TET1 and B-cell chronic lymphocytic leukemia: Silencing of Tet1 led to downregulation of MLL target genes including HOXA9, PBX3, and MEIS1. In this context, TET1 is shown to act as an oncogene instead of a tumor suppressor like TET2 and TET3. Rare TET1 and TET3 mutations have been found in other hematological malignancies including AML (TET1), T-cell lymphoma (TET3) and chronic lymphocytic leukemia (TET1 and TET3) (Langstein et al., 2018).