Influence of hematopoietic cells on primary breast cancer cells during ex vivo expansion. (A) Culture-enriched mammary carcinoma cells (solid symbols) and CD34⁺ enriched BPCs (open symbols) were cocultured at a ratio of 1:10 in 3-mL flasks in the presence of SCF, IL-1β, IL-3, IL-6, and EPO with (squares) or without (circles) 30 ng/mL of TGF-β1. Tumor cells were enumerated by immunocytochemistry using anti-CK and Ber-Ep4 antibodies. Mean values using cells from three different patients are shown. (B) Ten PKH-26–labeled tumor cells were suspended in 100 μL of FCS-containing IMDM or serum-free medium together with the indicated numbers of enriched CD34⁺ BPCs that had either not been precultured (CD34⁺) or that had been ex vivo expanded for 14 days in the presence of SCF, IL-1β, IL-3, IL-6, and EPO (expanded). After 3 days, the entire cultures were examined under a fluorescence microscope and all cells displaying a red fluorescence were counted. Results are the mean values ± SD of triplicate cultures and show a representative experiment.