Dual targeting of Raf and VEGF receptor 2 reduces growth and metastasis of pancreatic cancer through direct effects on tumor cells, endothelial cells, and pericytes.
The Ras/Raf/MEK pathway represents an important oncogenic signaling pathway in gastrointestinal malignancies, including pancreatic cancer. Although activating B-Raf mutations are infrequent in pancreatic cancer, we hypothesized that targeting Raf could be valuable for therapy of this cancer entity. Moreover, as vascular endothelial growth factor receptor 2 (VEGFR2) is involved in tumor angiogenesis, we sought to investigate the effects of dual inhibition of Raf and VEGFR2 on pancreatic tumor growth, vascularization, and metastasis. Effects of a Raf/VEGFR2 inhibitor (NVP-AAL881) on pancreatic cancer cells, endothelial cells, and vascular smooth muscle cells were determined by Western blotting, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide analysis, and migration assays, respectively. Changes in the expression of VEGF-A or survivin were investigated by ELISA and/or real-time PCR. The growth-inhibitory effects of Raf/VEGFR2 inhibition were additionally evaluated in orthotopic tumor models. Results showed that various Raf isoforms were activated in pancreatic cancer cells and NVP-AAL881 diminished the activation of MEK, Akt, Erk, and also STAT3. Moreover, dual inhibition of Raf/VEGFR2 significantly reduced VEGF expression and impaired cancer cell migration. Importantly, besides blocking VEGF-induced Erk and SAPK phosphorylation in endothelial cells, the Raf inhibitor diminished STAT3 phosphorylation, independent of a VEGFR2 blockade, and reduced the expression of survivin. In addition, cell proliferation and migration of both endothelial cells and vascular smooth muscle cells were significantly reduced. In vivo, blocking Raf/VEGFR2 significantly inhibited orthotopic tumor growth and vascularization and reduced cancer metastasis. In conclusion, blocking Raf exerts growth-inhibitory effects on pancreatic tumor cells, endothelial cells, and pericytes and elicits antiangiogenic properties. Dual targeting of Raf and VEGFR2 appears to be a valid strategy for therapy of pancreatic cancer.
Lang
Sven A
SA
Departments of Surgery and Surgical Oncology, University of Regensburg Medical Center, Franz-Josef-Strauss-Allee 11, Regensburg, Germany.
Schachtschneider
Philipp
P
Moser
Christian
C
Mori
Akira
A
Hackl
Christina
C
Gaumann
Andreas
A
Batt
David
D
Schlitt
Hans J
HJ
Geissler
Edward K
EK
Stoeltzing
Oliver
O
D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology / Q000627:therapeutic use*; D045744:Cell Line, Tumor; D002465:Cell Movement / Q000187:drug effects; D042783:Endothelial Cells / Q000187:drug effects* / Q000378:metabolism; D006801:Humans; D007546:Isoquinolines / Q000494:pharmacology / Q000627:therapeutic use*; D008297:Male; D051379:Mice; D008819:Mice, Nude; D009362:Neoplasm Metastasis / Q000473:pathology; D009389:Neovascularization, Pathologic / Q000188:drug therapy; D010190:Pancreatic Neoplasms / Q000188:drug therapy* / Q000473:pathology; D020286:Pericytes / Q000187:drug effects* / Q000378:metabolism; D015398:Signal Transduction; D040301:Vascular Endothelial Growth Factor Receptor-2 / Q000037:antagonists & inhibitors* / Q000378:metabolism; D048490:raf Kinases / Q000037:antagonists & inhibitors* / Q000378:metabolism
C514876:AAL 881; D000970:Antineoplastic Agents; D007546:Isoquinolines; D040301:Vascular Endothelial Growth Factor Receptor-2; D048490:raf Kinases