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Figure 3 | Breast Cancer Research

Figure 3

From: The estrogen receptor influences microtubule-associated protein tau (MAPT) expression and the selective estrogen receptor inhibitor fulvestrant downregulates MAPT and increases the sensitivity to taxane in breast cancer cells

Figure 3

The relationship between ER and MAPT expression. A: Downregulation of ER expression with siRNA. siRNA was used to knock down ER expression in MCF-7 and ZR75-1 cells. Cells were harvested 72 hours after transfection for Western blot analysis. The MAPT protein expression decreased after ER knockdown in both cells lines. B: Treatment with 17-β estradiol and tamoxifen. Cells were seeded in serum-free medium and incubated. After incubation for 24 hr, cells were cultivated in a medium containing 17-β estradiol alone, tamoxifen alone, or various combinations of these two agents for 72 hr. They were then harvested for Western blot analysis. In MCF7 cells, MAPT expression was increased by 17-β estradiol. In the absence of 17-β estradiol, tamoxifen increased MAPT expression. This effect was highest at concentrations of 500 nM and 1 μM, and decreased at higher concentrations. With 17-β estradiol, tamoxifen at low concentrations decreased MAPT expression, but a high stimulatory effect was found at 500 nM. This effect decreased at high concentrations. In ZR75-1 cells, these changes were observed for protein isoforms of less than 70 kDa. MCF-7 cells were exposed to 1.0 nM 17-β estradiol and ZR75-1 cells to 10 nM 17-β estradiol. E2: 17-β estradiol; Tam: tamoxifen. C: Stimulation with 17-β estradiol and fulvestrant. Cells were seeded in a serum-free medium and incubated. After a 24-hr incubation, cells were cultivated in a medium containing 17-β estradiol alone, fulvestrant alone, or various combinations of the two agents for 72 hr. They were then harvested for Western blot analysis. Fulvestrant decreased ER and MAPT protein expression in both cell lines. These changes were more noticeable for protein isoforms of less than 70 kDa in ZR75-1 cells. MCF-7 cells were exposed to 1.0 nM 17-β estradiol and ZR75-1 cells to 10 nM 17-β estradiol. E2, 17-β estradiol; Ful, fulvestrant.

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