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Mol Oncol. 2015 Mar;9(3):675-88. doi: 10.1016/j.molonc.2014.11.005. Epub 2014 Nov 22.

Endoplasmic reticulum stress and cell death in mTORC1-overactive cells is induced by nelfinavir and enhanced by chloroquine.

Author information

  • 1Institute of Cancer and Genetics, Cardiff University, Heath Park, Cardiff CF14 4XN, UK.
  • 2Department of Cell Physiology and Pharmacology, University of Leicester, The Henry Wellcome Building, University Road, Leicester LE1 9HN, UK.
  • 3Institute of Cancer and Genetics, Cardiff University, Heath Park, Cardiff CF14 4XN, UK. Electronic address: teea@cardiff.ac.uk.

Abstract

Inappropriate activation of mammalian/mechanistic target of rapamycin complex 1 (mTORC1) is common in cancer and has many cellular consequences including elevated endoplasmic reticulum (ER) stress. Cells employ autophagy as a critical compensatory survival mechanism during ER stress. This study utilised drug-induced ER stress through nelfinavir in order to examine ER stress tolerance in cell lines with hyper-active mTORC1 signalling. Our initial findings in wild type cells showed nelfinavir inhibited mTORC1 signalling and upregulated autophagy, as determined by decreased rpS6 and S6K1 phosphorylation, and SQTSM1 protein expression, respectively. Contrastingly, cells with hyper-active mTORC1 displayed basally elevated levels of ER stress which was greatly exaggerated following nelfinavir treatment, seen through increased CHOP mRNA and XBP1 splicing. To further enhance the effects of nelfinavir, we introduced chloroquine as an autophagy inhibitor. Combination of nelfinavir and chloroquine significantly increased ER stress and caused selective cell death in multiple cell line models with hyper-active mTORC1, whilst control cells with normalised mTORC1 signalling tolerated treatment. By comparing chloroquine to other autophagy inhibitors, we uncovered that selective toxicity invoked by chloroquine was independent of autophagy inhibition yet entrapment of chloroquine to acidified lysosomal/endosomal compartments was necessary for cytotoxicity. Our research demonstrates that combination of nelfinavir and chloroquine has therapeutic potential for treatment of mTORC1-driven tumours.

Copyright © 2014 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.

KEYWORDS:

Autophagy; Cancer; Chloroquine; ER stress; Nelfinavir; TSC; mTOR

PMID:
25498902
[PubMed - indexed for MEDLINE]
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