CXCR4 and Burkitt lymphoma: In agreement with our observations, inhibition of the CXCL12-CXCR4 axis by CXCR4 antagonists improved the efficacy of rituximab in Burkitt lymphoma [19, 20, 25] and CLL [20, 21] and, very recently, we reported that synergistic effect can be assumed when concomitantly administering rituximab and plerixafor to DLBCL cells, with combination treatment effect depending on factors such as drug concentration and administration sequence [26].