Decoding the Prognosis-Related S100A9^high Monocyte in Glioblastoma Using Single-Cell and Spatial Transcriptome...

Monocytes and macrophages are recognized as predominant immune populations in human glioblastoma, where they play vital roles in tumor progression. Despite their established significance, the heterogeneity of these cells-particularly within the monocyte compartment-remains incompletely characterized.

We comprehensively used scRNA-seq, spatial transcriptome sequencing combined with immunofluorescence and T cell co-culture assays to illuminate the heterogeneity and function of monocyte in glioblastoma.

In this study, from the perspective of ligand-receptor networks, we have identified and characterized three distinct glioblastoma subtypes. Single-cell RNA-seq analysis further revealed that the C3 subtype with bad prognosis exhibited a higher proportion of S100A9^high monocytes. Spatial transcriptomics combined with immunofluorescence assays demonstrated that these S100A9^high monocytes were spatially adjacent to M2 macrophages, exhausted CD8+ T cells, and endothelial cells. In vitro T cell co-culture assays revealed S100A9^high monocyte produced elevated levels of the immunosuppressive cytokine IL-10, reactive oxygen species (ROS) and inducible nitric oxide synthase (iNOS), all of which might impair T cell function and immune response. Notably, elevated abundance of S100A9^high monocyte correlated with poor patient prognosis.

In summary, our results deciphered the heterogeneity of monocytes in glioblastoma and identified a novel poor prognosis-associated monocyte subset, S100A9^high monocytes, which foster an immunosuppressive, pro-tumorigenic microenvironment.