Induction of sister chromatid exchanges in NIH 3T3 cells transformed by DNA from mice given cyclophosphamide.
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.
Murthy
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PB
Carcinogenicity Section, Department of Toxicology, Frederick Institute of Plant Protection and Toxicology, Padappai-601 301, T. Nadu, India.