CONSORT article: Single-cell sequencing analysis revealed CMKLR1+ macrophage as a subpopulation of macrophage with tumor-suppressive characteristics in oral squamous cell carcinoma.

BACKGROUND

Oral squamous cell carcinoma (OSCC) is an aggressive oral malignancy. Metastasis and postoperative recurrence are major causes of a high mortality of OSCC. The landscape of immune cells in OSCC remained to be comprehensively explored.

METHODS

Tumor tissues of OSCC patients were collected from the Gene Expression Omnibus database, based on which single-cell sequencing analysis was performed to identify subtypes of macrophages and to annotate the subpopulations according to the expression levels of cell marker genes. Functional enrichment analysis was performed to explore the biological processes involved in each cell subcluster. Gene regulatory networks driven by SPECIFIC transcription factors (TFs) were developed applying single-cell regulatory network inference and clustering (SCENIC) analysis. Binding strength between receptors and ligands between different cells was analyzed using cell communication analysis.

RESULTS

A single-cell landscape in OSCC was successfully developed and a total of 11 cell clusters were identified. Specifically, CD163 + macrophages were a crucial type of macrophage with 4 cell subpopulations, namely, SAT1 + macrophages, IDO1 + macrophages, TRIM29 + macrophages, and CMKLR1 + macrophages. IDO1 + macrophages and CMKLR1 + macrophages mainly had the characteristics of M1-type macrophages. CMKLR1 + macrophages fulfilled the function of M1-type macrophages to inhibit OSCC progression. IDO1 + macrophages and CMKLR1 + macrophages were both involved in the activation response of T cells. CMLKR1 + macrophages had a stronger activating effect on T cells. CMKLR1 + macrophages directly regulated the proliferation of epithelial cells and inhibited the progression of OSCC.

CONCLUSION

CMKLR1 + macrophages in OSCC were identified as a crucial cell subpopulation of macrophages in inhibiting tumor progression. Adjusting the infiltration abundance and cell activity of CMKLR1 + macrophages may be a novel therapeutic direction to improve OSCC prognosis.