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Related Experiment Videos

Gene amplification in the murine SEWA system.

G Levan1, F Ståhl, Y Wettergren

  • 1Department of Genetics, Gothenburg University, Sweden.

Mutation Research
|May 1, 1992
PubMed
Summary

SEWA cells exhibit spontaneous c-myc oncogene amplification, with gene amplification structures like double minutes (DM) and homogeneously staining regions (HSR) observed. Drug resistance can be superimposed, with amplicons found on large circular molecules.

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Area of Science:

  • Cancer research
  • Genetics
  • Molecular biology

Background:

  • The SEWA murine ascites tumor cell system is a model for studying DNA amplification.
  • Spontaneous amplification of the c-myc oncogene occurs in SEWA cells.
  • Gene amplification can manifest as double minutes (DM), C-bandless chromosomes (CM), and homogeneously staining regions (HSR).

Purpose of the Study:

  • To investigate the dynamics and molecular mechanisms of DNA amplification in SEWA cells.
  • To characterize the cytogenetic and molecular basis of drug resistance in amplified SEWA cells.
  • To explore the role of circular DNA molecules in gene amplification.

Main Methods:

  • Serial in vivo transplantation of SEWA cells.
  • In vitro drug selection to induce gene amplification.

Related Experiment Videos

  • Cytogenetic analysis to identify amplification structures (DM, HSR, CB).
  • Molecular analysis of amplified DNA, including sequencing of circular molecules.

    • Main Results:

    • Transitions between different cytogenetic forms of gene amplification (DM, CM, HSR) were observed during transplantation.
    • DM containing c-myc oncogene were lost in vitro but recovered upon re-injection into animals.
    • Superimposed gene amplification led to resistance against multiple drugs (methotrexate, actinomycin D, colcemid, vincristine).
    • Chromatin bodies (CB) were identified as carriers of resistance genes in hybrid cells.
    • In a colcemid-resistant line, DM were found to possess active centromeres.
    • Amplicons in multidrug-resistant SEWA sublines were located on ~2500 kb circular molecules containing multiple genes, including mouse mdr genes.

    Conclusions:

    • DNA amplification in SEWA cells is a dynamic process with diverse cytogenetic manifestations.
    • Gene amplification can be modulated by in vivo and in vitro conditions, influencing drug resistance.
    • Circular DNA molecules represent a significant mechanism for carrying amplified genes, including those conferring multidrug resistance.