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Methylation of TFPI-2 gene is not the sole cause of its silencing

Chilukuri N Rao1, Takehiko Segawa, Jason R Navari

  • 1Division of Biochemistry, Walter Reed Army Institute of Research, Silver Spring, MD 20910, USA. nageswararao.chilukuri@na.amedd.army.mil

International Journal of Oncology
|March 13, 2003
PubMed

Insights

Aberrant DNA methylation silences tissue factor pathway inhibitor-2 (TFPI-2) expression in cancer cells, potentially impacting tumor metastasis. This silencing is linked to hypermethylation but may involve additional regulatory pathway components.

Area of Science:

  • Molecular Biology
  • Cancer Research
  • Epigenetics

Background:

  • Tissue factor pathway inhibitor-2 (TFPI-2) is a serine protease inhibitor implicated in suppressing tumor cell invasion and metastasis.
  • Loss of TFPI-2 expression is frequently observed in various tumor-derived cells.
  • Aberrant DNA methylation is a known mechanism for gene silencing in cancer.

Purpose of the Study:

  • To investigate the association between aberrant hypermethylation at the 5' end of the TFPI-2 gene and its loss of expression in cancer cell lines.
  • To explore the role of DNA methylation in regulating TFPI-2 gene expression.

Main Methods:

  • Treatment of TFPI-2-negative cancer cell lines (HT1080, MCF-7, LNCaP) with 5-azacytidine to induce demethylation.
  • Detection of TFPI-2 transcripts using RT-PCR.
  • Analysis of TFPI-2 gene methylation status in both TFPI-2-expressing and non-expressing cell lines.
  • Functional assessment of a transiently transfected TFPI-2 promoter in different cell lines before and after 5-azacytidine treatment.

Main Results:

  • TFPI-2 transcripts were detected after 5-azacytidine treatment in cell lines that previously lacked TFPI-2 expression.
  • Methylation of the 5' end of the TFPI-2 gene was observed in cell lines with silenced TFPI-2 expression.
  • TFPI-2-expressing cell lines (PC-3, DU-145) showed no detectable methylation.
  • Despite methylation, unmethylated TFPI-2 alleles were present in silenced cell lines, suggesting methylation is not the sole silencing factor.
  • The TFPI-2 promoter was non-functional in silenced cell lines but became functional after 5-azacytidine treatment.

Conclusions:

  • DNA methylation of the TFPI-2 gene is associated with its silencing in cancer cells.
  • Methylation is not the exclusive cause of TFPI-2 silencing; other methylation-associated silenced regulatory components likely contribute.
  • Restoring TFPI-2 expression via demethylation offers potential therapeutic avenues for inhibiting tumor invasion and metastasis.

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