SDF-1α levels in hematopoietic regulation. (A) Cocultures were performed with T47D, ZR-75-30, DU4475, BT 483, or 2 primary BCCs from stage II BC (P1, P6). At 60% confluence, the following were added to cocultures: 10² PKH26-labeled CD34⁺/CD38^–/Lin^– cells and/or 0.1 ng/mL SDF-1α or 2 ng/mL anti–SDF-1α. At confluence, cells were examined microscopically; representative figures are shown. Arrows indicate location of BCCs. (B) Cocultures were established as described for panel A. At 10% to 20% confluence, PHK26-labeled CD34⁺/CD38^–/Lin^– cells were added, and after 16 hours the cells were studied by double immunofluorescence for stroma (APC/blue) and BCCs (FITC/green). Representative studies are shown for cocultures with T47D and stroma from 2 different donors. The cells were examined by fluorescence microscopy as for Figure 5B. (C) LTC-IC assays were performed in the presence or absence of 2 ng/mL anti–SDF-1α, 2 ng/mL nonimmune rabbit IgG, media alone, or 0.1 ng/mL SDF-1α. CFU-GM colonies are for 12-week cultures and are presented as the mean ± SD (n = 6). *P < .05 versus media alone or nonimmune IgG.