As the CXCR4/CXCL12 axis was well known for chemotaxis of tumor cells in bone metastasis [24,25], we co-cultured TNBC cell lines with reduced CTNND1 together with fibroblasts, osteoblasts and CXCL12 cytokine, respectively, as CXCL12 was mainly produced by fibroblasts and osteoblasts in bone. The gene discussed is CXCR4; the disease is neoplasm.