Micronucleus induction by neocarzinostatin and methyl methanesulfonate in ionizing radiation--sensitive Chinese hamster V79 cell mutants
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1Department of Toxicology, University of Würzburg, Germany. stopper@toxi.uni-wuerzburg.de
Abstract:
Two mutant V79 Chinese hamster cell lines (V-E5, XR-V15B) which show hypersensitivities to DNA damage and their two parental cell lines (V79-LE, V79-B) were used for micronucleus studies. The characteristics of V-E5 strongly resemble those of cells derived from patients suffering from the genomic instability syndrome ataxia telangiectasia, whereas XR-V15B has a decreased ability to rejoin double-strand breaks. The two cell lines V-E5 and XR-V15B showed increased spontaneous micronucleus frequencies and higher sensitivity for micronucleus induction by methyl methanesulfonate (MMS) and neocarzinostatin (NCS) both with and without the use of cytochalasin B in the micronucleus assay. Thus, defects in cellular responses to DNA damage are modulating factors in micronucleus formation.
Insights
Defects in DNA repair pathways increase spontaneous micronucleus formation and sensitivity to DNA-damaging agents in V79 cells. These findings highlight the role of DNA damage response in genomic instability and micronucleus development.
Area of Science:
- Cell Biology
- Genetics
- Molecular Toxicology
Background:
- Genomic instability syndromes, such as ataxia telangiectasia, are characterized by hypersensitivity to DNA damage.
- Understanding the cellular mechanisms underlying DNA damage response is crucial for assessing genotoxicity.
- Micronucleus formation is a biomarker for chromosomal damage and genomic instability.
Purpose of the Study:
- To investigate the relationship between DNA damage repair defects and micronucleus formation in V79 Chinese hamster cell lines.
- To compare the responses of two distinct mutant cell lines (V-E5 and XR-V15B) with known DNA repair deficiencies to genotoxic agents.
- To evaluate the impact of these defects on spontaneous and induced micronucleus frequencies.
Main Methods:
- Utilized two V79 Chinese hamster cell lines (V-E5, XR-V15B) with known DNA damage hypersensitivities and their parental lines (V79-LE, V79-B).
- Conducted micronucleus assays, assessing spontaneous and induced micronucleus frequencies.
- Exposed cells to methyl methanesulfonate (MMS) and neocarzinostatin (NCS) with and without cytochalasin B to evaluate sensitivity.
Main Results:
- Mutant cell lines V-E5 and XR-V15B exhibited significantly higher spontaneous micronucleus frequencies compared to parental lines.
- These mutant cell lines demonstrated increased sensitivity to micronucleus induction by MMS and NCS.
- The presence or absence of cytochalasin B did not alter the observed hypersensitivity of the mutant cell lines.
Conclusions:
- Defects in cellular responses to DNA damage, including those resembling ataxia telangiectasia and impaired double-strand break rejoining, directly modulate micronucleus formation.
- Increased spontaneous micronuclei and heightened sensitivity to genotoxic agents are consequences of compromised DNA repair mechanisms.
- These findings underscore the importance of DNA repair proficiency in maintaining genomic stability and reducing genotoxic risk.