Targeting CD206+ macrophages disrupts the establishment of a key anti-tumor immune axis [Bulk RNA-seq]
The direct and indirect effects of targeting specific tumor-associated macrophage (TAM) subsets in cancer are not well-defined. TAM targeting strategies are frequently based on the 'M1' or 'M2' polarization categories, even as substantial data challenges this binary modeling of macrophage cell state. One molecule consistently referenced as a delineator of a putative immunosuppressive 'M2' state is the surface protein CD206. We thus made a novel conditional CD206 (Mrc1) knock-in mouse to specifically visualize and/or deplete CD206+ TAMs and assess their correspondence with pro-tumoral immunity. Early, but not late depletion of CD206+ macrophages and monocytes (here, 'Mono/Macs') led to an indirect loss of a key anti-tumor network of NK cells, conventional type I dendritic cells (cDC1) and CD8 T cells. Among myeloid cells, we found that the CD206+ TAMs are the primary producers of CXCL9, and able to differentially attract activated CD8 T cells. In contrast, a population of stress-responsive TAMs (“Hypoxic” or Spp1+) and immature monocytes, which lack CD206 expression and become prominent following early depletion, expressed markedly diminished levels of CXCL9. Those NK and CD8 T cells which enter CD206-depleted tumors express vastly reduced levels of the corresponding receptor Cxcr3, the cDC1-attracting chemokine Xcl1 and cDC1 growth factor Flt3l transcripts. Consistent with the loss of this critical network, early CD206+ TAM depletion decreased tumor control by antigen specific CD8 T cells in mice. Likewise, in humans, the CD206Replete, but not the CD206Depleted Mono/Mac gene signature correlated robustly with CD8 T cell, NK cell and stimulatory cDC1 gene signatures and transcriptomic signatures skewed towards CD206Replete Mono/Macs associated with better survival. Together, these findings negate the unqualified classification of CD206+ 'M2-like' macrophages as immunosuppressive and provide further evidence of the context-dependence of macrophage function in tumors. Overall design: To identify patterns of gene expression within six broadly defined cell populations, we also performed cell sorting for bulk RNA-sequencing from freshly resected primary human tumors including compartments denoted: 1. “Live”: All viable cells at the time of sorting, 2. “Tconv”: sorted conventional CD4+ and CD8+ T cells, 3. “Treg”: CD25+ CD4+ (enriched for regulatory) T cells, 4. “Myeloid”: Lymphocyte-negative HLA-DR+ (enriched for myeloid) cells, 5. “Stromal”: CD45- CD44+Thy1+ cells, and 6. “Tumor”: all other CD45- cells. We use the bulk RNASeq data from the 'Tconv', 'Myeloid' and 'Live' compartments for this study from both previously published data and new data *************************************************************** The table below lists GEO accessions reused/reanalyzed for this study. ***************************************************************