a, ERE-luc assays in MCF-7 cells transiently transfected with WT-, Y537N-, Y537S-, or D538G-ER plasmids. Experiments were performed in triplicate and error bars indicate SD *P<0.05; **P<0.01; ***P<0.001. b, Experiments were performed in triplicate and error bars indicate SD. ns, not significant. *P<0.05; **P<0.01; ***P<0.001. c and d, Cells were transfected for 24 hours with two different IGF1Rβ siRNAs (100nM) and were maintained for 14 days in culture. 10μg of protein were loaded per well and the blot was probed with antibodies detecting IGF1Rβ; GAPDH was used as a loading control (c), Same cells were plated for soft agar assay and then treated with vehicle (-) or with Tam (100nM). Experiments were performed in triplicate and error bars indicate SD. ns, not significant, *P<0.5.