MicroRNA-101-mediated Akt activation and estrogen-independent growth.
MicroRNAs are gene regulators that work through a posttranscriptional repression mechanism. Dysregulation of microRNA expression could lead to a variety of disorders, in particular, human cancer, and has also been implicated in antihormone therapy resistance. However, little is known whether microRNAs have a role in estrogen-independent growth, leading to tamoxifen resistance in estrogen receptor (ER)-positive tumors. In this study, we use an in vivo selection system against a microRNA library using the MCF-7 model and demonstrate that miR-101 promotes estrogen-independent growth and causes the upregulation of phosphorylated Akt (pAkt) without impacting the ER level or activity. Importantly, although miR-101 suppresses cell growth in normal estradiol (E2)-containing medium, it promotes cell growth in E2-free medium. Moreover, estrogen deprivation greatly enhances miR-101-mediated Akt activation. Finally, we show that MAGI-2 (membrane-associated guanylate kinase), a scaffold protein required for PTEN (phosphatase and tensin homolog) activity, is a direct target for miR-101; suppression of MAGI-2 by miR-101 reduces PTEN activity, leading to Akt activation. Taken together, these results not only establish a role for miR-101 in estrogen-independent signaling but also provide a mechanistic link between miR-101 and Akt activation.
Sachdeva
M
M
Department of Medical Microbiology, Immunology and Cell Biology, Southern Illinois University School of Medicine, Springfield, IL, USA.
Wu
H
H
Ru
P
P
Hwang
L
L
Trieu
V
V
Mo
Y-Y
YY
D048868:Adaptor Proteins, Signal Transducing; D000230:Adenocarcinoma / Q000188:drug therapy / Q000378:metabolism; D018931:Antineoplastic Agents, Hormonal / Q000494:pharmacology; D001943:Breast Neoplasms / Q000188:drug therapy / Q000378:metabolism; D002352:Carrier Proteins / Q000378:metabolism; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D019008:Drug Resistance, Neoplasm; D004967:Estrogens / Q000378:metabolism*; D005260:Female; D051528:Guanylate Kinases; D006801:Humans; D035683:MicroRNAs / Q000378:metabolism*; D051059:PTEN Phosphohydrolase / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D011960:Receptors, Estrogen / Q000378:metabolism; D013629:Tamoxifen / Q000494:pharmacology; D015854:Up-Regulation
D048868:Adaptor Proteins, Signal Transducing; D018931:Antineoplastic Agents, Hormonal; D002352:Carrier Proteins; D004967:Estrogens; C534072:MIRN101 microRNA, human; D035683:MicroRNAs; D011960:Receptors, Estrogen; D013629:Tamoxifen; D051057:Proto-Oncogene Proteins c-akt; D051528:Guanylate Kinases; C485777:MAGI2 protein, human; D051059:PTEN Phosphohydrolase; C494929:PTEN protein, human