Fig. 5

Natural killer (NK) cell interaction with MCF-7 breast cancer cells evaluated by culturing IL-2-activated NK cells with DPMSCs at different NK:DPMSC ratios in a cytolytic experiment. Following 24-h incubation with DPMSCs, NK cells were harvested, purified, and then added to MCF-7 cells at a 1:10 MCF-7:NK ratio, and NK cytolytic activity against MCF-7 cells was then evaluated using microscopic examination and the xCELLigence real-time cell analyzer. Representative phase-contrast microscopic images show a complete lysis of MCF-7 cells (no sign of intact adherent MCF-7 and cells were also ruptured as cellular debris was obvious in suspension (arrowheads)) by untreated NK cells (NK cells were initially activated with 100 U/ml IL-2 for 72 h) (b), treated NK cells (IL-2-activated NK cells cocultured with DPMSCs at 10:1 and 20:1 NK:DPMSC ratios) (c,d) as compared with MCF-7 cells (arrow) cultured alone (a) within 24 h of culture. The results of the xCELLigence showed that after 70 h of culture, MCF-7 were completely lysed by untreated NK cells and treated NK cells (described above) as shown by the cell index (e) and growth slope (f). The cell index was reduced almost to zero for MCF-7 cocultured with NK cells indicating no sign of intact cells. Experiments were carried out in triplicate and repeated 10 times using NK cells and DPMSCs prepared from the peripheral blood of 10 different healthy donors and 10 different fetal membranes, respectively. Scale bars = 50 μm