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Chromosome breakage at a major fragile site associated with P-glycoprotein gene amplification in multidrug-resistant

M T Kuo1, R C Vyas, L X Jiang

  • 1Department of Molecular Pathology, University of Texas M. D. Anderson Cancer Center, Houston 77030.

Molecular and Cellular Biology
|August 1, 1994
PubMed

Insights

Chromosome breakage at fragile sites initiates DNA amplification, leading to drug resistance. Methotrexate and aphidicolin treatments enhance this process, suggesting fragile sites are key in gene amplification.

Area of Science:

  • Genetics
  • Cell Biology
  • Molecular Biology

Background:

  • Drug resistance in mammalian cells often involves gene amplification.
  • The breakage-fusion-bridge (BFB) mechanism is implicated in gene amplification.
  • The precise mechanism initiating chromosome breakage in BFB is not fully understood.

Purpose of the Study:

  • To identify the specific chromosomal site of breakage involved in P-glycoprotein (P-gp) gene amplification.
  • To investigate the role of chromosome fragile sites in initiating DNA amplification.
  • To explore the influence of specific chemical treatments on gene amplification frequency.

Main Methods:

  • Analysis of multidrug-resistant Chinese hamster ovary (CHO) cell lines.
  • Induction of chromosome fragile sites using methotrexate and aphidicolin.
  • Quantification of P-gp gene amplification and drug resistance.

Main Results:

  • Chromosome breakage associated with P-gp gene amplification via BFB was localized to 1q31 in CHO cells.
  • Site 1q31 is a known fragile site inducible by methotrexate and aphidicolin.
  • Pretreatment with these agents increased vinca alkaloid resistance and P-gp gene amplification frequency.

Conclusions:

  • Chromosome fragile sites are pivotal in initiating DNA amplification in mammalian cells.
  • Stress-induced chromosome breakage, independent of cytotoxic agent action, can initiate gene amplification.
  • Gene amplification provides a growth advantage to drug-resistant variants through target molecule overproduction.

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