title: MicroRNA-20b promotes cell growth of breast cancer cells partly via targeting phosphatase and tensin homologue (PTEN).
abstract: BACKGROUND
  MicroRNAs (miRNAs) are endogenous, small non-coding RNAs that play important roles in multiple biological processes. MiR-20b has been reported to participate in breast cancer tumorigenic progression, however, the functional roles are still unclear and under debating. The aim of this study is to explicit the molecular mechanism of miR-20b underlying breast cancer tumorigenesis.
  
  
  RESULTS
  In the present study, we showed that miR-20b was overexpressed in human breast cancer tissues and cell lines compared with paired adjacent normal tissues and normal cell lines, respectively. We identified PTEN, a well-known tumor suppressor, as the functional downstream target of miR-20b. Luciferase assays confirmed that miR-20b could directly bind to the 3' untranslated region(UTR) of PTEN and suppress translation. Alteration of miR-20b expression changed PTEN protein level but not mRNA expression in ZR-75-30 and MCF-7 breast cancer cells, suggesting miR-20b regulates PTEN gene expression at the posttranscriptional level. Furthermore, upregulation of miR-20b significantly promoted the proliferation, colony formation and DNA synthesis of ZR-75-30 and MCF-7 breast cancer cells. Conversely, knockdown of miR-20b expression inhibited the growth of breast cancer cells in vitro and in vivo.
  
  
  CONCLUSIONS
  Dysregulation of miR-20b plays critical roles in the breast cancer tumorigenesis, at least in part via targeting the tumor suppressor PTEN. This microRNA may serve as a potential diagnostic marker and therapeutic target for breast cancer.
authors.affiliation: Center Laboratory, The First Affiliated Hospital of Xiamen University, Xiamen, Fujian 361003 PR China ; School of Life Sciences, Xiamen University, Xiamen, Fujian 360112 PR China.
authors.forename: Weidong
authors.initials: W
authors.lastname: Zhou
authors.affiliation: Department of Rheumatology and Clinical Immunology, The First Affiliated Hospital of Xiamen University, Xiamen, Fujian 361003 PR China.
authors.forename: Guixiu
authors.initials: G
authors.lastname: Shi
authors.affiliation: School of Life Sciences, Xiamen University, Xiamen, Fujian 360112 PR China.
authors.forename: Qiuyan
authors.initials: Q
authors.lastname: Zhang
authors.affiliation: Center Laboratory, The First Affiliated Hospital of Xiamen University, Xiamen, Fujian 361003 PR China.
authors.forename: Qiuwan
authors.initials: Q
authors.lastname: Wu
authors.affiliation: School of Life Sciences, Xiamen University, Xiamen, Fujian 360112 PR China.
authors.forename: Boan
authors.initials: B
authors.lastname: Li
authors.affiliation: Center Laboratory, The First Affiliated Hospital of Xiamen University, Xiamen, Fujian 361003 PR China ; Department of Breast Surgery, The First Affiliated Hospital of Xiamen University, Xiamen, Fujian 361003 PR China.
authors.forename: Zhiming
authors.initials: Z
authors.lastname: Zhang
keywords: Breast cancer; MiR-20b; PTEN; Posttranscriptional regulation