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Original article
hTERT promotes the invasion of gastric cancer cells by enhancing FOXO3a ubiquitination and subsequent ITGB1 upregulation
  1. Changjiang Hu1,
  2. Zhenghong Ni2,
  3. Bo-sheng Li1,
  4. Xin Yong1,
  5. Xin Yang1,
  6. Jian-wei Zhang1,
  7. Dan Zhang1,
  8. Yong Qin1,
  9. Meng-meng Jie1,
  10. Hui Dong1,3,
  11. Song Li4,
  12. Fengtian He2,
  13. Shi-ming Yang1
  1. 1Department of Gastroenterology, Xinqiao Hospital, Third Military Medical University, Chongqing, China
  2. 2Department of Biochemistry and Molecular Biology, College of Basic Medical Sciences, Third Military Medical University, Chongqing, China
  3. 3Division of Gastroenterology, Department of Medicine, School of Medicine, University of California, San Diego, La Jolla, California, USA
  4. 4Department of Pharmaceutical Sciences, Center for Pharmacogenetics, School of Pharmacy, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
  1. Correspondence to Professor Shi-ming Yang, Department of Gastroenterology, Xinqiao Hospital, Third Military Medical University, Chongqing 400037, China; shimingyang{at}yahoo.com or Professor Fengtian He, Department of Biochemistry and Molecular Biology, College of Basic Medical Sciences, Third Military Medical University, Chongqing 400038, China; hefengtian06{at}aliyun.com

Abstract

Background and aims Human telomerase reverse transcriptase (hTERT) plays an important role in cancer invasion, but the relevant mechanism is not well known. This study aims to investigate the role and mechanism of hTERT in gastric cancer metastasis.

Design Proteomics analysis, qPCR and western blotting were used to screen for hTERT-regulated candidate molecules in gastric cancer invasion. Chromatin immunoprecipitation (ChIP) qPCR was performed to identify the binding sites of hTERT at the regulatory region of the integrin β1 (ITGB1) gene. ChIP assays were further applied to elucidate the transcription factors that bound to the regulatory region. The interactions between hTERT and the transcription factors were tested by co-immunoprecipitation (Co-IP) and glutathione S-transferase (GST) pull-down experiments. Moreover, the revealed pathway was verified in tumour-bearing nude mice and human gastric cancer tissues.

Results ITGB1 was identified as a downstream gene of hTERT, and there were two hTERT-binding regions within this gene. hTERT alleviated the binding of forkhead box O3 (FOXO3a) to FOXO3a binding element (+9972∼+9978), but it enhanced the binding of forkhead box M1 (FOXM1) to FOXM1 binding element (−1104∼−1109) in ITGB1 gene. Importantly, FOXO3a played a major role in hTERT-induced ITGB1 expression, and the hTERT/murine double minute 2 (MDM2) complex promoted the ubiquitin-mediated degradation of FOXO3a. Moreover, hTERT increased ITGB1 expression in xenograft gastric cancer, and the level of hTERT was positively correlated with that of ITGB1 in human gastric cancer tissues.

Conclusions The hTERT/MDM2–FOXO3a–ITGB1 pathway markedly contributes to hTERT-promoted gastric cancer invasion, suggesting that this pathway might be a novel target for the prevention and treatment of gastric cancer metastasis.

  • EXTRACELLULAR MATRIX
  • GASTRIC CANCER
  • MOLECULAR CARCINOGENESIS
  • MOLECULAR MECHANISMS
  • MOLECULAR ONCOLOGY

https://doi.org/10.1136/gutjnl-2015-309322

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    Footnotes

    • Contributors CH performed most of the experiments, analysed the data and drafted the manuscript. ZN performed the GST pull-down experiments and helped draft the manuscript. B-sL, XYo and XYa took part in qRT-PCR and western blot analysis. J-wZ and DZ contributed to statistical analysis. YQ and M-mJ participated in the collection of gastric cancer tissues and the corresponding adjacent non-cancerous tissues. HD and SL contributed to polish the manuscript. FH and S-mY conceived the study, participated in its design and coordination, supervised the experiments and drafted the manuscript. All authors read and approved the final manuscript.

    • Funding This work was supported by the National Natural Science Foundation of China (No. 81402034).

    • Competing interests None declared.

    • Patient consent Obtained.

    • Ethics approval Third Military Medical University Medical Ethics Committee.

    • Provenance and peer review Not commissioned; externally peer reviewed.