Tumor-associated macrophage subtypes on cancer immunity along with prognostic analysis and SPP1-mediated interactions between tumor cells and macrophages

Tumor-associated macrophages (TAM) subtypes have been shown to impact cancer prognosis and resistance to immunotherapy. However, there is still a lack of systematic investigation into their molecular characteristics and clinical relevance in different cancer types. Single-cell RNA sequencing data from three different tumor types were used to cluster and type macrophages. Functional analysis and communication of TAM subpopulations were performed by Gene Ontology-Biological Process and CellChat respectively. Differential expression of characteristic genes in subpopulations was calculated using zscore as well as edgeR and Wilcoxon rank sum tests, and subsequently gene enrichment analysis of characteristic genes and anti-PD-1 resistance was performed by the REACTOME database. We revealed the heterogeneity of TAM, and identified eleven subtypes and their impact on prognosis. These subtypes expressed different molecular functions respectively, such as being involved in T cell activation, apoptosis and differentiation, or regulating viral bioprocesses or responses to viruses. The SPP1 pathway was identified as a critical mediator of communication between TAM subpopulations, as well as between TAM and epithelial cells. Macrophages with high expression of SPP1 resulted in poorer survival. By in vitro study, we showed SPP1 mediated the interactions between TAM clusters and between TAM and tumor cells. SPP1 promoted the tumor-promoting ability of TAM, and increased PDL1 expression and stemness of tumor cells. Inhibition of SPP1 attenuated N-cadherin and beta-catenin expression and the activation of AKT and STAT3 pathway in tumor cells. Additionally, we found that several subpopulations could decrease the sensitivity of anti-PD-1 therapy in melanoma. SPP1 signal was a critical pathway of communication between macrophage subtypes. Some specific macrophage subtypes were associated with immunotherapy resistance and prognosis in some cancer types. Macrophages are natural immune cell-specialized, phagocytic cells, and many studies have been conducted to analyze the functional role of macrophages, but integrating macrophages from multiple cancers to analyze the molecular functions and interactions of macrophages is poorly known.We clustered and typed macrophages using single-cell RNA sequencing data from three different tumor types. Gene Ontology-Biological Processes and Cell Chat were used for functional analysis and communication of TAM subpopulations, respectively. We found heterogeneity of TAM and identified 11 subtypes and their impact on prognosis.The SPP1 pathway is recognized as a key mediator of communication between TAM subpopulations as well as between TAM and epithelial cells, and macrophages with high expression of SPP1 have a lower survival rate. Through in vitro studies, we also found that SPP1 mediated interactions between TAM clusters and between TAM and tumor cells. SPP1 promoted the tumor-promoting ability of TAM and increased PDL1 expression and stemness of tumor cells. In addition, we performed gene enrichment analysis using the REACTOME database and identified subpopulations that decrease the sensitivity of melanoma patients to anti-PD-1 therapy. Some specific macrophage subtypes are associated with immunotherapy resistance and prognosis in certain cancer types.