Effect of various agents on colony formation in MCF-7
cells. MCF-7CC or MCF-7TXT10 cells were assessed for their ability to form colonies after exposure to 10 ng/ml tumor-necrosis factor (TNF)-α, 10 μg/ml cycloheximide, or a combination of both agents for 24 hours (a). The ability of MCF-7TXT10 cells to form colonies in increasing concentrations of docetaxel in the absence (broken line) or presence (solid line) of a TNFR2 neutralizing antibody (5 μg/ml) was also examined (b). The effects of an NF-κB inhibitor SN-50 (7 μg/ml; broken gray line) or a control peptide SN-50 M (7 μg/ml; broken black line) on the colony-forming behavior of MCF-7TXT10 cells also were examined (c). Mean survival fractions (± standard error) are plotted. Significance of differences was assessed by using a Student t test; P values of < 0.05, < 0.01, and < 0.001 are represented by *, **, and *** symbols, respectively.