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Implementation of In Vitro Drug Resistance Assays: Maximizing the Potential for Uncovering Clinically Relevant Resistance Mechanisms
08:46

Implementation of In Vitro Drug Resistance Assays: Maximizing the Potential for Uncovering Clinically Relevant Resistance Mechanisms

Published on: December 9, 2015

Methotrexate resistance in vitro is achieved by a dynamic selectionprocess of tumor cell variants emerging during

Josep M de Anta1, Clara Mayo, Francesc Solé

  • 1Unitat de Biologia Cellular i Molecular, Institut Municipal d'Investigació Mèdica, Barcelona, Spain.

International Journal of Cancer
|May 4, 2006
PubMed

Insights

Cancer cells adapt to methotrexate treatment through dynamic selection, a process involving cell death and regrowth. This cycle drives genetic instability and stable drug resistance, even in initially sensitive populations.

Area of Science:

  • Cancer Biology
  • Pharmacology
  • Genetics

Background:

  • Tumor heterogeneity, driven by genetic instability, contributes to cancer drug resistance.
  • The origin of drug-resistant cells during acquired resistance remains poorly understood.
  • Methotrexate resistance in cancer cells is a significant clinical challenge.

Purpose of the Study:

  • To elucidate the mechanism of acquired methotrexate resistance in HT-29 colon cancer cells in vitro.
  • To characterize the role of cell density and turnover in the emergence of drug resistance.
  • To identify early genetic events associated with methotrexate-induced resistance.

Main Methods:

  • In vitro culture of HT-29 colon cancer cells under methotrexate treatment.
  • Analysis of cell density-dependent adaptation and survival.
  • Assessment of cell death, proliferation, and genomic instability (centrosome amplification, chromosome recombination).
  • Detection of chromosomal aberrations, specifically 5q amplification.

Main Results:

  • HT-29 cells adapt to methotrexate by reversibly growing at low cell density.
  • Repeated cycles of cell death and growth ('dynamic selection') lead to stable, increasing methotrexate resistance.
  • Methotrexate induces genomic instability, including centrosome amplification and aberrant chromosome recombination.
  • Early genetic events include low-level amplification of the 5q chromosome arm.

Conclusions:

  • Dynamic selection, driven by cell turnover rather than proliferation alone, is a key mechanism for acquiring stable methotrexate resistance.
  • Methotrexate-induced genomic instability facilitates the selection of resistant cell populations.
  • This study provides a model for how initially sensitive tumors can develop stable drug resistance through dynamic selection and genetic adaptation.

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