Immunohistochemical localization of polo like kinase in early human placenta

Polo like kinase (PLK) is the kinase that was first cloned by us from the cDNA library of human placenta. It belongs to the serine/threonine kinase family and plays a very important role in cell proliferation. In this study, the localization of PLK in early human placenta in vivo was investigated. Immunostaining revealed PLK protein in syncytiotrophoblastic cells and extravillous trophoblastic cells; however proliferating cell nuclear antigen was not. It is known that cytotrophoblastic cells proliferate highly in early human placental villi; however, PLK was not detected in those cells. These results suggest that PLK plays a different role in syncytiotrophoblastic cells than it does in other proliferating cells.