Abstract 4343: Inhibition of fatty acid synthase reduces mitochondrial respiration and addiction of colorectal cancer cells to glycolysis

Fatty Acid Synthase (FASN), a key enzyme of lipid biogenesis, is significantly up regulated in colorectal cancer (CRC) and its activity is associated with poor prognosis. Mitochondrial metabolism plays a crucial role in cancer cells proliferation and survival. However, very little is known about the role of de novo fatty acid synthesis in production of ATP via beta-oxidation and oxidative phosphorylation in CRC. The purpose of the present study was to determine: (i) the role of aberrant activation of FASN in cellular respiration, (ii) contribution of endogenously synthesized lipids to fatty acid oxidation, and (iii) consequences of FASN inhibition on mitochondrial properties and redox homeostasis in CRC. METHODS. We utilized KM20, HT29, and HCT116 CRC cells with stable knockdown of FASN. Cellular oxygen consumption rate (OCR) and extracellular acidification rate (ECAR) were measured using XF Cell Mito Stress and XF Glycolysis Stress tests, respectively. The XF Palmitate-BSA conjugate was used to assess oxidation of fatty acids (FAO). OCR, ECAR and FAO experiments were performed using the Seahorse XF96 Extracellular Flux Analyzer (Seahorse Bioscience, North Billerica, MA, USA). Intracellular ROS and mitochondrial membrane potential was measured by DCFDA and TMRE assays. RESULTS. We found that stable inhibition of FASN is associated with a significant decrease in glycolysis in all tested CRC cell lines. The glycolytic capacity and glycolytic reserve were significantly decreased in HCT116 cell line; however, no significant differences in these parameters were observed in HT29 and KM20 cells. Knock-down of FASN led to a significant decrease in OCR in CRC cells that is consistent with a decrease in cellular proliferation. Treatment with etomoxir demonstrated that CRC cell lines have the different level of dependence on fatty acid oxidation. Furthermore, using the Palmitate-BSA substrate we showed that CRC cells primarily utilize endogenously synthesized fatty acids and knockdown of FASN significantly decreases the capacity of cells to oxidize fatty acids. Finally, our data suggest that FASN regulates mitochondrial membrane potential and ROS production in CRC. CONCLUSIONS. Fatty acid oxidation is a dominant bioenergetic pathway in many cancers. This study suggests that up regulation of FASN and an increase in the level of de novo synthesized lipids are crucial for modulation of mitochondrial oxidative capacity in CRC cells. Furthermore, our results proposes that inhibition of FASN and a decrease in mitochondrial ATP production impair glycolysis in CRC cells. Together, our work demonstrates an importance of FASN in re-programming cellular energy metabolism, in particular, beta-oxidation. Further investigations into the mechanisms of regulation of mitochondrial function by FASN and interconnection with other metabolic pathways will uncover new therapeutic approaches in CRC. Citation Format: Yekaterina Zaytseva, Mihail Mitov, D. Allan Butterfield, Tianyan Gao, B. Mark Evers. Inhibition of fatty acid synthase reduces mitochondrial respiration and addiction of colorectal cancer cells to glycolysis. [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 4343. doi:10.1158/1538-7445.AM2014-4343