After analysis using The Cancer Genome Atlas database identified a role for C-X-C motif chemokine ligand 12 (CXCL12), C-X-C motif chemokine receptor 4 (CXCR4) signaling pathway in oncogenic CD8+ T cells from human breast cancer, CXCR4 inhibition could enhance the efficacy of immunotherapy in the treatment of metastatic breast cancer (Chen et al., 2019). Here, CXCL12 is linked to breast carcinoma.