title: Toll-like receptor 7 agonist, imiquimod, inhibits oral squamous carcinoma cells through apoptosis and necrosis.
abstract: BACKGROUND
  Toll-like receptor (TLR) agonists have anticancer effect by inducing apoptosis or activating immune cells. In this study, we investigated whether imiquimod, TLR7 agonist, inhibits the proliferation of oral cancer cells.
  
  
  METHODS
  Toll-like receptor 7 expression and IL-6/8 production by imiquimod were examined using RT-PCR and Enzyme-linked immunosorbent assay, respectively. Cell viability was examined by MTT assay. To examine apoptotic cell death, Annexin V/PI staining for flow cytometry and Western blot analysis were performed. Necrotic cell death was determined by leakage of lactate dehydrogenase (LDH), HMGB1, and PI staining in imiquimod-treated oral squamous cell carcinoma (OSCC) cells.
  
  
  RESULTS
  Toll-like receptor 7 mRNA was expressed in OSCC cells. Imiquimod induced IL-6 and IL-8 production in OSCC cells, suggesting the functional expression of TLR7. Imiquimod inhibited cells proliferation in a dose-dependent manner. The ratio of annexin V-positive cells and cleaved caspase-3/7 was increased by imiquimod treatment in OSCC cells, suggesting that imiquimod-induced cell death in OSCC cells may be owing to apoptosis. In addition, LDH secretion and PI staining were detected in OSCC cells treated with imiquimod, showing that imiquimod also induced necrotic cell death in the OSCC cells.
  
  
  CONCLUSIONS
  Imiquimod inhibited effectively the growth of OSCC cells by inducing apoptosis and necrosis.
authors.affiliation: Department of Pathology and Research Center for Oral Disease Regulation of the Aged, School of Dentistry, Chosun University, Gwangju, Korea.
authors.forename: Mee-Young
authors.initials: MY
authors.lastname: Ahn
authors.forename: Seong-Min
authors.initials: SM
authors.lastname: Kwon
authors.forename: Hak Hyun
authors.initials: HH
authors.lastname: Cheong
authors.forename: Jong-Hwan
authors.initials: JH
authors.lastname: Park
authors.forename: Jun
authors.initials: J
authors.lastname: Lee
authors.forename: Seung-Ki
authors.initials: SK
authors.lastname: Min
authors.forename: Sang-Gun
authors.initials: SG
authors.lastname: Ahn
authors.forename: Jung-Hoon
authors.initials: JH
authors.lastname: Yoon
mesh_terms: D000634:Aminoquinolines / Q000494:pharmacology*; D000704:Analysis of Variance; D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D002294:Carcinoma, Squamous Cell / Q000188:drug therapy* / Q000473:pathology; D049109:Cell Proliferation / Q000187:drug effects; D006801:Humans; D000077271:Imiquimod; D009062:Mouth Neoplasms / Q000188:drug therapy* / Q000473:pathology; D009336:Necrosis / Q000139:chemically induced; D051199:Toll-Like Receptor 7 / Q000819:agonists*; D014407:Tumor Cells, Cultured
chemical_list: D000634:Aminoquinolines; D000970:Antineoplastic Agents; D051199:Toll-Like Receptor 7; D000077271:Imiquimod