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DNA mismatch repair as an effector for promoting phorbol ester-induced apoptotic DNA damage and cell killing:

Ching-Tai Lin1, Wei-Hsin Lin, Kuan-Der Lee

  • 1Institute of Cancer Research, National Health Research Institutes, Taipei, Taiwan, Republic of China. linct@nhri.org.tw

International Journal of Cancer
|May 25, 2006
PubMed

Insights

Phorbol ester triggers cell death in colon cancer cells via DNA mismatch repair (MMR) proteins and reactive oxygen species (ROS). MMR deficiency promotes tumor growth by blocking apoptosis from ROS-induced DNA damage.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Cancer Research

Background:

  • Phorbol ester (12-O-tetradecanoylphorbol-13-acetate, TPA) activates protein kinase C (PKC), influencing cell proliferation, apoptosis, and oncogenic transformation.
  • The dual role of phorbol ester in stimulating both apoptosis and tumor promotion remains unclear.
  • DNA mismatch repair (MMR) proteins play a crucial role in maintaining genomic stability.

Purpose of the Study:

  • To elucidate the mechanism by which phorbol ester induces apoptosis in colon cancer cells.
  • To investigate the role of DNA mismatch repair (MMR) proteins in phorbol ester-induced cell death.
  • To understand how MMR deficiency may contribute to tumorigenesis.

Main Methods:

  • Treatment of MMR-proficient (DLD-1+Ch2; hMSH6+) and MMR-deficient (DLD-1; hMSH6-) human colon cancer cells with TPA.
  • Assessment of cell death, reactive oxygen species (ROS) production, and protein kinase C (PKC) inhibition (staurosporine).
  • Analysis of hMSH6 expression in TPA-resistant cells, including treatment with 5-aza-2'-deoxycytidine and bisulfite sequencing; siRNA knockdown of hMSH6 and hPMS2.

Main Results:

  • TPA induced rapid cell death in MMR-proficient cells, significantly reduced by staurosporine or antioxidants.
  • TPA-induced cell death was dependent on reactive oxygen species (ROS) but not sufficient on its own.
  • TPA-resistant cells exhibited loss of hMSH6 expression, which was restored by 5-aza-2'-deoxycytidine, resensitizing cells to TPA.
  • Knockdown of hMSH6 or hPMS2 conferred resistance to TPA-induced cell killing, implicating MMR proteins in the apoptotic response.

Conclusions:

  • DNA mismatch repair (MMR) proteins are essential for mediating TPA and ROS-induced apoptosis in colon cancer cells.
  • MMR deficiency may promote tumorigenesis by impairing apoptotic responses to ROS-mediated DNA damage.
  • Transcriptional silencing of hMSH6 via cytosine methylation is a mechanism for TPA resistance.

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