TGF-β/β2-spectrin/CTCF-regulated tumor suppression in human stem cell disorder Beckwith-Wiedemann syndrome
Jian Chen, … , Hidekazu Tsukamoto, Lopa Mishra
Jian Chen, … , Hidekazu Tsukamoto, Lopa Mishra
Published February 1, 2016; First published January 19, 2016
Citation Information: J Clin Invest. 2016;126(2):527-542. https://doi.org/10.1172/JCI80937.
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Research Article Stem cells

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

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.

Authors

Jian Chen, Zhi-Xing Yao, Jiun-Sheng Chen, Young Jin Gi, Nina M. Muñoz, Suchin Kundra, H. Franklin Herlong, Yun Seong Jeong, Alexei Goltsov, Kazufumi Ohshiro, Nipun A. Mistry, Jianping Zhang, Xiaoping Su, Sanaa Choufani, Abhisek Mitra, Shulin Li, Bibhuti Mishra, Jon White, Asif Rashid, Alan Yaoqi Wang, Milind Javle, Marta Davila, Peter Michaely, Rosanna Weksberg, Wayne L. Hofstetter, Milton J. Finegold, Jerry W. Shay, Keigo Machida, Hidekazu Tsukamoto, Lopa Mishra

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Figure 6

Increased TERT levels in Sptbn1+/– Smad3+/– mice.

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Increased TERT levels in Sptbn1+/– Smad3+/– mice. (A) Increased levels o...
(A) Increased levels of TERT in liver, pancreas, and stomach of Sptbn1+/– Smad3+/– mice were observed. Representative immunohistochemical staining of mouse TERT in wild-type or Sptbn1+/– Smad3+/– mouse organs. The arrows point to increased expression levels of TERT in Sptbn1+/– Smad3+/– mice. Scale bars: 20 μm. (B) Increased mRNA expression levels of Tert in Sptbn1+/–, Smad3+/–, and Sptbn1+/– Smad3+/– mouse livers were observed. *P < 0.001, 1-way ANOVA with post-hoc Bonferroni’s test. (n = 3). (C) β2SP and SMAD3 decrease TERT mRNA expression levels in a TGF-β–dependent manner. SNU398 cells were cotransfected with ectopic V5-β2SP and Flag-SMAD3 for 24 hours. Cells were then treated with 50 μM of TGFBR1 inhibitor SB431542 overnight. *P < 0.01, 1-way ANOVA with post-hoc Bonferroni’s test. (n = 3). (D) Reduction of TGF-β–induced Tert expression levels was observed in wild-type MEFs, but not in Sptbn1+/– Smad3+/– MEFs. Cells were treated with 200 pM TGF-β for 2 hours. Tert mRNA levels were detected by Q-PCR. *P < 0.001, 1-way ANOVA with post-hoc Bonferroni’s test. (n = 3). Error bars are shown as SD.