Spatial Location of SPP1⁺TAMs and Mutually Exclusive Subsets Based on Single-Cell and Transcriptome Data

To clarify locations and mutually exclusive subsets of SPP1⁺tumor associated macrophages (SPP1⁺TAMs) in lung adenocarcinoma (LUAD). Analyze the polarization type, mutually exclusive cell subset, and spatial location of SPP1⁺TAMs based on the transcriptome data of the Cancer Genome Atlas (TCGA) and Genotype-Tissue Expression (GTEx) database, single-cell and spatial transcriptome data of the Gene Expression Omnibus database (GEO), immunohistochemical data of the Human Protein Atlas (HPA) database and local LUAD to provide a scientific basis for precision treatment of LUAD. Secreted phosphoprotein-1 (SPP1) was identified as the central regulatory gene of LUAD. The single-cell transcriptome data showed that SPP1 is up-regulated in invasive lung carcinoma (ILC), while macrophage receptor with collagenous structure (MARCO) is up-regulated in adenocarcinoma in situ (AIS). MARCO⁺M2 macrophages and SPP1⁺M2 macrophages clustered in different positions in the uniform manifold approximation and projection (UMAP) to form mutually exclusive cell subsets. SPP1⁺M2 plays a major role in ILC and MARCO⁺M2 plays a major role in AIS. The spatial transcriptome data showed that some SPP1⁺M2 were clustered at the edge of the tumor, and this particular spatial location may increase tumor invasiveness. Further spatial distance analysis showed that the distance was greater from the SPP1⁺M2 to alveolar type 2 epithelial cell (AT2) than from the MARCO⁺M2. Immunohistochemical analysis showed that SPP1 expression was up-regulated in the tumor or ILC group and notably higher in inflammatory cells. In summary, SPP1⁺M2 and MARCO⁺M2 form mutually exclusive cell subsets, and MARCO⁺M2 and SPP1⁺M2 synergistically promote different stages of tumor progression.