NOX1 and malignant colon neoplasm: However, there is evidence that colon cancer cells up-regulate NOX1 [66], and so it is possible that DUOX is up-regulated by transformed cells in our fish model also, although our qPCR data would suggest that this is not the case (data not shown), and recent studies indicate that DUOX is constitutively expressed in zebrafish larval mucosal epithelia, including epidermis [67].