Journal Article

The lncRNA MIR2052HG regulates ERα levels and aromatase inhibitor resistance through LMTK3 by recruiting EGR1

Kubo, Michiaki, Goetz, Matthew P., Cairns, Junmei, Shepherd, Lois E., Kalari, Krishna R., Weinshilboum, Richard M., Wang, Liewei, Ingle, James N.

2019

Overview

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.

• Publisher: BioMed Central,Springer Nature B.V,BMC
• Subject: AKT protein / Androstenedione / Aromatase / Aromatase Inhibitors - pharmacology / Binding sites / Biomarkers / Biomedical and Life Sciences / Biomedicine / Breast cancer / Cancer Research / Cell Line, Tumor / Cell Proliferation / Cell Survival - genetics / Chromatin / Drug Resistance, Neoplasm - genetics / Early Growth Response Protein 1 - genetics / Early Growth Response Protein 1 - metabolism / EGR-1 protein / EGR1 / Endocrine therapy / ERα / ESR1 protein / Estrogen Receptor alpha - genetics / Estrogen Receptor alpha - metabolism / Estrogens / Extracellular signal-regulated kinase / Female / Fluorescence in situ hybridization / FOXO3 protein / Gene expression / Genome-wide association studies / Genomes / Humans / Immunoprecipitation / Kinases / Ligands / LMTK3 / Localization / Lon noncoding RNA / Lymphoblastoid cell lines / Medical prognosis / Membrane Proteins - genetics / Membrane Proteins - metabolism / MIR2052HG / Models, Biological / Oncology / Phosphorylation / PKC / Polymorphism, Single Nucleotide / Protein kinase C / Protein Stability / Protein-Serine-Threonine Kinases - genetics / Protein-Serine-Threonine Kinases - metabolism / Protein-tyrosine kinase / Proteins / Research Article / Ribonucleic acid / Ribosomal protein S6 kinase / RNA / RNA, Long Noncoding - genetics / RNA-binding protein / Signal Transduction / Single-nucleotide polymorphism / Surgical Oncology / Transcription factors / Transcription, Genetic / Tumors / Ubiquitin