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Related Experiment Videos

Decrease of c-erbB-2 and c-myc RNA levels in tamoxifen-treated breast cancer.

X Le Roy1, C Escot, J P Brouillet

  • 1INSERM Unité Hormones et Cancer (U148), Montpellier, France.

Oncogene
|March 1, 1991
PubMed
Summary
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Tamoxifen treatment significantly reduced c-myc and c-erbB-2 oncogene RNA levels in breast cancer patients. This study provides the first evidence of tamoxifen down-regulating genes in estrogen receptor-negative breast cancer cells in vivo.

Area of Science:

  • Oncology
  • Molecular Biology
  • Pharmacology

Background:

  • Breast carcinomas often exhibit amplification and/or overexpression of oncogenes like c-myc, c-erbB-2, hst, and int-2.
  • Tamoxifen is a widely used endocrine therapy for breast cancer, primarily targeting estrogen receptor-positive (ER+) tumors.

Purpose of the Study:

  • To investigate the effect of tamoxifen on the RNA levels of key oncogenes (c-myc, c-erbB-2, hst, int-2) in human breast cancer patients.
  • To explore potential differences in tamoxifen's effects based on estrogen receptor (ER) and progesterone receptor (PR) status.

Main Methods:

  • In situ hybridization coupled with computer-aided quantification was used to measure oncogene RNA levels.
  • RNA levels were compared between 19 breast cancer patients treated with tamoxifen for 3 weeks prior to surgery and 22 control patients.

Related Experiment Videos

  • Correlation analyses were performed to assess relationships between gene amplification, expression, and receptor status.

    • Main Results:

    • Tamoxifen treatment significantly decreased c-myc and c-erbB-2 RNA levels (P = 0.018, P = 0.003, respectively).
    • hst and int-2 RNA levels were low and not significantly affected by tamoxifen.
    • Gene amplification correlated with expression for c-erbB-2 and hst in controls.
    • Tamoxifen diminished c-erbB-2 expression in ER- and PR-negative populations, an effect not seen in vitro.

    Conclusions:

    • Tamoxifen effectively down-regulates c-myc and c-erbB-2 RNA levels in vivo in breast cancer cells.
    • Tamoxifen appears to act via distinct mechanisms in ER-positive and ER-negative breast cancers.
    • This study presents novel evidence for tamoxifen's in vivo gene down-regulation in ER-negative breast cancer.