Protein kinase CK2 is implicated in the regulation of the cell cycle. In addition to a variety of functions, CK2 has anti-apoptotic properties. So far the role of CK2 linking both pathways in the cell is not clear. Some years ago we found that CK2 phosphorylates cdc25C, one member of the cdc25 family of proteins. In this study, we showed that inhibition of CK2 activity by three different inhibitors led to a down-regulation of the level of cdc25C. Inhibition of CK2 activity by transfecting the dominant-negative CK2α subunit also resulted in a down-regulation of the level of cdc25C whereas inhibition of CK2α' had no effect on the cdc25C level. In both cases, we observed apoptosis by PARP cleavage as well as by an increase in γH2AX phosphorylation. These results show that down-regulation of the level of cdc25C is not a prerequisite for the induction of apoptosis.