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Anticancer drug action on poly(A) polymerase activity and isoforms during HeLa and WISH cell apoptosis

N A Balatsos1, M Havredaki, C M Tsiapalis

  • 1Department of Biochemistry, Papanikolaou Research Center, Saint Savvas Hospital, Aghia Paraskevi Attikis, Greece.

The International Journal of Biological Markers
|July 7, 2000
PubMed

Insights

Anticancer drugs like 5-fluorouracil (5-FU) impact Poly(A) polymerase (PAP) activity, influencing apoptosis. Reduced PAP activity correlates with increased apoptosis, suggesting PAP

Area of Science:

  • Molecular Biology
  • Biochemistry
  • Cancer Research

Background:

  • Poly(A) polymerase (PAP) plays a crucial role in mRNA polyadenylation.
  • PAP activity and isoform levels are known to fluctuate during cell cycle, transformation, and apoptosis.
  • Apoptosis is a primary mechanism of cell death induced by anticancer agents, and evasion of apoptosis confers drug resistance.

Purpose of the Study:

  • To investigate the effect of anticancer agents (interferon, 5-fluorouracil, tamoxifen) on Poly(A) polymerase (PAP) activity and phosphorylation.
  • To examine the relationship between PAP activity, its phosphorylated isoforms, and apoptosis induction in different cell lines (HeLa and WISH) treated with 5-fluorouracil (5-FU).
  • To explore the potential of PAP as a tumor marker for predicting cell commitment to apoptosis and anticancer drug sensitivity.

Main Methods:

  • Immunoblotting analysis to detect PAP dephosphorylation.
  • PAP enzyme assays to measure enzyme activity.
  • DAPI staining and DNA fragmentation assays to assess apoptotic tendencies.
  • Comparison of drug response in chemosensitive HeLa cells versus drug-resistant WISH cells.

Main Results:

  • Therapeutic agents (IFN, 5-FU, Tam) induced partial dephosphorylation and inactivation of PAP.
  • 5-FU treatment led to decreased PAP activity and increased apoptosis in HeLa and WISH cells.
  • Apoptosis induction was accompanied by reduced PAP activity and the appearance of lower mobility phosphorylated PAP isoforms (106 and 100 kDa).
  • Differential drug response was observed between HeLa (chemosensitive) and WISH (drug-resistant) cell lines.

Conclusions:

  • PAP activity levels and phosphorylation status are reversibly linked to apoptosis induction by anticancer drugs.
  • PAP may serve as a valuable tumor marker for assessing apoptosis commitment and predicting sensitivity to anticancer therapies.
  • Understanding PAP modulation by chemotherapeutic agents can enhance insights into tumor cell resistance mechanisms.

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