EPAS1 and breast cancer: This demonstrated significantly higher expression of HIF-2α in the HER2-overexpressing samples when compared to Luminal A, Luminal B and Basal subtypes, (P < 0.0001, ANOVA with Tukey’s post-test) with no significant differences between the other subtypes (Fig. 1a), suggesting a possible role for HER2 in regulating HIF-2α expression in breast cancer.