OBJECTIVETo investigate the function of POLH(polymerase eta) through establishment of the POLH gene-blocked cell line FL-POLH(-).

METHODSA mammalian expression vector expressing antisense POLH gene fragment pMAMneo-amp-POLHA (-) was constructed by cloning the 1473 - 2131 fragment of POLH gene into the mammalian expression vector pMAMneo-amp(-) in antisense orientation. The FL cells were transfected with this antisense RNA expressing vector and selected by G418. The mutation assay was conducted using the shuttle plasmid pZ189.

RESULTThe spontaneous mutation frequency of SupF tRNA gene in the plasmid replicated in the FL-POLH(-) was 13.5 x 10(-4), while it was 4.9x10(-4) and 3.7x10(-4) in the control cells FL and FL-M, respectively. The nontargeted mutation frequency of SupF tRNA gene decreased in the plasmid replicated in these cell lines pretreated with MNNG.

CONCLUSIONPOLH plays an important role in maintenance of genetic stability and genesis of nontargeted mutation.

Antisense Elements (Genetics) ; pharmacology ; Cell Line ; DNA-Directed DNA Polymerase ; genetics ; physiology ; Methylnitronitrosoguanidine ; toxicity ; Mutagenesis

Gastric cancer(GC), one of the most common malignancies worldwide, seriously threatens human health due to its high morbidity and mortality. Precancerous lesion of gastric cancer(PLGC) is a critical stage for preventing the occurrence of gastric cancer, and PLGC therapy has frequently been investigated in clinical research. Exploring the proper animal modeling methods is necessary since animal experiment acts as the main avenue of the research on GC treatment. At present, N-methyl-N'-nitro-N-nitroso-guanidine(MNNG) serves as a common chemical inducer for the rat model of GC and PLGC. In this study, MNNG-based methods for modeling PLGC rats in related papers were summarized, and the applications and effects of these methods were demonstrated by examples. Additionally, the advantages, disadvantages, and precautions of various modeling methods were briefly reviewed, and the experience of this research group in exploring modeling methods was shared. This study is expected to provide a reference for the establishment of MNNG-induced PLGC animal model, and a model support for the following studies on PLGC.
Animals ; Gastric Mucosa ; Methylnitronitrosoguanidine/toxicity* ; Precancerous Conditions/chemically induced* ; Rats ; Stomach Neoplasms/drug therapy*

OBJECTIVETo investigate the protein profile after treatment of low concentration of N- methyl-N'-nitro-N-nitrosoguanidine (MNNG) in human FL cells.

METHODSAfter MNNG treatment, whole cellular proteins were separated using two-dimensional gel electrophoresis and visualized by silver staining; the digitized images were analyzed with 2D analysis software. The differentially expressed protein spots were identified by matrix-assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF-MS).

RESULTMore than 60 proteins showed significant changes in MNNG-treated cells compared to control cells (DMSO treatment). There were 18 protein spots detected only after MNNG treatment, while 13 protein spots were detected only in the control cells. Moreover, the levels of another 31 proteins were either increased or decreased in MNNG-treated FL cells. And some of the proteins were identified by MALDI-TOF-MS.

CONCLUSIONThere are significant alterations of protein profile after MNNG attack.

Amnion ; chemistry ; cytology ; drug effects ; Cells, Cultured ; Electrophoresis, Gel, Two-Dimensional ; Humans ; Methylnitronitrosoguanidine ; toxicity ; Proteomics ; Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization

BACKGROUNDMutations in mitotic checkpoint genes have been detected in several human cancers, which exhibit chromosome instability. We wanted to know whether mutation of hBub1 could occur in transformed human embryo lung fibroblasts (HELF) cells induced by a chemical carcinogen.

METHODSHELF cells were transformed by N-methyl-N'-nitro-N-nitrosoguaridine (MNNG), and three flasks of transformed HELF cells (named as T1, T2, and T3) were selected as amplifiers, and mutations of hBub1 in these transformed cells were analyzed by PCR-SSCP and sequencing.

RESULTSIt was found that any one of three transformed cell lines exhibited aneuploidy with a low mitotic checkpoint function. Subsequent PCR-SSCP and sequence analysis showed an AGT to CGT or ATT mutation at codon 80 in hBub1 gene in T1 cells with a resultant change in amino acid sequence.

CONCLUSIONOur study demonstrated that the mitotic checkpoint genes could be targets of MNNG.

Cell Line, Transformed ; Chromosome Aberrations ; Down-Regulation ; Fibroblasts ; drug effects ; Humans ; Lung ; cytology ; Methylnitronitrosoguanidine ; toxicity ; Mitosis ; drug effects ; Mutation ; Protein Kinases ; genetics ; Protein-Serine-Threonine Kinases

OBJECTIVETo understand the up regulatory mechanism of human REV3 gene induced by the chemical carcinogen N-methyl-N'-nitro-N-nitrosoguanidine (MNNG).

METHODSBioinformatic analysis of human REV3 gene promoter region was based on BLAST alignment, promoter prediction software and recognition of transcriptional factor binding sites. Cloning of human REV3 gene promoter region was performed by nested PCR. Response of human REV3 gene promoter to the chemical carcinogen MNNG was measured by transient transfection assay based on the dual luciferase reporter assay system.

RESULTBioinformatic analysis showed that human REV3 gene promoter region was located on chromosome 6 PAC clone RP3-415N12, and that the hypothetical promoter region contained promoter sequences, rich CpG islands, and putative recognition sites for several transcriptional factors, including AP-1/c-Jun/c-Fos, AP-2, STAT, CREBP, and NF-kappaB. Reconstructed reporter plasmid pGL3- 2582 was established by inserting 2582 nucleotides from the promoter region into the luciferase reporter vector pGL3-Basic. Transient transfection assay showed the hypothetical REV3 promoter region had promoter function, and it responded to MNNG treatment (P<0.01).

CONCLUSIONHuman mutator REV3 gene promoter region has been successfully cloned. The response of REV3 promoter region to MNNG suggests that REV3 gene can be regulated at transcriptional level under conditions of genotoxic stress.

Base Sequence ; Binding Sites ; Cloning, Molecular ; Computational Biology ; DNA-Directed DNA Polymerase ; genetics ; Humans ; Methylnitronitrosoguanidine ; toxicity ; Molecular Sequence Data ; Polymerase Chain Reaction ; Promoter Regions, Genetic ; Saccharomyces cerevisiae Proteins ; genetics

OBJECTIVETo investigate the effect of MNNG on some of the transcription factors such as NF- kappaB, CREB, AP-1 and c-Myc.

METHODSThe activities of these transcription factors were measured by transient transfection assay of SEAP vectors.

RESULTThe expressions of AP-1, CREB and NF- kappaB driven reporter genes were elevated for about 1.3, 1.4 and 1.3 times in MNNG-treated cells, respectively, as compared to untreated controls. However, the exposure of MNNG had no effect on the activity of c-Myc.

CONCLUSIONThe activation of certain transcription factors might be involved in the process of untargeted mutation induced by low concentration of MNNG treatment.

Animals ; Cercopithecus aethiops ; Cyclic AMP Response Element-Binding Protein ; drug effects ; Methylnitronitrosoguanidine ; toxicity ; Mutation ; NF-kappa B ; drug effects ; Proto-Oncogene Proteins c-myc ; drug effects ; Transcription Factor AP-1 ; drug effects ; Transcription Factors ; drug effects ; Vero Cells

OBJECTIVETo study the effect of MNNG on inducement of non-targeted mutation and activation of several cellular signal transduction pathways, and to determine whether the activation of these signaling pathways was dependent on the DNA-damage.

METHODSVero cells were enucleated by discontinuous density centrifugation. The PKA activities were measured by enzyme-linked immunosorbent assay. The status of cell membrane receptors was studied with immunofluorescent staining and confocal microscopy.

RESULTIn enucleated cytoplasts, MNNG-treatment increased PKA activity for about 2.3-fold in accordance with the 2.7-fold up-regulation of PKA activity in whole vero cells exposed to MNNG. The clustering of cell surface receptors of epidermal growth factor and tumor necrosis factor alpha was also observed in cells exposed to MNNG; this phenomenon was also found in enucleated cells.

CONCLUSIONThe results indicate that the initiation of signal cascades induced by low concentration of MNNG might be associated with its interaction with cell surface receptors and/or direct activation of related signal proteins but not its DNA damage.

Animals ; Cell Nucleus ; physiology ; Cercopithecus aethiops ; Cyclic AMP-Dependent Protein Kinases ; metabolism ; DNA Damage ; Enzyme Activation ; drug effects ; Methylnitronitrosoguanidine ; toxicity ; Receptor, Epidermal Growth Factor ; drug effects ; metabolism ; Receptors, Tumor Necrosis Factor ; drug effects ; metabolism ; Signal Transduction ; drug effects ; Vero Cells

OBJECTIVETo investigate the role and possible mechanism of JWA in N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) induced human bronchial epithelial (HBE) cell apoptosis.

METHODSThe cell growth inhibition rate was detected by MTT, the cell apoptosis was measured by Hoechst staining, the expression of JWA protein was detected by Western blot, and the potential binding protein of JWA proximal promoter was detected by Southwestern assay.

RESULTSMNNG treatment of HBE cells for 24 hours induced apoptosis with significant dose-effect relationship and in this course the expression of JWA protein was elevated. The 2.0 microg/ml MNNG treated cells for 24 hours activated nuclear transcription factor expression that specifically bound to JWA proximal promoter.

CONCLUSIONThat MNNG treatment activates nuclear transcription factor binding to JWA proximal promoter may be involved in intracellular apoptosis associated signal pathway.

Apoptosis ; Bronchi ; cytology ; drug effects ; metabolism ; Cells, Cultured ; Dose-Response Relationship, Drug ; Epithelial Cells ; drug effects ; metabolism ; Heat-Shock Proteins ; biosynthesis ; physiology ; Humans ; Intracellular Signaling Peptides and Proteins ; physiology ; Methylnitronitrosoguanidine ; toxicity ; Signal Transduction ; Transcription Factors ; metabolism

OBJECTIVETo investigate the role and possible mechanism of JWA in N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) inducing human bronchial epithelial (HBE) cells' neoplastic transformation.

METHODSJWA overexpression vector and its stable transfection HBE cells were established. The characteristics of transformed HBE cells were determined by methyl thiazolyl tetrazolium (MTT) assay and the soft agar colony formation assay. The expressions of JWA and P53 were detected by Western blot.

RESULTSThe growth rates of the HBE cells which were treated with MNNG were significantly accelerated than the JWA overexpression HBE cells and controlled HBE cells (P < 0.05). The soft agar colony formation of JWA overexpression HBE cells with and without MNNG treatment (8.06% and 10.14%) was significantly lower than that of the normal HBE cells with MNNG treatment (26.80%) (P < 0.01). After exposure of MNNG, the P53 expressions were gradually increased in HBE cells with the increased passages. However, the expression of P53 in JWA over expressed HBE cells showed a different manner. P53 reached an over expression peak at early stage (the first passage), and then with a gradually down-regulated expression spectrum with increased passages of the cells.

CONCLUSIONJWA might be a key molecule and play an important role in MNNG inducing neoplastic transformation in HBE cells through regulation of the expression of P53.

Cell Transformation, Neoplastic ; drug effects ; metabolism ; Cells, Cultured ; Epithelial Cells ; drug effects ; metabolism ; pathology ; Heat-Shock Proteins ; metabolism ; Humans ; Intracellular Signaling Peptides and Proteins ; metabolism ; Methylnitronitrosoguanidine ; toxicity ; Tumor Suppressor Protein p53 ; metabolism