Effects of PPARα inhibition in head and neck paraganglioma cells

PLoS One. 2017 Jun 8;12(6):e0178995. doi: 10.1371/journal.pone.0178995. eCollection 2017.

Abstract

Head and neck paragangliomas (HNPGLs) are rare tumors that may cause important morbidity, because of their tendency to infiltrate the skull base. At present, surgery is the only therapeutic option, but radical removal may be difficult or impossible. Thus, effective targets and molecules for HNPGL treatment need to be identified. However, the lack of cellular models for this rare tumor hampers this task. PPARα receptor activation was reported in several tumors and this receptor appears to be a promising therapeutic target in different malignancies. Considering that the role of PPARα in HNPGLs was never studied before, we analyzed the potential of modulating PPARα in a unique model of HNPGL cells. We observed an intense immunoreactivity for PPARα in HNPGL tumors, suggesting that this receptor has an important role in HNPGL. A pronounced nuclear expression of PPARα was also confirmed in HNPGL-derived cells. The specific PPARα agonist WY14643 had no effect on HNPGL cell viability, whereas the specific PPARα antagonist GW6471 reduced HNPGL cell viability and growth by inducing cell cycle arrest and caspase-dependent apoptosis. GW6471 treatment was associated with a marked decrease of CDK4, cyclin D3 and cyclin B1 protein expression, along with an increased expression of p21 in HNPGL cells. Moreover, GW6471 drastically impaired clonogenic activity of HNPGL cells, with a less marked effect on cell migration. Notably, the effects of GW6471 on HNPGL cells were associated with the inhibition of the PI3K/GSK3β/β-catenin signaling pathway. In conclusion, the PPARα antagonist GW6471 reduces HNPGL cell viability, interfering with cell cycle and inducing apoptosis. The mechanisms affecting HNPGL cell viability involve repression of the PI3K/GSK3β/β-catenin pathway. Therefore, PPARα could represent a novel therapeutic target for HNPGL.

MeSH terms

  • Apoptosis / drug effects
  • Blotting, Western
  • Caspase 3 / metabolism
  • Caspase 6 / metabolism
  • Caspase 7 / drug effects
  • Caspase 7 / metabolism
  • Caspases / metabolism
  • Caspases, Initiator / metabolism
  • Cell Cycle / drug effects
  • Cell Survival / drug effects
  • Fluorescent Antibody Technique
  • Head and Neck Neoplasms / metabolism*
  • Humans
  • Immunohistochemistry
  • Oxazoles / pharmacology
  • PPAR alpha / agonists
  • PPAR alpha / antagonists & inhibitors*
  • PPAR alpha / metabolism*
  • Pyrimidines / pharmacology
  • Tumor Cells, Cultured
  • Tyrosine / analogs & derivatives
  • Tyrosine / pharmacology
  • Wound Healing / drug effects

Substances

  • GW 6471
  • Oxazoles
  • PPAR alpha
  • Pyrimidines
  • Tyrosine
  • pirinixic acid
  • CASP4 protein, human
  • CASP5 protein, human
  • Caspase 3
  • Caspase 6
  • Caspase 7
  • Caspases
  • Caspases, Initiator

Grants and funding

The study was supported by the Ministry of Education, University and Research (MIUR), Progetti di Ricerca di Interesse Nazionale (PRIN) funds (grant numbers 2010NFEB9L_008 and 2015B7M39T_006, http://prin.miur.it/) assigned to A. Cama and by the Associazione Italiana per la Ricerca sul Cancro (AIRC) funds (grant number IG 16932, http://www.airc.it/) assigned to RMC. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.