Proteomic comparison of the bone homing cell line to the parental MDA-MB-231 cells has identified several proteins with potential to be markers of bone metastasis risk including macrophage actin-capping protein-1 (CAPG) and PDZ domain-containing protein-1 (GIPC1) [21] as well as dedicator of cytokinesis-4 (DOCK4) [20,22] as upregulated specifically within bone-homing breast cancer cells. This evidence concerns the gene DOCK4 and breast cancer.