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Rich66 · 07-28-2009, 11:49 PM

Breast Cancer Res. 2010;12(3):R43. Epub 2010 Jun 28.
The estrogen receptor influences microtubule-associated protein tau (MAPT) expression and the selective estrogen receptor inhibitor fulvestrant downregulates MAPT and increases the sensitivity to taxane in breast cancer cells.

Ikeda H, Taira N, Hara F, Fujita T, Yamamoto H, Soh J, Toyooka S, Nogami T, Shien T, Doihara H, Miyoshi S.
Department of Cancer and Thoracic Surgery, Okayama University Graduate School of Medicine, Dentistry, and Pharmaceutical Sciences, 2-5-1 Shikata-cho, Okayama-city, Okayama, Japan. yashima_hirokuni@msn.com

FREE TEXT

Abstract

INTRODUCTION: Microtubule-associated protein tau (MAPT) inhibits the function of taxanes and high expression of MAPT decreases the sensitivity to taxanes. The relationship between estrogen receptor (ER) and MAPT in breast cancer is unclear. In this study, we examined the correlation of MAPT expression with the sensitivity of human breast cancer cells to taxanes, and the relationship between ER and MAPT.
METHODS: The correlation between MAPT expression and sensitivity to taxanes was investigated in 12 human breast cancer cell lines. Alterations in cellular sensitivity to taxanes were evaluated after knockdown of MAPT expression. ER expression was knocked down or stimulated in MAPT- and ER-positive cell lines to examine the relationship between ER and MAPT. The cells were also treated with hormone drugs (tamoxifen and fulvestrant) and taxanes.
RESULTS: mRNA expression of MAPT did not correlate with sensitivity to taxanes. However, expression of MAPT protein isoforms of less than 70 kDa was correlated with a low sensitivity to taxanes. Downregulation of MAPT increased cellular sensitivity to taxanes. MAPT protein expression was increased by stimulation with 17-beta-estradiol or tamoxifen, but decreased by ER downregulation and by fulvestrant, an ER inhibitor. The combination of fulvestrant with taxanes had a synergistic effect, whereas tamoxifen and taxanes had an antagonistic effect.
CONCLUSIONS: Expression of MAPT protein isoforms of less than 70 kDa is correlated with a low sensitivity to taxanes in breast cancer cells. ER influences MAPT expression and fulvestrant increases the sensitivity to taxanes in MAPT- and ER-positive breast cancer cells.





1: Breast Cancer Res Treat. 2009 Jul 22. [Epub ahead of print] Links: Fulvestrant (ICI 182,780) sensitizes breast cancer cells expressing estrogen receptor alpha to vinblastine and vinorelbine.

Sui M, Jiang D, Hinsch C, Fan W.
Program of Innovative Cancer Therapeutics, First Affiliated Hospital, Zhejiang University School of Medicine, 310003, Hangzhou, China.
Cumulative data suggest that some chemotherapeutic agents may be less effective in estrogen receptor alpha positive (ER+) breast tumors than ER negative (ER-) tumors, which has raised a clinically relevant question as to how to reverse this ER-mediated chemoresistance in ER+ breast tumors. This study is to investigate the possible influence of estrogen receptor alpha (ERalpha) on the therapeutic effects of vinblastine and vinorelbine on breast cancer cells and explore whether combination of anti-estrogen agent fulvestrant (ICI 182, 780) may enhance the sensitivity of ERalpha+ cells to these chemotherapeutic agents. Through comparing ER+ with ER- human breast tumor cells or through stable transfection of an ERalpha expression vector into ER negative human breast cancer BCap37 cells, a series of assays were applied to determine the sensitivity of ER+ and ER- breast tumor cells to vinblastine and vinorelbine in the presence or absence of 17-beta-estradiol and/or fulvestrant. 17-beta-Estradiol showed no effect on the sensitivity of ER- MDA-MB-468 and BCap37 cells to the treatment of vincristine or vinblastine, but it significantly reduced the sensitivity of ER+ T47D cells and BCap37 cells expressing ERalpha to the two drugs mentioned. Further analyses show that ERalpha has little effect on vinca alkaloids-induced mitotic arrest, but dramatically affects their ability to induce tumor cell apoptosis. Moreover, through a series of assays, we also demonstrated that the combination of fulvestrant, a selective ER down-regulator, could reverse the resistance of ER+ breast tumor cells to vinca alkaloids and even produce synergistic effects. The findings obtained from this study have provided important evidence that expression and subsequent activation of ERalpha are associated with resistance of breast cancer cells to vinca alkaloids. This study also suggested that the combination of anti-estrogen agents, such as fulvestrant, might be a novel strategy to reverse ER-mediated chemoresistance or sensitize ER+ breast tumors to vinca alkaloids and possibly other chemotherapeutic agents.

Surg Today. 1999;29(2):149-56.
Effects of experimental chemoendocrine therapy with a combination of a pure antiestrogen and 5-fluorouracil on human breast cancer cells implanted in nude mice.

Ogasawara Y, Doihara H, Shiroma K, Kanaya Y, Shimizu N.
Department of Surgery II, Okayama University Medical School, Japan.
The antitumor effects of an experimental chemoendocrine therapy combining a new pure antiestrogen ICI 182780 and 5-fluorouracil (5-FU) were studied on MCF-7 human breast cancer cells implanted in nude mice. ICI 182780 had a dose-dependent antitumor activity, which was potentiated by the concomitant use of 5-FU. When compared with the control group, the estrogen receptor (ER) level in the ICI 182780 group was lower and that in the combination group was markedly lower. Cell cycle analysis by flow cytometry (FCM) resulted in a lower percentage of S-phase cells (%S) in the treated mice. No significant difference was observed in the 5-FU concentrations in tumor cells, while the 5-FU content in RNA was significantly higher in the combination group. The changes in free thymidylate synthetase (TS) concentration indicated TS synthesis after the administration of 5-FU to be more greatly suppressed in the combination group than in the 5-FU group. These results suggest that ICI 182780 and 5-FU exert their combination effect mainly on ER-positive cells, and that the suppression of TS synthesis in tumor cells and the potentiation of the 5-FU-induced metabolic dysfunction of RNA are thus involved in the mode of action of this combination therapy.

PMID: 10030740 [PubMed - indexed for MEDLINE]

Breast Cancer Res Treat. 2009 Sep;117(1):69-75. Epub 2008 Nov 23.
Activity of fulvestrant versus exemestane in advanced breast cancer patients with or without visceral metastases: data from the EFECT trial.

Mauriac L, Romieu G, Bines J.
Institut Bergonié, Centre Régional de Lutte Contre le Cancer de Bordeaux et du Sud-Ouest, France. mauriac@bergonie.org

TEXT

Abstract

PURPOSE: Patients with visceral metastases (VM: lung and/or liver metastases) are generally regarded as being less responsive to hormonal therapy, and chemotherapy often becomes the default treatment. This paper reports a subgroup analysis from EFECT (The Evaluation of Faslodex versus Exemestane Clinical Trial) examining the efficacy of fulvestrant and exemestane in patients with or without VM.
METHODS: EFECT is a randomised, double-blind, multicentre, Phase III trial in postmenopausal women with advanced breast cancer progressing or recurring after prior non-steroidal aromatase inhibitor therapy.
RESULTS: Overall, approximately 57% of patients in EFECT had visceral involvement. Fulvestrant and exemestane demonstrated clinical benefit in 29.1% and 27.2% of patients with VM, respectively. Median duration of response was 13.5 vs 10.8 months and median duration of clinical benefit was 9.9 vs 8.1 months, respectively.
CONCLUSIONS: These results encourage the use of endocrine agents such as fulvestrant in treating patients with advanced breast cancer and VM.

PMID: 19030986 [PubMed - indexed for MEDLINE]

07-28-2009, 11:49 PM	#2
Rich66 Senior Member Join Date: Feb 2008 Location: South East Wisconsin Posts: 3,431	Re: Fulvestrant+chemo synergy Breast Cancer Res. 2010;12(3):R43. Epub 2010 Jun 28. The estrogen receptor influences microtubule-associated protein tau (MAPT) expression and the selective estrogen receptor inhibitor fulvestrant downregulates MAPT and increases the sensitivity to taxane in breast cancer cells. Ikeda H, Taira N, Hara F, Fujita T, Yamamoto H, Soh J, Toyooka S, Nogami T, Shien T, Doihara H, Miyoshi S. Department of Cancer and Thoracic Surgery, Okayama University Graduate School of Medicine, Dentistry, and Pharmaceutical Sciences, 2-5-1 Shikata-cho, Okayama-city, Okayama, Japan. yashima_hirokuni@msn.com FREE TEXT Abstract INTRODUCTION: Microtubule-associated protein tau (MAPT) inhibits the function of taxanes and high expression of MAPT decreases the sensitivity to taxanes. The relationship between estrogen receptor (ER) and MAPT in breast cancer is unclear. In this study, we examined the correlation of MAPT expression with the sensitivity of human breast cancer cells to taxanes, and the relationship between ER and MAPT. METHODS: The correlation between MAPT expression and sensitivity to taxanes was investigated in 12 human breast cancer cell lines. Alterations in cellular sensitivity to taxanes were evaluated after knockdown of MAPT expression. ER expression was knocked down or stimulated in MAPT- and ER-positive cell lines to examine the relationship between ER and MAPT. The cells were also treated with hormone drugs (tamoxifen and fulvestrant) and taxanes. RESULTS: mRNA expression of MAPT did not correlate with sensitivity to taxanes. However, expression of MAPT protein isoforms of less than 70 kDa was correlated with a low sensitivity to taxanes. Downregulation of MAPT increased cellular sensitivity to taxanes. MAPT protein expression was increased by stimulation with 17-beta-estradiol or tamoxifen, but decreased by ER downregulation and by fulvestrant, an ER inhibitor. The combination of fulvestrant with taxanes had a synergistic effect, whereas tamoxifen and taxanes had an antagonistic effect. CONCLUSIONS: Expression of MAPT protein isoforms of less than 70 kDa is correlated with a low sensitivity to taxanes in breast cancer cells. ER influences MAPT expression and fulvestrant increases the sensitivity to taxanes in MAPT- and ER-positive breast cancer cells. 1: Breast Cancer Res Treat. 2009 Jul 22. [Epub ahead of print] Links Fulvestrant (ICI 182,780) sensitizes breast cancer cells expressing estrogen receptor alpha to vinblastine and vinorelbine. Sui M, Jiang D, Hinsch C, Fan W. Program of Innovative Cancer Therapeutics, First Affiliated Hospital, Zhejiang University School of Medicine, 310003, Hangzhou, China. Cumulative data suggest that some chemotherapeutic agents may be less effective in estrogen receptor alpha positive (ER+) breast tumors than ER negative (ER-) tumors, which has raised a clinically relevant question as to how to reverse this ER-mediated chemoresistance in ER+ breast tumors. This study is to investigate the possible influence of estrogen receptor alpha (ERalpha) on the therapeutic effects of vinblastine and vinorelbine on breast cancer cells and explore whether combination of anti-estrogen agent fulvestrant (ICI 182, 780) may enhance the sensitivity of ERalpha+ cells to these chemotherapeutic agents. Through comparing ER+ with ER- human breast tumor cells or through stable transfection of an ERalpha expression vector into ER negative human breast cancer BCap37 cells, a series of assays were applied to determine the sensitivity of ER+ and ER- breast tumor cells to vinblastine and vinorelbine in the presence or absence of 17-beta-estradiol and/or fulvestrant. 17-beta-Estradiol showed no effect on the sensitivity of ER- MDA-MB-468 and BCap37 cells to the treatment of vincristine or vinblastine, but it significantly reduced the sensitivity of ER+ T47D cells and BCap37 cells expressing ERalpha to the two drugs mentioned. Further analyses show that ERalpha has little effect on vinca alkaloids-induced mitotic arrest, but dramatically affects their ability to induce tumor cell apoptosis. Moreover, through a series of assays, we also demonstrated that the combination of fulvestrant, a selective ER down-regulator, could reverse the resistance of ER+ breast tumor cells to vinca alkaloids and even produce synergistic effects. The findings obtained from this study have provided important evidence that expression and subsequent activation of ERalpha are associated with resistance of breast cancer cells to vinca alkaloids. This study also suggested that the combination of anti-estrogen agents, such as fulvestrant, might be a novel strategy to reverse ER-mediated chemoresistance or sensitize ER+ breast tumors to vinca alkaloids and possibly other chemotherapeutic agents. Surg Today. 1999;29(2):149-56. Effects of experimental chemoendocrine therapy with a combination of a pure antiestrogen and 5-fluorouracil on human breast cancer cells implanted in nude mice. Ogasawara Y, Doihara H, Shiroma K, Kanaya Y, Shimizu N. Department of Surgery II, Okayama University Medical School, Japan. The antitumor effects of an experimental chemoendocrine therapy combining a new pure antiestrogen ICI 182780 and 5-fluorouracil (5-FU) were studied on MCF-7 human breast cancer cells implanted in nude mice. ICI 182780 had a dose-dependent antitumor activity, which was potentiated by the concomitant use of 5-FU. When compared with the control group, the estrogen receptor (ER) level in the ICI 182780 group was lower and that in the combination group was markedly lower. Cell cycle analysis by flow cytometry (FCM) resulted in a lower percentage of S-phase cells (%S) in the treated mice. No significant difference was observed in the 5-FU concentrations in tumor cells, while the 5-FU content in RNA was significantly higher in the combination group. The changes in free thymidylate synthetase (TS) concentration indicated TS synthesis after the administration of 5-FU to be more greatly suppressed in the combination group than in the 5-FU group. These results suggest that ICI 182780 and 5-FU exert their combination effect mainly on ER-positive cells, and that the suppression of TS synthesis in tumor cells and the potentiation of the 5-FU-induced metabolic dysfunction of RNA are thus involved in the mode of action of this combination therapy. PMID: 10030740 [PubMed - indexed for MEDLINE] Breast Cancer Res Treat. 2009 Sep;117(1):69-75. Epub 2008 Nov 23. Activity of fulvestrant versus exemestane in advanced breast cancer patients with or without visceral metastases: data from the EFECT trial. Mauriac L, Romieu G, Bines J. Institut Bergonié, Centre Régional de Lutte Contre le Cancer de Bordeaux et du Sud-Ouest, France. mauriac@bergonie.org TEXT Abstract PURPOSE: Patients with visceral metastases (VM: lung and/or liver metastases) are generally regarded as being less responsive to hormonal therapy, and chemotherapy often becomes the default treatment. This paper reports a subgroup analysis from EFECT (The Evaluation of Faslodex versus Exemestane Clinical Trial) examining the efficacy of fulvestrant and exemestane in patients with or without VM. METHODS: EFECT is a randomised, double-blind, multicentre, Phase III trial in postmenopausal women with advanced breast cancer progressing or recurring after prior non-steroidal aromatase inhibitor therapy. RESULTS: Overall, approximately 57% of patients in EFECT had visceral involvement. Fulvestrant and exemestane demonstrated clinical benefit in 29.1% and 27.2% of patients with VM, respectively. Median duration of response was 13.5 vs 10.8 months and median duration of clinical benefit was 9.9 vs 8.1 months, respectively. CONCLUSIONS: These results encourage the use of endocrine agents such as fulvestrant in treating patients with advanced breast cancer and VM. PMID: 19030986 [PubMed - indexed for MEDLINE]