NOX5 and neuroblastoma: We note, however, that also the activity of NOX5, expressed by neuroblastoma cells (Fig. 3A), is stimulated by calcium; NOX5 does not require p22phox subunit [30] and is not involved in the PDGF induction of ROS and DUOX1-2 expression, since silencing of p22 phox inhibits PDGF induction as well as silencing of NOX2 (Figs. 3, 4 and 6).