ER-α36 mediates E2 or tamoxifen induced activation of the MAPK/ERK in MCF-7 cells.

<p>A, Western blot analysis of ER-α36 expression in MCF-7/V and MCF-7/ER36 cells. Levels of expression were normalized to levels of β-actin, and each bar represents mean value ± SEM (n = 3). *, P<0.05 compared to MCF-7/V cells. B and C, MCF-7/V cells treated with 10 nM E2 alone or with 2 µM Tam together for the indicated time points. Protein extracts were analyzed with Western blot analysis. Total ERK1/2 was used as loading control. Each bar represents mean value ± SEM (n = 3). *, P<0.05 compared to control cells. D, MCF-7/ER36 cells treated with 2 µM Tam for different time points were analyzed for ERK1/2 phosphorylation with Western blot. Levels of expression were normalized to levels of the total ERK1/2, and each bar represents mean value ± SEM (n = 3).*, P<0.05 compared for untreated cells. E, Lysates were prepared from MCF-7/ER36 cells treated with DMSO (Lanes 1, 2 and 3), 10 nM E2 (Lanes 2 and 5), 2 µM of Tam (Lanes 3 and 6) or pretreated with 10 µM U0126 (Lanes 4, 5 and 6) for 30 min and immunoblotted with antibodies against pERK1/2 or total ERK1/2.