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Oncotarget. 2017 Jun 9;8(40):67269-67286. doi: 10.18632/oncotarget.18428. eCollection 2017 Sep 15.

Vitamin C and Doxycycline: A synthetic lethal combination therapy targeting metabolic flexibility in cancer stem cells (CSCs).

Author information

1
Department of Pharmacy, Health and Nutritional Sciences, University of Calabria, Rende, Italy.
2
The Paterson Institute, University of Manchester, Withington, United Kingdom.
3
Translational Medicine, School of Environment and Life Sciences, Biomedical Research Centre (BRC), University of Salford, Greater Manchester, United Kingdom.

Abstract

Here, we developed a new synthetic lethal strategy for further optimizing the eradication of cancer stem cells (CSCs). Briefly, we show that chronic treatment with the FDA-approved antibiotic Doxycycline effectively reduces cellular respiration, by targeting mitochondrial protein translation. The expression of four mitochondrial DNA encoded proteins (MT-ND3, MT-CO2, MT-ATP6 and MT-ATP8) is suppressed, by up to 35-fold. This high selection pressure metabolically synchronizes the surviving cancer cell sub-population towards a predominantly glycolytic phenotype, resulting in metabolic inflexibility. We directly validated this Doxycycline-induced glycolytic phenotype, by using metabolic flux analysis and label-free unbiased proteomics. Next, we identified two natural products (Vitamin C and Berberine) and six clinically-approved drugs, for metabolically targeting the Doxycycline-resistant CSC population (Atovaquone, Irinotecan, Sorafenib, Niclosamide, Chloroquine, and Stiripentol). This new combination strategy allows for the more efficacious eradication of CSCs with Doxycycline, and provides a simple pragmatic solution to the possible development of Doxycycline-resistance in cancer cells. In summary, we propose the combined use of i) Doxycycline (Hit-1: targeting mitochondria) and ii) Vitamin C (Hit-2: targeting glycolysis), which represents a new synthetic-lethal metabolic strategy for eradicating CSCs. This type of metabolic Achilles' heel will allow us and others to more effectively "starve" the CSC population.

KEYWORDS:

cancer stem-like cells (CSCs); doxycycline; mitochondrial DNA (mt-DNA); mitochondrial biogenesis; vitamin C

Conflict of interest statement

CONFLICTS OF INTEREST MPL and FS hold a minority interest in Lunella, Inc.

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