The co-location of MARCO + macrophages and SPOCK1 + fibroblasts contributes to the poor prognosis and undesirable immunotherapy response in colorectal cancer

Intratumor macrophage infiltration plays a crucial role in various aspects of tumor immunity in colorectal cancer (CRC). However, the phenotypic heterogeneity, spatial distribution, and cellular interactions of these macrophages remain elusive. To overcome the limitations, bulk, single-cell, and spatial transcriptomics were utilized synergistically. We identified two distinct spatial patterns of macrophage infiltration: macrophage + and macrophage-. MARCO + macrophages were found to accumulate intratumorally in the macrophage + infiltration. Notably, bulk and spatial transcriptomics data revealed a consistent co-location of MARCO + macrophages with SPOCK1 + fibroblasts, which was further validated by multiplex immunofluorescence. The co-location of MARCO + macrophages and SPOCK1 + fibroblasts was associated with poor prognosis and undesirable immunotherapy response in CRC. MARCO + macrophages and SPOCK1 + fibroblasts collectively established an immunosuppressive tumor microenvironment. MARCO + macrophages promoted the proliferation of SPOCK1 + fibroblasts via SPP1 and EGF signaling pathways. Meanwhile, SPOCK1 + fibroblasts contributed to the M2 polarization of MARCO + macrophages through the C3-C3AR1 axis. Our findings suggest that targeting MARCO + macrophages, SPOCK1 + fibroblasts, or their interaction could represent a promising therapeutic strategy for CRC.