Dihydrofolate reductase amplification and sensitization to methotrexate of methotrexate-resistant colon cancer cells.
Mol Cancer Ther
; 8(2): 424-32, 2009 Feb.
Article
em En
| MEDLINE
| ID: mdl-19190117
ABSTRACT
Gene amplification is one of the most frequent manifestations of genomic instability in human tumors and plays an important role in tumor progression and acquisition of drug resistance. To better understand the factors involved in acquired resistance to cytotoxic drugs via gene amplification, we have analyzed the structure and dynamics of dihydrofolate reductase (DHFR) gene amplification in HT29 cells treated with methotrexate (MTX). Analysis of the DHFR gene amplification process shows that the amplicon exhibits a complex structure that is consistently reproduced in independent treatments. The cytogenetic manifestation of the amplification in advanced stages of the treatment may be in the form of double minutes or as a homogeneously stained region. To get insights into the mechanisms of resistance, we have also investigated the sensitization to MTX of MTX-resistant cells after drug withdrawal and reexposure to MTX. Passive loss of the DHFR amplicon by withdrawal of the drug results in MTX-sensitive cells exhibiting a substantial reduction of their capacity or even an incapacity to generate resistance when submitted to a second cycle of MTX treatment. On a second round of drug administration, the resistant cells generate a different amplicon structure, suggesting that the formation of the amplicon as in the first cycle of treatment is not feasible. These results indicate that DHFR gene amplification is a "wear and tear" process in HT29 cells and that MTX-resistant cells may become responsive to a second round of treatment if left untreated during a sufficient period of time.
Texto completo:
1
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Tetra-Hidrofolato Desidrogenase
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Amplificação de Genes
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Metotrexato
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Neoplasias do Colo
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Resistencia a Medicamentos Antineoplásicos
Limite:
Humans
Idioma:
En
Ano de publicação:
2009
Tipo de documento:
Article