Screening of therapeutic targets for canine mast cell tumors from a variety of kinase molecules.

Options of systemic treatment for canine MCT have been still limited and most canine cases with MCTs eventually undergo relapses even after achievement of a remission. Thus additional therapies are required to establish for the tumor. To identify the novel candidate therapeutic targets for canine MCT, the mRNA expression and phosphorylation statuses of several receptor or non-receptor kinases as well as the inhibitory effect of 95 specific inhibitors on the growth were assessed in three canine MCT cell lines (HRMC, VIMC1 and CMMC1). Among the 14 targets, the mRNAs of 11, 7 and 7 kinases were amplified in HRMC, VIMC1 and CMMC1, respectively. The mRNAs of VEGFR3, PDGFRα, SRC, YES, LCK and FYN were detected in all cell lines. The phosphorylation of 12, 8 and 7 kinases was observed by using specific antibody arrays in HRMC, VIMC1 and CMMC1, respectively. DTK, EPHB6, AMPKα1, CREB, STAT5a and STAT5b were phosphorylated in all cell lines. The 10, 9 and 17 inhibitors exhibited the biological activity against the growth of HRMC, VIMC1 and CMMC1, respectively. Only three inhibitors such as SB218078 (for Chk1), PDGF RTK inhibitor IV (for PDGFR) and radicicol (for Hsp90) suppressed the growth of all three cell lines. The present study indicated that several kinases, such as Chk1, PDGFR and Hsp90, could be used as therapeutic targets in the treatment for canine MCT. Further studies and clinical trials are warranted to apply the inhibitors for the treatment of the tumor.