Loss-of-function mutations in TET2 are associated with diverse myeloid and lymphoid malignancies in humans8, 9, 10, but diminished TET expression or activity are also prominent features of numerous other cancers including melanoma and glioblastoma; moreover, low TET1 levels in breast and other cancers have been shown to correlate with advanced disease, metastases and poor patient survival (reviewed in refs 11, 12). This evidence concerns the gene TET1 and cancer.