EPAS1 and breast cancer: We observed that HIF-2α protein expression was increased in HIF-2α-cDNA (HIF-2α OE)-transfected MCF7 and MDA-MB-231 cells compared with the negative control (NC) group by western blot (Fig. 2a, P < 0.01, P < 0.05, respectively), showing that breast cancer cells overexpressing HIF-2α were successfully constructed.