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Figure 3 | Breast Cancer Research

Figure 3

From: Elevated insulin-like growth factor 1 receptor signaling induces antiestrogen resistance through the MAPK/ERK and PI3K/Akt signaling routes

Figure 3

IGF-1R signal-induced antiestrogen resistance in MCF7/IGF-1R cells is independent of ER status. (a) Differential ER levels in response to antiestrogens TAM and FUL. Cells were treated with 100 nM TAM or FUL for three days following two-day starvation. (-), untreated. (b) Knockdown of ER expression by small interfering RNA (siRNA). (c) Effect of ERα knockdown by siRNA on cell proliferation in response to TAM (1 μM), E2 (1 nM) or E2 (1 nM) plus TAM (1 μM). siCtrl, siRNA control; siERa, siRNA ERα; **P < 0.01. (d) Effect of ERα knockdown on cell proliferation in response to IGF-1 (100 ng/mL), IGF-1 (100 ng/mL) plus TAM (1 μM) or a combination of IGF-1 (100 ng/mL), E2 (1 nM) and TAM (1 μM). SRB proliferation OD values were normalized to the control DMSO. Data are representative of three individual experiments. Data are expressed as means ± SD. (e) Estrogen response element (ERE)-dependent luciferase (Luc) activity of MCF7/IGF-1R cells in the presence of TAM (1 μM), E2 (1 nM), E2 (1 nM) plus TAM (1 μM) and a combination of IGF-1 (100 ng/mL), E2 (1 nM) and TAM (1 μM). Luciferase activity was normalized to DMSO control. Three individual ERE-luciferase assays were performed. Error bars represent ± SD.

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