The cell cycling–promoting effect of CXCL12 on PB CD34⁺cells is mediated by both CXCR7 and CXCR4. (A) PB CD34⁺ cells were stimulated for 48 hours in a serum- and cytokine-free StemαA medium in the presence or absence of CXCL12 (0.5 ng/mL), blocking anti-CXCR4 and/or -CXCR7 (11G8) antibodies, or isotype control; or (B) CCX704, CCX771, or CCX733 compounds. After Ki67/PI labeling, the percentages of cells in the G₀, G₁ or S+G₂/M phases were determined by flow cytometry. Dot plots show the results from 1 representative experiment (n > 3). The histograms show the modulations of the percentages of cells in G₀, G₁, or S+G₂/M phases vs control cells as a mean of fold changes ± SD (n > 3). Asterisks indicate significance vs control cells (*P ≤ .05, **P ≤ .01). Deltas indicate significance between conditions (ΔP ≤ .05, ΔΔP ≤ .01, ΔΔΔP ≤ .001).