Abstract 3351: Survival of colorectal cancer cells following chemotherapy relies on a SIRT1-dependent increase in oxidative phosphorylation
Authors: Vellinga Thomas T. , Boer Vincent C. de , Borovski Tijana , Trumpi Kari , Fatrai Szabolcs , Kranenburg Onno , Rinkes Inne H.M. Borel , Hagendoorn Jeroen 
Published: May 2015

Abstract
Background: Altered energy metabolism is one of the hallmarks of cancer. Tumor cells reprogram their energy metabolism to meet the demands of uncontrolled cell division. During tumorigenesis the vast majority of cancer cells become highly glycolytic (Warburg effect) accompanied by a decrease in oxidative metabolism. Chemotherapy is likely to affect the energy metabolism of tumor cells, but how specific drugs affect specific metabolic pathways is only beginning to be addressed.
Methods: the effects of cytotoxic agents on energy metabolism were assessed by flow cytometric uptake of Mitotracker®, the ratio of mitochondrial and nuclear DNA on qRT-PCR, western blotting for protein levels of the different complexes of the respiratory chain and oxygen consumption rate by the Seahorse Extracellular Flux Analyzer. Cell death was analyzed by flow cytometric uptake of Propidium Iodide, Nicoletti assay and protein levels of caspases 3 and 8.
Results: Gene expression analysis was performed on 119 resected liver metastases of colorectal tumors. Of all clinical variables tested, neoadjuvant chemotherapy was most prominently associated with changes in gene expression. Gene ontology and pathway analysis tools revealed that many of the chemotherapy-associated genes were involved in the regulation of oxidative phosphorylation (OxPhos). To test whether chemotherapy affects OxPhos patient derived colorectal spheroids were treated with the standard cytotoxic agents oxaliplatin and 5-fluorouracil. Chemotherapy strongly increases mitochondrial load, oxygen consumption rate and mitochondrial ATP synthesis.
In line with these results chemo-treated tumor cells displayed a higher ratio of mitochondrial-to-nuclear DNA and expression of respiratory complex components was strongly increased following chemotherapy. Chemotherapy strongly induced expression of the histone deacetylase SIRT1, which has been implicated in mitochondrial biogenesis. Inhibition (by either nicotinamide, EX-527, Tenovin-6) or knockdown of SIRT1 prevented the chemotherapy-induced increase in oxidative phosphorylation. Moreover, SIRT1 knockdown greatly reduced tumor cell survival and clonogenic capacity following removal of chemotherapy.
Conclusion: Chemotherapy induces an increase in oxidative phosphorylation via SIRT1 and this is required for tumor cell survival following drug removal. Since DNA repair requires ATP, mitochondrial biogenesis may be part of the tumor cell response to DNA-damaging agents. Post-chemotherapy targeting of SIRT1 (or OxPhos enzymes) may be an interesting novel approach to increase chemotherapy efficacy.
Citation Format: Thomas T. Vellinga, Vincent C. de Boer, Tijana Borovski, Kari Trumpi, Szabolcs Fatrai, Onno Kranenburg, Inne H.M. Borel Rinkes, Jeroen Hagendoorn. Survival of colorectal cancer cells following chemotherapy relies on a SIRT1-dependent increase in oxidative phosphorylation. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3351. doi:10.1158/1538-7445.AM2014-3351