Biomaterial Database

Tolerance to methylnitrosourea-induced DNA damage is associated with 6-thioguanine resistance in CHO cells. 1989

G Aquilina, and A Zijno, and N Moscufo, and E Dogliotti, and M Bignami

Laboratory of Comparative Toxicology and Ecotoxicology, Istituto Superiore di Sanita', Roma, Italy.

Clones (13 and B) of O6-methylguanine-DNA-methyl-transferase-proficient (MT+) CHO cells showing different levels of resistance to N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) but similar MT activity, were found to be sensitive to methyl methanesulphonate and resistant to N-methyl-N-nitrosourea (MNU). A 2.8-fold increase in resistance to MNU-induced cytotoxicity was observed in clone 13 and a 16-fold increase in clone B. A slight increase in survival (1.5-fold) after N-ethyl-N-nitrosourea treatment was observed in clone B. These data indicate that the resistant phenotype is specific for agents that preferentially methylate O atoms in DNA. The survival of MNNG- and MNU-resistant clones as well as of the parental CHO cell line was analysed after exposure to purine analogues substituted in different positions, 8-azaguanine (8-AG), 8-azaadenine (8-AA) and 6-thioguanine (6-TG). A 6-fold increase in resistance to 6-TG was found in clone B, although the hypoxanthine guanine phosphoribosyltransferase gene is functional in these cells. The same cytotoxicity was found in all the lines after treatment with 8-AG and 8-AA. These data are in agreement with the previous observation that clone 13 and clone B belong to two different classes of resistance, clone 13 resistance being explained by MT levels. The finding that clone B is cross-resistant to 6-TG is discussed in the light of a mechanism of tolerance to modifications at specific positions of guanine.

UI	MeSH Term	Description	Entries
D008741	Methyl Methanesulfonate	An alkylating agent in cancer therapy that may also act as a mutagen by interfering with and causing damage to DNA.	Methylmethane Sulfonate,Dimethylsulfonate,Mesilate, Methyl,Methyl Mesylate,Methyl Methylenesulfonate,Methylmesilate,Mesylate, Methyl,Methanesulfonate, Methyl,Methyl Mesilate
D008770	Methylnitrosourea	A nitrosourea compound with alkylating, carcinogenic, and mutagenic properties.	Nitrosomethylurea,N-Methyl-N-nitrosourea,NSC-23909,N Methyl N nitrosourea,NSC 23909,NSC23909
D008780	Methyltransferases	A subclass of enzymes of the transferase class that catalyze the transfer of a methyl group from one compound to another. (Dorland, 28th ed) EC 2.1.1.	Methyltransferase
D010053	Ovary	The reproductive organ (GONADS) in female animals. In vertebrates, the ovary contains two functional parts: the OVARIAN FOLLICLE for the production of female germ cells (OOGENESIS); and the endocrine cells (GRANULOSA CELLS; THECA CELLS; and LUTEAL CELLS) for the production of ESTROGENS and PROGESTERONE.	Ovaries
D002460	Cell Line	Established cell cultures that have the potential to propagate indefinitely.	Cell Lines,Line, Cell,Lines, Cell
D002470	Cell Survival	The span of viability of a cell characterized by the capacity to perform certain functions such as metabolism, growth, reproduction, some form of responsiveness, and adaptability.	Cell Viability,Cell Viabilities,Survival, Cell,Viabilities, Cell,Viability, Cell
D002999	Clone Cells	A group of genetically identical cells all descended from a single common ancestral cell by mitosis in eukaryotes or by binary fission in prokaryotes. Clone cells also include populations of recombinant DNA molecules all carrying the same inserted sequence. (From King & Stansfield, Dictionary of Genetics, 4th ed)	Clones,Cell, Clone,Cells, Clone,Clone,Clone Cell
D003412	Cricetulus	A genus of the family Muridae consisting of eleven species. C. migratorius, the grey or Armenian hamster, and C. griseus, the Chinese hamster, are the two species used in biomedical research.	Hamsters, Armenian,Hamsters, Chinese,Hamsters, Grey,Armenian Hamster,Armenian Hamsters,Chinese Hamster,Chinese Hamsters,Grey Hamster,Grey Hamsters,Hamster, Armenian,Hamster, Chinese,Hamster, Grey
D004249	DNA Damage	Injuries to DNA that introduce deviations from its normal, intact structure and which may, if left unrepaired, result in a MUTATION or a block of DNA REPLICATION. These deviations may be caused by physical or chemical agents and occur by natural or unnatural, introduced circumstances. They include the introduction of illegitimate bases during replication or by deamination or other modification of bases; the loss of a base from the DNA backbone leaving an abasic site; single-strand breaks; double strand breaks; and intrastrand (PYRIMIDINE DIMERS) or interstrand crosslinking. Damage can often be repaired (DNA REPAIR). If the damage is extensive, it can induce APOPTOSIS.	DNA Injury,DNA Lesion,DNA Lesions,Genotoxic Stress,Stress, Genotoxic,Injury, DNA,DNA Injuries
D004351	Drug Resistance	Diminished or failed response of an organism, disease or tissue to the intended effectiveness of a chemical or drug. It should be differentiated from DRUG TOLERANCE which is the progressive diminution of the susceptibility of a human or animal to the effects of a drug, as a result of continued administration.	Resistance, Drug