title: miR-143 and miR-145 synergistically regulate ERBB3 to suppress cell proliferation and invasion in breast cancer.
abstract: BACKGROUND
  ERBB3, one of the four members of the ErbB family of receptor tyrosine kinases, plays an important role in breast cancer etiology and progression. In the present study, we aimed to identify novel miRNAs that can potentially target ERBB3 and their biological functions.
  
  
  METHODS
  The expression levels of miR-143/145 and target mRNA were examined by relative quantification RT-PCR, and the expression levels of target protein were detected by Western blot. We used bioinformatic analyses to search for miRNAs that can potentially target ERBB3. Luciferase reporter plasmids were constructed to confirm direct targeting. Furthermore, the biological consequences of the targeting of ERBB3 by miR-143/145 were examined by cell proliferation and invasion assays in vitro and by the mouse xenograft tumor model in vivo.
  
  
  RESULTS
  We identified an inverse correlation between miR-143/145 levels and ERBB3 protein levels, but not between miR-143/145 levels and ERBB3 mRNA levels, in breast cancer tissue samples. We identified specific targeting sites for miR-143 and miR-145 (miR-143/145) in the 3'-untranslated region (3'-UTR) of the ERBB3 gene and regulate ERBB3 expression. We demonstrated that the repression of ERBB3 by miR-143/145 suppressed the proliferation and invasion of breast cancer cells, and that miR-143/145 showed an anti-tumor effect by negatively regulating ERBB3 in the xenograft mouse model. Interestingly, miR-143 and miR-145 showed a cooperative repression of ERBB3 expression and cell proliferation and invasion in breast cancer cells, such that the effects of the two miRNAs were greater than with either miR-143 or miR-145 alone.
  
  
  CONCLUSIONS
  Taken together, our findings provide the first clues regarding the role of the miR-143/145 cluster as a tumor suppressor in breast cancer through the inhibition of ERBB3 translation. These results also support the idea that different miRNAs in a cluster can synergistically repress a given target mRNA.
authors.forename: Xin
authors.initials: X
authors.lastname: Yan
authors.forename: Xi
authors.initials: X
authors.lastname: Chen
authors.forename: Hongwei
authors.initials: H
authors.lastname: Liang
authors.forename: Ting
authors.initials: T
authors.lastname: Deng
authors.forename: Weixu
authors.initials: W
authors.lastname: Chen
authors.forename: Suyang
authors.initials: S
authors.lastname: Zhang
authors.forename: Minghui
authors.initials: M
authors.lastname: Liu
authors.forename: Xiujuan
authors.initials: X
authors.lastname: Gao
authors.forename: Yanqing
authors.initials: Y
authors.lastname: Liu
authors.forename: Chihao
authors.initials: C
authors.lastname: Zhao
authors.forename: Xueliang
authors.initials: X
authors.lastname: Wang
authors.forename: Nan
authors.initials: N
authors.lastname: Wang
authors.forename: Jialu
authors.initials: J
authors.lastname: Li
authors.forename: Rui
authors.initials: R
authors.lastname: Liu
authors.forename: Ke
authors.initials: K
authors.lastname: Zen
authors.affiliation: Department of Gastrointestinal Medical Oncology, Tianjin Medical University Cancer Institute and Hospital, National Clinical Research Center of Cancer, Key Laboratory of Cancer Prevention and Therapy of Tianjin, Huanhuxi Road, Tiyuanbei, Tianjin 300060, China. cyzhang@nju.edu.cn.
authors.forename: Chen-Yu
authors.initials: CY
authors.lastname: Zhang
authors.forename: Baorui
authors.initials: B
authors.lastname: Liu
authors.forename: Yi
authors.initials: Y
authors.lastname: Ba
mesh_terms: D020413:3' Untranslated Regions; D000818:Animals; D001943:Breast Neoplasms / Q000378:metabolism / Q000473:pathology*; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D005260:Female; D006801:Humans; D061986:MCF-7 Cells; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D035683:MicroRNAs / Q000235:genetics* / Q000378:metabolism; D009361:Neoplasm Invasiveness / Q000235:genetics / Q000473:pathology; D009368:Neoplasm Transplantation; D020893:Receptor, ErbB-3 / Q000235:genetics / Q000378:metabolism*
chemical_list: D020413:3' Untranslated Regions; C542359:MIRN143 microRNA, human; C541010:MIRN145 microRNA, human; D035683:MicroRNAs; C581292:ERBB3 protein, human; D020893:Receptor, ErbB-3