Pervasive maintenance of a methylation-free state at TET2 bound promoters. (a) DNA methylation gain in primary tumours was remarkably scarce at the TET2 bound promoters identified in HCT116 cells (P <0.0001, binomial test). (b) Western blot for TET2 and beta TUBULIN from whole cell extracts of HCT116 cells stably transfected with a non-targeting shRNA control (shCtrl.) or with shRNA to TET2 (TET2C) or to TET2 and TET3 (TET2 + 3). Fold change in the knockdown was calculated relative to the shCtrl. (c) qRT-PCR for TET2 and TET3. (d) Global levels of 5hmC and 5mC by LCMS. (e) DNA methylation changes by Infinium arrays after depletion of TET2.