Fig. 3.

Overexpression of Nogo-B receptor (NgBR) increases the resistance of MCF-7 cells to tamoxifen. a Overexpression of NgBR in MCF-7 cells increases the membrane-associated H-Ras and K-Ras. The plasma membrane proteins were isolated by the ultracentrifugation method. Protein levels of pan-cadherin, NgBR, H-Ras, K-Ras and Hsp90 in MCF-7 cells were determined using western blot analysis. b Viability of MCF-7 cells treated with 4-OHT (0, 1 or 5 μM) was determined using CCK-8 assay. Overexpression of either human influenza hemagglutinin (HA)-tagged NgBR or HER2 in MCF-7 cells decreases their sensitivity to 4-OHT. Knockdown NgBR in MCF-7 cells restores the sensitivity of MCF-7 cells overexpressing HER2-HA to 4-OHT. The number of viable cells in the untreated group is referred as 100% (*p < 0.05, n = 3). c Viability of MCF-7-TamR cells treated with 4-OHT (0, 1 or 5 μM) was determined using CCK-8 assay. Knockdown of NgBR in MCF-7-TamR cells increases their sensitivity to 4-OHT. Overexpression of NgBR decreases the sensitivity of NgBR-knockdown MCF-7-TamR cells to 4-OHT. Knockdown of Nogo-B in MCF-7-TamR cells does not affect their sensitivity to 4-OHT. The number of viable cells in the untreated group is referred to as 100% (*p < 0.05, n = 3). d NgBR regulates the expression of ERα, p53 and survivin independent of its ligand Nogo-B. MCF-7-TamR cells were transfected with control siRNA or NgBR siRNAs targeting either NgBR or Nogo-B. In MCF-7-TamR cells transfected with siRNA targeting the untranslated region of NgBR, NgBR expression was restored by the transfection of NgBR-HA plasmid DNA