High-resolution analysis of mononuclear phagocytes reveals clinically relevant markers in human colo-rectal liver metastasis - Visium Spatial Transcriptomics

Macrophages (Mf) are the most abundant mononuclear phagocytes in tumor tissues and hold promise as therapeutic targets and indicators of disease progression. In this work, we mapped by single-cell analysis the distinct Mf populations infiltrating the invasive margin and normal adjacent regions of human colo-rectal liver metastasis (CLM), and we exploited this information to identify non redundant markers with clinical relevance. Different populations were enriched in the invasive margin, including early-mature, inflammatory Mf (MoMf) expressing the monocytic markers S100A12 and SERPINB2, and a more mature population (TAMs) expressing CD68, GPNMB and TREM2. TAMs were enriched in pathways of matrix degradation, angiogenesis and lipid metabolism, similarly to dysfunctional macrophages described in other tumors. Cell-cell interaction analysis with CD8+ T cells defined opposing roles of MoMf, predicted to interact via IL-15, and TAMs, engaging T cells via IL-20 and IL-10. By multiplex immunofluorescence in CLM sections, we confirmed that SERPINB2 and GPNMB are expressed by different Mf subsets, with distinct topographical distribution and opposite association with patient clinical outcome. Overall design: Four-µm FFPE tissue sections were stained with hematoxylin and eosin (H&E) and the appropriate tissue regions (inclusive of tumor and IM) were selected for further processing.