title: Trastuzumab produces therapeutic actions by upregulating miR-26a and miR-30b in breast cancer cells.
abstract: OBJECTIVE
  Trastuzumab has been used for the treatment of HER2-positive breast cancer (BC). However, a subset of BC patients exhibited resistance to trastuzumab therapy. Thus, clarifying the molecular mechanism of trastuzumab treatment will be beneficial to improve the treatment of HER2-positive BC patients. In this study, we identified trastuzumab-responsive microRNAs that are involved in the therapeutic effects of trastuzumab.
  
  
  RESULTS
  RNA samples were obtained from HER2-positive (SKBR3 and BT474) and HER2-negetive (MCF7 and MDA-MB-231) cells with and without trastuzumab treatment for 6 days. Next, we conducted a microRNA profiling analysis using these samples to screen those microRNAs that were up- or down-regulated only in HER2-positive cells. This analysis identified miR-26a and miR-30b as trastuzumab-inducible microRNAs. Transfecting miR-26a and miR-30b induced cell growth suppression in the BC cells by 40% and 32%, respectively. A cell cycle analysis showed that these microRNAs induced G1 arrest in HER2-positive BC cells as trastuzumab did. An Annexin-V assay revealed that miR-26a but not miR-30b induced apoptosis in HER2-positive BC cells. Using the prediction algorithms for microRNA targets, we identified cyclin E2 (CCNE2) as a target gene of miR-30b. A luciferase-based reporter assay demonstrated that miR-30b post-transcriptionally reduced 27% (p = 0.005) of the gene expression by interacting with two binding sites in the 3'-UTR of CCNE2.
  
  
  CONCLUSIONS
  In BC cells, trastuzumab modulated the expression of a subset of microRNAs, including miR-26a and miR-30b. The upregulation of miR-30b by trastuzumab may play a biological role in trastuzumab-induced cell growth inhibition by targeting CCNE2.
authors.affiliation: Department of Nanobio Drug Discovery, Graduate School of Pharmaceutical Sciences, Kyoto University, Kyoto, Japan.
authors.forename: Takehiro
authors.initials: T
authors.lastname: Ichikawa
authors.forename: Fumiaki
authors.initials: F
authors.lastname: Sato
authors.forename: Kazuya
authors.initials: K
authors.lastname: Terasawa
authors.forename: Soken
authors.initials: S
authors.lastname: Tsuchiya
authors.forename: Masakazu
authors.initials: M
authors.lastname: Toi
authors.forename: Gozoh
authors.initials: G
authors.lastname: Tsujimoto
authors.forename: Kazuharu
authors.initials: K
authors.lastname: Shimizu
mesh_terms: D020413:3' Untranslated Regions; D061067:Antibodies, Monoclonal, Humanized / Q000494:pharmacology*; D000970:Antineoplastic Agents / Q000494:pharmacology; D001943:Breast Neoplasms / Q000378:metabolism*; D002453:Cell Cycle; D045744:Cell Line, Tumor; D005260:Female; D020869:Gene Expression Profiling; D015972:Gene Expression Regulation, Neoplastic; D017930:Genes, Reporter; D006801:Humans; D035683:MicroRNAs / Q000096:biosynthesis*; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000096:biosynthesis; D000068878:Trastuzumab
chemical_list: D020413:3' Untranslated Regions; D061067:Antibodies, Monoclonal, Humanized; D000970:Antineoplastic Agents; D035683:MicroRNAs; D018719:Erb-b2 Receptor Tyrosine Kinases; D000068878:Trastuzumab; C528163:MIRN26 microRNA, human; C546086:MIRN30b microRNA, human