HIFs are present and active in human OS cells.

<p>A, 143B and MG-63 human OS cells showed increases in HIF-2α protein expression by western blot when cultured for 72 hour under hypoxic conditions (0.5% O₂). The HIF-2α downstream target, Oct4, was also increased, indicating HIF signaling activity. β-tubulin was the loading control. B, MNNG/HOS human OS cells were cultured under hypoxia for up to 48 hour and compared to a normoxia (0 hour) control. Both HIF-1α and HIF-2α levels were increased as seen by western blot. β-tubulin was used as a loading control.