title: The propensity for gene amplification: a comparison of protocols, cell lines, and selection agents.
abstract: We have studied cell lines of rodent and human origin for their propensity to become resistant to antifolates (methotrexate, trimetrexate), phosphonacetyl-L-aspartate (PALA), and colcemid, resistances associated with amplification of the DHFR, CAD, and MDR1 genes, respectively. We have employed two different methods: (1) a shallow step-wise selection protocol, where time to attain specified resistance is the quantitative measure, (2) the frequency of resistant colonies at specified drug concentrations. Although there are advantages and disadvantages to both methods, the two methods gave the same relative ranking of cell lines. Striking differences in the propensity for gene amplification (resistance) were found: human cell lines were less prone to amplify genes than Chinese hamster ovary (CHO) cells. This ranking was similar with all of the agents employed. Additionally, we observed that whereas PALA resistance in CHO cells is associated with amplification of the CAD gene, PALA resistance in the two human cell lines studied (HeLaS3 and VA13) was not associated with amplification and/or overexpression of the CAD gene, and thus this resistance to PALA occurs by an unknown mechanism.
authors.affiliation: Department of Biological Sciences, Stanford University 94305.
authors.forename: R C
authors.initials: RC
authors.lastname: Sharma
authors.forename: R T
authors.initials: RT
authors.lastname: Schimke
mesh_terms: D000818:Animals; D000964:Antimetabolites, Antineoplastic / Q000633:toxicity*; D001221:Aspartate Carbamoyltransferase / Q000235:genetics*; D001224:Aspartic Acid / Q000031:analogs & derivatives* / Q000633:toxicity; D016466:CHO Cells; D002223:Carbamoyl-Phosphate Synthase (Glutamine-Hydrolyzing) / Q000235:genetics*; D002461:Cell Line, Transformed; D006224:Cricetinae; D003703:Demecolcine / Q000633:toxicity; D004080:Dihydroorotase / Q000235:genetics*; D004305:Dose-Response Relationship, Drug; D004351:Drug Resistance / Q000235:genetics*; D005347:Fibroblasts / Q000187:drug effects; D005493:Folic Acid Antagonists / Q000633:toxicity; D005784:Gene Amplification; D006367:HeLa Cells; D006801:Humans; D007928:Lethal Dose 50; D008727:Methotrexate / Q000633:toxicity; D009097:Multienzyme Complexes / Q000235:genetics*; D010746:Phosphonoacetic Acid / Q000031:analogs & derivatives* / Q000633:toxicity; D012333:RNA, Messenger / Q000032:analysis; D012107:Research Design; D013762:Tetrahydrofolate Dehydrogenase / Q000235:genetics; D016597:Trimetrexate / Q000633:toxicity
chemical_list: D000964:Antimetabolites, Antineoplastic; C033626:CAD trifunctional enzyme; D005493:Folic Acid Antagonists; D009097:Multienzyme Complexes; D012333:RNA, Messenger; D001224:Aspartic Acid; C013195:sparfosic acid; D013762:Tetrahydrofolate Dehydrogenase; D001221:Aspartate Carbamoyltransferase; D004080:Dihydroorotase; D002223:Carbamoyl-Phosphate Synthase (Glutamine-Hydrolyzing); D010746:Phosphonoacetic Acid; D016597:Trimetrexate; D008727:Methotrexate; D003703:Demecolcine