Different effects of IL-13 and IL-4 on M in the presence of IL-10

Tumor-associated macrophages (TAM) represent an abundant cell population of the immune infiltrate in solid tumors and have been shown to orchestrate escape from immune surveillance. Macrophages display a very plastic phenotype which is recapitulated in vitro by classifying certain subsets according to exposure with defined, individual cytokines. The tumor-promoting M2 macrophages are polarized in vitro by differentiating human monocyte-derived macrophages with the T helper cell type 2 (Th2) response cytokines interleukin-4 and interleukin-13 or the immunosuppressive cytokine interleukin-10. Notably, only the latter macrophage subset undergoes apoptosis when treated with the colony stimulating factor 1 receptor (CSF1R) blocking antibody emactuzumab. However, under physiologic conditions the phenotype of TAM is shaped by a combination of cytokines. Hence, we evaluated if the addition of IL-10 to IL-4 or IL-13 differentiated macrophages is able to override IL-4/-13 mediated signaling and to restore susceptibility to emactuzumab. Though addition of IL-10 did not restore emactuzumab susceptibility, we surprisingly detected that only IL-4 differentiated macrophages sustained their specific marker expression while IL-10 skewed the IL-13 differentiated macrophage profile towards the IL-10 regulated phenotype. In-depth characterization by gene expression profiling revealed unique signatures of IL-4+IL-10 and IL-13+IL-10 differentiated macrophage subsets characterized by upregulation of the canonical NFB signaling or Wnt/-catenin signaling pathways, respectively. In silico-based analysis of a large cohort of cancer patients revealed distinct interleukin-4 or interleukin-13 overexpression patterns in a subset of patients with partial co-expression of IL-10 but almost absent IL-4/IL-13 co-expression. These patients may have less TAM depletion under therapy with CSF1R inhibitors.

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