title: MiRNA-26b inhibits cellular proliferation by targeting CDK8 in breast cancer.
abstract: OBJECTIVE
  MicroRNA-26b (miR-26b) has been reported to be down-regulated in a wide range of malignant tumors, However, the mechanism by which miR-26b is implicated in breast cancer tumorigenesis is incompletely understood. This study was undertaken to evaluate the expression pattern of miR-26b and characterize its biological role in human breast cancer.
  
  
  METHODS
  Reverse transcription-polymerase chain reaction (RT-PCR) was used to quantify the expression levels of miR-26b in breast cancer and adjacent non-cancerous breast tissues. MTT, colony formation assay and cell cycle assay were carried out to characterize the miR-26b function. Finally, to validate the target gene of miR-26b, luciferase reporter assay was employed, followed by RT-PCR and Western blot confirmation.
  
  
  RESULTS
  Here, we found that miR-26b expression was relatively downregulated in breast cancer specimens (P<0.01). Overexpression of miR-26b dramatically suppressed cell proliferation, colony formation and induced G0/G1 cell cycle arrest of MDA-MB-231 and Mcf-7 cells. Luciferase assays revealed that miR-26b directly targeted the 3'UTR of CDK8. Overexpression of miR-26b led to the downregulation of CDK8 and β-catenin expression. Similarly, CDK8 knockdown by siRNA suppressed cell growth and subsequent β-catenin expression.
  
  
  CONCLUSIONS
  These findings suggest that miR-26b exerts a tumor suppressive role in breast cancer and the miR-26b-mediated growth inhibition is achieved through suppression of a new target gene CDK8.
authors.affiliation: Department of Breast and Thyroid, Shanghai Tenth People's Hospital, College of Medicine, Tongji University Shanghai, China.
authors.forename: Jia
authors.initials: J
authors.lastname: Li
authors.affiliation: Department of Breast and Thyroid, Shanghai Tenth People's Hospital, College of Medicine, Tongji University Shanghai, China.
authors.forename: Xiaoyu
authors.initials: X
authors.lastname: Li
authors.affiliation: Department of Breast and Thyroid, Shanghai Tenth People's Hospital, College of Medicine, Tongji University Shanghai, China.
authors.forename: Xiangjie
authors.initials: X
authors.lastname: Kong
authors.affiliation: Department of Breast and Thyroid, Shanghai Tenth People's Hospital, College of Medicine, Tongji University Shanghai, China.
authors.forename: Qifeng
authors.initials: Q
authors.lastname: Luo
authors.affiliation: Department of Breast and Thyroid, Shanghai Tenth People's Hospital, College of Medicine, Tongji University Shanghai, China.
authors.forename: Junfeng
authors.initials: J
authors.lastname: Zhang
authors.affiliation: Department of Breast and Thyroid, Shanghai Tenth People's Hospital, College of Medicine, Tongji University Shanghai, China.
authors.forename: Lin
authors.initials: L
authors.lastname: Fang
keywords: CDK8; MiR-26b; breast cancer; cell cycle; proliferation
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