Enhancement of the incorporation of 5-fluorodeoxyuridylate into DNA of HL-60 cells by metabolic modulations.

The exposure of HL-60 human promyelocytic leukemia cells to 0.5 microM 5-fluoro-2'-[3H]deoxyuridine (FdUrd) for 16 hr resulted in the incorporation of 5.14 +/- 0.31 (S.D.) X 10(-7) mol FdUrd into DNA per mol of DNA nucleotide, which corresponds to 0.146 +/- 0.082 pmol FdUrd per 10(7) cells. Pretreatment with 50 microM deoxythymidine for 24 hr led to a 2.7-fold increase in the incorporation of this analogue into newly synthesized DNA during the ensuing 16-hr exposure to 0.5 microM [3H]FdUrd. Pretreatment with 0.5 microM methotrexate for 3 hr also increased the [3H]FdUrd incorporation into newly synthesized DNA approximately 5-fold. The coexistence of deoxythymidine or methotrexate with [3H]FdUrd, however, led to decreased incorporation of FdUrd into DNA. More than 50% of the radioactivity in DNA separated by Cs2SO4 equilibrium density gradient centrifugation was proven to be fluorodeoxyuridylate by means of its binding to Lactobacillus casei deoxythymidine monophosphate synthetase.