TGF-β/β2-spectrin/CTCF-regulated tumor suppression in human stem cell disorder Beckwith-Wiedemann syndrome

J Clin Invest. 2016 Feb;126(2):527-42. doi: 10.1172/JCI80937. Epub 2016 Jan 19.

Abstract

Beckwith-Wiedemann syndrome (BWS) is a human stem cell disorder, and individuals with this disease have a substantially increased risk (~800-fold) of developing tumors. Epigenetic silencing of β2-spectrin (β2SP, encoded by SPTBN1), a SMAD adaptor for TGF-β signaling, is causally associated with BWS; however, a role of TGF-β deficiency in BWS-associated neoplastic transformation is unexplored. Here, we have reported that double-heterozygous Sptbn1+/- Smad3+/- mice, which have defective TGF-β signaling, develop multiple tumors that are phenotypically similar to those of BWS patients. Moreover, tumorigenesis-associated genes IGF2 and telomerase reverse transcriptase (TERT) were overexpressed in fibroblasts from BWS patients and TGF-β-defective mice. We further determined that chromatin insulator CCCTC-binding factor (CTCF) is TGF-β inducible and facilitates TGF-β-mediated repression of TERT transcription via interactions with β2SP and SMAD3. This regulation was abrogated in TGF-β-defective mice and BWS, resulting in TERT overexpression. Imprinting of the IGF2/H19 locus and the CDKN1C/KCNQ1 locus on chromosome 11p15.5 is mediated by CTCF, and this regulation is lost in BWS, leading to aberrant overexpression of growth-promoting genes. Therefore, we propose that loss of CTCF-dependent imprinting of tumor-promoting genes, such as IGF2 and TERT, results from a defective TGF-β pathway and is responsible at least in part for BWS-associated tumorigenesis as well as sporadic human cancers that are frequently associated with SPTBN1 and SMAD3 mutations.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Animals
  • Beckwith-Wiedemann Syndrome / genetics
  • Beckwith-Wiedemann Syndrome / metabolism*
  • CCCTC-Binding Factor
  • Carrier Proteins / genetics
  • Carrier Proteins / metabolism*
  • Chromosomes, Human, Pair 11 / genetics
  • Chromosomes, Human, Pair 11 / metabolism
  • Cyclin-Dependent Kinase Inhibitor p57 / genetics
  • Cyclin-Dependent Kinase Inhibitor p57 / metabolism
  • Hep G2 Cells
  • Humans
  • Insulin-Like Growth Factor II / genetics
  • Insulin-Like Growth Factor II / metabolism
  • KCNQ1 Potassium Channel / genetics
  • KCNQ1 Potassium Channel / metabolism
  • Mice
  • Mice, Knockout
  • Microfilament Proteins / genetics
  • Microfilament Proteins / metabolism*
  • Neoplasm Proteins / genetics
  • Neoplasm Proteins / metabolism*
  • Neoplasms / genetics
  • Neoplasms / metabolism*
  • Repressor Proteins / genetics
  • Repressor Proteins / metabolism*
  • Signal Transduction / genetics
  • Smad3 Protein / genetics
  • Smad3 Protein / metabolism
  • Telomerase / biosynthesis
  • Telomerase / genetics
  • Telomerase / metabolism
  • Transforming Growth Factor beta / genetics
  • Transforming Growth Factor beta / metabolism*

Substances

  • CCCTC-Binding Factor
  • CDKN1C protein, human
  • CTCF protein, human
  • Carrier Proteins
  • Cdkn1c protein, mouse
  • Ctcf protein, mouse
  • Cyclin-Dependent Kinase Inhibitor p57
  • IGF2 protein, human
  • IGF2 protein, mouse
  • KCNQ1 Potassium Channel
  • KCNQ1 protein, human
  • Kcnq1 protein, mouse
  • Microfilament Proteins
  • Neoplasm Proteins
  • Repressor Proteins
  • SMAD3 protein, human
  • Smad3 Protein
  • Smad3 protein, mouse
  • Transforming Growth Factor beta
  • fodrin
  • Insulin-Like Growth Factor II
  • TERT protein, human
  • Telomerase
  • Tert protein, mouse