Protection of CLL B cells from spontaneous apoptosis in vitro is partially mediated by SDF-1.

(A) Synthetic SDF-1α could protect CLL cells from spontaneous apoptosis. Displayed is the mean relative viability of CLL cells from each of 6 representative CLL patients cultured with (squares) or without (circles and diamonds) NLC. Cultures without NLC were supplemented with SDF-1α at 500 ng/mL on day 0 (circles) or were cultured in medium alone (diamonds). Viability was assessed at the times indicated on the horizontal axis. Without NLC, leukemia cells cultured with SDF-1α had significantly higher viability than did leukemia cells cultured without SDF-1 (P < .005; Student t test). Nonetheless, the viability of CLL cells cultured without NLC and SDF-1α (circles) was less than that of CLL cells cultured with NLC (boxes). (B) Anti–SDF-1 antibody inhibits the survival of CLL B cells in cultures with NLC. CLL cells were separated from NLC as described and were replated into wells with (solid symbols) or without (open symbols) NLC. To wells with or without NLC, anti–SDF-1 antibody at 10 μg/mL (circles) or 1 μg/mL (triangles), or a control IgG (squares), was added at day 0. Viability was subsequently determined for each of these conditions at the time points indicated on the horizontal axis. Displayed are the mean (±SD) viability values of samples from each of 3 representative patients.