Expression of adipocyte/macrophage fatty acid binding protein in tumor associated macrophages promotes breast cancer progression

Tumor associated macrophages (TAM) play a critical role in cancer development and progression. However, the heterogeneity of TAM presents a major challenge to identify clinically-relevant markers for pro-tumor TAM. Here, we report that expression of adipocyte/macrophage fatty acid binding protein (A-FABP) in TAM promotes breast cancer progression. While upregulation of A-FABP was inversely associated with breast cancer survival, deficiency of A-FABP significantly reduced mammary tumor growth and metastasis. Furthermore, the pro-tumor effect of A-FABP was mediated by TAM, in particular in a subset of TAM with a CD11b+F4/80+MHCII-Ly6C- phenotype. A-FABP expression in TAM facilitated pro-tumor IL-6/STAT3 signaling through regulation of NFκB/miR-29b pathway. Collectively, our results suggest A-FABP as a new functional marker for pro-tumor TAM.

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