Breast cancer resistance protein exports sulfated estrogens but not free estrogens

Yasuo Imai, Sakiyo Asada, Satomi Tsukahara, Etsuko Ishikawa, Takashi Tsuruo, Yoshikazu Sugimoto

Research output: Contribution to journalArticle

176 Citations (Scopus)

Abstract

Breast cancer resistance protein (BCRP), an ATP-binding cassette transporter, confers resistance to a series of anticancer reagents such as mitoxantrone, 7-ethyl-10-hydroxycamptothecin, and topotecan. We reported previously that estrone and 17β-estradiol reverse BCRP-mediated multidrug resistance. In the present study, we demonstrate that BCRP exports estrogen metabolites. First, we generated BCRP-transduced LLC-PK1 (LLC/BCRP) cells, in which exogenous BCRP is expressed in the apical membrane, and investigated transcellular transport of 3H-labeled compounds using cells plated on microporous filter membranes. The basal-to-apical transport (excretion) of mitoxantrone, estrone, and 17β-estradiol was greater in LLC/BCRP cells than in LLC-PK1 cells. Thin-layer chromatography of transported steroids revealed that the transport of estrone and 17β-estradiol was independent of BCRP expression. Alternatively, increased excretion of estrone sulfate and 17β-estradiol sulfate was observed in LLC/BCRP cells. BCRP inhibitors completely inhibited the increased excretion of sulfated estrogens across the apical membrane. Conversion of estrogens into their sulfate conjugates was similar between LLC/BCRP and LLC-PK1 cells, suggesting that the increased excretion of estrogen sulfates was attributable to BCRP-mediated transport. Next, the uptake of 3H-labeled compounds in membrane vesicles from BCRP-transduced K562 (K562/BCRP) cells was investigated. 3H-labeled estrone sulfate, but not 3H-labeled estrone or 17β-estradiol, was taken up by membrane vesicles from K562/BCRP cells, and this was ATP-dependent. Additionally, BCRP inhibitors suppressed the transport of estrone sulfate in membrane vesicles from K562/BCRP cells. These results suggest that BCRP does not transport either free estrone or 17β-estradiol but exports sulfate conjugates of these estrogens.

Original languageEnglish
Pages (from-to)610-618
Number of pages9
JournalMolecular Pharmacology
Volume64
Issue number3
DOIs
Publication statusPublished - 2003 Sep 1
Externally publishedYes

Fingerprint

Estrogens
Breast Neoplasms
Proteins
Estrone
Membranes
Estradiol
LLC-PK1 Cells
P-Glycoproteins
Mitoxantrone
irinotecan
Sulfates
Topotecan
Transcytosis
ATP-Binding Cassette Transporters
Protein Transport
Thin Layer Chromatography
Protein Binding
Adenosine Triphosphate
Steroids

ASJC Scopus subject areas

  • Pharmacology

Cite this

Breast cancer resistance protein exports sulfated estrogens but not free estrogens. / Imai, Yasuo; Asada, Sakiyo; Tsukahara, Satomi; Ishikawa, Etsuko; Tsuruo, Takashi; Sugimoto, Yoshikazu.

In: Molecular Pharmacology, Vol. 64, No. 3, 01.09.2003, p. 610-618.

Research output: Contribution to journalArticle

Imai, Yasuo ; Asada, Sakiyo ; Tsukahara, Satomi ; Ishikawa, Etsuko ; Tsuruo, Takashi ; Sugimoto, Yoshikazu. / Breast cancer resistance protein exports sulfated estrogens but not free estrogens. In: Molecular Pharmacology. 2003 ; Vol. 64, No. 3. pp. 610-618.
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abstract = "Breast cancer resistance protein (BCRP), an ATP-binding cassette transporter, confers resistance to a series of anticancer reagents such as mitoxantrone, 7-ethyl-10-hydroxycamptothecin, and topotecan. We reported previously that estrone and 17β-estradiol reverse BCRP-mediated multidrug resistance. In the present study, we demonstrate that BCRP exports estrogen metabolites. First, we generated BCRP-transduced LLC-PK1 (LLC/BCRP) cells, in which exogenous BCRP is expressed in the apical membrane, and investigated transcellular transport of 3H-labeled compounds using cells plated on microporous filter membranes. The basal-to-apical transport (excretion) of mitoxantrone, estrone, and 17β-estradiol was greater in LLC/BCRP cells than in LLC-PK1 cells. Thin-layer chromatography of transported steroids revealed that the transport of estrone and 17β-estradiol was independent of BCRP expression. Alternatively, increased excretion of estrone sulfate and 17β-estradiol sulfate was observed in LLC/BCRP cells. BCRP inhibitors completely inhibited the increased excretion of sulfated estrogens across the apical membrane. Conversion of estrogens into their sulfate conjugates was similar between LLC/BCRP and LLC-PK1 cells, suggesting that the increased excretion of estrogen sulfates was attributable to BCRP-mediated transport. Next, the uptake of 3H-labeled compounds in membrane vesicles from BCRP-transduced K562 (K562/BCRP) cells was investigated. 3H-labeled estrone sulfate, but not 3H-labeled estrone or 17β-estradiol, was taken up by membrane vesicles from K562/BCRP cells, and this was ATP-dependent. Additionally, BCRP inhibitors suppressed the transport of estrone sulfate in membrane vesicles from K562/BCRP cells. These results suggest that BCRP does not transport either free estrone or 17β-estradiol but exports sulfate conjugates of these estrogens.",
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