MET and breast cancer: Because of the findings of activated stem cell signaling from c-Met/β1 complex formation (Figure 1C) and because breast cancer stem cells have been shown to be a subset of breast cancer cells with enriched metastatic capacity (9), we then asked whether the ability of the c-Met/β1 complex to drive metastases (7) reflected an ability of the complex to enrich the breast cancer stem cell population.