Synergistic antitumor activity of ZD6474, an inhibitor of vascular endothelial growth factor receptor and epidermal growth factor receptor signaling, with gemcitabine and ionizing radiation against pancreatic cancer.
OBJECTIVE
Standard treatments have modest effect against pancreatic cancer, and current research focuses on agents targeting molecular pathways involved in tumor growth and angiogenesis. This study investigated the interactions between ZD6474, an inhibitor of tyrosine kinase activities of vascular endothelial growth factor receptor-2 and epidermal growth factor receptor (EGFR), gemcitabine, and ionizing radiation in human pancreatic cancer cells and analyzed the molecular mechanisms underlying this combination.


METHODS
ZD6474, ionizing radiation, and gemcitabine, alone or in combination, were given in vitro to MIA PaCa-2, PANC-1, and Capan-1 cells and in vivo to MIA PaCa-2 tumor xenografts. The effects of treatments were studied by the evaluation of cytotoxicity, apoptosis, cell cycle, EGFR and Akt phosphorylation, modulation of gene expression of enzymes related to gemcitabine activity (deoxycytidine kinase and ribonucleotide reductase), as well as vascular endothelial growth factor immunohistochemistry and microvessel count.


RESULTS
In vitro, ZD6474 dose dependently inhibited cell growth, induced apoptosis, and synergistically enhanced the cytotoxic activity of gemcitabine and ionizing radiation. Moreover, ZD6474 inhibited phosphorylation of EGFR and Akt and triggered cell apoptosis. PCR analysis showed that ZD6474 increased the ratio between gene expression of deoxycytidine kinase and ribonucleotide reductase. In vivo, ZD6474 showed significant antitumor activity alone and in combination with radiotherapy and gemcitabine, and the combination of all three modalities enhanced MIA PaCA-2 tumor growth inhibition compared with gemcitabine alone.


CONCLUSIONS
ZD6474 decreases EGFR and Akt phosphorylation, enhances apoptosis, favorably modulates gene expression in cancer cells, and acts synergistically with gemcitabine and radiotherapy to inhibit tumor growth. These findings support the investigation of this combination in the clinical setting.
Bianco
Cataldo
C
Division of Radiotherapy, Department of Oncology, Transplants and Advanced Technologies in Medicine, University of Pisa, Pisa, Italy.
Giovannetti
Elisa
E
Ciardiello
Fortunato
F
Mey
Valentina
V
Nannizzi
Sara
S
Tortora
Giampaolo
G
Troiani
Teresa
T
Pasqualetti
Francesco
F
Eckhardt
Gail
G
de Liguoro
Mario
M
Ricciardi
Simona
S
Del Tacca
Mario
M
Raben
David
D
Cionini
Luca
L
Danesi
Romano
R
D000818:Animals; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000494:pharmacology* / Q000627:therapeutic use; D017209:Apoptosis / Q000187:drug effects / Q000528:radiation effects; D002453:Cell Cycle / Q000187:drug effects / Q000528:radiation effects; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects / Q000528:radiation effects; D003131:Combined Modality Therapy; D003841:Deoxycytidine / Q000031:analogs & derivatives* / Q000494:pharmacology / Q000627:therapeutic use; D003842:Deoxycytidine Kinase / Q000235:genetics / Q000528:radiation effects; D004195:Disease Models, Animal; D004307:Dose-Response Relationship, Radiation; D004354:Drug Screening Assays, Antitumor; D004357:Drug Synergism; D066246:ErbB Receptors / Q000037:antagonists & inhibitors*; D005260:Female; D020869:Gene Expression Profiling; D006801:Humans; D051379:Mice; D008819:Mice, Nude; D010190:Pancreatic Neoplasms / Q000175:diagnosis / Q000188:drug therapy* / Q000532:radiotherapy*; D010766:Phosphorylation; D010880:Piperidines / Q000494:pharmacology* / Q000627:therapeutic use; D016133:Polymerase Chain Reaction; D011237:Predictive Value of Tests; D011799:Quinazolines / Q000494:pharmacology* / Q000627:therapeutic use; D011839:Radiation, Ionizing; D040262:Receptors, Vascular Endothelial Growth Factor / Q000037:antagonists & inhibitors* / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D014183:Transplantation, Heterologous; D000093542:Gemcitabine
D010880:Piperidines; D011799:Quinazolines; D003841:Deoxycytidine; D003842:Deoxycytidine Kinase; D066246:ErbB Receptors; D040262:Receptors, Vascular Endothelial Growth Factor; C452423:vandetanib; D000093542:Gemcitabine