Figure 1

TAMR cells in comparison to TAMS cells constitutively express higher levels of prosurvival mediators and cholesterol-rich lipid microdomains. (a) TAMR cell lines MCF-7/TAMR and MCF-7/HER-2, as well as TAMS parental MCF-7/TAMS and MCF-7/Neo cells, were treated with TAM at 1 μM or VEH (ethanol) in steroid-depleted media containing 17β-estradiol (10^-9 M) for 2 days. Molecular profile of prosurvival mediators was determined with Western blot analyses. (pHER-1/tHER-1 and pHER-2/tHER-2 were not detected in the MCF-7/TAMS and MCF-7/Neo cells). (b) The expression of lipid microdomains was determined by staining the cells with fluorescein-tagged DiLC16 lipid-raft marker and viewed with a fluorescence microscope. (c) The expression of cholesterol-rich lipid microdomains was determined by staining cells with fluorescein-labeled filipin, a cholesterol marker, and viewed by using a fluorescence microscope. (a-c) Data are representative of a minimum of three independent experiments. DiIC-16, dialkylindocarbocyanine; HER, human epidermal growth factor; MCF-7/HER-2, Clone 18 MCF-7 cells overexpressing HER-2; MCF-7/TAMR, acquired tamoxifen-resistant MCF-7; MCF-7/TAMS, TAM-sensitive MCF-7/parental; pHER-1, phosphorylated-HER-1; pHER-2, phosphorylated-HER-2; TAM, tamoxifen; TAMR, tamoxifen resistant; TAMS, tamoxifen sensitive; VEH, vehicle control.