Page 21 - SDIR5 Abstract book 21 12 2021.

CANCER AND METABOLISM

Dual targeting of energy metabolism and lysosomes as an anticancer strategy; It is not all
about autophagy

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Ljubica Harhaji-Trajkovic , Milica Kosic , Verica Paunovic , Biljana Ristic , Mihajlo Bosnjak , Nevena
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Zogovic , Milos Mandic , Gordana Tovilovic , Kristina Janjetovic , Vladimir Trajkovic
1 Department of Neurophysiology, Institute for Biological Research “Sinisa Stankovic”-National Institute of Republic
of Serbia, University of Belgrade, Belgrade, Serbia
2 Institute of Microbiology and Immunology, Faculty of Medicine, University of Belgrade, Belgrade, Serbia

Background: Intensive proliferation of tumor cells consumes a lot of energy. In nutrient deficiency
substrates for energy metabolism are obtained by lysosomal degradation of unnecessary/dysfunctional
intracellular organelles/molecules in the process of autophagy. Leakage of enlarged unstable lysosomes,
which characterize tumor cells, causes cell death. We investigated antitumor effect of combined targeting
of lysosomes/autophagy and energy metabolism. Material and Methods: Toxicity against U251 human
glioma and B16 mouse melanoma cells was measured by viability tests. Type/mechanisms of cell death
were determined by flow cytometry, immunoblot, fluorescent/electron microscopy and confirmed by
appropriate genetic/pharmacological inhibitors. Therapeutic potential was estimated in B16 melanoma-
bearing C57Bl/6 mice. Results: In the first study, lysosomotropic autophagy inhibitor chloroquine (CQ)
rapidly killed tumor cells incubated in the absence of serum. CQ-induced lysosomal destabilization
triggered: oxidative stress, mitochondrial depolarization, and mixed apoptosis/necrosis of serum-deprived
cells. In the second study, lysosomal detergent N-dodecylimidazole (NDI) synergized in antitumor activity
with the glycolytic inhibitor 2-deoxy-D-glucose (2DG). NDI-triggered release of lysosomal enzymes into the
cytoplasm caused mitochondrial damage and blocked oxidative phosphorylation, which synergized with
2DG-mediated glycolysis block in ATP reduction, oxidative stress, and necrosis. Interestingly, although both
serum deprivation and 2DG stimulated autophagy, CQ- and NDI-induced autophagy suppression was
irrelevant for their cytotoxicity. Importantly, CQ+food restriction and 2DG+NDI reduced melanoma growth
in vivo. Conclusion: Autophagy independent antitumor effects of combined energy metabolism suppression
and lysosomal destabilization might be exploited in cancer therapy.

Keywords: Autophagy; Combined Therapy; Energy Metabolism; Lysosomes.

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