Antiproliferative effects of masitinib and imatinib against canine oral fibrosarcoma in vitro.
BACKGROUND
Canine oral fibrosarcoma (COF) is one of the most common oral tumors in dogs and carries a guarded prognosis due to a lack of effective systemic therapeutic options. Mastinib and imatinib are two commonly used tyrosine kinase inhibitors (TKIs) in veterinary oncology but their potential efficacy against COF is uncharacterized. To begin investigating the rationale for use of these TKIs against COF, the present study tested for the presence TKI targets PDGFR-α, PDGFR-β, Kit, and VEGFR-2 and examined the in vitro effects on cell viability after TKI treatment alone or with doxorubicin. Immunohistochemistry for PDGFR-α, PDGFR-β, Kit, and VEGFR-2 was performed in 6 COF tumor biopsies. Presence of these same receptors within 2 COF cell lines was probed by reverse transcription-polymerase chain reaction and, for those with mRNA detected, confirmed via western blot. Effects on cell viability were assessed using an MTS assay after masitinib or imatinib treatment alone (0-100 μM), or in combination with doxorubicin (0-3000 nM doxorubicin). Anti-PDGFRB siRNA knockdown was performed and the effect on cell viability quantified.


RESULTS
Expression of the TKI targets evaluated was similar between the 2 COF cell lines and the 6 COF tumor biopsies: PDGFR-α and PDGFR-β were detected in neoplastic cells from most COF tumor biopsies (5/6 and 6/6, respectively) and were present in both COF cell lines; KIT and KDR were not detected in any sample. Masitinib and imatinib IC50 values ranged from 7.9-33.4 μM, depending on the specific TKI and cell line tested. The addition of doxorubicin resulted in synergistic cytotoxicity with both TKIs. Anti-PDGFRB siRNA transfection reduced PDGFR-β protein expression by 77% and 67% and reduced cell viability by 24% (p < 0.0001) and 28% (0 = 0.0003) in the two cell lines, respectively.


CONCLUSIONS
These results provide rationale for further investigation into the use of TKIs, possibly in combination with doxorubicin, as treatment options for COF.
Department of Clinical Sciences, College of Veterinary Medicine, Oregon State University, Corvallis, OR, 97331, USA. milan.milovancev@oregonstate.edu.
Milan
M
Milovancev
Department of Clinical Sciences, College of Veterinary Medicine, Oregon State University, Corvallis, OR, 97331, USA.
Stuart C
SC
Helfand
Department of Clinical Sciences, College of Veterinary Medicine, Oregon State University, Corvallis, OR, 97331, USA.
Kevin
K
Marley
Department of Clinical Sciences, College of Veterinary Medicine, Oregon State University, Corvallis, OR, 97331, USA.
Cheri P
CP
Goodall
Department of Biomedical Sciences, College of Veterinary Medicine, Oregon State University, Corvallis, OR, 97331, USA.
Christiane V
CV
Löhr
Department of Clinical Sciences, College of Veterinary Medicine, Oregon State University, Corvallis, OR, 97331, USA.
Shay
S
Bracha
D000818:Animals; D000970:Antineoplastic Agents / Q000627:therapeutic use*; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000627:therapeutic use; D001549:Benzamides; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D004283:Dog Diseases / Q000188:drug therapy*; D004285:Dogs; D004317:Doxorubicin / Q000627:therapeutic use; D005354:Fibrosarcoma / Q000188:drug therapy / Q000662:veterinary*; D000068877:Imatinib Mesylate / Q000627:therapeutic use*; D009062:Mouth Neoplasms / Q000188:drug therapy / Q000662:veterinary*; D010880:Piperidines; D047428:Protein Kinase Inhibitors / Q000627:therapeutic use*; D019009:Proto-Oncogene Proteins c-kit / Q000378:metabolism; D011725:Pyridines; D020796:Receptor, Platelet-Derived Growth Factor alpha / Q000037:antagonists & inhibitors; D020797:Receptor, Platelet-Derived Growth Factor beta / Q000037:antagonists & inhibitors; D013844:Thiazoles / Q000627:therapeutic use*; D040301:Vascular Endothelial Growth Factor Receptor-2 / Q000037:antagonists & inhibitors
D000970:Antineoplastic Agents; D001549:Benzamides; D010880:Piperidines; D047428:Protein Kinase Inhibitors; D011725:Pyridines; D013844:Thiazoles; D004317:Doxorubicin; D000068877:Imatinib Mesylate; D019009:Proto-Oncogene Proteins c-kit; D020796:Receptor, Platelet-Derived Growth Factor alpha; D020797:Receptor, Platelet-Derived Growth Factor beta; D040301:Vascular Endothelial Growth Factor Receptor-2; C526575:masitinib
Dog; Imatinib; Masitinib; Oral fibrosarcoma; Platelet-derived growth factor receptor