title: Proteomic characterization of breast cancer xenografts identifies early and late bevacizumab-induced responses and predicts effective drug combinations.
abstract: OBJECTIVE
  Neoangiogenesis is an important feature in tumor growth and progression, and combining chemotherapy and antiangiogenic drugs have shown clinical efficacy. However, as treatment-induced resistance often develops, our goal was to identify pathways indicating response and/or evolving resistance to treatment and inhibit these pathways to optimize the treatment strategies.
  
  
  METHODS
  To identify markers of response and/or resistance, reverse-phase protein array (RPPA) was used to characterize treatment-induced changes in a bevacizumab-responsive and a nonresponsive human breast cancer xenograft. Results were combined with bioinformatic modeling to predict druggable targets for optimization of the treatment.
  
  
  RESULTS
  RPPA analysis showed that both tumor models responded to bevacizumab with an early (day 3) upregulation of growth factor receptors and downstream signaling pathways, with persistent mTOR signaling until the end of the in vivo experiment. Adding doxorubicin to bevacizumab showed significant and superior growth inhibition of basal-like tumors, whereas no additive effect was seen in the luminal-like model. The combination treatment corresponded to a continuous late attenuation of mTOR signaling in the basal-like model, whereas the inhibition was temporary in the luminal-like model. Integrating the bevacizumab-induced dynamic changes in protein levels with bioinformatic modeling predicted inhibition of phosphoinositide 3-kinase (PI3K) pathway to increase the efficacy of bevacizumab monotherapy. In vivo experiments combining bevacizumab and the PI3K/mTOR inhibitor BEZ235 confirmed their significant and additive growth-inhibitory effect in the basal-like model.
  
  
  CONCLUSIONS
  Treatment with bevacizumab caused compensatory upregulation of several signaling pathways. Targeting such pathways increased the efficacy of antiangiogenic therapy.
authors.affiliation: Authors' Affiliations: Departments of Tumor Biology and Genetics, Institute for Cancer Research, The Norwegian Radium Hospital, Oslo University Hospital; Department of Oncology, Oslo University Hospital, Ullevaal and Institute of Clinical Medicine, University of Oslo, Oslo; Department of Pharmacy, Faculty of Health Sciences, University of Tromsø, Tromsø, Norway; and Department of Systems Biology, The University of Texas M.D. Anderson Cancer Center, Houston, Texas.
authors.forename: Evita M
authors.initials: EM
authors.lastname: Lindholm
authors.forename: Marit
authors.initials: M
authors.lastname: Krohn
authors.forename: Sergio
authors.initials: S
authors.lastname: Iadevaia
authors.forename: Alexandr
authors.initials: A
authors.lastname: Kristian
authors.forename: Gordon B
authors.initials: GB
authors.lastname: Mills
authors.forename: Gunhild M
authors.initials: GM
authors.lastname: Mælandsmo
authors.forename: Olav
authors.initials: O
authors.lastname: Engebraaten
mesh_terms: D020533:Angiogenesis Inhibitors / Q000008:administration & dosage / Q000494:pharmacology*; D000818:Animals; D061067:Antibodies, Monoclonal, Humanized / Q000008:administration & dosage / Q000494:pharmacology; D000970:Antineoplastic Agents / Q000008:administration & dosage / Q000494:pharmacology*; D000068258:Bevacizumab; D001943:Breast Neoplasms / Q000188:drug therapy / Q000378:metabolism* / Q000473:pathology; D045744:Cell Line, Tumor; D004195:Disease Models, Animal; D004317:Doxorubicin / Q000008:administration & dosage / Q000494:pharmacology; D004359:Drug Therapy, Combination; D005260:Female; D006801:Humans; D051379:Mice; D018295:Neoplasms, Basal Cell / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology; D000081082:Phosphoinositide-3 Kinase Inhibitors; D020543:Proteome; D040901:Proteomics; D015398:Signal Transduction / Q000187:drug effects; D058570:TOR Serine-Threonine Kinases / Q000037:antagonists & inhibitors; D016896:Treatment Outcome; D040301:Vascular Endothelial Growth Factor Receptor-2 / Q000378:metabolism; D023041:Xenograft Model Antitumor Assays
chemical_list: D020533:Angiogenesis Inhibitors; D061067:Antibodies, Monoclonal, Humanized; D000970:Antineoplastic Agents; D000081082:Phosphoinositide-3 Kinase Inhibitors; D020543:Proteome; D000068258:Bevacizumab; D004317:Doxorubicin; D040301:Vascular Endothelial Growth Factor Receptor-2; D058570:TOR Serine-Threonine Kinases