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

ABSTRACT 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, TRMC4 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.