Three-dimensional responses of MCF7/IGF-1R cells to TAM (1 μM), E2 and IGF-1. Compared to parental MCF7 cells (a), MCF7/IGF-1R cells (b) in three-dimensional (3D) culture formed bigger acini in response to IGF-1 stimulation and displayed significant TAM resistance when treated with TAM (1 μM) + E2 + IGF-1, which was removable by kinase inhibitors BMS-536924, U0126 and BEZ235 (c). Cells (10,000/well) were seeded in 96-well plates. Acini were formed on 100% Matrigel and cultured for 14 days in starving medium containing 2% Matrigel and 5% charcoal/dextran-stripped fetal bovine serum with the treatments as indicated. Concentrations used: TAM (1 μM), E2 (1 nM) and IGF-1 (100 ng/mL). Confocal image original magnification, × 20. Red, rhodamine phalloidin (actin). Blue, Hoechst blue stain. Results are representative of two individual experiments.