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Induction of sister chromatid exchanges in NIH 3T3 cells transformed by DNA from mice given cyclophosphamide
1Carcinogenicity Section, Department of Toxicology, Frederick Institute of Plant Protection and Toxicology, Padappai-601 301, T. Nadu, India.
Abstract:
The rationale behind this experiment was to investigate the role of sister chromatid exchange (SCE) in the transformation process in vitro. High molecular weight DNA was extracted from bone marrow cells of mice given 20 mg cyclophosphamide/kg body weight. 30 mug of this DNA was used to transfect NIH 3T3 in Eagle's medium seeded at 0.7 x 10(6) cells/plate. Morphologically visible foci were picked up after 16-21 days. The foci were trypsinized, washed and allowed to grow in the presence of bromodeoxyuridine (25 mum) for 72 hr in the dark. Analysis of SCE per chromosome indicated a 20-fold increase in the frequency of exchanges as compared with the induction seen in negative controls. These data suggest that the transformation process of NIH 3T3 cells by DNA from mice treated with cyclophosphamide is associated with an increased induction of SCEs.
Insights
This study shows that DNA from cyclophosphamide-treated mice increases sister chromatid exchange (SCE) in NIH 3T3 cells. This suggests a link between SCE and the in vitro transformation process.
Area of Science:
- Molecular Biology
- Genetics
- Cell Biology
Background:
- Sister chromatid exchange (SCE) is a mechanism of DNA repair.
- Cyclophosphamide is a known genotoxic agent.
- Cellular transformation is a key step in carcinogenesis.
Purpose of the Study:
- To investigate the role of SCE in the in vitro transformation of NIH 3T3 cells.
- To determine if DNA from cyclophosphamide-treated mice induces SCE during cell transformation.
Main Methods:
- Extraction of high molecular weight DNA from mouse bone marrow cells after cyclophosphamide treatment.
- Transfection of NIH 3T3 cells with the extracted DNA.
- Culturing and selection of morphologically transformed foci.
- Analysis of SCE frequency per chromosome after bromodeoxyuridine labeling.
Main Results:
- A 20-fold increase in SCE frequency was observed in NIH 3T3 cells transfected with DNA from cyclophosphamide-treated mice compared to controls.
- Morphologically transformed foci were successfully generated.
Conclusions:
- The transformation of NIH 3T3 cells by DNA from cyclophosphamide-treated mice is associated with an increased induction of SCE.
- SCE may play a role in the mechanism of chemically induced cell transformation.
