In vivo tumor imaging using polo-box domain of polo-like kinase 1 targeted peptide.

Polo-like kinase 1 (Plk1) is a regulator of cell cycle progression during mitosis; it is overexpressed in many different tumors and has been implicated as a potential antimitotic target. Plks are characterized by the presence of a highly conserved C-terminal polo-box domain (PBD) that is involved in regulating kinase activity. The phosphopeptide Pro-Leu-His-Ser-p-Thr (PLHSpT) is a potent selective inhibitor of the PBD of human plk1 that acts by inducing mitotic arrest and apoptotic cell death in cancer cells. We synthesized cRGDyK-S-S-CPLHSpT to exploit the drug delivery and molecular imaging using positron emission tomography (PET). The peptide was blocked dramatically proliferation of tumor in vitro and in vivo. It was attempted to develop and show a tumor PET image with the radiolabeled-peptide. Here we showed the peptide is promising not only as an anticancer drug, but also as a radioligand for tumor diagnosis with PET. We expect that our contribution will provide new insights into the design of Plk1 peptide inhibitors and have significant implications for anticancer therapy and tumor diagnosis.