Regulation of estrogen receptor and epidermal growth factor receptor by tamoxifen under high and low estrogen environments in MCF-7 cells grown in athymic mice.

  • Authors:
    • Y Koibuchi
    • Y Iino
    • T Uchida
    • T Andoh
    • Y Horii
    • M Nagasawa
    • J Horiguchi
    • M Maemura
    • H Takei
    • T Yokoe
    • Y Morishita
  • View Affiliations

  • Published online on: January 1, 2000     https://doi.org/10.3892/or.7.1.135
  • Pages: 135-175
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Abstract

The purpose of this study was to investigate whether tamoxifen (TAM) treatment causes a downregulation of estrogen receptor (ER) and whether TAM induces epidermal growth factor receptor-1 (EGFR). We investigated the expression of ER and EGFR after the treatment of TAM in MCF-7 tumors grown in athymic mice under high and low estrogen environments. MCF-7 tumors were grown in ovariectomized athymic mice by implanting a sustained release 17beta-estradiol (E2) pellet. The E2 pellets were removed after 3 weeks of E2 treatment. Animals were then divided into the following 4 groups: i) an E2 (0. 72 mg/pellet) pellet [E2(+)]; ii) an E2 and a TAM (5 mg/pellet) pellets [E2(+)TAM]; iii) no treatment [E2(-)]; iv) a TAM pellet [E2(-)TAM]. A significant reduction in tumor size was observed in the estrogen-depleted group [E2(-) and E2(-)TAM] compared with the estrogen-completed group [E2(+) and E2(+)TAM]. TAM inhibited estrogen-stimulated growth in the estrogen-completed mice. No additional reduction of the tumor by TAM was observed in the estrogen-depleted mice. Both ER and EGFR protein levels in the tumors of the estrogen-depleted mice were higher than in the estrogen-completed mice. Expression of ER and EGFR protein was increased by TAM in the estrogen-completed mice, however it was decreased by TAM in the estrogen-depleted mice. Changes of ER and EGFR protein levels were similar in all treatments. Transforming growth factor-alpha (TGF-alpha) in tumors, which is known as a ligand of EGFR and as an estrogen-inducible protein in ER positive MCF-7 cells, was decreased by TAM in the estrogen-completed mice, by contrast, it was increased by TAM in the estrogen-depleted mice. Downregulation of ER was observed in TAM-treated mice in an estrogen-depleted environment, this action of TAM was similar to E2. These results suggest that increase of EGFR expression does not lead to a loss of ER after short-term TAM treatment in MCF-7 tumors.

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Jan-Feb 2000
Volume 7 Issue 1

Print ISSN: 1021-335X
Online ISSN:1791-2431

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Spandidos Publications style
Koibuchi Y, Iino Y, Uchida T, Andoh T, Horii Y, Nagasawa M, Horiguchi J, Maemura M, Takei H, Yokoe T, Yokoe T, et al: Regulation of estrogen receptor and epidermal growth factor receptor by tamoxifen under high and low estrogen environments in MCF-7 cells grown in athymic mice.. Oncol Rep 7: 135-175, 2000.
APA
Koibuchi, Y., Iino, Y., Uchida, T., Andoh, T., Horii, Y., Nagasawa, M. ... Morishita, Y. (2000). Regulation of estrogen receptor and epidermal growth factor receptor by tamoxifen under high and low estrogen environments in MCF-7 cells grown in athymic mice.. Oncology Reports, 7, 135-175. https://doi.org/10.3892/or.7.1.135
MLA
Koibuchi, Y., Iino, Y., Uchida, T., Andoh, T., Horii, Y., Nagasawa, M., Horiguchi, J., Maemura, M., Takei, H., Yokoe, T., Morishita, Y."Regulation of estrogen receptor and epidermal growth factor receptor by tamoxifen under high and low estrogen environments in MCF-7 cells grown in athymic mice.". Oncology Reports 7.1 (2000): 135-175.
Chicago
Koibuchi, Y., Iino, Y., Uchida, T., Andoh, T., Horii, Y., Nagasawa, M., Horiguchi, J., Maemura, M., Takei, H., Yokoe, T., Morishita, Y."Regulation of estrogen receptor and epidermal growth factor receptor by tamoxifen under high and low estrogen environments in MCF-7 cells grown in athymic mice.". Oncology Reports 7, no. 1 (2000): 135-175. https://doi.org/10.3892/or.7.1.135