Tamoxifen downregulates IFITM1 and PLSCR1 expression. (A, upper panel) MCF-7:5C cells were treated with E2 (1 nM), 4OHT (1 μM) or fulvestrant (1 μM) for 72 hours. The cell extracts were examined by Western blotting using anti-PLSCR1, anti-IFITM1, anti-ERα and anti-β-actin. (A, lower panel) IFITM1 and PLSCR1 protein levels were quantified using the ImageJ software (downloaded from the NIH website) and normalized to β-actin. (B) Cells were transfected with siCon, siPLSCR1 or siIFITM1 for 24 hours and then treated with 1 nM E2 or 1 μM 4-hydroxytamoxifen (4OHT) for an additional 24 hours. Cells were then harvested and analyzed by Western blotting to assess PLSCR1, IFITM1, PARP and β-actin protein levels. All the illustrated data are expressed as mean values of three independent experiments. Standard deviations are shown. *P <0.05 versus control; #P <0.05 versus 4OHT treatment. E2, 17β-estradiol; ERα, estrogen receptor α; IFITM1, interferon induced transmembrane protein1; NIH, National Institutes of Health; PARP, poly ADP ribose polymerase; PLSCR1, phospholipid scramblase 1.