Activation of mTOR Signaling Pathway in Hepatocellular Carcinoma

Int J Mol Sci. 2020 Feb 13;21(4):1266. doi: 10.3390/ijms21041266.

Abstract

Hepatocellular carcinoma (HCC) is the most frequent primary liver cancer and occurs mainly in patients with liver cirrhosis. The mammalian target of rapamycin (mTOR) signaling pathway is involved in many hallmarks of cancer including cell growth, metabolism re-programming, proliferation and inhibition of apoptosis. The mTOR pathway is upregulated in HCC tissue samples as compared with the surrounding liver cirrhotic tissue. In addition, the activation of mTOR is more intense in the tumor edge, thus reinforcing its role in HCC proliferation and spreading. The inhibition of the mTOR pathway by currently available pharmacological compounds (i.e., sirolimus or everolimus) is able to hamper tumor progression both in vitro and in animal models. The use of mTOR inhibitors alone or in combination with other therapies is a very attractive approach, which has been extensively investigated in humans. However, results are contradictory and there is no solid evidence suggesting a true benefit in clinical practice. As a result, neither sirolimus nor everolimus are currently approved to treat HCC or to prevent tumor recurrence after curative surgery. In the present comprehensive review, we analyzed the most recent scientific evidence while providing some insights to understand the gap between experimental and clinical studies.

Keywords: everolimus; hepatocellular carcinoma; liver transplantation; mTOR; sirolimus; sorafenib.

Publication types

  • Review

MeSH terms

  • Apoptosis / drug effects
  • Carcinoma, Hepatocellular / drug therapy
  • Carcinoma, Hepatocellular / genetics*
  • Carcinoma, Hepatocellular / pathology
  • Cell Proliferation / drug effects
  • Everolimus / therapeutic use
  • Gene Expression Regulation, Neoplastic / drug effects
  • Humans
  • Liver Neoplasms / drug therapy
  • Liver Neoplasms / genetics*
  • Liver Neoplasms / pathology
  • Neoplasm Recurrence, Local / drug therapy
  • Neoplasm Recurrence, Local / genetics*
  • Neoplasm Recurrence, Local / pathology
  • Signal Transduction / drug effects
  • Sirolimus / therapeutic use
  • TOR Serine-Threonine Kinases / genetics*

Substances

  • Everolimus
  • MTOR protein, human
  • TOR Serine-Threonine Kinases
  • Sirolimus