title: Induction of autophagy by ARHI (DIRAS3) alters fundamental metabolic pathways in ovarian cancer models.
abstract: Autophagy is a bulk catabolic process that modulates tumorigenesis, therapeutic resistance, and dormancy. The tumor suppressor ARHI (DIRAS3) is a potent inducer of autophagy and its expression results in necroptotic cell death in vitro and tumor dormancy in vivo. ARHI is down-regulated or lost in over 60 % of primary ovarian tumors yet is dramatically up-regulated in metastatic disease. The metabolic changes that occur during ARHI induction and their role in modulating death and dormancy are unknown.
  
  
  
  We employed Nuclear Magnetic Resonance (NMR)-based metabolomic strategies to characterize changes in key metabolic pathways in both cell culture and xenograft models of ARHI expression and autophagy. These pathways were further interrogated by cell-based immunofluorescence imaging, tracer uptake studies, targeted metabolic inhibition, and in vivo PET/CT imaging.
  
  
  
  Induction of ARHI in cell culture models resulted in an autophagy-dependent increase in lactate production along with increased glucose uptake and enhanced sensitivity to glycolytic inhibitors. Increased uptake of glutamine was also dependent on autophagy and dramatically sensitized cultured ARHI-expressing ovarian cancer cell lines to glutaminase inhibition. Induction of ARHI resulted in a reduction in mitochondrial respiration, decreased mitochondrial membrane potential, and decreased Tom20 staining suggesting an ARHI-dependent loss of mitochondrial function. ARHI induction in mouse xenograft models resulted in an increase in free amino acids, a transient increase in [18F]-FDG uptake, and significantly altered choline metabolism.
  
  
  
  ARHI expression has previously been shown to trigger autophagy-associated necroptosis in cell culture. In this study, we have demonstrated that ARHI expression results in decreased cellular ATP/ADP, increased oxidative stress, and decreased mitochondrial function. While this bioenergetic shock is consistent with programmed necrosis, our data indicates that the accompanying up-regulation of glycolysis and glutaminolysis is autophagy-dependent and serves to support cell viability rather than facilitate necroptotic cell death. While the mechanistic basis for metabolic up-regulation following ARHI induction is unknown, our preliminary data suggest that decreased mitochondrial function and increased metabolic demand may play a role. These alterations in fundamental metabolic pathways during autophagy-associated necroptosis may provide the basis for new therapeutic strategies for the treatment of dormant ovarian tumors.
authors: Department of Cancer Systems Imaging, the University of Texas M.D. Anderson Cancer Center, Houston, USA.
authors: Argentina
authors: A
authors: Ornelas
authors: Department of Cancer Systems Imaging, the University of Texas M.D. Anderson Cancer Center, Houston, USA.
authors: Christopher R
authors: CR
authors: McCullough
authors: Department of Experimental Therapeutics, the University of Texas M.D. Anderson Cancer Center, Houston, USA.
authors: Zhen
authors: Z
authors: Lu
authors: Department of Cancer Systems Imaging, the University of Texas M.D. Anderson Cancer Center, Houston, USA.|Department of Bioengineering, Rice University, Houston, USA.
authors: Niki M
authors: NM
authors: Zacharias
authors: Department of Cancer Systems Imaging, the University of Texas M.D. Anderson Cancer Center, Houston, USA.
authors: Lindsay E
authors: LE
authors: Kelderhouse
authors: Department of Cancer Systems Imaging, the University of Texas M.D. Anderson Cancer Center, Houston, USA.
authors: Joshua
authors: J
authors: Gray
authors: Department of Experimental Therapeutics, the University of Texas M.D. Anderson Cancer Center, Houston, USA.
authors: Hailing
authors: H
authors: Yang
authors: Department of Cancer Systems Imaging, the University of Texas M.D. Anderson Cancer Center, Houston, USA.
authors: Brian J
authors: BJ
authors: Engel
authors: Department of Experimental Therapeutics, the University of Texas M.D. Anderson Cancer Center, Houston, USA.
authors: Yan
authors: Y
authors: Wang
authors: Department of Experimental Therapeutics, the University of Texas M.D. Anderson Cancer Center, Houston, USA.
authors: Weiqun
authors: W
authors: Mao
authors: Department of Experimental Therapeutics, the University of Texas M.D. Anderson Cancer Center, Houston, USA.
authors: Margie N
authors: MN
authors: Sutton
authors: Department of Cancer Systems Imaging, the University of Texas M.D. Anderson Cancer Center, Houston, USA.
authors: Pratip K
authors: PK
authors: Bhattacharya
authors: Department of Experimental Therapeutics, the University of Texas M.D. Anderson Cancer Center, Houston, USA.
authors: Robert C
authors: RC
authors: Bast
authors: Department of Cancer Systems Imaging, the University of Texas M.D. Anderson Cancer Center, Houston, USA. smillward@mdanderson.org.|Department of Bioengineering, Rice University, Houston, USA. smillward@mdanderson.org.
authors: Steven W
authors: SW
authors: Millward
mesh_terms: D000818:Animals; D001343:Autophagy; D045744:Cell Line, Tumor; D004195:Disease Models, Animal; D005260:Female; D005947:Glucose / Q000378:metabolism; D005971:Glutamates / Q000378:metabolism; D005973:Glutamine / Q000378:metabolism; D006019:Glycolysis; D064593:Heterografts; D006801:Humans; D053078:Membrane Potential, Mitochondrial; D053858:Metabolic Networks and Pathways; D051379:Mice; D008928:Mitochondria / Q000378:metabolism; D010051:Ovarian Neoplasms / Q000000981:diagnostic imaging / Q000378:metabolism* / Q000473:pathology*; D018384:Oxidative Stress; D000072078:Positron Emission Tomography Computed Tomography; D020741:rho GTP-Binding Proteins / Q000378:metabolism*
chemical_list: C117386:DIRAS3 protein, human; D005971:Glutamates; D005973:Glutamine; D020741:rho GTP-Binding Proteins; D005947:Glucose
keywords: ARHI; Autophagy; Glutaminolysis; Metabolism; NMR; Necroptosis; Ovarian cancer