In addition, tumor volumes and weights in the HIF-2α-cDNA + PTX (5 mg/kg, every two days, i.p.)mice were notably increased than those in NC-cDNA + PTX mice (Fig. 5c, d, Additional file 3: Figure S3b, c), suggesting that HIF-2α increased the resistance of breast cancer cells to PTX in vivo. Here, EPAS1 is linked to breast cancer.