title: Aurora kinase B is important for antiestrogen resistant cell growth and a potential biomarker for tamoxifen resistant breast cancer.
abstract: BACKGROUND
  Resistance to antiestrogen therapy is a major clinical challenge in the treatment of estrogen receptor α (ER)-positive breast cancer. The aim of the study was to explore the growth promoting pathways of antiestrogen resistant breast cancer cells to identify biomarkers and novel treatment targets.
  
  
  METHODS
  Antiestrogen sensitive and resistant T47D breast cancer cell lines were used as model systems. Parental and fulvestrant resistant cell lines were subjected to a kinase inhibitor library. Kinase inhibitors preferentially targeting growth of fulvestrant resistant cells were identified and the growth inhibitory effect verified by dose-response cell growth experiments. Protein expression and phosphorylation were investigated by western blot analysis. Cell cycle phase distribution and cell death were analyzed by flow cytometry. To evaluate Aurora kinase B as a biomarker for endocrine resistance, immunohistochemistry was performed on archival primary tumor tissue from breast cancer patients who have received adjuvant endocrine treatment with tamoxifen.
  
  
  RESULTS
  The selective Aurora kinase B inhibitor barasertib was identified to preferentially inhibit growth of fulvestrant resistant T47D breast cancer cell lines. Compared with parental cells, phosphorylation of Aurora kinase B was higher in the fulvestrant resistant T47D cells. Barasertib induced degradation of Aurora kinase B, caused mitotic errors, and induced apoptotic cell death as measured by accumulation of SubG1 cells and PARP cleavage in the fulvestrant resistant cells. Barasertib also exerted preferential growth inhibition of tamoxifen resistant T47D cell lines. Finally, high percentage of Aurora kinase B positive tumor cells was significantly associated with reduced disease-free and overall survival in 261 ER-positive breast cancer patients, who have received tamoxifen as first-line adjuvant endocrine treatment.
  
  
  CONCLUSIONS
  Our results indicate that Aurora kinase B is a driving factor for growth of antiestrogen resistant T47D breast cancer cell lines, and a biomarker for reduced benefit of tamoxifen treatment. Thus, inhibition of Aurora kinase B, e.g. with the highly selective kinase inhibitor barasertib, could be a candidate new treatment for breast cancer patients with acquired resistance to antiestrogens.
authors.affiliation: Breast Cancer Group, Unit of Cell Death and Metabolism, Danish Cancer Society Research Center, Copenhagen, Denmark. sarahline@outlook.com.
authors.forename: Sarah L
authors.initials: SL
authors.lastname: Larsen
authors.affiliation: Breast Cancer Group, Unit of Cell Death and Metabolism, Danish Cancer Society Research Center, Copenhagen, Denmark. cwy@cancer.dk.
authors.forename: Christina W
authors.initials: CW
authors.lastname: Yde
authors.affiliation: Department of Pathology, Slagelse Hospital, Slagelse, Denmark. anlae@regionsjaelland.dk.
authors.forename: Anne-Vibeke
authors.initials: AV
authors.lastname: Laenkholm
authors.affiliation: Department of Pathology, Herlev Hospital, Herlev, Denmark. birgitte.bruun.rasmussen@regionh.dk.
authors.forename: Birgitte B
authors.initials: BB
authors.lastname: Rasmussen
authors.affiliation: Statistics, Bioinformatics and Registry, Danish Cancer Society Research Center, Copenhagen, Denmark. annduu@cancer.dk.
authors.forename: Anne Katrine
authors.initials: AK
authors.lastname: Duun-Henriksen
authors.affiliation: Department of Clinical Pathology, Odense University Hospital, Odense, Denmark. Martin.bak@rsyd.dk.
authors.forename: Martin
authors.initials: M
authors.lastname: Bak
authors.affiliation: Breast Cancer Group, Unit of Cell Death and Metabolism, Danish Cancer Society Research Center, Copenhagen, Denmark. al@cancer.dk.
authors.forename: Anne E
authors.initials: AE
authors.lastname: Lykkesfeldt
authors.affiliation: Breast Cancer Group, Unit of Cell Death and Metabolism, Danish Cancer Society Research Center, Copenhagen, Denmark. tokc@regionsjaelland.dk.|Present address: Department of Surgery, Køge Hospital, Køge, Denmark. tokc@regionsjaelland.dk.
authors.forename: Tove
authors.initials: T
authors.lastname: Kirkegaard
mesh_terms: D018931:Antineoplastic Agents, Hormonal / Q000494:pharmacology* / Q000627:therapeutic use; D017209:Apoptosis / Q000187:drug effects; D064107:Aurora Kinase B / Q000378:metabolism*; D015415:Biomarkers; D001943:Breast Neoplasms / Q000188:drug therapy / Q000378:metabolism* / Q000401:mortality / Q000473:pathology; D002453:Cell Cycle / Q000187:drug effects; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D019008:Drug Resistance, Neoplasm; D004958:Estradiol / Q000031:analogs & derivatives / Q000494:pharmacology; D020847:Estrogen Receptor Modulators / Q000494:pharmacology* / Q000627:therapeutic use; D005260:Female; D000077267:Fulvestrant; D006801:Humans; D008938:Mitosis / Q000187:drug effects; D009364:Neoplasm Recurrence, Local; D010755:Organophosphates / Q000494:pharmacology; D010766:Phosphorylation; D011379:Prognosis; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D059748:Proteolysis; D011799:Quinazolines / Q000494:pharmacology; D016019:Survival Analysis; D013629:Tamoxifen / Q000494:pharmacology* / Q000627:therapeutic use
chemical_list: C520647:2-((3-((4-((5-(2-((3-fluorophenyl)amino)-2-oxoethyl)-1H-pyrazol-3-yl)amino)quinazolin-7-yl)oxy)propyl)(ethyl)amino)ethyl dihydrogen phosphate; D018931:Antineoplastic Agents, Hormonal; D015415:Biomarkers; D020847:Estrogen Receptor Modulators; D010755:Organophosphates; D047428:Protein Kinase Inhibitors; D011799:Quinazolines; D013629:Tamoxifen; D000077267:Fulvestrant; D004958:Estradiol; D064107:Aurora Kinase B