title: Effect of antiangiogenic therapy on tumor growth, vasculature and kinase activity in basal- and luminal-like breast cancer xenografts.
abstract: Several clinical trials have investigated the efficacy of bevacizumab in breast cancer, and even if growth inhibiting effects have been registered when antiangiogenic treatment is given in combination with chemotherapy no gain in overall survival has been observed. One reason for the lack of overall survival benefit might be that appropriate criteria for selection of patients likely to respond to antiangiogenic therapy in combination with chemotherapy, are not available. To determine factors of importance for antiangiogenic treatment response and/or resistance, two representative human basal- and luminal-like breast cancer xenografts were treated with bevacizumab and doxorubicin alone or in combination. In vivo growth inhibition, microvessel density (MVD) and proliferating tumor vessels (pMVD = proliferative microvessel density) were analysed, while kinase activity was determined using the PamChip Tyrosine kinase microarray system. Results showed that both doxorubicin and bevacizumab inhibited basal-like tumor growth significantly, but with a superior effect when given in combination. In contrast, doxorubicin inhibited luminal-like tumor growth most effectively, and with no additional benefit of adding antiangiogenic therapy. In agreement with the growth inhibition data, vascular characterization verified a more pronounced effect of the antiangiogenic treatment in the basal-like compared to the luminal-like tumors, demonstrating total inhibition of pMVD and a significant reduction in MVD at early time points (three days after treatment) and sustained inhibitory effects until the end of the experiment (day 18). In contrast, luminal-like tumors only showed significant effect on the vasculature at day 10 in the tumors having received both doxorubicin and bevacizumab. Kinase activity profiling in both tumor models demonstrated that the most effective treatment in vivo was accompanied with increased phosphorylation of kinase substrates of growth control and angiogenesis, like EGFR, VEGFR2 and PLCγ1. This may be a result of regulatory feedback mechanisms contributing to treatment resistance, and may suggest response markers of value for the prediction of antiangiogenic treatment efficacy.
authors.affiliation: Department of Tumor Biology, Institute for Cancer Research, Oslo University Hospital, The Norwegian Radium Hospital, Pb 4953 Nydalen, 0424 Oslo, Norway. Evita.Lindholm@rr-research.no
authors.forename: Evita M
authors.initials: EM
authors.lastname: Lindholm
authors.forename: Alexandr
authors.initials: A
authors.lastname: Kristian
authors.forename: Hawa
authors.initials: H
authors.lastname: Nalwoga
authors.forename: Kristi
authors.initials: K
authors.lastname: Krüger
authors.forename: Ståle
authors.initials: S
authors.lastname: Nygård
authors.forename: Lars A
authors.initials: LA
authors.lastname: Akslen
authors.forename: Gunhild M
authors.initials: GM
authors.lastname: Mælandsmo
authors.forename: Olav
authors.initials: O
authors.lastname: Engebraaten
mesh_terms: D020533:Angiogenesis Inhibitors / Q000494:pharmacology / Q000627:therapeutic use*; D000818:Animals; D061067:Antibodies, Monoclonal, Humanized / Q000494:pharmacology / Q000627:therapeutic use; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000627:therapeutic use; D000068258:Bevacizumab; D015153:Blotting, Western; D001943:Breast Neoplasms / Q000098:blood supply* / Q000188:drug therapy* / Q000201:enzymology / Q000473:pathology; D049109:Cell Proliferation / Q000187:drug effects; D004317:Doxorubicin / Q000494:pharmacology / Q000627:therapeutic use; D005260:Female; D006801:Humans; D051379:Mice; D008819:Mice, Nude; D009363:Neoplasm Proteins / Q000378:metabolism; D009389:Neovascularization, Pathologic / Q000188:drug therapy*; D010766:Phosphorylation / Q000187:drug effects; D011494:Protein Kinases / Q000378:metabolism*; D015203:Reproducibility of Results; D023041:Xenograft Model Antitumor Assays
chemical_list: D020533:Angiogenesis Inhibitors; D061067:Antibodies, Monoclonal, Humanized; D009363:Neoplasm Proteins; D000068258:Bevacizumab; D004317:Doxorubicin; D011494:Protein Kinases