The Action of Discoidin Domain Receptor 2 in Basal Tumor Cells and Stromal Cancer-Associated Fibroblasts Is Critical for Breast Cancer Metastasis

High levels of collagen deposition in human and mouse breast tumors are associated with poor outcome due to increased local invasion and distant metastases. Using a genetic approach, we show that, in mice, the action of the fibrillar collagen receptor discoidin domain receptor 2 (DDR2) in both tumor and tumor-stromal cells is critical for breast cancer metastasis yet does not affect primary tumor growth. In tumor cells, DDR2 in basal epithelial cells regulates the collective invasion of tumor organoids. In stromal cancer-associated fibroblasts (CAFs), DDR2 is critical for extracellular matrix production and the organization of collagen fibers. The action of DDR2 in CAFs also enhances tumor cell collective invasion through a pathway distinct from the tumor-cell-intrinsic function of DDR2. This work identifies DDR2 as a potential therapeutic target that controls breast cancer metastases through its action in both tumor cells and tumor-stromal cells at the primary tumor site.