However, simultan eous exposure to tozasertib and HDAC inhibitors in long term survival assays may selleckchem Ivacaftor result in enhanced cell death following treatment with low concentrations of these compounds. Efficacy of cotreatment with HDAC and Aurora kinase inhibitors in BCR ABL positive primary CML cells Because cotreatment with HDAC and Aurora kinase inhibitors induces significant inhibition of growth in BCR ABL expressing cell lines, we next investigated the effects of these compounds in BCR ABL positive primary CML samples and blastic phase samples. Indeed, treatment with tozasertib and vorinostat or pracinostat inhibited cell growth in BCR ABL positive CML samples and blastic phase samples. Although we did perform statis tical analyses of the data, the sample size was too small to obtain meaningful statistics.

Intracellular signaling was also examined. Cotreatment with both tozasertib and vorinostat or pracinostat decreased apparent Crk L phosphorylation, while apparent PARP and acetyl histone H4 activity was increased, again indicating the potential efficacy of tozasertib and vorinostat or pracinostat in BCR ABL positive primary cells. Conclusion In the current study, HDAC inhibitors induced apoptosis in BCR ABL positive leukemia cells. In particular, pro found inhibition of cell growth and induction of apoptosis were observed in response to HDAC inhibitors in BCR ABL positive K562 and mouse pro B Ba F3 cells with ectopic expression of wt and mutant T315I. This response was amplified by cotreatment with an Aurora kinase inhibitor.

In this study, we also demonstrated that Aurora kinase proteins were degraded by vorinostat or pracinostat in a dose dependent manner. Although the levels of Aurora family proteins were not directly reduced by tozasertib treatment, tozasertib inhibited the expression of HDAC proteins. As such, our data indicated that vorinostat or pracinostat and tozasertib affected the activities of both Aurora kinase and HDAC, in turn in creasing Brefeldin_A antitumor activity in this system. Clinical trials using tozasertib have been discontinued. However, other pan Aurora BCR ABL dual inhibitors may exhibit a similar {profile, and these continue to be studied clinically. Our findings suggest that cotreatment with these compounds and specific molecular targeted drugs could benefit pa tients with leukemic BCR ABL cells that are resistant to more conventional treatments. Methods Reagents and antibodies The HDAC inhibitors vorinostat and pracinostat were provided by Selleck Chemicals LLC. Tozasertib was kindly donated by Vertex Phar maceuticals Inc. Stock solutions of vorinostat, pracinostat, and tozasertib were dissolved in dimethyl sulfoxide and subsequently diluted to the desired concentration in growth medium.