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The LEF1/CYLD axis and cIAPs regulate RIP1 deubiquitination and trigger apoptosis in selenite-treated colorectal

P Wu1, K J Shi1, J J An1

  • 1State Key Laboratory of Medical Molecular Biology, Department of Biochemistry and Molecular Biology, Institute of Basic Medicine Sciences and School of Basic Medicine, Peking Union Medical College and Chinese Academy of Medical Sciences, Beijing, China.

Cell Death & Disease
|March 1, 2014
PubMed

Insights

Selenite enhances colorectal cancer cell apoptosis by downregulating cellular inhibitor-of-apoptosis proteins (cIAPs) and upregulating cylindromatosis (CYLD) via lymphoid enhancer factor-1 (LEF1). This promotes RIP1 deubiquitination, leading to cell death.

Area of Science:

  • Oncology
  • Molecular Biology
  • Biochemistry

Background:

  • Inhibitor-of-apoptosis protein (IAP) inhibitors enhance chemotherapy efficacy by depleting cellular IAPs (cIAPs).
  • Understanding mechanisms of apoptosis induction in colorectal cancer (CRC) is crucial for developing novel therapies.

Purpose of the Study:

  • To investigate the role of cIAP silencing in selenite-induced apoptosis in colorectal cancer (CRC) cells.
  • To elucidate the molecular mechanisms underlying selenite's effect on apoptosis, focusing on RIP1 ubiquitination and deubiquitination.

Main Methods:

  • CRISPR/Cas9-mediated cIAP silencing in CRC cells.
  • Selenite treatment and assessment of apoptosis markers.
  • Western blotting to analyze protein levels of cIAP1, cIAP2, CYLD, and RIP1.
  • Ubiquitination assays to detect K63-linked ubiquitin chains on RIP1.
  • Chromatin immunoprecipitation (ChIP) assays to study LEF1 binding to the CYLD promoter.
  • In vivo studies using a CRC xenograft mouse model.

Main Results:

  • cIAP silencing sensitized CRC cells to selenite-induced apoptosis.
  • Selenite treatment led to the removal of K63-linked ubiquitin chains on RIP1, promoting death-inducing complex formation and caspase-8 activation.
  • Selenite downregulated cIAP1 and cIAP2 while upregulating CYLD.
  • LEF1 dissociated from the CYLD promoter upon selenite treatment, relieving transcriptional repression of CYLD.
  • Findings were validated in a CRC xenograft model.

Conclusions:

  • Selenite induces apoptosis in colorectal cancer cells by upregulating CYLD via LEF1 and downregulating cIAPs.
  • This process involves the degradation of ubiquitin chains on RIP1, leading to caspase-8 activation.
  • The LEF1-binding site in the CYLD promoter represents a potential therapeutic target for combination therapies in CRC.

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