Independent Antibody Validation (Figure 2) shows similar CXCR4 expression profile in both human and mouse cell lines detected by two independent anti-CXCR4 antibodies that recognize different epitopes, 1009 against N-terminus ectodomain and 1012 against the second extracellular loop.  CXCR4 proteins are detected in most of the cell lines, but not in THP-1 cells by the two independent antibodies.  Additionally, Figure 2 shows the mouse CXCR4 protein in NIH/3T3 and C2C12 cell lines migrates slightly slower than human isoform b detected by both CXCR4 antibodies (1009 and 1012), which is well correlated with their calculated molecular masses (40.4 kDa vs 39.7 kDa).  

siRNA knockdown validation (Figure 3): Anti-CXCR4 antibody (1012) specificity was further verified by CXCR4 specific siRNA knockdown. CXCR4 signal in HeLa cells transfected with CXCR4 siRNAs was weaker in comparison with that in HeLa cells transfected with control siRNAs.

Animal Species Reactivity (Figure 4): Anti-CXCR4 antibodies (1009 and 1012) can detect the expression of CXCR4 protein in rat thymus, but not in rat brain and rat heart.

CXCR4 signaling plays an important role in the migration, proliferation and quiescence of hematopoietic stem cell and their retention within the bone marrow, where it has high levels of SDF-1/CXCL12(2). It has been demonstrated that CXCR4 signaling mediates CD20 up-regulation on B cells (3).

CXCR4 is highly expressed in more than 23 types of cancer, including breast cancer, ovarian cancer, melanoma, and prostate cancer, while there is very less or no expression of CXCR4 in healthy tissues. CXCR4 expression in cancer cells has been reported to be associated with tumor survival, growth and metastasis in tissues with high levels of SDF-1/CXCL12, such as lungs, liver and bone marrow (4,5).

CXCR4 has been shown to regulate neuronal migration, cell positioning and axon wiring (6,7). CXCR4 mutant mice displayed aberrant neuronal distribution, which implicates the role in neuronal disorders such as epilepsy. CXCR4 is also involved in WHIM syndrome (8). WHIM mutations in CXCR4 were recently found in patients with Waldenstrom's macroglobulinemia, and these mutations are correlated to clinical resistance to ibrutinib (9,10).