title: DNA topoisomerase II inhibition and gene amplification in V79/B7 cells.
abstract: Topoisomerase II inhibitors such as etoposide (VP16) are able to stabilize the enzyme-DNA complex by trapping the topoisomerase on DNA without affecting its strand-break activity. To test if this inhibition resulting in chromosomal breakage via double-strand breaks could underlie gene amplification, we performed VP16 treatments followed by selection for PALA resistance in V79/B7 Chinese hamster cells. We found that VP16 induced PALA-resistant cells very efficiently, and in a dose-dependent manner. On the other hand VP16 in combination with 3-aminobenzamide (3AB), an inhibitor of poly(ADP-ribose) polymerase involved in DNA repair, reduced the frequency of PALA-resistant cells. Cytogenetic analysis revealed a higher number of chromosomal aberrations in VP16-treated cells than in cells treated with VP16 plus 3AB. These results suggest a correlation between frequency of chromosomal aberrations and frequency of PALA-resistant cells, and are consistent with models which consider chromosomal breakage as an important step in initiating gene amplification.
authors.affiliation: Dipartimento di Biologia Cellulare e dello Sviluppo, A. Monroy, University of Palermo, Italy.
authors.forename: A
authors.initials: A
authors.lastname: Di Leonardo
authors.forename: P
authors.initials: P
authors.lastname: Cavolina
authors.forename: A
authors.initials: A
authors.lastname: Maddalena
mesh_terms: D000818:Animals; D001221:Aspartate Carbamoyltransferase / Q000235:genetics; D001224:Aspartic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D001549:Benzamides / Q000633:toxicity; D002223:Carbamoyl-Phosphate Synthase (Glutamine-Hydrolyzing) / Q000235:genetics; D002478:Cells, Cultured; D002869:Chromosome Aberrations; D006224:Cricetinae; D003412:Cricetulus; D004249:DNA Damage; D004260:DNA Repair / Q000187:drug effects*; D004080:Dihydroorotase / Q000235:genetics; D004351:Drug Resistance / Q000235:genetics; D005047:Etoposide / Q000633:toxicity*; D005784:Gene Amplification; D009097:Multienzyme Complexes / Q000235:genetics; D010746:Phosphonoacetic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D059005:Topoisomerase II Inhibitors
chemical_list: D001549:Benzamides; C033626:CAD trifunctional enzyme; D009097:Multienzyme Complexes; D059005:Topoisomerase II Inhibitors; D001224:Aspartic Acid; D005047:Etoposide; C013195:sparfosic acid; C025160:3-aminobenzamide; D001221:Aspartate Carbamoyltransferase; D004080:Dihydroorotase; D002223:Carbamoyl-Phosphate Synthase (Glutamine-Hydrolyzing); D010746:Phosphonoacetic Acid