CXCR4 and leukemia: We first analyzed the CXCR4 and ACKR3 cell surface expression levels in CHO-K1, HEK293T and THP-1 cells (with no to low CXCR4 expression), and Raji, Jurkat and CCRF-CEM human leukemia/lymphoma-derived cell lines (endogenously expressing high levels of CXCR4) by flow cytometry (Fig. 3A).