Importantly, consistent with the results obtained in the experimental metastasis model, null or conditional mutations or specific inhibitors (antibodies/small molecules) in almost all the genes described in this study, including IL4Ra, Flt1, Ccl3/Ccr1, Vegfa and Csf1/Csf1r, inhibited spontaneous metastasis in mouse models of breast cancer [13,18,21]. Here, CCR1 is linked to breast cancer.