UCP2 inhibition induces ROS/Akt/mTOR axis: Role of GAPDH nuclear translocation in genipin/everolimus anticancer synergism

Free Radic Biol Med. 2017 Dec;113:176-189. doi: 10.1016/j.freeradbiomed.2017.09.022. Epub 2017 Sep 27.

Abstract

Several studies indicate that mitochondrial uncoupling protein 2 (UCP2) plays a pivotal role in cancer development by decreasing reactive oxygen species (ROS) produced by mitochondrial metabolism and by sustaining chemoresistance to a plethora of anticancer drugs. Here, we demonstrate that inhibition of UCP2 triggers Akt/mTOR pathway in a ROS-dependent mechanism in pancreatic adenocarcinoma cells. This event reduces the antiproliferative outcome of UCP2 inhibition by genipin, creating the conditions for the synergistic counteraction of cancer cell growth with the mTOR inhibitor everolimus. Inhibition of pancreatic adenocarcinoma cell growth and induction of apoptosis by genipin and everolimus treatment are functionally related to nuclear translocation of the cytosolic glycolytic enzyme glyceraldehyde 3-phosphate dehydrogenase (GAPDH). The synthetic compound (S)-benzyl-2-amino-2-(S)-3-bromo-4,5-dihydroisoxazol-5-yl-acetate (AXP3009), which binds GAPDH at its redox-sensitive Cys152, restores cell viability affected by the combined treatment with genipin and everolimus, suggesting a role for ROS production in the nuclear translocation of GAPDH. Caspase-mediated apoptosis by genipin and everolimus is further potentiated by the autophagy inhibitor 3-methyladenine revealing a protective role for Beclin1-mediated autophagy induced by the treatment. Mice xenograft of pancreatic adenocarcinoma further confirmed the antiproliferative outcome of drug combination without toxic effects for animals. Tumor masses from mice injected with UCP2 and mTOR inhibitors revealed a strong reduction in tumor volume and number of mitosis associated with a marked GAPDH nuclear positivity. Altogether, these results reveal novel mechanisms through which UCP2 promotes cancer cell proliferation and support the combined inhibition of UCP2 and of Akt/mTOR pathway as a novel therapeutic strategy in the treatment of pancreatic adenocarcinoma.

Keywords: Cell death; Everolimus; GAPDH; Pancreas cancer; UCP2; Uncoupling proteins; mTOR.

MeSH terms

  • Antineoplastic Agents / pharmacology
  • Antineoplastic Agents / therapeutic use
  • Apoptosis
  • Carcinoma, Pancreatic Ductal / drug therapy
  • Carcinoma, Pancreatic Ductal / enzymology
  • Carcinoma, Pancreatic Ductal / metabolism*
  • Carcinoma, Pancreatic Ductal / physiopathology
  • Cell Line, Tumor
  • Cell Proliferation / drug effects
  • Everolimus / pharmacology*
  • Everolimus / therapeutic use
  • Female
  • Glyceraldehyde-3-Phosphate Dehydrogenases / metabolism*
  • Humans
  • Iridoids / pharmacology*
  • Iridoids / therapeutic use
  • Male
  • Pancreatic Neoplasms / drug therapy
  • Pancreatic Neoplasms / enzymology
  • Pancreatic Neoplasms / metabolism*
  • Pancreatic Neoplasms / physiopathology
  • Protein Transport
  • Proto-Oncogene Proteins c-akt / metabolism
  • Reactive Oxygen Species / metabolism
  • Signal Transduction
  • TOR Serine-Threonine Kinases / antagonists & inhibitors*
  • TOR Serine-Threonine Kinases / metabolism
  • Uncoupling Protein 2 / antagonists & inhibitors*
  • Uncoupling Protein 2 / metabolism
  • Xenograft Model Antitumor Assays

Substances

  • Antineoplastic Agents
  • Iridoids
  • Reactive Oxygen Species
  • Uncoupling Protein 2
  • Everolimus
  • genipin
  • Glyceraldehyde-3-Phosphate Dehydrogenases
  • Proto-Oncogene Proteins c-akt
  • TOR Serine-Threonine Kinases