PDCD1 and breast carcinoma: Inhibition of CXCR4-CXCL12 mobilizes CD8+ T cells in the tumor and synergizes with anti-PD-L1 immunotherapy [210,216]; CXCR4 antagonist AMD3100 is used to improve efficacy of bortezomib treatment [186] and anti-PD-1 and anti-CTLA-4 therapy in breast cancer mouse models [224].