First, the strong antioxidant systems of tumors,[5] including elevated concentrations of glutathione (GSH) and highly active heme oxygenase‐1 (HO‐1), are highly effective in scavenging ROS.[6] Second, the supply of H2O2 is insufficient for therapy despite the concentration of H2O2 at tumor sites (50–100 μm) being markedly higher than that in normal cells.[7] Third, the ROS generation rate of most nanomedicines is seriously limited. This evidence concerns the gene HMOX1 and neoplasm.