Antitumor effects of inhibitors of ERK and Akt pathways in canine histiocytic sarcoma cell lines.

Canine histiocytic sarcoma (CHS) is characterized by aggressive biological behavior. In our previous study, ERK and Akt pathways were found to be activated in CHS tissues. Thus, the objective of this study was set to investigate the relationships between the activation status of these pathways and the proliferation of CHS cell lines by examining the effects of single and co-administrations of drugs targeting these pathways. First, we evaluated the changes in cell proliferations and the activations of ERK and Akt pathways after treatments with ERK and Akt-specific inhibitors in CHS cells. Then, these changes after treatments with dasatinib and trametinib were also examined in CHS cells. Inhibitors specific to ERK and Akt pathways successfully inhibited the respective pathways in CHS cell lines. It was also indicated that these pathways were associated with the regulations of proliferations of CHS cells, although the anti-proliferative effect was not necessarily observed by inhibition of Akt pathway alone. Dasatinib and trametinib also showed the inhibitions of Akt and ERK pathway activations, respectively, in CHS cells. However, the anti-proliferative effects of these drugs varied among CHS cell lines, and co-administration showed enhanced anti-proliferative effects in only a part of CHS cell lines. Further studies are needed to investigate the molecular mechanisms associated with the sensitivities to these molecular-targeted drugs in CHS cells.