Reversal of the Warburg effect in breast cancer cells by a novel agent.

Abstract

e13566 Background: It is well known that most cancer cells display a Warburg effect, a state of active glycolysis with lactate production under aerobic conditions. NF-κB has been shown to play a role in modulating cancer metabolism and control the balance between glycolysis and mitochondrial respiration. We have previously shown that panepoxydone (PP), a compound isolated from an edible mushroom, interferes with NF-κB mediated signal transduction. Additionally, we have shown that PP decreases cell viability and proliferation in breast cancer cells. To further characterize the antitumor effect of PP, here we have evaluated it ability to modulate cancer metabolism. Methods: The metabolic action of PP was evaluated in estrogen receptor positive (MCF-7) and triple negative (MDAMB-231) breast cancer cell lines. Cytotoxicity was determined by the cell titer glow assay and expressed as IC50. Metabolic activity, expressed as basal oxygen consumption rate (OCR, an indicator of oxidative phosphorylation) and extracellular acidification rate (ECAR, an indicator of lactate acid production), was measured in real-time using the XF24 Extracellular Flux Analyzer. Mitochondrial membrane potential (MMP) alteration was determined through flow cytometry and LDH-A expression was analyzed via western blot. Results: Significant antitumor activity with PP was seen in both MCF-7 (IC50 5 µM) and MDAMB-231 cells (IC50 15 µM). This correlated to a significant dose-dependent reduction in OCAR in MCF-7 (2-fold, p<0.05) and MDAMB-231 cells (3.5-fold, p<0.01). However, while a decrease in ECAR (1.5-fold, p<0.05), along with decreased LDHA expression was noted in the 231 cells (3.5-fold, p<0.01), this was not seen with the MCF-7 cells. A similar trend was noted with increased damaged mitochondria noted in 231-cells, but again no significant difference in MCF-7 cells. Conclusions: Taken together, these results indicate that PP has the potential to modulate metabolism in breast cancer cells, especially triple negative cells, as noted by its ability to inhibit glycolysis. The inhibition of glycolysis has become an important strategy in treating cancer and development of novel glycolytic inhibitors, such as PP, warrants its further investigation in breast cancer treatment.