title: Identifying novel hypoxia-associated markers of chemoresistance in ovarian cancer.
abstract: BACKGROUND
  Ovarian cancer is associated with poor long-term survival due to late diagnosis and development of chemoresistance. Tumour hypoxia is associated with many features of tumour aggressiveness including increased cellular proliferation, inhibition of apoptosis, increased invasion and metastasis, and chemoresistance, mostly mediated through hypoxia-inducible factor (HIF)-1α. While HIF-1α has been associated with platinum resistance in a variety of cancers, including ovarian, relatively little is known about the importance of the duration of hypoxia. Similarly, the gene pathways activated in ovarian cancer which cause chemoresistance as a result of hypoxia are poorly understood. This study aimed to firstly investigate the effect of hypoxia duration on resistance to cisplatin in an ovarian cancer chemoresistance cell line model and to identify genes whose expression was associated with hypoxia-induced chemoresistance.
  
  
  METHODS
  Cisplatin-sensitive (A2780) and cisplatin-resistant (A2780cis) ovarian cancer cell lines were exposed to various combinations of hypoxia and/or chemotherapeutic drugs as part of a 'hypoxia matrix' designed to cover clinically relevant scenarios in terms of tumour hypoxia. Response to cisplatin was measured by the MTT assay. RNA was extracted from cells treated as part of the hypoxia matrix and interrogated on Affymetrix Human Gene ST 1.0 arrays. Differential gene expression analysis was performed for cells exposed to hypoxia and/or cisplatin. From this, four potential markers of chemoresistance were selected for evaluation in a cohort of ovarian tumour samples by RT-PCR.
  
  
  RESULTS
  Hypoxia increased resistance to cisplatin in A2780 and A2780cis cells. A plethora of genes were differentially expressed in cells exposed to hypoxia and cisplatin which could be associated with chemoresistance. In ovarian tumour samples, we found trends for upregulation of ANGPTL4 in partial responders and down-regulation in non-responders compared with responders to chemotherapy; down-regulation of HER3 in partial and non-responders compared to responders; and down-regulation of HIF-1α in non-responders compared with responders.
  
  
  CONCLUSIONS
  This study has further characterized the relationship between hypoxia and chemoresistance in an ovarian cancer model. We have also identified many potential biomarkers of hypoxia and platinum resistance and provided an initial validation of a subset of these markers in ovarian cancer tissues.
authors.affiliation: Department of Histopathology TCD, Sir Patrick Dun's Laboratory, Central Pathology Laboratory, St James's Hospital, Dublin 8, Ireland. lmmcevoy@tcd.ie.|Department of Obstetrics and Gynaecology, Trinity Centre for Health Sciences, St James's Hospital, Dublin 8, Ireland. lmmcevoy@tcd.ie.
authors.forename: Lynda M
authors.initials: LM
authors.lastname: McEvoy
authors.affiliation: Department of Obstetrics and Gynaecology, Trinity Centre for Health Sciences, St James's Hospital, Dublin 8, Ireland. shotoole@tcd.ie.
authors.forename: Sharon A
authors.initials: SA
authors.lastname: O'Toole
authors.affiliation: Molecular Pathology Laboratory, Coombe Women and Infants' University Hospital, Dublin 8, Ireland. clspilla@tcd.ie.
authors.forename: Cathy D
authors.initials: CD
authors.lastname: Spillane
authors.affiliation: Molecular Pathology Laboratory, Coombe Women and Infants' University Hospital, Dublin 8, Ireland. cmartin3@tcd.ie.
authors.forename: Cara M
authors.initials: CM
authors.lastname: Martin
authors.affiliation: Molecular Pathology Laboratory, Coombe Women and Infants' University Hospital, Dublin 8, Ireland. gallagmi@tcd.ie.
authors.forename: Michael F
authors.initials: MF
authors.lastname: Gallagher
authors.affiliation: Department of Histopathology TCD, Sir Patrick Dun's Laboratory, Central Pathology Laboratory, St James's Hospital, Dublin 8, Ireland. brittastordal@gmail.com.
authors.forename: Britta
authors.initials: B
authors.lastname: Stordal
authors.affiliation: Department of Histopathology TCD, Sir Patrick Dun's Laboratory, Central Pathology Laboratory, St James's Hospital, Dublin 8, Ireland. blackshg@tcd.ie.
authors.forename: Gordon
authors.initials: G
authors.lastname: Blackshields
authors.affiliation: Department of Histopathology TCD, Sir Patrick Dun's Laboratory, Central Pathology Laboratory, St James's Hospital, Dublin 8, Ireland. osheils@tcd.ie.
authors.forename: Orla
authors.initials: O
authors.lastname: Sheils
authors.affiliation: Department of Histopathology TCD, Sir Patrick Dun's Laboratory, Central Pathology Laboratory, St James's Hospital, Dublin 8, Ireland. olearyjj@tcd.ie.|Molecular Pathology Laboratory, Coombe Women and Infants' University Hospital, Dublin 8, Ireland. olearyjj@tcd.ie.
authors.forename: John J
authors.initials: JJ
authors.lastname: O'Leary
mesh_terms: D000075803:Angiopoietin-Like Protein 4; D042682:Angiopoietins / Q000235:genetics; D000970:Antineoplastic Agents / Q000494:pharmacology*; D014408:Biomarkers, Tumor / Q000235:genetics* / Q000378:metabolism; D015687:Cell Hypoxia / Q000187:drug effects; D045744:Cell Line, Tumor; D002945:Cisplatin / Q000494:pharmacology*; D019008:Drug Resistance, Neoplasm; D005260:Female; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000235:genetics / Q000378:metabolism; D010051:Ovarian Neoplasms / Q000188:drug therapy* / Q000235:genetics* / Q000473:pathology; D020893:Receptor, ErbB-3 / Q000235:genetics
chemical_list: C474772:ANGPTL4 protein, human; D000075803:Angiopoietin-Like Protein 4; D042682:Angiopoietins; D000970:Antineoplastic Agents; D014408:Biomarkers, Tumor; C497442:HIF1A protein, human; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; C581292:ERBB3 protein, human; D020893:Receptor, ErbB-3; D002945:Cisplatin