title: Human myeloma cells acquire resistance to difluoromethylornithine by amplification of ornithine decarboxylase gene.
abstract: Stepwise increments of the concentration of 2-difluoromethylornithine (DFMO), a mechanism-based irreversible inhibitor of mammalian ornithine decarboxylase (ODC), resulted in a selection of cultured human IgG-myeloma cells (Sultan cell line) capable of growing in the presence of up to 3 mM-DFMO. This capacity was associated with 10-fold increase in ODC activity in the dialysed extracts of drug-resistant myeloma cells, markedly enhanced synthesis rate for ODC enzyme molecules, as revealed by a 20 min [35S]methionine labelling of cellular proteins, followed by specific immunoprecipitation and SDS/polyacrylamide-gel electrophoresis, dose-dependently increased expression of ODC mRNA in resistant cells (effective dose causing 50% inhibition), dose-dependent amplification of ODC gene sequences in a 9-kilobase-pairs EcoRI genomic DNA fragment, and (v) a 10-fold increase in the ED50 (effective dose causing 50% inhibition) for the anti-proliferative action of DFMO in these myeloma cells. These results represent one of the few gene amplifications described in cultured human cells.
mesh_terms: D002460:Cell Line; D011232:Chemical Precipitation; D004351:Drug Resistance / Q000235:genetics; D000518:Eflornithine / Q000494:pharmacology*; D005784:Gene Amplification; D005838:Genotype; D006801:Humans; D009101:Multiple Myeloma / Q000201:enzymology / Q000235:genetics*; D009955:Ornithine Decarboxylase / Q000235:genetics* / Q000276:immunology; D012333:RNA, Messenger / Q000235:genetics
chemical_list: D012333:RNA, Messenger; D009955:Ornithine Decarboxylase; D000518:Eflornithine