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Evidence for linear extrachromosomal elements mediating gene amplification in the multidrug-resistant J774.2 murine

E U Meese1, S B Horwitz, J M Trent

  • 1Department of Radiation Oncology, University of Michigan Medical Center, Ann Arbor 48109-0668.

Cancer Genetics and Cytogenetics
|March 1, 1992
PubMed

Insights

Gene amplification of p-glycoprotein (mdr) drives colchicine resistance in murine cells. Extrachromosomal elements in J7.Cl-30 cells transform into homogeneously staining regions (HSRs) as resistance increases, offering insights into gene amplification.

Area of Science:

  • * Molecular biology
  • * Cell biology
  • * Genetics

Background:

  • * Cytogenetic alterations are linked to drug resistance.
  • * Murine cell lines (J774.2) develop colchicine resistance.
  • * Gene amplification of p-glycoprotein (mdr) is observed in resistant sublines.

Purpose of the Study:

  • * To analyze the localization and organization of the mdr gene in colchicine-resistant cells.
  • * To investigate the relationship between extrachromosomal elements, HSRs, and increasing drug resistance.
  • * To explore theories of extrachromosomal gene amplification.

Main Methods:

  • * Cytogenetic analysis of J774.2 murine cell line and sublines.
  • * Pulsed-field gel electrophoresis (PFGE) to determine extrachromosomal element sizes.
  • * Characterization of extrachromosomal elements and homogeneously staining regions (HSRs).

Main Results:

  • * J7.Cl-30 subline exhibits mdr gene amplification on extrachromosomal elements (circular and linear, >2,500 kb, 800 kb, 400 kb).
  • * J7.Cl-100 subline shows mdr gene amplification within HSRs.
  • * Increasing colchicine resistance correlates with the replacement of extrachromosomal elements by HSRs.

Conclusions:

  • * Linear extrachromosomal elements may serve as precursors to HSRs.
  • * Findings provide a novel perspective on extrachromosomal gene amplification mechanisms.
  • * The J7.Cl-30 cell line is a valuable model for studying extrachromosomal element formation and structure.

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