NOX4 and cancer: NOX1 and NOX4, and the common subunit P22PHOX (encoded by CYBA) are, in contrast, activated in cancer cells (Ha et al., 2016; Ito et al., 2016) and have been associated with keratinocyte-specific activity (Chamulitrat et al., 2004; Nam et al., 2010; Sun et al., 2016).