Modulation of EPAS-1 and HIF-1α levels by different chemical agents. Immunoblots of whole-cell extracts (100 μg) with MoAb 190b (upper panels) and MoAb 28b (lower panels). (A) HeLa(B) and Hep3B cells were cultured in normoxia (N), 1% oxygen (H), 100 μmol/L DFO, or 100 μmol/L cobaltous chloride (CoCl₂). (B) HeLa(B) cells were exposed to normoxia (N) or 1% oxygen (H) in the presence (+) or absence (−) of 1 mmol/L potassium cyanide (KCN). To ascertain that the effect of KCN was not caused by cell death, cells in the right-hand lane [+] were exposed to 1 mmol/L KCN for 4 hours, washed twice, and exposed to 1% oxygen for 4 hours in fresh medium. (C) HeLa(B) cells were exposed to the selective proteasomal inhibitor N-CBZ-Leu-Leu-Norvalinal (CBZ-LLL). (D) HeLa(B) cells were exposed to the antioxidant N-(2-mercaptopropionyl)-glycine (NMPG).