Inhibition of casein kinase I delta alters mitotic spindle formation and induces apoptosis in trophoblast cells

The serine/threonine-specific casein kinase I delta (CKI delta) is ubiquitously expressed in all tissues, is p53 dependently induced in stress situations and plays an important role in various cellular processes. Our immunohistochemical analysis of the human placenta revealed strongest expression of CKId in extravillous trophoblast cells and in choriocarcinomas. Investigation of the functional role of CKId in an extravillous trophoblast hybrid cell line revealed that CKId was constitutively localized at the centrosomes and the mitotic spindle. Inhibition of CKId with the CKI-specific inhibitor IC261 led to structural alterations of the centrosomes, the formation of multipolar spindles, the inhibition of mitosis and, in contrast to other cell lines, the induction of apoptosis. Our findings indicate that CKId plays an important role in the mitotic progression and in the survival of cells of trophoblast origin. Therefore, IC261 could provide a new tool in treating choriocarcinomas.