Wiskott-Aldrich Syndrome Protein Regulates Leukocyte-Dependent Breast Cancer Metastasis

• WASp is required for paracrine signaling between TAMs and breast carcinoma cells
• WASp is required for EGF secretion, aiding breast carcinoma cell invasion in vitro
• WASp is required for breast carcinoma cell motility and invasion in vivo
• WASp is required for efficient lung metastasis, but not for tumor growth

SummaryA paracrine interaction between epidermal growth factor (EGF)-secreting tumor-associated macrophages (TAMs) and colony-stimulating factor 1 (CSF-1)-secreting breast carcinoma cells promotes invasion and metastasis. Here, we show that mice deficient in the hematopoietic-cell-specific Wiskott-Aldrich syndrome protein (WASp) are unable to support TAM-dependent carcinoma cell invasion and metastasis in both orthotopic and transgenic models of mammary tumorigenesis. Motility and invasion defects of tumor cells were recapitulated ex vivo upon coculture with WASp−/− macrophages. Mechanistically, WASp is required for macrophages to migrate toward CSF-1-producing carcinoma cells, as well as for the release of EGF through metalloprotease-dependent shedding of EGF from the cell surface of macrophages. Our findings suggest that WASp acts to support both the migration of TAMs and the production of EGF, which in concert promote breast tumor metastasis.

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