title: Lopinavir up-regulates expression of the antiviral protein ribonuclease L in human papillomavirus-positive cervical carcinoma cells.
abstract: BACKGROUND
  We have previously shown that the HIV protease inhibitor lopinavir has selective toxicity against human papillomavirus (HPV)-positive cervical carcinoma cells via an unknown mechanism.
  
  
  METHODS
  SiHa cervical carcinoma cells were stably transfected with the proteasome sensor vector pZsProSensor-1 to confirm lopinavir inhibits the proteasome in these cells. The Panorama Xpress profiler 725 antibody array was then used to analyse specific changes in protein expression in lopinavir-treated versus control untreated SiHa cells followed by PCR and western blotting. Colorimetric growth assays of lopinavir-treated E6/E7 immortalised versus control human keratinocytes were performed. Targeted small interfering RNA gene silencing followed by growth assay comparison of lopinavir-treated/untreated SiHa cells was also used.
  
  
  RESULTS
  Lopinavir induced an increase in the fluorescence of pZsProSensor-1 transfected SiHa cells, indicative of proteasomal inhibition. Ribonuclease L (RNASEL) protein was shown to be up-regulated in lopinavir-treated SiHa cells, which was confirmed by PCR and western blot. Targeted silencing of RNASEL reduced the sensitivity of SiHa cells to lopinavir. Selective toxicity against E6/E7 immortalised keratinocytes versus control cells was also seen with lopinavir and was associated with up-regulated RNASEL expression.
  
  
  CONCLUSIONS
  These data are consistent with the toxicity of lopinavir against HPV-positive cervical carcinoma cells being related to its ability to block viral proteasome activation and induce an up-regulation of the antiviral protein RNASEL. This is supported by the drug's selective toxicity and up-regulation of RNASEL in E6/E7 immortalised keratinocytes combined with the increased resistance to lopinavir observed in SiHa cells following silencing of RNASEL gene expression.
authors.affiliation: Gynaecological Oncology Laboratories, School of Cancer & Enabling Sciences, University of Manchester, St Mary's Hospital, Manchester, UK.
authors.forename: Gavin
authors.initials: G
authors.lastname: Batman
authors.forename: Anthony W
authors.initials: AW
authors.lastname: Oliver
authors.forename: Ingeborg
authors.initials: I
authors.lastname: Zehbe
authors.forename: Christina
authors.initials: C
authors.lastname: Richard
authors.forename: Lynne
authors.initials: L
authors.lastname: Hampson
authors.forename: Ian N
authors.initials: IN
authors.lastname: Hampson
mesh_terms: D000998:Antiviral Agents / Q000494:pharmacology*; D002294:Carcinoma, Squamous Cell / Q000188:drug therapy / Q000378:metabolism / Q000821:virology*; D045744:Cell Line, Tumor / Q000187:drug effects; D004722:Endoribonucleases / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism; D005260:Female; D017320:HIV Protease Inhibitors / Q000494:pharmacology; D052162:Human papillomavirus 16 / Q000378:metabolism; D006801:Humans; D061466:Lopinavir; D030361:Papillomavirus Infections / Q000188:drug therapy* / Q000378:metabolism / Q000821:virology; D011744:Pyrimidinones / Q000494:pharmacology*; D015854:Up-Regulation / Q000187:drug effects*; D002583:Uterine Cervical Neoplasms / Q000188:drug therapy / Q000378:metabolism / Q000821:virology
chemical_list: D000998:Antiviral Agents; D017320:HIV Protease Inhibitors; D011744:Pyrimidinones; D061466:Lopinavir; D004722:Endoribonucleases; C031956:2-5A-dependent ribonuclease