title: Functional cooperation of miR-125a, miR-125b, and miR-205 in entinostat-induced downregulation of erbB2/erbB3 and apoptosis in breast cancer cells.
abstract: We reported that the class I HDAC inhibitor entinostat induced apoptosis in erbB2-overexpressing breast cancer cells via downregulation of erbB2 and erbB3. Here, we study the molecular mechanism by which entinostat dual-targets erbB2/erbB3. Treatment with entinostat had no effect on erbB2/erbB3 mRNA, suggesting a transcription-independent mechanism. Entinostat decreased endogenous but not exogenous erbB2/erbB3, indicating it did not alter their protein stability. We hypothesized that entinostat might inhibit erbB2/erbB3 protein translation via specific miRNAs. Indeed, entinostat significantly upregulated miR-125a, miR-125b, and miR-205, that have been reported to target erbB2 and/or erbB3. Specific inhibitors were then used to determine whether these miRNAs had a causal role in entinostat-induced downregulation of erbB2/erbB3 and apoptosis. Transfection with a single inhibitor dramatically abrogated entinostat induction of miR-125a, miR-125b, or miR-205; however, none of the inhibitors blocked entinostat action on erbB2/erbB3. In contrast, co-transfection with two inhibitors not only reduced their corresponding miRNAs, but also significantly abrogated entinostat-mediated reduction of erbB2/erbB3. Moreover, simultaneous inhibition of two, but not one miRNA significantly attenuated entinostat-induced apoptosis. Interestingly, although the other HDAC inhibitors, such as SAHA and panobinostat, exhibited activity as potent as entinostat to induce growth inhibition and apoptosis in erbB2-overexpressing breast cancer cells, they had no significant effects on the three miRNAs. Instead, both SAHA- and panobinostat-decreased erbB2/erbB3 expression correlated with the reduction of their mRNA levels. Collectively, we demonstrate that entinostat specifically induces expression of miR-125a, miR-125b, and miR-205, which act in concert to downregulate erbB2/erbB3 in breast cancer cells. Our data suggest that epigenetic regulation via miRNA-dependent or -independent mechanisms may represent a novel approach to treat breast cancer patients with erbB2-overexpressing tumors.
authors.affiliation: Department of Pathology, School of Medicine, University of Colorado Anschutz Medical Campus, Aurora, CO, USA.
authors.forename: S
authors.initials: S
authors.lastname: Wang
authors.forename: J
authors.initials: J
authors.lastname: Huang
authors.forename: H
authors.initials: H
authors.lastname: Lyu
authors.forename: C-K
authors.initials: CK
authors.lastname: Lee
authors.forename: J
authors.initials: J
authors.lastname: Tan
authors.forename: J
authors.initials: J
authors.lastname: Wang
authors.forename: B
authors.initials: B
authors.lastname: Liu
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis; D001549:Benzamides / Q000494:pharmacology*; D001943:Breast Neoplasms / Q000188:drug therapy / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D045744:Cell Line, Tumor; D044127:Epigenesis, Genetic / Q000187:drug effects; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects*; D056572:Histone Deacetylase Inhibitors / Q000494:pharmacology*; D006801:Humans; D006877:Hydroxamic Acids / Q000494:pharmacology; D007211:Indoles / Q000494:pharmacology; D035683:MicroRNAs / Q000235:genetics* / Q000378:metabolism; D000077767:Panobinostat; D014176:Protein Biosynthesis; D011725:Pyridines / Q000494:pharmacology*; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism; D020893:Receptor, ErbB-3 / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects
chemical_list: D000970:Antineoplastic Agents; D001549:Benzamides; D056572:Histone Deacetylase Inhibitors; D006877:Hydroxamic Acids; D007211:Indoles; D035683:MicroRNAs; D000077767:Panobinostat; D011725:Pyridines; D018719:Erb-b2 Receptor Tyrosine Kinases; D020893:Receptor, ErbB-3; C531888:MIRN125 microRNA, human; C534425:MIR205, human; C118739:entinostat; C508053:ERBB2 protein, human; C581292:ERBB3 protein, human