The contribution of ALDH1 to chemo- and radio-therapy resistance resides in its metabolic role within the tumor cell, that means the conversion of aldehyde groups into the less toxic carboxylate groups, thus metabolizing active compounds into less active molecules, as well as the maintenance of reactive oxygen species (ROS) at low levels, through a ROS-scavenging activity that is protective against oxidative stress [95]. Here, ALDH1A1 is linked to neoplasm.