Fig. 1.

HER2 promotes HIF-2α expression in patient samples and a cell line model of HER2 overexpression. a HIF-2α is significantly higher in the HER2-positive subtype when compared to Luminal A, Luminal B or Basal (P < 0.0001, one-way ANOVA). b Western blotting of MCF7 and MCF7-HER2 cell lines shows increased HIF-2α levels in normoxia when HER2 is overexpressed. This was shown in untreated cells (U) and also cells treated with 200 ng/ml NRG-1β for 1–6 h. NRG-1β treatment had no discernible effect on HIF-2α levels in either cell line. The bar graph shows mean densitometry values of HIF-2α in untreated MCF7 and MCF7-HER2 whole cell lysates (n = 5 experiments, error bars represent SEM). HIF-2α protein level was significantly higher in MCF7-HER2 when compared to wild-type MCF7 (P = 0.0041, unpaired t test). c Treatment of MCF7-HER2 with 10 μM lapatinib over 8, 24 and 48 h reduces normoxic HIF-2α expression. Mean densitometry values for HIF-2α relative to DMSO controls are shown, with SEM represented by error bars and individual experimental repeats plotted. A representative western image of this result is also shown (n = 4). d RT-PCR of HIF-1α and HIF-2α expression in MCF7 and MCF7-HER2 cell lines over 72 h hypoxia (0.5% oxygen). HIF-2α but not HIF-1α expression is significantly higher in the HER2-overexpressing cell line when compared to wild-type MCF7 in normoxia (P < 0.0001). HIF-2α expression was also significantly higher in MCF7-HER2 than in MCF7 cells after 8, 24, 48 and 72 h in hypoxia (0.5% oxygen) (P < 0.0001, one-way ANOVA with Tukey’s multiple comparisons test (n = 3)). * = P < 0.05, ** = P < 0.01, *** = P < 0.005, **** = P < 0.0001