TGF-β1 protects colon tumor cells from apoptosis through XAF1 suppression

Jung Rock Moon, Shin Ju Oh, Chang Kyun Lee, Sung Gil Chi, Hyo Jong Kim

Research output: Contribution to journalArticlepeer-review

20 Citations (Scopus)


Transforming growth factor-β1 (TGF-β1) is a multifunctional cytokine that functions as a growth suppressor in normal epithelial cells and early stage tumors, but acts as a tumor promoter during malignant progression. However, the molecular basis underlying the conversion of TGF-β1 function remains largely undefined. X‑linked inhibitor of apoptosis‑associated factor 1 (XAF1) is a pro‑apoptotic tumor suppressor that frequently displays epigenetic inactivation in various types of human malignancies, including colorectal cancer. The present study explored whether the anti-apoptotic effect of TGF-β1 is linked to its regulatory effect on XAF1 induction in human colon cancer cells under stressful conditions. The results revealed that TGF-β1 treatment protected tumor cells from various apoptotic stresses, including 5‑fluorouracil, etoposide and γ-irradiation. XAF1 expression was activated at the transcriptional level by these apoptotic stresses and TGF-β1 blocked the stress-mediated activation of the XAF1 promoter. The study also demonstrated that mitogen-activated protein kinase kinase inhibition or extracellular signal-activated kinase (Erk)1/2 depletion induced XAF1 induction, while the activation of K‑Ras (G12C) led to its reduction. In addition, TGF-β1 blocked the stress-mediated XAF1 promoter activation and induction of apoptosis. This effect was abrogated if Erk1/2 was depleted, indicating that TGF-β1 represses XAF1 transcription through Erk activation, thereby protecting tumor cells from apoptotic stresses. These findings point to a novel molecular mechanism underlying the tumor-promoting function of TGF-β1, which may be utilized in the development of a novel therapeutic strategy for the treatment of colorectal cancer.

Original languageEnglish
Pages (from-to)2117-2126
Number of pages10
JournalInternational journal of oncology
Issue number6
Publication statusPublished - 2019 Jun

Bibliographical note

Funding Information:
This study was supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Science and ICT (grant no. NRF-2017R1A5A2014768).

Publisher Copyright:
2019 © Spandidos Publications. All Rights Reserved.


  • Cell apoptosis
  • Colon tumor
  • Ras/extracellular signal‑regulated kinase signaling pathway
  • Transforming growth factor-β1
  • XIAP‑associated factor 1

ASJC Scopus subject areas

  • Oncology
  • Cancer Research


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