In vitro effects of the tyrosine kinase inhibitor, masitinib mesylate, on canine hemangiosarcoma cell lines

This study evaluated the in vitro activity of masitinib mesylate against canine hemangiosarcoma ( HSA ) cell lines after treatment with increasing concentrations of masitinib mesylate (0.01–100 µM) for 24, 48 and 72 h. Results indicated that masitinib mesylate caused a dose‐ and time‐dependent decrease in HSA cell proliferation. The 50% inhibitory concentration ( IC 50 ) at 72 h for three HSA cell lines ( DEN , Fitz and SB ) was found to be 8.56, 9.41 and 10.65 µM, respectively. Further investigation demonstrated that masitinib mesylate induced apoptosis in all HSA cell lines, including activation of caspase‐3/7. Measurement of VEGF levels in cell supernatant found a statistically significant increased VEGF in close proximity to the IC 50 of each cell line followed by a decline back towards baseline. These findings indicate that masitinib mesylate causes dose‐dependent HSA cell death in vitro and supports future clinical trials of masitinib for canine HSA .