Polo-like kinase 1 inhibition sensitizes neuroblastoma cells for vinca alkaloid-induced apoptosis

Oncotarget. 2016 Feb 23;7(8):8700-11. doi: 10.18632/oncotarget.3901.

Abstract

High polo-like kinase 1 (PLK1) expression has been linked to poor outcome in neuroblastoma (NB), indicating that it represents a relevant therapeutic target in this malignancy. Here, we identify a synergistic induction of apoptosis by the PLK1 inhibitor BI 2536 and vinca alkaloids in NB cells. Synergistic drug interaction of BI 2536 together with vincristine (VCR), vinblastine (VBL) or vinorelbine (VNR) is confirmed by calculation of combination index (CI). Also, BI 2536 and VCR act in concert to reduce long-term clonogenic survival. Importantly, BI 2536 significantly enhances the antitumor activity of VCR in an in vivo model of NB. Mechanistically, BI 2536/VCR co-treatment triggers prolonged mitotic arrest, which is necessary for BI 2536/VCR-mediated apoptosis, since pharmacological inhibition of mitotic arrest by the CDK1 inhibitor RO-3306 significantly reduces cell death. Prolonged mitotic arrest leads to phosphorylation-mediated inactivation of BCL-2 and BCL-XL as well as downregulation of MCL-1, since inhibition of mitotic arrest by RO-3306 also prevents phosphorylation of BCL-2 and BCL-XL and MCL-1 downregulation. This inactivation of antiapoptotic BCL-2 proteins promotes activation of BAX and BAK, cleavage of caspase-9 and -3 and caspase-dependent apoptosis. Engagement of the mitochondrial pathway of apoptosis is critically required for BI 2536/VCR-induced apoptosis, since ectopic expression of a non-degradable MCL-1 phospho-mutant, BCL-2 overexpression or BAK knockdown significantly reduce BI 2536/VCR-mediated apoptosis. Thus, PLK1 inhibitors may open new perspectives for chemosensitization of NB.

Keywords: BCL-2; PLK1; apoptosis; mitosis; neuroblastoma.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Antineoplastic Agents / pharmacology
  • Apoptosis / drug effects*
  • Blotting, Western
  • Cell Cycle / drug effects
  • Cell Cycle Proteins / antagonists & inhibitors*
  • Cell Proliferation / drug effects
  • Humans
  • Neuroblastoma / drug therapy*
  • Neuroblastoma / enzymology
  • Neuroblastoma / pathology*
  • Polo-Like Kinase 1
  • Protein Serine-Threonine Kinases / antagonists & inhibitors*
  • Proto-Oncogene Proteins / antagonists & inhibitors*
  • Tumor Cells, Cultured
  • Vinca Alkaloids / pharmacology*

Substances

  • Antineoplastic Agents
  • Cell Cycle Proteins
  • Proto-Oncogene Proteins
  • Vinca Alkaloids
  • Protein Serine-Threonine Kinases