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Bis(pivaloyloxymethyl) thymidine 5'-phosphate is a cell membrane-permeable precursor of thymidine 5'-phosphate in

Saeed R Khan1, Billie Nowak, William Plunkett

  • 1The Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins, Baltimore, MD 21231, USA. khansa@jhmi.edu

Biochemical Pharmacology
|April 14, 2005
PubMed

Insights

Bis(pivaloyloxymethyl) thymidine 5-phosphate (POM(2)-dTMP) effectively inhibits cell growth in both normal and thymidine kinase-deficient cells. This membrane-permeable prodrug serves as a viable source of thymidine monophosphate (dTMP).

Area of Science:

  • Pharmacology
  • Cell Biology
  • Biochemistry

Background:

  • Thymidine (TdR) is crucial for DNA synthesis but requires thymidine kinase (TK) for activation.
  • TK-deficient cells exhibit resistance to TdR, limiting its therapeutic applications.
  • Developing membrane-permeable prodrugs of thymidine monophosphate (dTMP) is essential for overcoming TK deficiency.

Purpose of the Study:

  • To evaluate bis(pivaloyloxymethyl) thymidine 5-phosphate (POM(2)-dTMP) as a prodrug of dTMP.
  • To compare the growth inhibitory activity of POM(2)-dTMP and TdR in wild-type and TK-deficient CCRF CEM cells.
  • To investigate the mechanism of POM(2)-dTMP uptake and its conversion to dTMP.

Main Methods:

  • Cell culture of wild-type (CEM) and TK-deficient (CEM tk-) CCRF CEM cells.
  • Antiproliferative assays to determine IC(50) values for POM(2)-dTMP and TdR.
  • Radiolabeling studies using [methyl-(3)H]dTMP and [methyl-(3)H]TdR to assess cellular uptake and incorporation.

Main Results:

  • POM(2)-dTMP exhibited significant and equal growth inhibition (IC(50)=5 microM) in both CEM and CEM tk- cells.
  • TdR showed potent activity against CEM cells (IC(50)=27 microM) but weak activity against CEM tk- cells (IC(50)=730 microM).
  • CEM tk- cells incorporated radioactivity from POM(2)-dTMP into acid-insoluble residue at a substantial rate, unlike with TdR.

Conclusions:

  • POM(2)-dTMP effectively bypasses the requirement for thymidine kinase.
  • This prodrug demonstrates efficient cellular penetration and serves as a valuable source of dTMP.
  • POM(2)-dTMP holds potential as a therapeutic agent for conditions involving TK deficiency.

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