Spatially Segregated Macrophage Populations Predict Distinct Outcomes in Colon Cancer

Area of Science:

• Immunology
• Cancer Biology
• Tissue Microenvironment

Background:

• Tumor-associated macrophages (TAMs) exhibit transcriptional heterogeneity, but their spatial distribution and interactions within tissues are not well understood.
• Understanding the spatial organization of TAMs is crucial for deciphering their diverse roles in cancer progression and patient outcomes.

Purpose of the Study:

• To spatially resolve distinct human macrophage populations within normal and malignant breast and colon tissues.
• To characterize the cellular associations and micro-environmental niches occupied by these macrophage populations.
• To investigate the functional roles and prognostic significance of specific macrophage subsets in cancer.

Main Methods:

• Spatial transcriptomics and multiplex immunofluorescence were employed to identify and map macrophage populations.
• Analysis of cellular co-localization and tissue microenvironments in healthy and cancerous human breast and colon samples.
• Correlation of macrophage subset abundance and location with clinical outcomes in colon cancer.

Main Results:

• Five distinct human macrophage populations were identified in spatially segregated niches with conserved cellular compositions across healthy and diseased tissues.
• IL4I1+ macrophages were associated with high cell turnover and favorable outcomes in colon cancer.
• SPP1+ macrophages were enriched in hypoxic/necrotic tumor regions, correlating with worse outcomes; FOLR2+ macrophages interacted with plasma cells; NLRP3+ macrophages co-localized with neutrophils, activating inflammasomes.

Conclusions:

• A limited number of unique human macrophage niches act as fundamental tissue building blocks.
• Distinct macrophage populations exert specific roles in cancer growth, offering potential predictive biomarkers.
• These findings highlight macrophage population-specific therapeutic targets for cancer treatment.