Silencing of caspase-8 in murine hepatocellular carcinomas is mediated via methylation of an essential promoter element

Christian Liedtke ¹, Nils-Holger Zschemisch , Anne Cohrs

⁰Department of Medicine III, University Hospital Aachen, Aachen University, Aachen, Germany.

Gastroenterology +

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November 16, 2005

View abstract on PubMed

Summary

Hepatocellular carcinoma (HCC) often shows silenced caspase-8 expression due to promoter hypermethylation. This epigenetic silencing inhibits SP1 binding, preventing apoptosis and promoting liver cancer development.

Area Of Science

Molecular Biology
Cancer Research
Epigenetics

Background

Caspase-8 is crucial for initiating Fas-induced apoptosis.
Hepatocellular carcinoma (HCC) is a common liver cancer.
Understanding apoptosis regulation is key to cancer treatment.

Purpose Of The Study

Investigate caspase-8 expression in HCC.
Determine the mechanisms of caspase-8 silencing in HCC.
Explore the role of epigenetic modifications in HCC pathogenesis.

Main Methods

Utilized c-myc and IgEGF transgenic mouse models for HCC.
Assessed caspase-8 mRNA levels using reverse-transcription polymerase chain reaction.
Analyzed caspase-8 promoter activity via luciferase reporter assays and bisulfite sequencing for methylation analysis.

Main Results

Frequent lack of caspase-8 mRNA expression observed in HCCs.
Genomic deletions were not responsible for caspase-8 silencing.
Significant hypermethylation of CpG sites in tumor-derived caspase-8 promoter sequences was identified.
Methylation of SP1 binding sites in the promoter region inhibited SP1 complex formation and reduced promoter activity.

Conclusions

HCC frequently exhibits silenced caspase-8 expression.
CpG methylation of the caspase-8 promoter inhibits SP1-dependent transactivation, leading to gene silencing.
Inhibition of apoptosis, driven by caspase-8 silencing, is implicated in hepatocarcinogenesis.

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