Nonetheless, tumor stem cells (CSCs), a subgroup of colon cancer cells, can counteract 5-FU-induced oxidative damage in colon cancer cells by producing an adaptive cellular response to ROS, closely related to Nrf2 activation, which causes upregulation of antioxidant enzymes and increases cancer cell resistance to 5-FU (147, 148). This evidence concerns the gene NFE2L2 and neoplasm.