231-CXCR7 cells were incubated with 300 ng/ml CXCL12, 300 μM peptide, or vehicle control along with ≈ 10 ng/ml CXCL12-GL for one hour at 37°C. 231-control cells incubated with vehicle control and CXCL12-GL were used to measure CXCR7-independent uptake of CXCL12-GL. Cells were acid-washed to removed extracellular chemokine prior to quantifying internalized CXCL12-GL bioluminescence. Graph shows mean values + SEM for bioluminescence quantified as photon flux (n = 4 per condition). ***, p < 0.005; **, p < 0.01; *, p < 0.05 relative to uptake in 231-CXCR7 cells incubated with vehicle control.