microRNA regulation of mammalian target of rapamycin expression and activity controls estrogen receptor function and RAD001 sensitivity

Elizabeth C. Martin, Lyndsay V. Rhodes, Steven Elliott, Adrienne E. Krebs, Kenneth Nephew, Erik K. Flemington, Bridgette M. Collins-Burow, Matthew E. Burow

Research output: Contribution to journalArticle

12 Citations (Scopus)

Abstract

Background: The AKT/mammalian target of rapamycin (mTOR) signaling pathway is regulated by 17α-estradiol (E2) signaling and mediates E2-induced proliferation and progesterone receptor (PgR) expression in breast cancer. Methods and results: Here we use deep sequencing analysis of previously published data from The Cancer Genome Atlas to demonstrate that expression of a key component of mTOR signaling, rapamycin-insensitive companion of mTOR (Rictor), positively correlated with an estrogen receptor-α positive (ERα<sup>+</sup>) breast tumor signature. Through increased microRNA-155 (miR-155) expression in the ERα<sup>+</sup> breast cancer cells we demonstrate repression of Rictor enhanced activation of mTOR complex 1 (mTORC1) signaling with both qPCR and western blot. miR-155-mediated mTOR signaling resulted in deregulated ERα signaling both in cultured cells in vitro and in xenografts in vivo in addition to repressed PgR expression and activity. Furthermore we observed that miR-155 enhanced mTORC1 signaling (observed through western blot for increased phosphorylation on mTOR S2448) and induced inhibition of mTORC2 signaling (evident through repressed Rictor and tuberous sclerosis 1 (TSC1) gene expression). mTORC1 induced deregulation of E2 signaling was confirmed using qPCR and the mTORC1-specific inhibitor RAD001. Co-treatment of MCF7 breast cancer cells stably overexpressing miR-155 with RAD001 and E2 restored E2-induced PgR gene expression. RAD001 treatment of SCID/CB17 mice inhibited E2-induced tumorigenesis of the MCF7 miR-155 overexpressing cell line. Finally we demonstrated a strong positive correlation between Rictor and PgR expression and a negative correlation with Raptor expression in Luminal B breast cancer samples, a breast cancer histological subtype known for having an altered ERα-signaling pathway. Conclusions: miRNA mediated alterations in mTOR and ERα signaling establishes a new mechanism for altered estrogen responses independent of growth factor stimulation.

Original languageEnglish
Article number229
JournalMolecular Cancer
Volume13
Issue number1
DOIs
StatePublished - Oct 6 2014

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Sirolimus
MicroRNAs
Estrogen Receptors
Progesterone Receptors
Breast Neoplasms
Western Blotting
Everolimus
Raptors
Gene Expression
High-Throughput Nucleotide Sequencing
SCID Mice
Atlases
Heterografts
Estradiol
Cultured Cells
Intercellular Signaling Peptides and Proteins
Estrogens
Carcinogenesis
Phosphorylation
Genome

Keywords

  • breast cancer
  • Estrogen receptor
  • miR-155
  • miRNA
  • mTOR

ASJC Scopus subject areas

  • Cancer Research
  • Molecular Medicine
  • Oncology

Cite this

microRNA regulation of mammalian target of rapamycin expression and activity controls estrogen receptor function and RAD001 sensitivity. / Martin, Elizabeth C.; Rhodes, Lyndsay V.; Elliott, Steven; Krebs, Adrienne E.; Nephew, Kenneth; Flemington, Erik K.; Collins-Burow, Bridgette M.; Burow, Matthew E.

In: Molecular Cancer, Vol. 13, No. 1, 229, 06.10.2014.

Research output: Contribution to journalArticle

Martin, Elizabeth C. ; Rhodes, Lyndsay V. ; Elliott, Steven ; Krebs, Adrienne E. ; Nephew, Kenneth ; Flemington, Erik K. ; Collins-Burow, Bridgette M. ; Burow, Matthew E. / microRNA regulation of mammalian target of rapamycin expression and activity controls estrogen receptor function and RAD001 sensitivity. In: Molecular Cancer. 2014 ; Vol. 13, No. 1.
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abstract = "Background: The AKT/mammalian target of rapamycin (mTOR) signaling pathway is regulated by 17α-estradiol (E2) signaling and mediates E2-induced proliferation and progesterone receptor (PgR) expression in breast cancer. Methods and results: Here we use deep sequencing analysis of previously published data from The Cancer Genome Atlas to demonstrate that expression of a key component of mTOR signaling, rapamycin-insensitive companion of mTOR (Rictor), positively correlated with an estrogen receptor-α positive (ERα+) breast tumor signature. Through increased microRNA-155 (miR-155) expression in the ERα+ breast cancer cells we demonstrate repression of Rictor enhanced activation of mTOR complex 1 (mTORC1) signaling with both qPCR and western blot. miR-155-mediated mTOR signaling resulted in deregulated ERα signaling both in cultured cells in vitro and in xenografts in vivo in addition to repressed PgR expression and activity. Furthermore we observed that miR-155 enhanced mTORC1 signaling (observed through western blot for increased phosphorylation on mTOR S2448) and induced inhibition of mTORC2 signaling (evident through repressed Rictor and tuberous sclerosis 1 (TSC1) gene expression). mTORC1 induced deregulation of E2 signaling was confirmed using qPCR and the mTORC1-specific inhibitor RAD001. Co-treatment of MCF7 breast cancer cells stably overexpressing miR-155 with RAD001 and E2 restored E2-induced PgR gene expression. RAD001 treatment of SCID/CB17 mice inhibited E2-induced tumorigenesis of the MCF7 miR-155 overexpressing cell line. Finally we demonstrated a strong positive correlation between Rictor and PgR expression and a negative correlation with Raptor expression in Luminal B breast cancer samples, a breast cancer histological subtype known for having an altered ERα-signaling pathway. Conclusions: miRNA mediated alterations in mTOR and ERα signaling establishes a new mechanism for altered estrogen responses independent of growth factor stimulation.",
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AU - Martin, Elizabeth C.

AU - Rhodes, Lyndsay V.

AU - Elliott, Steven

AU - Krebs, Adrienne E.

AU - Nephew, Kenneth

AU - Flemington, Erik K.

AU - Collins-Burow, Bridgette M.

AU - Burow, Matthew E.

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KW - breast cancer

KW - Estrogen receptor

KW - miR-155

KW - miRNA

KW - mTOR

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