title: Molecular/cytogenetic alterations accompanying the development of multidrug resistance in the J774.2 murine cell line.
abstract: Mouse macrophage-like J774.2 cells were selected for resistance to colchicine and examined by molecular/cytogenetic analysis to determine whether the acquisition of the multidrug resistant (mdr) phenotype was associated with specific chromosomal rearrangements. Cytogenetic studies of the J774.2 parental and two colchicine-resistant (CLCR) sublines--J7.Cl-30 (770-fold CLCR) and J7.Cl-100 (2500-fold CLCR)--demonstrated specific numeric and structural karyotypic alterations accompanying the emergence of mdr. The parental cells demonstrated a modal chromosome number of 63, while the modal number of the J7.Cl-30 subline was 53. The most striking difference between the parental and J7.Cl-30 subline was the presence of an average of 60 double minutes (DMs) per cell in the CLCR cells. The 2500-fold resistant J7.Cl-100 subline displayed a modal number of 50, which included structural rearrangements involving chromosomes 2 and 7 and concomitant replacement of DMs by a homogeneously staining region (HSR). Southern blotting analysis demonstrated a approximately 35-fold amplification of P-glycoprotein homologous sequences in the J7.Cl-30 subline and approximately 70-fold amplification in the J7.Cl-100 subline. Chromosomal in situ hybridization localized the amplified P-glycoprotein sequences to DMs (J7.Cl-30) and the HSR (J7.Cl-100) in these CLCR sublines. Our results suggest that CLCR in J774.2 cells results from overexpression of P-glycoprotein via gene amplification which was accompanied by chromosomal evolution from DMs to an HSR.
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000818:Animals; D002460:Cell Line; D002869:Chromosome Aberrations; D003078:Colchicine / Q000494:pharmacology*; D004351:Drug Resistance; D005784:Gene Amplification; D008264:Macrophages / Q000648:ultrastructure; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism; D051379:Mice; D009374:Neoplasms, Experimental / Q000235:genetics*; D009693:Nucleic Acid Hybridization
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D008562:Membrane Glycoproteins; D003078:Colchicine