Activated Ras requires autophagy to maintain oxidative metabolism and tumorigenesis

  1. Eileen White1,2,4,9
  1. 1The Cancer Institute of New Jersey, New Brunswick, New Jersey 08903, USA;
  2. 2Department of Molecular Biology and Biochemistry, Rutgers University, Piscataway, New Jersey 08854, USA;
  3. 3Department of Biochemistry, Center for Advanced Biotechnology and Medicine, Piscataway, New Jersey 08854, USA;
  4. 4University of Medicine and Dentistry of New Jersey, Robert Wood Johnson Medical School, Piscataway, New Jersey 08854, USA;
  5. 5Department of Chemistry, Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, New Jersey 08544, USA;
  6. 6Division of Medical Oncology, University of Medicine and Dentistry of New Jersey, Robert Wood Johnson Medical School, New Jersey 08854, USA;
  7. 7Department of Molecular Biology, Princeton University, Princeton, New Jersey 08544, USA
    1. 8 These authors contributed equally to this work.

    Abstract

    Autophagy is a catabolic pathway used by cells to support metabolism in response to starvation and to clear damaged proteins and organelles in response to stress. We report here that expression of a H-rasV12 or K-rasV12 oncogene up-regulates basal autophagy, which is required for tumor cell survival in starvation and in tumorigenesis. In Ras-expressing cells, defective autophagosome formation or cargo delivery causes accumulation of abnormal mitochondria and reduced oxygen consumption. Autophagy defects also lead to tricarboxylic acid (TCA) cycle metabolite and energy depletion in starvation. As mitochondria sustain viability of Ras-expressing cells in starvation, autophagy is required to maintain the pool of functional mitochondria necessary to support growth of Ras-driven tumors. Human cancer cell lines bearing activating mutations in Ras commonly have high levels of basal autophagy, and, in a subset of these, down-regulating the expression of essential autophagy proteins impaired cell growth. As cancers with Ras mutations have a poor prognosis, this “autophagy addiction” suggests that targeting autophagy and mitochondrial metabolism are valuable new approaches to treat these aggressive cancers.

    Keywords

    Footnotes

    • Received November 25, 2010.
    • Accepted January 18, 2011.
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