title: Inhibition of polo-like kinase 1 leads to the suppression of osteosarcoma cell growth in vitro and in vivo.
abstract: Osteosarcoma is the most common type of primary bone cancer in children and adolescents. Treatment options for osteosarcoma may include surgery, chemotherapy, and radiotherapy. Unfortunately, many patients eventually relapse, resulting in an unsatisfactory outcome. The serine/threonine-specific polo-like kinase 1 (PLK1) is a kinase that plays an important role in mitosis and the maintenance of genomic stability. PLK1 has been found to be highly expressed in the malignant cells of osteosarcoma. Here, we describe the in-vitro and in-vivo effects of BI 2536, a small-molecule inhibitor of PLK1, which through inhibiting PLK1 enzymatic activity, causes mitotic arrest and eventually induces cancer cell apoptosis. In this study, we show that the PLK1 inhibitor, BI 2536, inhibits proliferation and induces apoptosis in two-dimensional and three-dimensional cultures of osteosarcoma cell lines, KHOS and U-2OS. A proliferation assay performed both in two-dimensional and three-dimensional culture showed that the growth of both cell lines was inhibited by BI 2536. Cell cycle analysis showed that the cells treated with BI 2536 were mainly arrested in the G2/M phase. Immunofluorescence and western blotting analysis confirmed that the administration of BI 2536 led to significant decrease of PLK1 and Mcl-1 protein expression levels in dose-dependent and time-dependent manners. Furthermore, BI 2536-induced apoptosis in the osteosarcoma cell lines was shown by poly (ADP-ribose) polymerase cleavage and caspase assay. Finally, in mouse osteosarcoma xenografts, BI 2536-treated mice had significantly smaller tumors compared with the control mice. These findings offer evidence of the potential role for targeting PLK1 in osteosarcoma therapy.
authors.affiliation: Department of Orthopaedic Surgery, Center for Sarcoma and Connective Tissue Oncology, Massachusetts General Hospital, Boston, Massachusetts 02114, USA.
authors.forename: Xianzhe
authors.initials: X
authors.lastname: Liu
authors.forename: Edwin
authors.initials: E
authors.lastname: Choy
authors.forename: David
authors.initials: D
authors.lastname: Harmon
authors.forename: Shuhua
authors.initials: S
authors.lastname: Yang
authors.forename: Cao
authors.initials: C
authors.lastname: Yang
authors.forename: Henry
authors.initials: H
authors.lastname: Mankin
authors.forename: Francis J
authors.initials: FJ
authors.lastname: Hornicek
authors.forename: Zhenfeng
authors.initials: Z
authors.lastname: Duan
mesh_terms: D000818:Animals; D001859:Bone Neoplasms / Q000188:drug therapy* / Q000201:enzymology* / Q000235:genetics / Q000473:pathology; D018797:Cell Cycle Proteins / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D002455:Cell Division / Q000187:drug effects; D048708:Cell Growth Processes / Q000187:drug effects; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D005260:Female; D016195:G2 Phase / Q000187:drug effects; D006801:Humans; D051379:Mice; D008819:Mice, Nude; D008938:Mitosis / Q000187:drug effects; D012516:Osteosarcoma / Q000188:drug therapy* / Q000201:enzymology* / Q000235:genetics / Q000473:pathology; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D011621:Pteridines / Q000494:pharmacology*; D023041:Xenograft Model Antitumor Assays; D000097869:Polo-Like Kinase 1
chemical_list: D018797:Cell Cycle Proteins; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D011621:Pteridines; D000097869:Polo-Like Kinase 1; C518477:BI 2536