Overexpression of pyruvate dehydrogenase kinase 1 in retinoblastoma: A potential therapeutic opportunity for targeting vitreous seeds and hypoxic regions

PLoS One. 2017 May 15;12(5):e0177744. doi: 10.1371/journal.pone.0177744. eCollection 2017.

Abstract

Pyruvate dehydrogenase kinase 1 (PDK1), a key enzyme implicated in metabolic reprogramming of tumors, is induced in several tumors including glioblastoma, breast cancer and melanoma. However, the role played by PDK1 is not studied in retinoblastoma (RB). In this study, we have evaluated the expression of PDK1 in RB clinical samples, and studied its inhibition as a strategy to decrease cell growth and migration. We show that PDK1 is specifically overexpressed in RB patient samples especially in vitreous seeds and hypoxic regions and cell lines compared to control retina using immunohistochemistry and real-time PCR. Our results further demonstrate that inhibition of PDK1 using small molecule inhibitors dichloroacetic acid (DCA) and dichloroacetophenone (DAP) resulted in reduced cell growth and increased apoptosis. We also confirm that combination treatment of DCA with chemotherapeutic agent carboplatin further enhanced the therapeutic efficacy compared to single drug treatment. In addition, we observed changes in glucose uptake, lactate and reactive oxygen species (ROS) levels as well as decreased cell migration in response to PDK1 inhibition. Additionally, we show that DCA treatment led to inhibition of PI3K/Akt pathway and reduction in PDK1 protein levels. Overall, our data suggest that targeting PDK1 could be a novel therapeutic strategy for RB.

MeSH terms

  • Antineoplastic Agents / pharmacology
  • Apoptosis / drug effects
  • Cell Line, Tumor
  • Cell Movement / drug effects
  • Cell Proliferation / drug effects
  • Dichloroacetic Acid / pharmacology
  • Drug Synergism
  • Gene Expression*
  • Humans
  • Hypoxia / genetics
  • Hypoxia / metabolism
  • Immunohistochemistry
  • Lactic Acid / biosynthesis
  • Molecular Targeted Therapy
  • Protein Serine-Threonine Kinases / antagonists & inhibitors
  • Protein Serine-Threonine Kinases / genetics*
  • Protein Serine-Threonine Kinases / metabolism
  • Proto-Oncogene Proteins c-akt / metabolism
  • Pyruvate Dehydrogenase Acetyl-Transferring Kinase
  • Reactive Oxygen Species / metabolism
  • Retinoblastoma / drug therapy
  • Retinoblastoma / genetics*
  • Retinoblastoma / metabolism

Substances

  • Antineoplastic Agents
  • PDK1 protein, human
  • Pyruvate Dehydrogenase Acetyl-Transferring Kinase
  • Reactive Oxygen Species
  • Lactic Acid
  • Dichloroacetic Acid
  • Protein Serine-Threonine Kinases
  • Proto-Oncogene Proteins c-akt

Grants and funding

Support was provided by Department of Biotechnology, Government of India, BT/Bio-CARe/07/9859/2013-14 for MR.