title: Mitotic arrest and slippage induced by pharmacological inhibition of Polo-like kinase 1.
abstract: Exposure to drugs that interfere with microtubule dynamics block cell cycle progression at mitosis by prolonged activation of the spindle assembly checkpoint (SAC). Cells can evade mitotic arrest and proceed to interphase without chromosome segregation by a process termed mitotic slippage that involves Cyclin B1 degradation without checkpoint inactivation. Here, we explored the cellular response to small-molecule inhibitors of Polo-like kinase 1 (Plk1), an important regulator of cell division. We found that the clinical Plk1 inhibitors BI 2536 and BI 6727, both unexpectedly, induced a dose-dependent cellular drug response: While mitotic arrest was induced in cancer cell lines and primary non-transformed cells across the entire range of concentrations tested, only high concentrations seemed to promote mitotic slippage. Since this observation contrasts with the effects expected from studies reporting RNAi-mediated Plk1 depletion in cancer cells, we wondered whether both ATP-competitive inhibitors target unknown kinases that are involved in signaling from the spindle assembly checkpoint (SAC) and might contribute to the mitotic slippage. A chemical proteomics approach used to profile the selectivity of both inhibitors revealed that SAC kinases are not targeted directly. Still, the activities of Cdk1/Cyclin B1 and Aurora B, which plays important roles in the error correction of false microtubule-kinetochore attachments and in checkpoint signaling, were shown to be downregulated at high inhibitor concentrations. Our data suggest that the inhibition of Plk1 activity below a certain threshold influences Aurora B activity via reduced phosphorylation of Fox M1 and Survivin leading to diminished levels of Aurora B protein and alteration of its subcellular localization. Within the spectrum of SAC proteins that are degraded during mitotic slippage, the degradation of Cyclin B1 and the downregulation of Aurora B activity by Plk1 inhibition seem to be critical promoters of mitotic slippage. The results indicate that careful dose-finding studies in cancer trials are necessary to limit or even prevent mitotic slippage, which could be associated with improved cancer cell survival.
authors.affiliation: Department of Gynecology, School of Medicine, Goethe University, Theodor-Stern-Kai 7, 60590 Frankfurt, Germany.
authors.forename: Monika
authors.initials: M
authors.lastname: Raab
authors.affiliation: Department of Gynecology, School of Medicine, Goethe University, Theodor-Stern-Kai 7, 60590 Frankfurt, Germany.
authors.forename: Andrea
authors.initials: A
authors.lastname: Krämer
authors.affiliation: Department of Radiotherapy and Oncology, Goethe University, Germany.
authors.forename: Stephanie
authors.initials: S
authors.lastname: Hehlgans
authors.affiliation: Department of Gynecology, School of Medicine, Goethe University, Theodor-Stern-Kai 7, 60590 Frankfurt, Germany.
authors.forename: Mourad
authors.initials: M
authors.lastname: Sanhaji
authors.affiliation: Department of Gynecology, School of Medicine, Goethe University, Theodor-Stern-Kai 7, 60590 Frankfurt, Germany.
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Kurunci-Csacsko
authors.affiliation: Department of Gynecology, School of Medicine, Goethe University, Theodor-Stern-Kai 7, 60590 Frankfurt, Germany.
authors.forename: Christina
authors.initials: C
authors.lastname: Dötsch
authors.affiliation: Department of Medicine, Hematology/Oncology, Goethe University, Germany.
authors.forename: Gesine
authors.initials: G
authors.lastname: Bug
authors.affiliation: Department of Medicine, Hematology/Oncology, Goethe University, Germany.
authors.forename: Oliver
authors.initials: O
authors.lastname: Ottmann
authors.affiliation: Department of Gynecology, School of Medicine, Goethe University, Theodor-Stern-Kai 7, 60590 Frankfurt, Germany.
authors.forename: Sven
authors.initials: S
authors.lastname: Becker
authors.affiliation: Technische Universität München, Emil Erlenmeyer Forum 5, 85354 Freising, Germany.
authors.forename: Fiona
authors.initials: F
authors.lastname: Pachl
authors.affiliation: Technische Universität München, Emil Erlenmeyer Forum 5, 85354 Freising, Germany; German Cancer Consortium (DKTK), Heidelberg, Germany.
authors.forename: Bernhard
authors.initials: B
authors.lastname: Kuster
authors.affiliation: Department of Gynecology, School of Medicine, Goethe University, Theodor-Stern-Kai 7, 60590 Frankfurt, Germany; German Cancer Consortium (DKTK), Heidelberg, Germany. Electronic address: strebhardt@em.uni-frankfurt.de.
authors.forename: Klaus
authors.initials: K
authors.lastname: Strebhardt
mesh_terms: D018797:Cell Cycle Proteins / Q000037:antagonists & inhibitors* / Q000378:metabolism; D045744:Cell Line, Tumor; D005260:Female; D061307:Human Umbilical Vein Endothelial Cells; D006801:Humans; D059566:M Phase Cell Cycle Checkpoints / Q000187:drug effects*; D008297:Male; D009363:Neoplasm Proteins / Q000037:antagonists & inhibitors* / Q000378:metabolism; D009369:Neoplasms / Q000188:drug therapy / Q000201:enzymology* / Q000473:pathology; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000037:antagonists & inhibitors* / Q000378:metabolism; D011621:Pteridines / Q000494:pharmacology*; D000097869:Polo-Like Kinase 1
chemical_list: D018797:Cell Cycle Proteins; D009363:Neoplasm Proteins; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D011621:Pteridines; D000097869:Polo-Like Kinase 1; C518477:BI 2536; C541363:BI 6727
keywords: Cell cycle; Mitotic arrest; Polo-like kinase 1; Slippage