title: Effects of vatalanib on tumor growth can be potentiated by mTOR blockade in vivo.
abstract: The vascular endothelial growth factor (VEGF) is a central mediator of tumor-induced angiogenesis. Everolimus, a mammalian target of rapamycin (mTOR) inhibitor, decreases VEGF-secretion of cancer cells. Vatalanib is a selective inhibitor of VEGF receptors 1-3. In the present study it was hypothesized that dual inhibition of VEGF signaling by inhibition of VEGF production and VEGF receptor signaling leads to synergistic anti-tumor effects. In vitro, effects of vatalanib and everolimus on cell proliferation, cell cycle, apoptosis and signal transduction were examined in three gastric cancer cell lines. Effects on angiogenesis were assessed using tube formation assays of cultured human umbilical vein endothelial cells (HUVECs). In vivo, the antitumor effect of compounds was studied using a gastric cancer xenograft nude mouse model. VEGF of murine origin (mVEGF) and human cancer cell-derived VEGF (hVEGF) were studied separately by specific ELISAs. Tumor vascularization and proliferation were quantified by immunohistochemistry. In vitro, everolimus but not vatalanib decreased gastric cancer proliferation without inducing apoptosis. Vatalanib abolished endothelial cell tube formation, whereas inhibition of tube formation by everolimus was incomplete. In vivo, the combination of vatalanib with everolimus was superior to single agent treatments and reduced tumor size by about 50% relative to everolimus monotherapy (p < 0.005). Pharmacodynamic analysis of VEGF plasma level showed a decrease of hVEGF by everolimus and indicated a trend towards lower mVEGF level only in the combination group. In line, there was a tendency for lower vascular density and proliferation for combination treatment. We conclude that in a preclinical model of gastric cancer the antitumor activity of vatalanib can be augmented by everolimus.
authors.affiliation: Department of Clinical Pharmacology, Medical University, Vienna, Austria.
authors.forename: Agnes
authors.initials: A
authors.lastname: Jaeger-Lansky
authors.forename: Daniel
authors.initials: D
authors.lastname: Cejka
authors.forename: Liu
authors.initials: L
authors.lastname: Ying
authors.forename: Matthias
authors.initials: M
authors.lastname: Preusser
authors.forename: Doris
authors.initials: D
authors.lastname: Hoeflmayer
authors.forename: Thorsten
authors.initials: T
authors.lastname: Fuereder
authors.forename: Stefan
authors.initials: S
authors.lastname: Koehrer
authors.forename: Volker
authors.initials: V
authors.lastname: Wacheck
mesh_terms: D000818:Animals; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000627:therapeutic use*; D017209:Apoptosis / Q000187:drug effects; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D004357:Drug Synergism; D004797:Enzyme-Linked Immunosorbent Assay; D000068338:Everolimus; D006801:Humans; D007166:Immunosuppressive Agents / Q000494:pharmacology; D051379:Mice; D008819:Mice, Nude; D009389:Neovascularization, Pathologic / Q000378:metabolism / Q000517:prevention & control; D010793:Phthalazines / Q000008:administration & dosage / Q000494:pharmacology*; D047428:Protein Kinase Inhibitors / Q000008:administration & dosage / Q000494:pharmacology; D011725:Pyridines / Q000008:administration & dosage / Q000494:pharmacology*; D040262:Receptors, Vascular Endothelial Growth Factor / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D020123:Sirolimus / Q000008:administration & dosage / Q000031:analogs & derivatives / Q000494:pharmacology; D013274:Stomach Neoplasms / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D058570:TOR Serine-Threonine Kinases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D047368:Tumor Burden / Q000187:drug effects; D042461:Vascular Endothelial Growth Factor A / Q000097:blood / Q000378:metabolism; D023041:Xenograft Model Antitumor Assays
chemical_list: D007166:Immunosuppressive Agents; D010793:Phthalazines; D047428:Protein Kinase Inhibitors; D011725:Pyridines; D042461:Vascular Endothelial Growth Factor A; C404768:vatalanib; D000068338:Everolimus; D040262:Receptors, Vascular Endothelial Growth Factor; D058570:TOR Serine-Threonine Kinases; D020123:Sirolimus