The mTOR pathway in hepatic malignancies

Authors

  • Mamatha Bhat,

    1. Division of Gastroenterology, McGill University Health Centre, Montreal, Canada
    2. Department of Biochemistry, Goodman Cancer Research Center, McGill University, Montreal, Canada
    3. Division of Gastroenterology and Hepatology, College of Medicine, Mayo Clinic, Rochester, MN
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  • Nahum Sonenberg,

    1. Department of Biochemistry, Goodman Cancer Research Center, McGill University, Montreal, Canada
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  • Gregory J. Gores

    Corresponding author
    1. Division of Gastroenterology and Hepatology, College of Medicine, Mayo Clinic, Rochester, MN
    • Address reprint requests to: Gregory J. Gores, M.D., Division of Gastroenterology and Hepatology, College of Medicine, 200 First Street SW, Mayo Clinic, Rochester, MN 55905. E-mail: gores.gregory@mayo.edu.

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  • Potential conflict of interest: Nothing to report.

Abstract

The mechanistic/mammalian target of rapamycin (mTOR) pathway plays a critical role in cellular metabolism, growth, and proliferation and has been evaluated as a target for therapy in various malignancies. The mTOR pathway is a major tumor-initiating pathway in hepatocellular carcinoma, with up-regulation seen in up to 50% of tumors. Metformin, which represses mTOR signaling by activating adenosine monophosphate–activated protein kinase, has been shown to decrease liver carcinogenesis in population studies. mTOR inhibitors such as everolimus have been evaluated as adjunctive chemotherapy with some success, although efficacy has been limited by the lack of complete mTOR pathway inhibition. The active site mTOR inhibitors hold greater promise, given that they offer complete mTOR suppression. There is also evidence of mTOR pathway activation in cholangiocarcinoma, although its biological significance in initiating and promoting tumor progression remains ambiguous. This review provides an overview of the complex biochemistry behind the mTOR pathway and its role in carcinogenesis, especially as it pertains to hepatic malignancies. (HEPATOLOGY 2013;58:810–818)

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