HIF-1 modulation by hypoxia and CA-4-P. A: Hypoxic accumulation and normoxic degradation of HIF-1. Western blot analysis showed that T24 tumour cells exposed to increasing lengths of time under hypoxia accumulated HIF-1a, and HIF-1a degraded rapidly under aerobic conditions. B: Increasing concentrations of CA-4-P modulate the hypoxic accumulation of HIF-1. Sparse and dense endothelial and tumour cells were treated for 24h with increasing concentrations of CA-4-P (0 - 1mM), and subjected for the final 4h to hypoxia, prior to protein extraction and detection of HIF-1a by Western blot analysis. Similar results were obtained in >3 independent experiments; representative photographs are shown. C: Short pre-exposure to CA-4-P reduces hypoxic HIF-1 accumulation. T24 tumour cells exposed for 1h to CA-4-P showed a reduction in hypoxic HIF-1 accumulation 4h and 48h later, compared to untreated cells.