Single-Cell RNA-Seq Combined With Bulk RNA-Seq Revealed the Involvement of Pancreatic Cancer Tissue-Resident Macrophages in Tumour Progression and the Immunotherapy Response.

Pancreatic cancer remains a highly lethal malignancy with limited therapeutic efficacy and untapped immunotherapeutic potential, largely constrained by immune cell heterogeneity in the tumour microenvironment. Tumour-associated macrophages (TAMs), especially tissue-resident macrophages (TRMs), exert complex regulatory roles in tumour progression. Here, we integrated single-cell RNA sequencing (scRNA-seq) and bulk RNA sequencing (bulk-seq) data from the GEO and TCGA databases to characterize macrophage heterogeneity and its functional impacts in pancreatic cancer. We delineated the tumour microenvironment landscape and identified a specific TRM subpopulation. Cell communication analysis revealed extensive interactions between TRMs and other cell types, including CXCL/MIF and notably upregulated SPP1 signalling in tumour tissues. We further established a TAM scoring system and found that clusters 4, 5, 9 and 10 were significantly associated with patient survival. Among them, TRM cluster 4 showed the highest predictive efficacy for 5-year and 10-year mortality, and effectively stratified patients into high- and low-risk groups with distinct differences in survival, immune cell infiltration and immune checkpoint expression. Importantly, TRM_C4 scores exhibited significant changes after immunotherapy, with decreased scores in responders and increased scores in non-responders. Together, our findings demonstrate the critical involvement of pancreatic cancer tissue-resident macrophages in tumour progression and immunotherapy response, and suggest that targeting specific macrophage subpopulations may represent a novel strategy to enhance immunotherapy efficacy and improve clinical outcomes for pancreatic cancer patients.