant cells. Immunohistochemical techniques and proteomics analysis were performed to investigate the role of intercellular interaction between malignant cells and TAMs in the recurrence of malignant glioma. RESULTS: Six subgroups of TAMs were annotated and M2‐like TAMs were found to increase in recurrent malignant glioma significantly. A pseudotime trajectory and a dynamic gene expression profiling during the recurrence of malignant glioma were reconstructed. Up‐regulation of several cancer pathways and intercellular interaction‐related genes are associated with the recurrence of malignant glioma. Moreover, the M2‐like TAMs can activate the PI3K/Akt/HIF‐1α/CA9 pathway in the malignant glioma cells via SPP1‐CD44‐mediated intercellular interaction. Interestingly, high expression of CA9 can trigger the immunosuppressive response in the malignant glioma, thus promoting the degree of malignancy and drug resistance. CONCLUSION: Our study uncovers the distinction of M2‐like TAMs between primary and recurrent glioma, which offers unparalleled insights into the immune microenvironment of primary and recurrent malignant glioma.