Mouse modeling dissecting macrophage-breast cancer communication uncovered roles of PYK2 in macrophage recruitment and breast tumorigenesis

Macrophage infiltration in mammary tumors is associated with enhanced tumor progression, metastasis, and poor clinical outcome, and considered as target for therapeutic intervention. Here we used different genetic mouse models and show that ablation of the tyrosine kinase PYK2, either in breast cancer cells, only in the tumor microenvironment, or both, markedly reduced the number of infiltrating tumor macrophages and concomitantly inhibited tumor angiogenesis and tumor growth. Strikingly, PYK2 depletion only in macrophages was sufficient to induce similar effects. These phenotypic changes were associated with reduced monocyte recruitment and a substantial decrease in tumor-associated macrophages (TAMs). Mechanistically, we show that PYK2 mediates mutual communication between breast cancer cells and macrophages through critical effects on key receptor signaling. Specifically, PYK2 ablation inhibited Notch1 signaling and consequently reduced CCL2 secretion by breast cancer cells, and concurrently reduced the levels of CCR2, CXCR4, IL4R, and Stat6 activation in macrophages. These bidirectional effects modulate monocyte recruitment, macrophage polarization and tumor angiogenesis. PYK2 expression is correlated with infiltrated macrophages in breast cancer patients, and its significant effects on macrophage infiltration and their pro-tumorigenic phenotype suggest that PYK2 targeting can be utilized as an effective strategy to modulate TAMs and possibly sensitize breast cancer to immunotherapy. Bone marrow derived macrophages (BMDM) were differentiated from bone marrow cells extracted from WT and PYK2 KO mice. RNA was extratcted seven days after isolation. RNA-seq was performed on BMDM extracted from three mice from each group.