Enhancing the activity of TET proteins with vitamin C (Figure 5) can protect hematopoietic stem cells that have Tet2 mutations from aberrant proliferation in vitro and leukemia progression in vivo (Agathocleous et al., 2017; Cimmino et al., 2017; Das et al., 2019) (reviewed in Ang et al., 2018; Cimmino et al., 2018; Yue and Rao, 2020). This evidence concerns the gene TET2 and leukemia.