Figure 5. Phenotypic screening of the anti-CSC activity of oleacein mimetics (II).Top panels. MTT reduction-based measurement of cell viability is expressed as percentage uptake (OD570) relative to untreated controls (=100% cell viability). Bottom panels. Representative microscope images (×2.5 magnification) of mammospheres formed by MDA-MB-436 cells growing in sphere medium for 6 days in the absence or presence of graded concentrations of oleacein mimetics. The number of mammospheres (>100 μm diameter) is expressed as means (columns) ± SD (bars). *P < 0.05 and **P < 0.005, statistically significant differences from the untreated (control) group.