Estrogen Response element-GFP (ERE-GFP) introduced MCF-7 cells demonstrated the coexistence of multiple estrogen-deprivation resistant mechanisms

Natsu Fujiki, Hiromi Konno, Yosuke Kaneko, Tatsuyuki Gohno, Toru Hanamura, Koshi Imami, Yasushi Ishihama, Kyoko Nakanishi, Toshifumi Niwa, Yuko Seino, Yuri Yamaguchi, Shin Ichi Hayashi

Research output: Contribution to journalArticlepeer-review

18 Citations (Scopus)

Abstract

The acquisition of estrogen-deprivation resistance and estrogen receptor (ER) signal-independence in ER-positive breast cancer is one of the crucial steps in advancing the aggressiveness of breast cancer; however, this has not yet been elucidated in detail. To address this issue, we established several estrogen-deprivation-resistant (EDR) breast cancer cell lines from our unique MCF-7 cells, which had been stably transfected with an ERE-GFP reporter plasmid. Three cell lines with high ER activity and another 3 cell lines with no ER activity were established from cell cloning by monitoring GFP expression in living cells. The former three ERE-GFP-positive EDR cell lines showed the overexpression of ER and high expression of several ER-target genes. Further analysis of intracellular signaling factors revealed a marked change in the phosphorylation status of ERα on Ser167 and Akt on Thr308 by similar mechanisms reported previously; however, we could not find any changes in MAP-kinase factors. Comprehensive phospho-proteomic analysis also indicated the possible contribution of the Akt pathway to the phosphorylation of ERα. On the other hand, constitutive activation of c-Jun N-terminal kinase (JNK) was observed in ERE-GFP-negative EDR cells, and the growth of these cells was inhibited by a JNK inhibitor. An IGF1R-specific inhibitor diminished the phosphorylation of JNK, which suggested that a novel signaling pathway, IGF1R-JNK, may be important for the proliferation of ER-independent MCF-7 cells. These results indicate that ER-positive breast cancer cells can acquire resistance by more than two mechanisms at a time, which suggests that multiple mechanisms may occur simultaneously. This finding also implies that breast cancers with different resistance mechanisms can concomitantly occur and mingle in an individual patient, and may be a cause of the recurrence of cancer.

Original languageEnglish
Pages (from-to)61-72
Number of pages12
JournalJournal of Steroid Biochemistry and Molecular Biology
Volume139
DOIs
Publication statusPublished - 2014

Keywords

  • Breast cancer
  • Estrogen
  • Estrogen-deprivation resistance
  • Hormonal therapy
  • Keywords

ASJC Scopus subject areas

  • Endocrinology, Diabetes and Metabolism
  • Biochemistry
  • Molecular Medicine
  • Molecular Biology
  • Endocrinology
  • Clinical Biochemistry
  • Cell Biology

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