Increased human polo-like kinase-1 expression in gliomas

PLK-1 (polo-like kinase) belongs to the family of serine/threonine kinases and is involved in spindle formation, centrosome cycles and chromosome segr egation. Hence, the kinase is tightly linked to cell proliferation. We coul d detect immunohistochemically highly expressed PLK protein in astrocytic t umours depending on the grade of anaplasia, in commercially available human glioma cell lines (U87MG, U118MG, U138MG), in one immortalized cell cultur e derived from a glioblastoma patient and in a primary culture derived from a glioblastoma patient. The highest labelling of PLK-1 was demonstrated in glioblastomas. There was a significant correlation between the PLK express ion and the nuclear immunoreactivity of MIB-1. PLK-mRNA, found in all tumou r specimens investigated emphasizes the close correlation to proliferation and growth. Furthermore, the relation of the PLK-1 expression to the Mitoge n-activated Protein Kinase Cascades was studied by applying various highly specific inhibitors. While all inhibitors minimized the cell density, only the PLC gamma inhibitor clearly lead to a reduced PLK-1 expression in the t hree cell lines U87MG, U118MG, U138MG.