title: MicroRNA-17-5p post-transcriptionally regulates p21 expression in irradiated betel quid chewing-related oral squamous cell carcinoma cells.
abstract: OBJECTIVE
  Betel nut chewing is associated with oral cavity cancer in Taiwan. OC3 is an oral carcinoma cell line that was established from cells collected from a long-term betel nut chewer who does not smoke. After we found that microRNA-17-5p (miR-17-5p) is induced in OC3 cells, we used this cell line to examine the biological role(s) of this microRNA in response to exposure to ionizing radiation.
  
  
  METHODS
  A combined SYBR green-based real-time PCR and oligonucleotide ligation assay was used to examine the expression of the miR-17 polycistron in irradiated OC3 cells. The roles of miR-17-5p and p21 were evaluated with specific antisense oligonucleotides (ODN) that were designed and used to inhibit their expression. Expression of the p21 protein was evaluated by Western blotting. The clonogenic assay and annexin V staining were used to evaluate cell survival and apoptosis, respectively. Cells in which miR-17-5p was stably knocked down were used to create ectopic xenografts to evaluate in vivo the role of miR-17-5p.
  
  
  RESULTS
  A radiation dose of 5 Gy significantly increased miR-17-5p expression in irradiated OC3 cells. Inhibition of miR-17-5p expression enhanced the radiosensitivity of the OC3 cells. We found that miR-17-5p downregulates radiation-induced p21 expression in OC3 cells and, by using a tumor xenograft model, it was found that p21 plays a critical role in increasing the radiosensitivity of OC3 cells in vitro and in vivo.
  
  
  CONCLUSIONS
  miR-17-5p is induced in irradiated OC3 cells and it downregulates p21 protein expression, contributing to the radioresistance of OC3 cells.
authors.affiliation: Department of Radiation-oncology, Wan Fang Hospital, Taipei Medical University, Taipei, Taiwan.
authors.forename: S-Y
authors.initials: SY
authors.lastname: Wu
authors.forename: K-C
authors.initials: KC
authors.lastname: Lin
authors.forename: J-F
authors.initials: JF
authors.lastname: Chiou
authors.forename: S-C
authors.initials: SC
authors.lastname: Jeng
authors.forename: W-H
authors.initials: WH
authors.lastname: Cheng
authors.forename: C-I
authors.initials: CI
authors.lastname: Chang
authors.forename: W-C
authors.initials: WC
authors.lastname: Lin
authors.forename: L-L
authors.initials: LL
authors.lastname: Wu
authors.forename: H-L
authors.initials: HL
authors.lastname: Lee
authors.forename: R-J
authors.initials: RJ
authors.lastname: Chen
mesh_terms: D000284:Administration, Oral; D001114:Areca / Q000506:poisoning*; D002294:Carcinoma, Squamous Cell / Q000235:genetics*; D045744:Cell Line, Tumor; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000235:genetics*; D015536:Down-Regulation / Q000235:genetics / Q000528:radiation effects; D015972:Gene Expression Regulation, Neoplastic / Q000235:genetics* / Q000528:radiation effects; D006801:Humans; D035683:MicroRNAs / Q000235:genetics*; D009062:Mouth Neoplasms / Q000235:genetics*; D012323:RNA Processing, Post-Transcriptional / Q000235:genetics* / Q000528:radiation effects; D011836:Radiation Tolerance / Q000235:genetics
chemical_list: C493956:CDKN1A protein, human; D050759:Cyclin-Dependent Kinase Inhibitor p21; C524941:MIRN17 microRNA, human; D035683:MicroRNAs