It has also been reported that Ser16 is a target for calmodulindependent protein kinases (CamKII), Ser25 is specifically phosphorylated by mitogen-activated protein (MAP) kinase, and Ser38 is a target for cycline-dependent kinase-2 (CDK2) [26] . To test the activation status of upstream kinases catalyzing the incorporation of phosphoryl groups to each of these residues, specific antibodies against active forms of CaMKII, MAPK and CDK2 (responsible for the stathmin phosphorylation on Ser16, Ser25 and Ser38, respectively) were used. In accordance with the increase in p-Ser16 and p-Ser38 of stathmin in bortezomib-treated cells, a parallel activation of CamKII and CDK2 was detected after bortezomib treatment ( Fig. 4B ). At the same time, the decrease in phosphorylation levels of Ser25 was correlated with the inactivation of MAPK, a critical kinase for cell survival.