Inhibition of polo-like kinase 1 in glioblastoma multiforme induces mitotic catastrophe and enhances radiosensitisation

Eur J Cancer. 2013 Sep;49(14):3020-8. doi: 10.1016/j.ejca.2013.05.013. Epub 2013 Jun 18.

Abstract

Glioblastoma multiforme (GBM) is the most common primary brain tumour in the United States of America (USA) with a median survival of approximately 14 months. Low survival rates are attributable to the aggressiveness of GBM and a lack of understanding of the molecular mechanisms underlying GBM. The disruption of signalling pathways regulated either directly or indirectly by protein kinases is frequently observed in cancer cells and thus the development of inhibitors of specific kinases has become a major focus of drug discovery in oncology. To identify protein kinases required for the survival of GBM we performed a siRNA-based RNAi screen focused on the human kinome in GBM. Inhibition of the polo-like kinase 1 (PLK1) induced a reduction in the viability in two different GBM cell lines. To assess the potential of inhibiting PLK1 as a treatment strategy for GBM we examined the effects of a small molecule inhibitor of PLK1, GSK461364A, on the growth of GBM cells. PLK1 inhibition arrested cells in the mitotic phase of the cell cycle and induced cell kill by mitotic catastrophe. GBM engrafts treated with GSK461364A showed statistically significant inhibition of tumour growth. Further, exposure of different GBM cells to RNAi or GSK461364A prior to radiation resulted in an increase in their radiosensitivity with dose enhancement factor ranging from 1.40 to 1.53 with no effect on normal cells. As a measure of DNA double strand breaks, γH2AX levels were significantly higher in the combined modality as compared to the individual treatments. This study suggests that PLK1 is an important therapeutic target for GBM and can enhance radiosensitivity in GBM.

Keywords: GSK461364A; Glioblastoma multiforme; PLK1; Radiation; siRNA.

Publication types

  • Research Support, N.I.H., Intramural

MeSH terms

  • Animals
  • Apoptosis / drug effects
  • Apoptosis / genetics
  • Apoptosis / radiation effects
  • Blotting, Western
  • Cell Cycle Checkpoints / drug effects
  • Cell Cycle Checkpoints / genetics
  • Cell Cycle Checkpoints / radiation effects
  • Cell Cycle Proteins / antagonists & inhibitors
  • Cell Cycle Proteins / genetics*
  • Cell Cycle Proteins / metabolism
  • Cell Line
  • Cell Line, Tumor
  • Cell Survival / drug effects
  • Cell Survival / genetics
  • Cell Survival / radiation effects
  • Dose-Response Relationship, Drug
  • Dose-Response Relationship, Radiation
  • Female
  • Glioblastoma / genetics*
  • Glioblastoma / pathology
  • Glioblastoma / therapy
  • Humans
  • Mice
  • Mice, Nude
  • Mitosis / drug effects
  • Mitosis / genetics*
  • Mitosis / radiation effects
  • Protein-Serine-Threonine Kinases / antagonists & inhibitors
  • Protein-Serine-Threonine Kinases / genetics*
  • Protein-Serine-Threonine Kinases / metabolism
  • Proto-Oncogene Proteins / antagonists & inhibitors
  • Proto-Oncogene Proteins / genetics*
  • Proto-Oncogene Proteins / metabolism
  • RNA Interference*
  • Thiophenes / pharmacology
  • Xenograft Model Antitumor Assays

Substances

  • Cell Cycle Proteins
  • GSK 461364A
  • Proto-Oncogene Proteins
  • Thiophenes
  • Protein-Serine-Threonine Kinases
  • polo-like kinase 1