Bis(pivaloyloxymethyl) thymidine 5′-phosphate is a cell membrane-permeable precursor of thymidine 5′-phosphate in thymidine kinase deficient CCRF CEM cells
摘要:
Bis(pivaloyloxymethyl) thymidine 5-phosphate (POM2-dTMP) has been investigated as a membrane-permeable prodrugs of dTMP. The growth inhibitory activity of POM2-TMP has been compared with thymidine (TdR) in wild type CCRF CEM cells (CEM) and a strain that lacks TdR kinase (CEM tk-). After 72 h incubation at 37 degrees C, TdR showed significant antiproliferative activity (IC50 = 27 mu M) against CEM cells but was weakly effective (IC50 = 730 mu M) against the mutant cell line. By comparison, bis(pivaloyloxymethyl) thymidine 5'-monophosphate (POM2-dTMP) was equally inhibitory (IC50 = 5 mu M) to both cell lines. The growth inhibitory effects were reversed by deoxycytidine. Cellular [methyl-H-3]dTTP pools increased linearly over 2 h during incubation of CEM or CEM tk- with 5 mu M POM2-[methyl-H-3]dTMP. The incorporation of [methyl-H-3]TdR into HClO4-insoluble cell residue by CEM tk-was < 0.1% that of CEM and did not increase over I h. In contrast, CEM tk- incorporated radioactivity from POM2-dTMP into acid insoluble residue at a rate 59% that of CEM. These results demonstrate that POM2-dTMP can penetrate into cells and serve as a source of dTMP. (c) 2005 Elsevier Inc. All rights reserved.