Efficient internalization of the polo-box of polo-like kinase 1 fused to an Antennapedia peptide results in inhibition of cancer cell proliferation.

Polo-like kinases (Plk) regulate multiple stages in mitosis. Plk1 is overexpressed in tumors. The COOH-terminal regions of Plks contain a conserved domain, termed polo-box, which is required for subcellular localization and for physical interaction with substrates. We linked the polo-box (amino acids 410-429) of Plk1 to an Antennapedia peptide and studied its impact on tumor cells. Whereas the wild-type polo-box inhibited the proliferation of tumor cells associated with induction of apoptosis, a mutated derivative was much less effective. The treatment caused mitotic arrest, misaligned chromosomes, and multiple centrosomes. Taken together, membrane-permeable polo-box peptides inhibit cancer cell proliferation efficiently.