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 January 19, 2016
Citation Information: J Clin Invest. 2016;126(2):527-542. https://doi.org/10.1172/JCI80937.
View: Text | PDF
Research Article

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

×

Figure 7

β2SP/SMAD3/CTCF complex transcriptionally regulates TERT.

Options: View larger image (or click on image) Download as PowerPoint
β2SP/SMAD3/CTCF complex transcriptionally regulates TERT. (A) β2SP decre...
(A) β2SP decreases TERT transcriptional activity. A luciferase reporter containing TERT promoter region (–1,000 base pairs) was cotransfected with indicated plasmids into SNU398 cells. *P < 0.001, 1-way ANOVA with post-hoc Bonferroni’s test. (n = 3). (B) β2SP regulates TERT transcriptional activity through SMAD3 and/or CTCF. HepG2–sh-Ctrl, HepG2–sh-SMAD3, or HepG2–sh-CTCF cells were cotransfected with indicated plasmids. *P < 0.05; **P < 0.01; ***P < 0.001, 1-way ANOVA with post-hoc Bonferroni’s test. (n = 3). (C) CTCF is required for TGF-β/β2SP/SMAD3-mediated TERT transcriptional activity. HepG2–sh-Ctrl or HepG2–sh-CTCF cells were cotransfected with indicated plasmids. Cells were treated with 200 pM TGF-β1 for 2 hours. *P < 0.05; **P < 0.001, 1-way ANOVA with post-hoc Bonferroni’s test. (n = 3). (D) Binding ability of SMAD3 and CTCF on the TERT promoter region is β2SP dependent. ChIP assays were performed. *P < 0.001 versus indicated, 1-way ANOVA with post-hoc Bonferroni’s test. (n = 3). (E) Decreased binding abilities of CTCF, H3K27me3, and increased binding abilities of H3k4me2 on the Tert and Igf2 promoter regions were observed in Sptbn1+/– Smad3+/– MEFs. *P < 0.05; **P < 0.001, 1-way ANOVA with post-hoc Bonferroni’s test. (n = 3). Error bars are shown as SD. (F) Proposed model of the role of the β2SP/SMAD3/CTCF complex in the regulation of TERT transcriptional activity.