NOX4 and renal cell carcinoma: CM harvested from hypoxia-induced scrambled transfected cells resulted in a 2.5 fold increase in cell migration compared to normoxic scr control; whereas CM from hypoxia-induced RCC 786-O cells transfected with siRNA Nox4 (siNox4) showed a significant reduction in cell migration compared to hypoxia-induced scr control (Fig. 4C).