Diketo hexenoic acid derivatives are novel selective non-nucleoside inhibitors of mammalian terminal deoxynucleotidyl transferases, with potent cytotoxic effect against leukemic cells

Mol Pharmacol. 2005 Aug;68(2):538-50. doi: 10.1124/mol.105.013326. Epub 2005 May 18.


Mammalian terminal deoxyribonucleotidyl transferase (TDT) catalyzes the non-template-directed polymerization of deoxyribonucleoside triphosphates and has a key role in V(D)J recombination during lymphocyte and repertoire development. More than 90% of leukemic cells in acute lymphocytic leukemia and approximately 30% of leukemic cells in the chronic myelogenous leukemia crisis show elevated TDT activity. This finding is connected to a poor prognosis and response to chemotherapy and reduced survival time. On the other hand, recent data indicated that TDT is not the only terminal deoxyribonucleotidyl transferase in mammalian cells. Its close relative, DNA polymerase lambda, can synthesize DNA both in a template-dependent (polymerase) and template-independent (terminal deoxyribonucleotidyl transferase) fashion. DNA polymerase lambda might be involved in the nonhomologous end-joining recombinational repair pathway of DNA double-strand breaks. In this work, we report the characterization of the mechanism of action of three diketo hexenoic acid (DKHA) derivatives, which proved to be extremely selective for the terminal deoxyribonucleotidyl transferase activity of DNA polymerase lambda and TDT. They seem to be the first non-nucleoside-specific inhibitors of mammalian terminal transferases reported. Moreover, the DKHA analog 6-(1-phenylmethyl-1H-indol-3-yl)-2,4-dioxo-5-hexenoic acid (RDS2119) was not toxic toward HeLa cells (CC(50) > 100 muM), whereas it showed significant cytotoxicity against the TDT(+) leukemia cell line MOLT-4 (CC(50) = 14.9 muM), thus having the potential to be further developed as a novel antitumor agent.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cell Line, Tumor
  • Cell Survival / drug effects
  • Cell Survival / physiology
  • DNA Nucleotidylexotransferase / antagonists & inhibitors*
  • DNA Nucleotidylexotransferase / metabolism*
  • Dose-Response Relationship, Drug
  • Enzyme Inhibitors / pharmacology
  • Enzyme Inhibitors / therapeutic use
  • HeLa Cells
  • Hexuronic Acids / chemistry
  • Hexuronic Acids / pharmacology*
  • Hexuronic Acids / therapeutic use*
  • Humans
  • Leukemia / drug therapy*
  • Leukemia / enzymology


  • Enzyme Inhibitors
  • Hexuronic Acids
  • hexenuronic acid
  • DNA Nucleotidylexotransferase