To this end, we first established BRD4 knockout A375 melanoma and A2780 OC cells using the CRISPR/Cas9 system and exposed these cells and the control cells to normoxia (20% O2) or hypoxia (1% O2) to induce HIF1α protein for 24 h (Fig. 7a, b). The gene discussed is BRD4; the disease is melanoma.