mercaptopurine and Leukemia-L5178

We evaluated the relationship between the onset of DNA damage and the characteristics of 5 model chemical mutagens with the single-cell gel electrophoresis (SCG) assay using L5178Y mouse lymphoma cells. We treated the cells with each chemical for 3 h and sampled them 0, 21, and 45 h after treatment. DNA damage induced by UV mimetic mutagens MMS and MNU, and X-ray mimetic mutagen BLM was observed just after treatment, crosslinking agent MMC-induced DNA damage was detected 21 h after treatment, and 6-MP as an inhibitor of DNA synthesis did not induce DNA damage at any sampling time. These results suggest that the SCG assay detects DNA lesions just after treatment with UV and X-ray mimetic mutagens, but needs a waiting period after treatment with crosslinking agents.

Topics: Animals; Bleomycin; Cross-Linking Reagents; DNA Damage; Electrophoresis; Leukemia L5178; Mercaptopurine; Methyl Methanesulfonate; Methylnitrosourea; Mice; Mitomycin; Mutagenicity Tests; Mutagens; Nucleic Acid Synthesis Inhibitors; Time Factors; Tumor Cells, Cultured; Ultraviolet Rays; X-Rays

A full account is given of the first syntheses of 6-mercaptopurine 7-N-oxide (4) and 6-methylthiopurine 7-N-oxide (5). The synthesis of 4 followed a "phenacylamine route", which started from condensation of 4,6-dichloro-5-nitropyrimidine (15) with N-(4-methoxybenzyl)phenacylamine to form the phenacylaminopyrimidine derivative (11) and proceeded through conversion into the mercapto derivative, intramolecular cyclization between the NO2 nitrogen atom and the phenacyl carbanion to give 6-mercapto-9-(4-methoxybenzyl)purine 7-N-oxide (12), and removal of the 4-methoxybenzyl group. S-Methylation of 12 and removal of the 4-methoxybenzyl group afforded 5. The location of the oxygen function in 4,5, and 12 was confirmed by X-ray crystallographic analysis of 5.H2O, which was shown to exist in the N(7)-OH form (19). A UV spectroscopic approach suggested that the neutral species of 4 exists in H2O as the N(7)-OH tautomer (21), whereas that of 5 exists as an equilibrated mixture of the N(7)-oxide (5) and the N(7)-OH (19) tautomers. In the in vitro bioassay of antileukemic activity against murine L5178Y cells, the N-oxides 4 and 12 were found to be weakly cytotoxic.

Topics: Animals; Antineoplastic Agents; Cyclic N-Oxides; Leukemia L5178; Mercaptopurine; Mice; Molecular Structure; Oxides; Purines; Structure-Activity Relationship; Tumor Cells, Cultured

Mammalian cells incorporate 6-thioguanosine into their nucleic acids when grown in the presence of 6-mercaptopurine. 35S-labeled total RNA was prepared from L5178Y murine lymphoma cells grown in vitro in the presence of 6-[35S]mercaptopurine. Base analyses of this RNA suggested that 6-thioguanosine residues in RNA molecules undergo posttranscriptional modification. Thus, enzymatic peak-shifting analyses using anion-exchange high-performance liquid chromatography were applied to the hydrolysis products released from total RNA preparations by digestion with nuclease P1 or nuclease P1 plus nucleotide pyrophosphatase. At least eight 35S-labeled, phosphatase-sensitive compounds structurally different from [35S]6thioGMP were found in nuclease P1 digests. Four of these compounds were susceptible to cleavage with nucleotide pyrophosphatase, thus indicating that they contained phosphoric acid anhydride bonds. Individual RNA species were not separately examined, the radiochromatographic data, however, which were obtained from digests of total RNA preparations, present evidence that 6-thioguanosine 5'-diphosphate and 6-thioguanosine 5'-triphosphate exist as 5'-terminal starting nucleotides (in tRNA and rRNA) and that 6-thioguanosine becomes incorporated into the highly modified dinucleoside triphosphate structures (caps) which commonly block the 5'-termini of eukaryotic poly(A)+ mRNA-molecules.

Topics: Animals; Chromatography, High Pressure Liquid; Guanosine; Leukemia L5178; Leukemia, Experimental; Mercaptopurine; Mice; Ribonucleosides; RNA Processing, Post-Transcriptional; RNA, Neoplasm; Sulfur Radioisotopes; Thionucleosides

To determine whether the antitumor activities of thioguanine-platinum(II) [TG-Pt(II)] and selenoguanine-platinum(II) [SeG-Pt(II)] are due to direct actions of these compounds or to the actions of their hydrolysis products, studies were made on a purine antagonist-resistant, murine lymphoma L5178Y/MP subline that lacked the anabolic enzyme hypoxanthine-guanine phosphoribosyltransferase necessary for tumor inhibition. The L5178Y/MP subline proved to be highly resistant to both TG-Pt(II) and thioguanine; the resistance ratios to the two compounds were almost identical. The subline showed high resistance to selenoguanine, but the cross-resistance to SeG-Pt(II) was negligible. Whether the compounds exhibit the delayed cytotoxicity characteristic of purine antagonists was also investigated. Delayed cytotoxicity was demonstrated for TG-Pt(II) as well as for thioguanine and other purine antagonists but not for SeG-Pt(II) or cis-dichlorodiammineplatinum(II). Experiments on cross-resistance and delayed cytotoxicity showed differences in the cytotoxicities of TG-Pt(II) and SeG-Pt(II): TG-Pt(II) exerted its activity through its hydrolysis product thioguanine, whereas SeG-Pt(II) compound was cytotoxic itself.

Topics: Animals; Antineoplastic Agents; Cell Division; Cell Line; Guanine; Leukemia L5178; Leukemia, Experimental; Mercaptopurine; Mice; Organoplatinum Compounds; Thioguanine