5-fluoro-2--deoxycytidine and Lung-Neoplasms

The metabolic products formed and incorporated into the nucleic acids (RNA and DNA) of mice bearing Lewis lung carcinoma (LLC) following optimal doses of 5-fluorouracil (FUra), 5-fluoro-2'-deoxyuridine (FdUrd), and 5-fluoro-2'-deoxycytidine (FdCyd) coadministered with tetrahydrouridine (H4Urd), a potent inhibitor of cytidine deaminase, were examined. Treatment with FdCyd plus H4Urd resulted in a tumor-selective incorporation and formation of antimetabolites compared to either FUra or FdUrd treatments. Between 45- and greater than 5400-fold higher levels of the potent thymidylate synthetase inhibitor, 5-fluoro-2'-deoxyuridylate (FdUMP), were formed in tumor than in any of the normal tissues analyzed. RNA-level antimetabolites (FUra, 5-fluorouridine, and 5-fluorouridylate) were also between 3 and greater than 990-fold higher in tumor compared to normal tissue following FdCyd plus H4Urd administration. DNA-level antimetabolites (FdCyd, 5-fluorodeoxycytidylate, FdUrd, and FdUMP) were from 2- to 6-fold higher in tumor compared to normal tissue. FUra and FdUrd treatments resulted in between 3 and greater than 1300-fold higher RNA-level antimetabolites and from 4 to greater than 1020-fold higher FdUMP pools in normal tissues than FdCyd plus H4Urd treatment. DNA-level antimetabolites were also from 4- to 32-fold higher in normal tissues following optimal doses of FUra or FdUrd. In tumor tissue, optimal doses of FUra or FdUrd resulted in lower (a) FdUMP levels (5- to 2-fold), (b) RNA-level antimetabolites (6- to 3-fold), and (c) DNA-level antimetabolites (10- to 4-fold) compared to an optimal dosage of FdCyd plus H4Urd. In serum, the administration of H4Urd resulted in the protection of FdCyd from systemic catabolism, unlike that found with FUra or FdUrd. Substantial levels of FdUMP, FUrd, and FUMP were noted in serum following FUra or FdUrd treatment. The formation of di- and triphosphate antimetabolite pools and the incorporation of antimetabolites into the RNA and DNA of normal and tumor tissues demonstrated trends similar to those mentioned above with nucleoside, mononucleotide, and free base pools. H4Urd treatment of 25 mg/kg did not affect the elevated levels of deoxycytidine kinase or deoxycytidylate deaminase in LLC tumor tissue or the low levels found in normal tissue. A critical feature of this chemotherapeutic strategy using FdCyd plus H4Urd was that the elevated level of cytidine deaminase in LLC tumor tissue was inhibited less than 10% by the administ

Topics: Animals; Antimetabolites; Deoxycytidine; Female; Floxuridine; Fluorouracil; Lung Neoplasms; Mice; Tetrahydrouridine; Uridine

The role of DNA methylation in the expression of the metastatic phenotype in B16 murine melanoma cells in syngeneic C57BL/6 mice has been investigated. B16 cultures were incubated in vitro for either 6 or 18 h with the DNA hypomethylating agents, 5-azacytidine (5-Aza-CR) or 5-fluoro-2'-deoxycytidine (FCdR). At various times (1-13 days) following treatment, tumor cells were tested for their ability to form metastatic deposits when injected at different doses either i.v. (experimental metastasis) or s.c. in the footpad (spontaneous metastasis). Both 5-Aza-CR (0.5-15 microM) and FCdR (0.3-30 microM) caused a dose-dependent increase in the ability of B16 cells to form experimental pulmonary metastases. Increased capacity to form experimental pulmonary metastases was evident 24 h following treatment with 5-Aza-CR and 13 days following treatment with FCdR. The enhanced metastatic burden involved both an increase in the median number of lung colonies and a substantial increase in the size of individual lesions. 5-Aza-CR or FCdR treatment of B16 cell populations did not influence either the tumorigenicity or their ability to form spontaneous metastases. Parallel in vitro experiments using high-performance liquid chromatography analysis of cellular DNA demonstrated that under conditions in which 5-Aza-CR and FCdR enhanced formation of experimental metastases by B16 cells, there were readily detectable alterations in the 5-methylcytosine levels in DNA extracted from drug-treated cultures. These data suggest that drug-induced alterations in DNA methylation can affect biochemical pathway(s) whose expression is associated with the successful organ colonization by circulating tumor cells.

Topics: Animals; Azacitidine; Deoxycytidine; DNA, Neoplasm; Female; Lung Neoplasms; Melanoma; Methylation; Mice; Mice, Inbred C57BL; Neoplasm Metastasis

In view of the 20- to 80-fold elevation of deoxycytidine-5'-phosphate (dCMP) deaminase in many human malignant tumors, we have utilized 5-fluorodeoxycytidine ( FdCyd ) coadministered with tetrahydrouridine ( H4Urd ) as a combination of antitumor agents against two murine solid tumors which possess high levels of dCMP deaminase. This approach is based on our past studies in which we demonstrated that FdCyd is an excellent substrate for mammalian 2'-deoxycytidine kinase, and that H4Urd increases the toxicity of FdCyd in the mouse. Cell culture studies utilizing 2'- deoxytetrahydrouridine which inhibits cytidine deaminase and as 2'- deoxytetrahydrouridine -5'-monophosphate inhibits dCMP deaminase, provide indirect evidence for the pathway that we had proposed in the past, 2'- Deoxytetrahydrouridine antagonized the toxicity of FdCyd to a greater extent than did H4Urd and showed marked antagonism in cytidine deaminase-deficient cells. Cell lines lacking both cytidine and 2'-deoxycytidine-5'-monophosphate deaminase were markedly resistant to FdCyd . Thymidine and deoxyuridine antagonized toxicity in a manner consistent with the proposed pathway of anabolism of FdCyd and consistent with its resulting in the inhibition of thymidylate synthetase. We have established the efficacy of FdCyd + H4Urd chemotherapy utilizing adenocarcinoma 755 and Lewis lung carcinoma in C57BL X DBA/2 F1 mice. An example of an optimum schedule versus Lewis lung carcinoma is FdCyd , 10 to 12 mg/kg, plus H4Urd , 25 mg/kg, coadministered simultaneously, once per day on Days 1 to 7 after tumor implantation. Tumor inhibitions on Days 12, 14, and 16 were 95, 90, and 80%, respectively, with 8% maximum weight loss. Comparative studies were undertaken only with Lewis lung carcinoma and it was established that FdCyd + H4Urd surpasses the efficacies of 5-fluorouracil and 5-fluorodeoxyuridine as well as FdCyd when administered without H4Urd . We propose that the administration of FdCyd with H4Urd can result in preferential, tumor-directed conversion of a nontoxic nucleoside analogue to a toxic antimetabolite by an enzyme that is markedly elevated in human tumor tissue. The analogues of deoxycytidine are resistant to catabolism and are anabolized by a different subset of enzymes than are 5-fluorouracil or 5-fluorodeoxyuridine; therefore, it is a novel approach. Not only are there intrinsic selectivity, metabolic stability, and the advantages that accrue from prodrug therapy in this strategy, but in a

Topics: Animals; Antineoplastic Combined Chemotherapy Protocols; Carcinoma, Ehrlich Tumor; Carcinoma, Squamous Cell; Cell Line; Cell Survival; Cricetinae; Cricetulus; DCMP Deaminase; Deoxycytidine; DNA Replication; Drug Evaluation, Preclinical; Female; Humans; Leukemia L1210; Leukemia, Experimental; Lung Neoplasms; Mammary Neoplasms, Experimental; Mice; Nucleotide Deaminases; Ovary; Tetrahydrouridine; Uridine