VHL and neoplasm: To test whether auraptene affected HIF-1α induction in the context of hypoxic conditions representative of the tumor environment, we reconstituted VHL in RCC4 cells, which lack endogenous VHL, and assessed the effects of auraptene (100 μM) on these RCC4/VHL cells under normoxic (20% O2) and hypoxic (1% O2) conditions.