azaguanine and Cell-Transformation--Neoplastic

Hamster cells transformed with avian sarcoma virus, which had been selected for resistance to 8-azaguanine, were cloned. Several single cell clones were isolated which differed significantly in their tumorigenicity in comparison to the parental highly tumorigenic cells. The nontumorigenic cell clones contained rescuable avian virus. Both parental and resistant cells possessed transformed phenotype. Comparative studies with parental highly tumorigenic cells and nontumorigenic cell clones failed to detect any difference in the expression of p60src, in this phosphorylation and in phosphokinase activity. The isolated nontumorigenic cells represent cell mutants in which the viral src gene is controlled by a suppressor gene. The cells might be useful for further characterization of a putative antioncogene.

Topics: Animals; Avian Sarcoma Viruses; Azaguanine; Cell Transformation, Neoplastic; Cells, Cultured; Clone Cells; Cricetinae; Drug Resistance; Mutation; Protein Kinases

Altered queuine modification of tRNA has been associated with cellular development, differentiation, and neoplastic transformation. Present methods of evaluating agents for their ability to induce queuine hypomodification of tRNA are tedious, time-consuming, and not readily amenable to examining cell-type or tissue specificity. Therefore, a rapid, small-scale assay was developed to identify agents that alter queuine modification of tRNA in cultured cells. Monolayer cultures (2cm2) of Chinese hamster embryo cells depleted of queuine for 24 h were evaluated for their ability to incorporate [3H]dihydroqueuine into acid precipitable material (tRNA) in the presence and absence of potential inhibitors. Known inhibitors of the queuine modification enzyme tRNA-guanine ribosyltransferase (e.g., 7-methylguanine, 6-thio-guanine, and 8-azaguanine) were very effective in blocking incorporation of the radiolabel, and the dose-dependent results exhibited small standard deviations in independent experiments. The data indicate that the method is rapid, reliable, and potentially useful with a variety of cell types.

Topics: Animals; Azaguanine; Cell Differentiation; Cell Transformation, Neoplastic; Cells, Cultured; Cricetinae; Cricetulus; Guanine; Pentosyltransferases; RNA, Transfer, Amino Acid-Specific; RNA, Transfer, Amino Acyl; Thioguanine

Topics: Animals; Azaguanine; Benzo(a)pyrene; Carcinogens; Cell Line; Cell Survival; Cell Transformation, Neoplastic; Cricetinae; Drug Resistance; Methylnitronitrosoguanidine; Mice; Mutation; Ouabain

To determine whether 5-azacytidine (5-AzaCR)-induced transformation and/or differentiation of C3H/10T 1/2 clone B (10T 1/2) cells might have a mutational basis, we studied whether 5-AzaCR and structurally related nucleoside analogs could mutate 10T 1/2 and Chinese hamster V79 cells. In an assay for mutation to ouabain resistance in 10T 1/2 cells, which detects base substitution mutations but not frameshift mutations, 5-AzaCR and 6-azacytidine were not significantly mutagenic. 5-Aza-2'-deoxycytidine, 5-fluoro-2'-deoxycytidine, 5,6-dihydro-5-azacytidine, 5-fluoro-2'-deoxyuridine (FUdR), 5-bromo-2'-deoxyuridine (BUdR), and 1-beta-D-arabinofuranosylcytosine (ara-C) were only weakly mutagenic. In an assay for mutation to ouabain resistance in V79 cells, which also detects base substitution mutations but not frameshift mutations, 5-AzaCR, 5-aza-2'-deoxycytidine, FUdR, and ara-C were not detectably mutagenic, and BUdR was moderately mutagenic at highly cytotoxic concentrations. In an assay for mutation to 8-azaguanine resistance in V79 cells, which detects base substitution and frameshift mutations, 5-fluoro-2'-deoxycytidine and ara-C were weakly mutagenic, BUdR was moderately mutagenic at very cytotoxic concentrations, and 5-AzaCR, 5-aza-2'-deoxycytidine, FUdR, 6-azacytidine, and 5,6-dihydro-5-azacytidine were not significantly mutagenic. Therefore, 5-AzaCR and related cytosine analogs can be considered as negligibly mutagenic. This study does not provide support for a mutational basis for 5-AzaCR-induced differentiation in 10T 1/2 cells. Further, there was no correlation between the mutagenicity of the nucleosides 5-AzaCR, ara-C, BUdR, and FUdR studied here and their previously reported abilities to transform 10T 1/2 cells. The mutagenicities of 5-AzaCR and FUdR were so low that the biological significance of these effects is uncertain. Hence, it is not clear to what extent, if any, mutation contributes to the transformation caused by these two compounds, and other possible mechanisms of transformation should also be investigated.

Topics: Animals; Azacitidine; Azaguanine; Cell Differentiation; Cell Transformation, Neoplastic; Clone Cells; Cricetinae; Cricetulus; Drug Resistance; Mice; Mice, Inbred C3H; Mutagenicity Tests; Mutation; Ouabain

The effect of 3' methyl-4-dimethylaminoazobenzene (3'-Me-DAB) in the induction of malignant transformation and of 8-azaguanine-resistant mutations and chromosomal aberrations was studied in a diploid strain derived from normal rat liver cells. The cells were malignantly transformed by treatment with 3'-Me-DAB 1.7 micrograms/ml for 130 to 221 d or 1.7 micrograms/ml for 53 d followed by 24.9 micrograms/ml for 27 to 77 d. The untreated control cells did not transform spontaneously until the 232nd d in culture. Some properties of the 3'-Me-DAB-treated cells were compared to those of untreated control cells but no reliable marker for predicting the tumorigenic potential of the cells was found. The single addition of 3'-Me-DAB caused little induction of 8-azaguanine-resistant mutations and chromosomal aberrations to the cells. However, mutations and chromosomal aberrations were significantly induced by N-acetoxy-4-methylaminoazobenzene, an active metabolite of 4-dimethylaminoazobenzene or 3'-Me-DAB in the presence of liver microsomes.

Topics: Animals; Azaguanine; Cell Transformation, Neoplastic; Chromosome Aberrations; Clone Cells; Drug Resistance; Liver; Liver Neoplasms; Methyldimethylaminoazobenzene; Neoplasms, Experimental; p-Dimethylaminoazobenzene; Rats

Topics: Aminopyrine; Animals; Azaguanine; Cell Transformation, Neoplastic; Cells, Cultured; Cricetinae; Drug Resistance; Embryo, Mammalian; Female; Mesocricetus; Mutation; Nitrites; Pregnancy; Sodium Nitrite

Primed syngeneic or unprimed allogeneic mouse spleen cells were stimulated with azaguanine-resistant P815 tumor cells that were killed by the addition of aminopterin to the stimulation medium. The recovery of lymphocytes and their cytolytic activity and specificity were similar to those obtained after stimulation with irradiated cells. This method conveniently replaces the inactivation of stimulatory cells by irradiation or mitomycin treatment. Moreover, it has the advantage of inactivating not only the stimulatory cells but also the tumor cells that often contaminate the spleens of tumor-bearing animals, provided these animals have been inoculated with azaguanine-resistant tumor cell mutants.

Topics: Aminopterin; Animals; Azaguanine; Cell Transformation, Neoplastic; Culture Media; Cytotoxicity, Immunologic; Hypoxanthines; Mast-Cell Sarcoma; Mice; Mice, Inbred C57BL; Mice, Inbred DBA; Mutation; T-Lymphocytes; Thymidine

Hamster embryos were treated with various doses of NaNO2 in utero, by its oral administration to the mothers, and then the embryonic cells were examined for micronucleus formation, chromosomal aberrations, morphological or malignant transformation and drug-resistant mutations. For induction of resistant mutations, the cells were cultured in normal medium for 72 h, and then selected in media containing 8-azaguanine (10 or 20 microgram/ml) or 1 mM ouabain. This treatment with NaNO2 caused marked dose-dependent induction of 8-azaguanine- and ouabain-resistant mutations. Cultured embryonic fibroblasts in the resting state also showed a marked dose-dependent increase in micronucleus formation but not an increase in chromosomal aberrations. This treatment also caused morphological and neoplastic transformation of the cells. Transplacental oral treatment with DMN, as a positive control, caused changes of similar extent in biological effects of embryonic fibroblasts, and in addition it caused chromosomal aberrations in metaphase plates. On the contrary, transplacental oral application of NaNO2 did not induce any biological change in cultured embryonic fibroblasts.

Topics: Abnormalities, Drug-Induced; Animals; Azaguanine; Carcinogens; Cell Transformation, Neoplastic; Chromosome Aberrations; Cricetinae; Drug Evaluation, Preclinical; Drug Resistance; Embryo, Mammalian; Female; Maternal-Fetal Exchange; Mesocricetus; Mutagens; Nitrites; Ouabain; Pregnancy; Sodium Nitrite; Teratogens

Topics: 4-Nitroquinoline-1-oxide; Azaguanine; Cell Transformation, Neoplastic; Drug Resistance; Genes; Mutation; Nitroquinolines; Ouabain; Rauscher Virus

Hamster embryonic fibroblasts were treated directly with various concentrations of methylnitrosocyanamide (MNC), a nitrosated product of methylguanidine (MG) or N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). Then they were examined for chromosomal aberrations, morphological transformation and mutations resistant to 8-azaguanine (8AG) and 6-thioguanine (6TG). Direct treatment with 2 to 10 X 10(-6) M MNC caused a marked, dose-dependent appearance of 8AG- and 6TG-resistant mutations. The ability of MNC to induce mutations was similar to that of MNNG. Cultured embryonic fibroblasts in metaphase plates also showed a marked dose-dependent increase in chromosomal aberrations within 24 h after direct treatment with MNC or MNNG. Moreover, MNC and MNNG caused similar rates of morphological transformation.

Topics: Animals; Azaguanine; Cell Line; Cell Transformation, Neoplastic; Chromosome Aberrations; Chromosomes; Cricetinae; Dose-Response Relationship, Drug; Drug Resistance; Guanidines; Mesocricetus; Methylguanidine; Methylnitronitrosoguanidine; Mutation; Nitrosamines; Thioguanine

Topics: Animals; Azacitidine; Azaguanine; Cell Line; Cell Separation; Cell Transformation, Neoplastic; Clone Cells; Gammaretrovirus; Mice; Mice, Inbred BALB C; Mitomycins; Mutagens; Neoplasm Transplantation; Sarcoma Viruses, Murine

Mouse cells transformed by murine sarcoma virus were made resistant to 8-azaguanine. Resistant cells and cell clones isolated from them were deficient in hypoxanthine-guanine phosphoribosyl transferase (HGPRT) activity. They did not grow in HATG medium, did not incorporate labeled hypoxanthine, and had negligible HGPRT activity. The resistance was genetically stable. The resistant cells were hyperdiploid and contained telocentric chromosomes only. The resistant cells as well as the progenitor cells were slightly tumorigenic in mice, the plating efficiency in soft agar was very low. The parental cells and aza-G resistant cells produced C-type viral particles having RNA-dependent DNA polymerase activity. The resistance to aza-G did not influenced the expression of murine sarcoma virus genome in cells. The resistant cells are suitable for preparation of cell hybrids.

Topics: Animals; Azaguanine; Cell Transformation, Neoplastic; Cells, Cultured; DNA, Viral; Drug Resistance; Gammaretrovirus; Hypoxanthine Phosphoribosyltransferase; Hypoxanthines; Neoplasms, Experimental; Retroviridae; RNA-Directed DNA Polymerase; Sarcoma Viruses, Murine; Virus Replication

Chloroethylene oxide and 2-chloroacetaldehyde, two possibly carcinogenic metabolities of vinyl chloride in mammals, caused a dose-dependent induction of 8-azaguanine- and ouabain-resistant mutants in Chinese hamster V79 cells in vitro. Up to one-hundred-fold higher concentrations of 2-chloroethanol or monochloroacetic acid, a urinary vinyl chloride metabolite in rats and man, were inactive.

Topics: Acetaldehyde; Animals; Azaguanine; Cell Line; Cell Transformation, Neoplastic; Chemical Phenomena; Chemistry; Cricetinae; Dose-Response Relationship, Drug; Mutation; Ouabain; Stimulation, Chemical; Vinyl Chloride; Vinyl Compounds

Mechanisms of segregation have been examined in hybrids between Chinese hamster cells, where chromosome loss in comparison to other systems is minimal. Hybrid cells were grown in HAT medium and subjected to back selection with bromodeoxyuridine (BUDR) or azaguanine (AZG). In AZG or BUDR at 30 mug/ml, segregation began with a random high frequency event that gave rise to cells capable of growth in both HAT and back selection medium, unlike the precursor hybrid or original parental cell types. BUDR-resistant segregants were propagated serially in the presence of BUDR, and were examined by clonal analysis for changes in plating properties during long term culture. Over a period of 300 days the HAT/BUDR plating ratio for sergregant cells declined continuously. A parallel decrease was observed in the rate of H3-thymidine incorporation, along with a drop in thymidine kinase activity. These shifts took place only in the presence of BUDR, and could be reversed by altered selection in HAT medium. Clonal studies showed that the evolution of segregant properties occurred in most if not all cells of the population, and did not arise from variation and selection of minority cell types. These properties of the segregating system are not consistent with models based on gene mutation, chromosome rearrangements, or chromosome loss. The evolution of segregants resembles more closely a sorting-out progress, taking place by intracellular selection over many generations. The segregating units may conceivably be cytoplasmic determinants linked functionally to nuclear genes, and which serve to modulate the events of phenotypic expression. Several lines of evidence which bear on this concept are discussed.

Topics: Azaguanine; Bromodeoxyuridine; Cell Division; Cell Line; Cell Transformation, Neoplastic; Chromosome Deletion; Chromosomes; Drug Resistance; Genes; Genetic Linkage; Hybrid Cells; Mitosis; Thymidine Kinase

Topics: Adenoviridae; Animals; Autoradiography; Azaguanine; Carcinoma, Squamous Cell; Cell Fusion; Cell Line; Cell Transformation, Neoplastic; Cricetinae; Dactinomycin; Deoxyuridine; Inclusion Bodies, Viral; Laryngeal Neoplasms; Mitomycins; Parainfluenza Virus 1, Human; Phenylalanine; Puromycin; Thiouracil; Thymidine; Tritium; Virus Replication

Topics: Animals; Antigens, Viral; Avian Sarcoma Viruses; Azaguanine; Carbon Radioisotopes; Cell Division; Cell Fusion; Cell Survival; Cell Transformation, Neoplastic; Cells, Cultured; Chick Embryo; Chickens; Chromosome Mapping; Clone Cells; Cricetinae; Drug Resistance; Genotype; Glycine; Hypoxanthines; Methotrexate; Neoplasms, Experimental; Pentosyltransferases; Phenotype; Polyploidy; Thymidine

Topics: Animals; Azaguanine; Cattle; Cell Adhesion; Cell Division; Cell Line; Cell Transformation, Neoplastic; Cricetinae; Culture Media; Diploidy; Drug Resistance; Glucosephosphate Dehydrogenase; Humans; Hypoxanthines; Immunosuppression Therapy; Isoenzymes; Karyotyping; L-Lactate Dehydrogenase; Methylcellulose; Mice; Mice, Inbred BALB C; Neoplasm Transplantation; Neoplasms, Experimental; Pentosyltransferases; Phenotype; Rabbits; Rats; Thioguanine; Thymus Gland

Topics: Animals; Azaguanine; Bromodeoxyuridine; Cell Line; Cell Transformation, Neoplastic; Chromosome Aberrations; Chromosome Disorders; Chromosomes; Chromosomes, Human, 6-12 and X; Clone Cells; Crosses, Genetic; Drug Resistance; Fibroblasts; Guanine; Humans; Hybrid Cells; Hypoxanthines; Karyotyping; Klinefelter Syndrome; Lesch-Nyhan Syndrome; Male; Mice; Mutation; Pentosyltransferases; Simian virus 40; Skin; Thymidine Kinase

Topics: Animals; Antimetabolites; Azaguanine; Cell Line; Cell Transformation, Neoplastic; Dactinomycin; Fibroblasts; Haplorhini; Idoxuridine; In Vitro Techniques; Kidney; Mice; Mitomycins; Phenylalanine; Puromycin; Simian virus 40; Thiouracil

Topics: Alkaloids; Antibiotics, Antineoplastic; Antineoplastic Agents; Azaguanine; Blood Vessel Prosthesis; Blood-Brain Barrier; Brain; Brain Neoplasms; Bromodeoxyuridine; Cell Division; Cell Transformation, Neoplastic; Disease Models, Animal; Fluorouracil; Glioblastoma; Humans; Injections, Intra-Arterial; Injections, Spinal; Mechlorethamine; Methotrexate; Nitroso Compounds; Thiotepa; Time Factors; Urea; Vincristine