title: Specific blockade of VEGF and HER2 pathways results in greater growth inhibition of breast cancer xenografts that overexpress HER2.
abstract: We have previously reported that breast cancer cells which overexpress HER2 produce higher levels of VEGF than cells with low levels of HER2. This study tested the hypothesis that dual targeting of the VEGF (with VEGF-Trap) and HER2 (with trastuzumab) pathways would result in greater growth inhibition of HER2-overexpressing breast cancer xenografts than either agent alone. In this study we found that human and murine endothelial cells expressed high levels of VEGF receptors (VEGFR1, VEGFR2, & VEGFR3). VEGF-Trap decreased levels of secreted VEGF derived from both human and murine cells and effectively blocked VEGF-induced tyrosine phosphorylation of VEGFR2. VEGF-Trap as a single treatment inhibited tumor microvessel density (MVD), tumor vasculature, cell proliferation and tumor growth of BT474 xenografts in a dose-dependent manner from 2.5 mg/kg to 25 mg/kg. VEGF-Trap decreased levels of both human VEGF and PlGF protein in vivo. Trastuzumab as a single agent effectively inhibited BT474 tumor growth in a dose-dependent manner, associated with a decrease in human VEGF, tumor MVD and tumor cell proliferation. Treatment with a combination of VEGF-Trap (2.5-10 mg/kg) and trastuzumab (1 mg/kg) produced significantly greater inhibition of BT474 tumor growth than either individual agent, associated with greater inhibition of tumor MVD and tumor cell proliferation. Thus, VEGF-Trap in combination with trastuzumab produces superior growth inhibition of tumor xenografts which overexpress HER2, which may result from inhibition of both tumor angiogenesis and proliferation. Similar mechanisms may contribute to the clinical anti-tumor activity of trastuzumab in combination with inhibitors of VEGF signaling pathway in women with breast cancers which overexpress HER2.
authors.affiliation: Department of Experimental Therapeutics, University of Texas M.D. Anderson Cancer Center, Houston, Texas, USA. xfle@mdanderson.org
authors.forename: Xiao-Feng
authors.initials: XF
authors.lastname: Le
authors.forename: Weiqun
authors.initials: W
authors.lastname: Mao
authors.forename: Chunhua
authors.initials: C
authors.lastname: Lu
authors.forename: Angela
authors.initials: A
authors.lastname: Thornton
authors.forename: John V
authors.initials: JV
authors.lastname: Heymach
authors.forename: Anil K
authors.initials: AK
authors.lastname: Sood
authors.forename: Robert C
authors.initials: RC
authors.lastname: Bast
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000494:pharmacology / Q000627:therapeutic use; D061067:Antibodies, Monoclonal, Humanized; D001943:Breast Neoplasms / Q000188:drug therapy / Q000378:metabolism* / Q000473:pathology*; D045744:Cell Line, Tumor / Q000187:drug effects; D049109:Cell Proliferation; D042783:Endothelial Cells / Q000187:drug effects / Q000378:metabolism; D005260:Female; D006801:Humans; D008024:Ligands; D051379:Mice; D008819:Mice, Nude; D009389:Neovascularization, Pathologic / Q000378:metabolism; D020286:Pericytes / Q000187:drug effects / Q000378:metabolism; D019000:Phosphotyrosine / Q000378:metabolism; D000072483:Placenta Growth Factor; D011257:Pregnancy Proteins / Q000378:metabolism; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000378:metabolism*; D040262:Receptors, Vascular Endothelial Growth Factor / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D000068878:Trastuzumab; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism*; D023041:Xenograft Model Antitumor Assays
chemical_list: D000911:Antibodies, Monoclonal; D061067:Antibodies, Monoclonal, Humanized; D008024:Ligands; D019000:Phosphotyrosine; D000072483:Placenta Growth Factor; D011257:Pregnancy Proteins; D018719:Erb-b2 Receptor Tyrosine Kinases; D040262:Receptors, Vascular Endothelial Growth Factor; D000068878:Trastuzumab; D042461:Vascular Endothelial Growth Factor A; C000608036:PGF protein, human; C000608037:Pgf protein, mouse