Figure 1.

The hypoxia‐response element–luciferase (HRE‐Luc) reporter system is suitable for evaluation of hypoxia‐inducible factor (HIF) activity. (a, b) SUIT‐2/HRE‐Luc cells cultured under normoxic conditions were exposed to hypoxic conditions (1% O₂) for the indicated time periods and luciferase activity (a) and HIF‐α protein levels (b) were analyzed. The bioluminescent intensity of luciferase is shown as relative light units (RLU) (n = 3). (c) 786‐O‐VHL cells were established by introducing wild‐type von Hippel‐Lindau (VHL) expression vector into VHL‐null 786‐O cells. 786‐O‐VHL cells were cotransfected with pEF/HRE‐RLuc and pEF/FLuc reporter plasmids and cultured under normoxic (21% O₂) or hypoxic (1% O₂) conditions. The bioluminescent intensity of RLuc was divided by that of FLuc and the normalized signal is shown as relative luciferase activity (n = 3). *P < 0.05. The experiments were repeated three times and representative data are shown.