It has been demonstrated that all the hallmarks of cancer that were classified by Hanahan and Weinberg [61] and reviewed [62] (e.g., sustaining proliferative signaling, evading growth suppressors, resisting cell death, enabling replicative immortality, inducing angiogenesis, activating invasion and metastasis, reprogramming energy metabolism, and evading immune responses) can be modulated by ROS derived from NADPH oxidase isoform activities in a redox-regulated manner. This evidence concerns the gene FMO5 and cancer.