Downregulation of microRNA-515-5p by the estrogen receptor modulates sphingosine kinase 1 and breast cancer cell proliferation.
Sphingosine kinase 1 (SK1) plays an important role in estrogen-dependent breast tumorigenesis, but its regulation is poorly understood. A subset of microRNAs (miRNA, miR) is regulated by estrogen and contributes to cellular proliferation and cancer progression. Here, we describe that miR-515-5p is transcriptionally repressed by estrogen receptor α (ERα) and functions as a tumor suppressor in breast cancer. Its downregulation enhances cell proliferation and estrogen-dependent SK1 activity, mediated by a reduction of miR-515-5p posttranscriptional repression. Enforced expression of miR-515-5p in breast cancer cells causes a reduction in SK1 activity, reduced cell proliferation, and the induction of caspase-dependent apoptosis. Conversely, opposing effects occur with miR-515-5p inhibition and by SK1 silencing. Notably, we show that estradiol (E2) treatment downregulates miR-515-5p levels, whereas the antiestrogen tamoxifen causes a decrease in SK1, which is rescued by silencing miR-515-5p. Analysis of chromatin immunoprecipitation sequencing (ChIP-Seq) data reveals that miR-515-5p suppression is mediated by a direct interaction of ERα within its promoter. RNA-sequencing (RNA-Seq) analysis of breast cancer cells after overexpressing miR-515-5p indicates that it partly modulates cell proliferation by regulating the Wnt pathway. The clinical implications of this novel regulatory system are shown as miR-515-5p is significantly downregulated in ER-positive (n = 146) compared with ER-negative (n = 98) breast cancers. Overall, we identify a new link between ERα, miR-515-5p, proliferation, and apoptosis in breast cancer tumorigenesis.
Authors' Affiliations: Division of Oncology, Department of Surgery & Cancer, Imperial Centre for Translational and Experimental Medicine (ICTEM); Department of Medicine and HPB Surgical Unit, Department of Surgery & Cancer, Imperial College; Department of Oncology, Imperial College Healthcare NHS Trust, Charing Cross Hospital, London; and School of Medicine, University of East Anglia, Norwich, United Kingdom.
Filipa G
FG
Pinho
Adam E
AE
Frampton
Joao
J
Nunes
Jonathan
J
Krell
Heba
H
Alshaker
Jimmy
J
Jacob
Loredana
L
Pellegrino
Laura
L
Roca-Alonso
Alexander
A
de Giorgio
Victoria
V
Harding
Jonathan
J
Waxman
Justin
J
Stebbing
Dmitry
D
Pchejetski
Leandro
L
Castellano
D018931:Antineoplastic Agents, Hormonal / Q000494:pharmacology; D017209:Apoptosis; D015153:Blotting, Western; D001943:Breast Neoplasms / Q000188:drug therapy / Q000235:genetics / Q000473:pathology*; D049109:Cell Proliferation; D047628:Estrogen Receptor alpha / Q000235:genetics / Q000378:metabolism*; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D035683:MicroRNAs / Q000235:genetics* / Q000378:metabolism; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000235:genetics / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013629:Tamoxifen / Q000494:pharmacology; D014407:Tumor Cells, Cultured; D000099157:Sphingosine Kinase
D018931:Antineoplastic Agents, Hormonal; D047628:Estrogen Receptor alpha; D035683:MicroRNAs; D017853:Phosphotransferases (Alcohol Group Acceptor); D012333:RNA, Messenger; D013629:Tamoxifen; D000099157:Sphingosine Kinase; C506487:ESR1 protein, human