Macrophages display spatiotemporal specificity in intrahepatic cholangiocarcinoma and drive tumour progression via OSM and THBS1

Background & Aims: Tumour-associated macrophages (TAMs) are abundantly found in intrahepatic cholangiocarcinoma (ICC) and are associated with poor prognosis, yet their spatiotemporal dynamics and role in ICC progression remain unclear. This study aimed to elucidate the transcriptional regulation heterogeneity of TAMs and uncover their interactions with ICC cells in driving tumour malignancy beyond immune suppression. Methods: Using a time-resolved AKT1/NICD1 ICC model and patient datasets, we mapped the spatiotemporal macrophage landscape and their role in tumour progression. By integrating cell-cell communication analysis with phosphoproteomics, we validated key signalling cascades using TAM-ICC co-culture, multiplex immunofluorescence, gene silencing, and conditional knockout mouse models. Single-cell ATAC-seq further revealed epigenomic profiles of TAM subsets and identified their regulatory networks. Results: Immune response Mφ_CXCL9 and inflammatory Mφ_S100A were enriched in early ICC lesions, while in advanced tumours an M2-like subset, Mφ_VEGFA, with high VEGFA, ARG1, GPNMB, SPP1, and C1QA, emerged as the major population and correlated with poor prognosis. Spatial transcriptomics revealed abundant Mφ_VEGFA infiltration at tumour boundaries with secretory and proliferative signatures. Further, Mφ_VEGFA drove tumour cell proliferation via the OSM-OSMR-STAT3-CCND1 axis and promoted invasion through THBS1-CD47-mTOR-DNB1 signalling. Lastly, MAFB directed M2 polarisation and upregulated OSM/THBS1 in Mφ_VEGFA. Conclusions: Mφ_VEGFA TAMs accumulate at the tumour boundary in late-stage ICC, driving proliferation and invasion via OSM and THBS1 signalling, underscoring the potential of macrophage-targeted therapy in ICC.