The lncRNA MIR2052HG Regulates ERα Levels and Aromatase Inhibitor Resistance Through LMTK3 by Recruiting EGR1

Breast Cancer Res. 2019 Apr 3;21(1):47. doi: 10.1186/s13058-019-1130-3.

Abstract

Background: Our previous genome-wide association study using the MA.27 aromatase inhibitors adjuvant trial identified SNPs in the long noncoding RNA MIR2052HG associated with breast cancer-free interval. MIR2052HG maintained ERα both by promoting AKT/FOXO3-mediated ESR1 transcription and by limiting ubiquitin-mediated ERα degradation. Our goal was to further elucidate MIR2052HG's mechanism of action.

Methods: RNA-binding protein immunoprecipitation assays were performed to demonstrate that the transcription factor, early growth response protein 1 (EGR1), worked together with MIR2052HG to regulate that lemur tyrosine kinase-3 (LMTK3) transcription in MCF7/AC1 and CAMA-1 cells. The location of EGR1 on the LMTK3 gene locus was mapped using chromatin immunoprecipitation assays. The co-localization of MIR2052HG RNA and the LMTK3 gene locus was determined using RNA-DNA dual fluorescent in situ hybridization. Single-nucleotide polymorphisms (SNP) effects were evaluated using a panel of human lymphoblastoid cell lines.

Results: MIR2052HG depletion in breast cancer cells results in a decrease in LMTK3 expression and cell growth. Mechanistically, MIR2052HG interacts with EGR1 and facilitates its recruitment to the LMTK3 promoter. LMTK3 sustains ERα levels by reducing protein kinase C (PKC) activity, resulting in increased ESR1 transcription mediated through AKT/FOXO3 and reduced ERα degradation mediated by the PKC/MEK/ERK/RSK1 pathway. MIR2052HG regulated LMTK3 in a SNP- and aromatase inhibitor-dependent fashion: the variant SNP increased EGR1 binding to LMTK3 promoter in response to androstenedione, relative to wild-type genotype, a pattern that can be reversed by aromatase inhibitor treatment. Finally, LMTK3 overexpression abolished the effect of MIR2052HG on PKC activity and ERα levels.

Conclusions: Our findings support a model in which the MIR2052HG regulates LMTK3 via EGR1, and LMTK3 regulates ERα stability via the PKC/MEK/ERK/RSK1 axis. These results reveal a direct role of MIR2052HG in LMTK3 regulation and raise the possibilities of targeting MIR2052HG or LMTK3 in ERα-positive breast cancer.

Keywords: Aromatase inhibitor; EGR1; ERα; LMTK3; Lon noncoding RNA; MIR2052HG; PKC.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aromatase Inhibitors / pharmacology*
  • Biomarkers
  • Cell Line, Tumor
  • Cell Proliferation
  • Cell Survival / genetics
  • Drug Resistance, Neoplasm / genetics*
  • Early Growth Response Protein 1 / genetics*
  • Early Growth Response Protein 1 / metabolism
  • Estrogen Receptor alpha / genetics*
  • Estrogen Receptor alpha / metabolism
  • Female
  • Humans
  • Membrane Proteins / genetics*
  • Membrane Proteins / metabolism
  • Models, Biological
  • Polymorphism, Single Nucleotide
  • Protein Stability
  • Protein-Serine-Threonine Kinases / genetics*
  • Protein-Serine-Threonine Kinases / metabolism
  • RNA, Long Noncoding / genetics*
  • Signal Transduction
  • Transcription, Genetic

Substances

  • Aromatase Inhibitors
  • Biomarkers
  • EGR1 protein, human
  • Early Growth Response Protein 1
  • Estrogen Receptor alpha
  • Membrane Proteins
  • RNA, Long Noncoding
  • estrogen receptor alpha, human
  • LMTK3 protein, human
  • Protein-Serine-Threonine Kinases