tetrahydrouridine and 5-methyldeoxycytidine

The present experiments were conducted to test the effects of the potent cytidine deaminase inhibitor tetrahydrouridine (THU) on the metabolism and cytotoxicity of 5-methyl-2'-deoxycytidine (5-Med-Cyd) in several human leukemia cell lines in vitro. It was observed that 5-Med-Cyd exerts its effects via deamination to thymidine, which is particularly toxic to human promyelocytic (HL-60) and T-cell (JM) leukemia cell lines in vitro. The deamination and the cytotoxicity of 5-Med-Cyd were effectively hindered by 10(-3) M THU in 3-day cultures of HL-60 cells. Although the catabolism of [14C]5-Med-Cyd in the HL-60 cell cultures was blocked by THU, no radioactive 5-Med-Cyd was incorporated into DNA. The cytotoxicity and DNA incorporation of fluorodeoxycytidine are enhanced by THU. Unlike that compound 5-Med-Cyd resembled more bromodeoxycytidine and iododeoxycytidine; THU decreases the toxicity of both of these deoxycytidine analogues.

Topics: Biotransformation; Cell Line; Cell Survival; Deoxycytidine; Humans; Kinetics; Neoplasms; Tetrahydrouridine; Uridine