CXCR4 and neoplasm: In chronic lymphocytic leukemia (CLL) cells, SDF1 produced by stromal cells can interact with CXCR4 and activate extracellular signal-regulated kinase 1/2 (ERK1/2) and Akt (also known as protein kinase B (PKB)) pathways, leading to anti-apoptotic responses and promoting tumor cell survival [53, 54].