Figure 3. MCF7-Y537S cells are resistant to the inhibitory effects of Tamoxifen during mammosphere formation: Representative images. Note that overall 4-OHT (1 µM) treatement reduces mammosphere formation; however, MCF7-Y537S cells remain largely unaffected. Representative images are shown. The MCF7-Y537S cells show an obvious resistance to 4-OHT. The images were obtained with an Olympus microscope (4X objective, bright field).