title: MicroRNA-99a induces G1-phase cell cycle arrest and suppresses tumorigenicity in renal cell carcinoma.
abstract: BACKGROUND
  A growing body of evidence suggests that microRNAs (miRNAs) play an important role in cancer diagnosis and therapy. MicroRNA-99a (miR-99a), a potential tumor suppressor, is downregulated in several human malignancies. The expression and function of miR-99a, however, have not been investigated in human renal cell carcinoma (RCC) so far. We therefore examined the expression of miR-99a in RCC cell lines and tissues, and assessed the impact of miR-99a on the tumorigenesis of RCC.
  
  
  METHODS
  MiR-99a levels in 40 pairs of RCC and matched adjacent non-tumor tissues were assessed by real-time quantitative Reverse Transcription PCR (qRT-PCR). The RCC cell lines 786-O and OS-RC-2 were transfected with miR-99a mimics to restore the expression of miR-99a. The effects of miR-99a were then assessed by cell proliferation, cell cycle, transwell, and colony formation assay. A murine xenograft model of RCC was used to confirm the effect of miR-99a on tumorigenicity in vivo. Potential target genes were identified by western blotting and luciferase reporter assay.
  
  
  RESULTS
  We found that miR-99a was remarkably downregulated in RCC and low expression level of miR-99a was correlated with poor survival of RCC patients. Restoration of miR-99a dramatically suppressed RCC cells growth, clonability, migration and invasion as well as induced G1-phase cell cycle arrest in vitro. Moreover, intratumoral delivery of miR-99a could inhibit tumor growth in murine xenograft models of human RCC. In addition, we also fond that mammalian target of rapamycin (mTOR) was a direct target of miR-99a in RCC cells. Furthermore, siRNA-mediated knockdown of mTOR partially phenocopied the effect of miR-99a overexpression, suggesting that the tumor suppressive role of miR-99a may be mediated primarily through mTOR regulation.
  
  
  CONCLUSIONS
  Collectively, these results demonstrate for the first time, to our knowledge, that deregulation of miR-99a is involved in the etiology of RCC partially via direct targeting mTOR pathway, which suggests that miR-99a may offer an attractive new target for diagnostic and therapeutic intervention in RCC.
authors.affiliation: Department of Urology, The Third Affiliated Hospital of Soochow University, 185 Juqian Street, Changzhou, 213003, China.
authors.forename: Li
authors.initials: L
authors.lastname: Cui
authors.forename: Hua
authors.initials: H
authors.lastname: Zhou
authors.forename: Hu
authors.initials: H
authors.lastname: Zhao
authors.forename: Yaojun
authors.initials: Y
authors.lastname: Zhou
authors.forename: Renfang
authors.initials: R
authors.lastname: Xu
authors.forename: Xianlin
authors.initials: X
authors.lastname: Xu
authors.forename: Lu
authors.initials: L
authors.lastname: Zheng
authors.forename: Zhong
authors.initials: Z
authors.lastname: Xue
authors.forename: Wei
authors.initials: W
authors.lastname: Xia
authors.forename: Bo
authors.initials: B
authors.lastname: Zhang
authors.forename: Tao
authors.initials: T
authors.lastname: Ding
authors.forename: Yunjie
authors.initials: Y
authors.lastname: Cao
authors.forename: Zinong
authors.initials: Z
authors.lastname: Tian
authors.forename: Qianqian
authors.initials: Q
authors.lastname: Shi
authors.forename: Xiaozhou
authors.initials: X
authors.lastname: He
mesh_terms: D020413:3' Untranslated Regions / Q000235:genetics; D000818:Animals; D015153:Blotting, Western; D002292:Carcinoma, Renal Cell / Q000235:genetics* / Q000473:pathology / Q000517:prevention & control; D002460:Cell Line; D045744:Cell Line, Tumor; D002465:Cell Movement / Q000235:genetics; D049109:Cell Proliferation; D015536:Down-Regulation; D059585:G1 Phase Cell Cycle Checkpoints / Q000235:genetics*; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D053208:Kaplan-Meier Estimate; D007680:Kidney Neoplasms / Q000235:genetics* / Q000473:pathology / Q000517:prevention & control; D051379:Mice; D008819:Mice, Nude; D035683:MicroRNAs / Q000008:administration & dosage / Q000235:genetics*; D034622:RNA Interference; D020133:Reverse Transcriptase Polymerase Chain Reaction; D058570:TOR Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism; D014162:Transfection; D023041:Xenograft Model Antitumor Assays
chemical_list: D020413:3' Untranslated Regions; C561679:MIRN99 microRNA, human; D035683:MicroRNAs; D058570:TOR Serine-Threonine Kinases