Quantification of chemical mutagenesis in diploid human fibroblasts: Induction of azaguanine-resistant mutants by N-methyl-N′-nitro-N-nitrosoguanidine

Jacobs, Lois; DeMars, Robert

doi:10.1016/0165-1161(78)90377-1

Cited by 67 publications

(3 citation statements)

References 39 publications

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“…Third, Ramos exhibits no increase in the background mutation rate as assayed by the spontaneous generation of hypoxanthine phosphoribosyl transferase (HPRT) mutants (Sale & Neuberger 1998). The rate observed at the HPRT locus in Ramos (51.0^2.8 Â10 77 per locus per generation) is comparable with that determined for other cell lines (Kaden et al 1989;Monnat 1989;Umar et al 1998) and a variety of primary cell types (Green et al 1995;Jacobs & Demars 1978). In contrast, cells de¢cient in mismatch repair proteins, including Msh2, exhibit mutation rates between ten-and 100-fold higher (Modrich & Lahue 1996).…”

Section: G:c-biased Somatic Hypermutation and Isotype Switchingsupporting

confidence: 78%

In vivoandin vitrostudies of immunoglobulin gene somatic hypermutation

Sale

Bemark

Williams

et al. 2001

Phil. Trans. R. Soc. Lond. B

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Following antigen encounter, two distinct processes modify immunoglobulin genes. The variable region is diversi¢ed by somatic hypermutation while the constant region may be changed by class-switch recombination. Although both genetic events can occur concurrently within germinal centre B cells, there are examples of each occurring independently of the other. Here we compare the contributions of classswitch recombination and somatic hypermutation to the diversi¢cation of the serum immunoglobulin repertoire and review evidence that suggests that, despite clear di¡erences, the two processes may share some aspects of their mechanism in common.

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Section: G:c-biased Somatic Hypermutation and Isotype Switchingsupporting

confidence: 78%

In vivoandin vitrostudies of immunoglobulin gene somatic hypermutation

Sale

Bemark

Williams

et al. 2001

Phil. Trans. R. Soc. Lond. B

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“…Cells undergoing necroptosis lacked γH2AX (and therefore DNA damage) and surviving cells did not acquire HPRT mutations, attributing the mutagenicity of Smac mimetics to their caspase-activating function. Although drug-treated surviving cells were cultured for a standard 7 day phenotypic lag period prior to incubation in 6-TG to ensure stable expression of a HPRT mutant phenotype 36 , it is possible that a shorter incubation time could potentially reveal some HPRT mutant clones emerging after a necroptotic stimulus, given that these clones maintained colony forming potential. LN18 cells that were engineered to express RIPK3 became sensitive to necroptotic stimuli and failed to acquire HPRT mutations under caspase-independent conditions that enabled MLKL phosphorylation, whereas mutations ensued in caspase-proficient, MLKL-independent conditions.…”

Section: Discussionmentioning

confidence: 99%

“…Ten (MEF) or 20,000 (LN18) cells were seeded in 24-wells a day before treatment. Following treatment, cells were washed with PBS and cultured for 7 days to ensure any residual HPRT enzymatic function was lost 36 , recounted with trypan blue to exclude dead cells then 3 × 10 5 cells seeded in media containing 6-TG (1 or 30 µM, MEF or LN18 cells respectively) in 15 cm culture dishes. Colonies were stained with methylene blue (1.25 g/L in 50% methanol) after 7 (MEF) or 18 (LN18) days.…”

Section: Methodsmentioning

confidence: 99%

In vitro analysis reveals necroptotic signaling does not provoke DNA damage or HPRT mutations

Miles

Hawkins

2020

Cell Death Dis

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Most anticancer drugs provoke apoptotic signaling by damaging DNA or other means. Genotoxic therapies may enhance a patient's risk of developing "therapy-related cancers" due to the accumulation of oncogenic mutations that may occur in noncancerous cells. Mutations can also form upon apoptotic signaling due to sublethal caspase activity, implying that apoptosis activating drugs may also be oncogenic. Necroptosis is a different way of killing cancer cells: this version of caspase-independent cell death is characterized by receptor-interacting protein kinase-3 (RIPK3) and mixed lineage kinase-like domain protein (MLKL) activation, leading to cell membrane rupture and controlled cell lysis. The mutagenic potential of sublethal necroptotic signaling has not yet been directly investigated. Smac mimetics drugs, which activate apoptotic or necroptotic cell death, do not induce mutations but the mechanistic basis for this lack of mutagenic activity has not been determined. In this study, we compared the mutagenic potential of these two cell death pathways by engineering cells to activate either apoptotic or necroptotic signaling by exposing them to Smac mimetics with or without TNFα, and/or enforcing or preventing expression of apoptotic or necroptotic regulators. We discovered that sublethal concentrations of Smac mimetics in contexts that activated apoptotic signaling provoked DNA damage and mutations in surviving cells. Mutagenesis was dependent on executioner caspase activation of the nuclease CAD. In contrast, RIPK3-and MLKL-dependent necroptotic signaling following Smac mimetic treatment was not mutagenic. Likewise, DNA damage was not provoked in cells expressing a lethal constitutively active MLKL mutant. These data reveal that cells surviving sublethal necroptotic signaling do not sustain genomic damage and provide hope for a reduced risk of therapy-related malignancies in patients treated with necroptosis-inducing drugs.

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Anaphase aberrations: A measure of genotoxicity in mutagen‐treated fish cells

1982

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Rainbow trout gonad cells (RTG-2) were cultured for various lengths of time in the presence of several classes of known mutagenic chemicals and several related compounds that possessed no known mutagenic/carcinogenic activity. During the course of exposure the cells were examined for the presence of abnormalities in the chromosome arrangement of anaphase figures during mitosis. Untreated and solvent-treated (dimethylsulfoxide-treated) cells exhibited a background abnormality rate of 12% with only minor chromosomal defects being observed. This was also true for those cells exposed to naphthol and anthracene, two chemicals with no proven mutagenic or carcinogenic activity. Conversely, significant increases in the frequency of anaphase aberrations were produced in cells treated with N-methyl-N'-nitro-N-nitrosoguanidine, benzo(a)pyrene, 9-aminoacridine and mitomycin-C. These abnormalities were also far more complex and extensive than those observed in the control and nonmutagen-treated cells. Many species of fish have extremely small and numerous chromosomes, making resolution of chromosome defects such as sister chromatid exchange and deletions more difficult than in most mammalian diploid cells, which generally have larger and fewer chromosomes. Examination of cells during anaphase eliminates the need to observe each chromosome separately as well as the need to produce well-spread metaphase chromosomes. Since the sensitivity of anaphase aberrations to known mutagenic/carcinogenic compounds appears to be quite high in trout cells and since hundreds of suitable cells are available for analysis, this may be an appropriate alternative or addition to some of the more standard chromosome macrolesion tests developed in mammalian systems.

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Quantification of chemical mutagenesis in diploid human fibroblasts: Induction of azaguanine-resistant mutants by N-methyl-N′-nitro-N-nitrosoguanidine

Cited by 67 publications

References 39 publications

In vivoandin vitrostudies of immunoglobulin gene somatic hypermutation

In vivoandin vitrostudies of immunoglobulin gene somatic hypermutation

In vitro analysis reveals necroptotic signaling does not provoke DNA damage or HPRT mutations

Anaphase aberrations: A measure of genotoxicity in mutagen‐treated fish cells

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