EVIDENCE FOR CYCLOPHOSPHAMIDE-INDUCED GENE CONVERSION AND MUTATION INMOUSE GERM-CELLS

Cyclophosphamide (CP) is a widely used antineoplastic drug. It tests p ositive in several genotoxicity assays, including those with endpoints such as chromosomal aberrations in mammalian cells, mitotic recombina tion in Drosophila melanogaster, and dominant lethal mutations in rode nts. We have explored the effects of CP on genome stability of mouse ( Mus domesticus) spermatogenic cells, using a recombination-based trans genic assay called MUSCA-TEER. In this system, intrachromosomal gene c onversion events between two mutually defective lacZ genes generates B -galactosidase activity in spermatids. The frequency of gene conversio n events is determined by scoring spermatids stained with the lacZ sub strate, X-gal. A dose-dependent induction of lacZ-positive spermatids was observed following single intraperitoneal CP exposures of 10, 100, and 200 mg/kg. At 200 mg/kg, there was a 25-fold increase over baseli ne. Treatment of a control transgenic line containing only a frameshif ted lacZ transgene provided an indication that CP also induced reversi on mutations. The timing of the response indicated that the induction of recombination and/or mutation occurred primarily in meiotic stage c ells. These results demonstrate potent germline mutagenicity of CP, an d validate the utility and sensitivity of genetic recombination as a r apid indicator of genotoxicity in whole animals. (C) 1997 Academic Pre ss.