Endoxifen (4-hydroxy-N-desmethyl-tamoxifen) has anti-estrogenic effects in breast cancer cells with potency similar to 4-hydroxy-tamoxifen

Young Chai Lim, Zeruesenay Desta, David A. Flockhart, Todd Skaar

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216 Citations (Scopus)

Abstract

Purpose: Tamoxifen is an effective drug for the treatment and prevention of breast cancer. It is extensively metabolized by the human cytochrome P450 enzyme system into several metabolites. Of these, 4-hydroxy-tamoxifen (4-OH-Tam) is an active metabolite, which has greater anti-estrogenic potency than the parent drug, tamoxifen. We reported recently that 4-hydroxy-N-desmethyl- tamoxifen (endoxifen) could also be active. The progesterone receptor (PR) messenger ribonucleic acid (mRNA) expression is commonly studied as a marker of estrogenic effect in breast cancer cells and PR levels in breast cancer patients are correlated with tamoxifen response. We, therefore, determined the effect of endoxifen and 4-OH-Tam on 17β-estradiol (E2)-induced PR mRNA expression in an estrogen receptor-positive human breast cancer cell line. Methods: MCF-7 cells were treated with drugs for 24 h. The total ribonucleic acid (RNA) was harvested and transcribed into complementary deoxyribonucleic acids (cDNAs). The PR mRNA level was measured by using real-time reverse transcription polymerase chain reaction (RT-PCR). The PR expression data were normalized using a glyceraldehyde-3-phosphate dehydrogenase (GAPDH) gene expression. We measured the metabolite concentrations in the cultured media by high performance liquid chromatography (HPLC) to determine whether there was conversion of one metabolite to the other. Results: Consistent with previous reports, the dose-response of the E2 effect on the PR expression indicated an ED50 value of approximately 60 pM and the maximum induction of PR mRNA was nearly ten-fold. When 10-10 M E2 was used, induction of the PR expression was observed in 2 h and reached its maximum at 24 h. In this assay, neither endoxifen nor 4-OH-Tam alone produced any change in the PR mRNA expression. However, both endoxifen and 4-OH-Tam decreased the E2-induced PR expression with similar potency. There was very little interconversion between the two metabolites during the culture. Conclusions: Since endoxifen is present at greater concentrations than 4-OH-Tam in human plasma of breast cancer patients receiving chronic tamoxifen, these results provide further evidence that endoxifen is as important as, or more important than, 4-OH-Tam to the anti-estrogenic action of tamoxifen.

Original languageEnglish
Pages (from-to)471-478
Number of pages8
JournalCancer Chemotherapy and Pharmacology
Volume55
Issue number5
DOIs
StatePublished - May 2005

Fingerprint

Progesterone Receptors
Tamoxifen
Estrogens
Cells
Breast Neoplasms
Metabolites
RNA
Cytochrome P-450 Enzyme System
4-hydroxy-N-desmethyltamoxifen
afimoxifene
Pharmaceutical Preparations
Plasma (human)
Glyceraldehyde-3-Phosphate Dehydrogenases
Polymerase chain reaction
MCF-7 Cells
High performance liquid chromatography
Transcription
Gene expression
Estrogen Receptors
Reverse Transcription

Keywords

  • 4-hydroxy-tamoxifen
  • Breast cancer
  • Endoxifen
  • mRNA expression
  • Progesterone receptor
  • Tamoxifen

ASJC Scopus subject areas

  • Cancer Research
  • Pharmacology
  • Oncology

Cite this

@article{d4ef743d80a84f8b963109da9568062e,
title = "Endoxifen (4-hydroxy-N-desmethyl-tamoxifen) has anti-estrogenic effects in breast cancer cells with potency similar to 4-hydroxy-tamoxifen",
abstract = "Purpose: Tamoxifen is an effective drug for the treatment and prevention of breast cancer. It is extensively metabolized by the human cytochrome P450 enzyme system into several metabolites. Of these, 4-hydroxy-tamoxifen (4-OH-Tam) is an active metabolite, which has greater anti-estrogenic potency than the parent drug, tamoxifen. We reported recently that 4-hydroxy-N-desmethyl- tamoxifen (endoxifen) could also be active. The progesterone receptor (PR) messenger ribonucleic acid (mRNA) expression is commonly studied as a marker of estrogenic effect in breast cancer cells and PR levels in breast cancer patients are correlated with tamoxifen response. We, therefore, determined the effect of endoxifen and 4-OH-Tam on 17β-estradiol (E2)-induced PR mRNA expression in an estrogen receptor-positive human breast cancer cell line. Methods: MCF-7 cells were treated with drugs for 24 h. The total ribonucleic acid (RNA) was harvested and transcribed into complementary deoxyribonucleic acids (cDNAs). The PR mRNA level was measured by using real-time reverse transcription polymerase chain reaction (RT-PCR). The PR expression data were normalized using a glyceraldehyde-3-phosphate dehydrogenase (GAPDH) gene expression. We measured the metabolite concentrations in the cultured media by high performance liquid chromatography (HPLC) to determine whether there was conversion of one metabolite to the other. Results: Consistent with previous reports, the dose-response of the E2 effect on the PR expression indicated an ED50 value of approximately 60 pM and the maximum induction of PR mRNA was nearly ten-fold. When 10-10 M E2 was used, induction of the PR expression was observed in 2 h and reached its maximum at 24 h. In this assay, neither endoxifen nor 4-OH-Tam alone produced any change in the PR mRNA expression. However, both endoxifen and 4-OH-Tam decreased the E2-induced PR expression with similar potency. There was very little interconversion between the two metabolites during the culture. Conclusions: Since endoxifen is present at greater concentrations than 4-OH-Tam in human plasma of breast cancer patients receiving chronic tamoxifen, these results provide further evidence that endoxifen is as important as, or more important than, 4-OH-Tam to the anti-estrogenic action of tamoxifen.",
keywords = "4-hydroxy-tamoxifen, Breast cancer, Endoxifen, mRNA expression, Progesterone receptor, Tamoxifen",
author = "Lim, {Young Chai} and Zeruesenay Desta and Flockhart, {David A.} and Todd Skaar",
year = "2005",
month = "5",
doi = "10.1007/s00280-004-0926-7",
language = "English",
volume = "55",
pages = "471--478",
journal = "Cancer Chemotherapy and Pharmacology",
issn = "0344-5704",
publisher = "Springer Verlag",
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}

TY - JOUR

T1 - Endoxifen (4-hydroxy-N-desmethyl-tamoxifen) has anti-estrogenic effects in breast cancer cells with potency similar to 4-hydroxy-tamoxifen

AU - Lim, Young Chai

AU - Desta, Zeruesenay

AU - Flockhart, David A.

AU - Skaar, Todd

PY - 2005/5

Y1 - 2005/5

N2 - Purpose: Tamoxifen is an effective drug for the treatment and prevention of breast cancer. It is extensively metabolized by the human cytochrome P450 enzyme system into several metabolites. Of these, 4-hydroxy-tamoxifen (4-OH-Tam) is an active metabolite, which has greater anti-estrogenic potency than the parent drug, tamoxifen. We reported recently that 4-hydroxy-N-desmethyl- tamoxifen (endoxifen) could also be active. The progesterone receptor (PR) messenger ribonucleic acid (mRNA) expression is commonly studied as a marker of estrogenic effect in breast cancer cells and PR levels in breast cancer patients are correlated with tamoxifen response. We, therefore, determined the effect of endoxifen and 4-OH-Tam on 17β-estradiol (E2)-induced PR mRNA expression in an estrogen receptor-positive human breast cancer cell line. Methods: MCF-7 cells were treated with drugs for 24 h. The total ribonucleic acid (RNA) was harvested and transcribed into complementary deoxyribonucleic acids (cDNAs). The PR mRNA level was measured by using real-time reverse transcription polymerase chain reaction (RT-PCR). The PR expression data were normalized using a glyceraldehyde-3-phosphate dehydrogenase (GAPDH) gene expression. We measured the metabolite concentrations in the cultured media by high performance liquid chromatography (HPLC) to determine whether there was conversion of one metabolite to the other. Results: Consistent with previous reports, the dose-response of the E2 effect on the PR expression indicated an ED50 value of approximately 60 pM and the maximum induction of PR mRNA was nearly ten-fold. When 10-10 M E2 was used, induction of the PR expression was observed in 2 h and reached its maximum at 24 h. In this assay, neither endoxifen nor 4-OH-Tam alone produced any change in the PR mRNA expression. However, both endoxifen and 4-OH-Tam decreased the E2-induced PR expression with similar potency. There was very little interconversion between the two metabolites during the culture. Conclusions: Since endoxifen is present at greater concentrations than 4-OH-Tam in human plasma of breast cancer patients receiving chronic tamoxifen, these results provide further evidence that endoxifen is as important as, or more important than, 4-OH-Tam to the anti-estrogenic action of tamoxifen.

AB - Purpose: Tamoxifen is an effective drug for the treatment and prevention of breast cancer. It is extensively metabolized by the human cytochrome P450 enzyme system into several metabolites. Of these, 4-hydroxy-tamoxifen (4-OH-Tam) is an active metabolite, which has greater anti-estrogenic potency than the parent drug, tamoxifen. We reported recently that 4-hydroxy-N-desmethyl- tamoxifen (endoxifen) could also be active. The progesterone receptor (PR) messenger ribonucleic acid (mRNA) expression is commonly studied as a marker of estrogenic effect in breast cancer cells and PR levels in breast cancer patients are correlated with tamoxifen response. We, therefore, determined the effect of endoxifen and 4-OH-Tam on 17β-estradiol (E2)-induced PR mRNA expression in an estrogen receptor-positive human breast cancer cell line. Methods: MCF-7 cells were treated with drugs for 24 h. The total ribonucleic acid (RNA) was harvested and transcribed into complementary deoxyribonucleic acids (cDNAs). The PR mRNA level was measured by using real-time reverse transcription polymerase chain reaction (RT-PCR). The PR expression data were normalized using a glyceraldehyde-3-phosphate dehydrogenase (GAPDH) gene expression. We measured the metabolite concentrations in the cultured media by high performance liquid chromatography (HPLC) to determine whether there was conversion of one metabolite to the other. Results: Consistent with previous reports, the dose-response of the E2 effect on the PR expression indicated an ED50 value of approximately 60 pM and the maximum induction of PR mRNA was nearly ten-fold. When 10-10 M E2 was used, induction of the PR expression was observed in 2 h and reached its maximum at 24 h. In this assay, neither endoxifen nor 4-OH-Tam alone produced any change in the PR mRNA expression. However, both endoxifen and 4-OH-Tam decreased the E2-induced PR expression with similar potency. There was very little interconversion between the two metabolites during the culture. Conclusions: Since endoxifen is present at greater concentrations than 4-OH-Tam in human plasma of breast cancer patients receiving chronic tamoxifen, these results provide further evidence that endoxifen is as important as, or more important than, 4-OH-Tam to the anti-estrogenic action of tamoxifen.

KW - 4-hydroxy-tamoxifen

KW - Breast cancer

KW - Endoxifen

KW - mRNA expression

KW - Progesterone receptor

KW - Tamoxifen

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