EPAS1 and hepatocellular carcinoma: In previous studies, we stably transfected MCF-7 and HCC-1954 cells with lentiviral expression vectors encoding a non-targeting control (NTC) short hairpin RNA (shRNA) or shRNA targeting HIF-1α (sh1α) or HIF-2α (sh2α) or both (double knockdown [DKD]) [17, 26].