Abstract 2802: Evaluation of metabolic changes induced by loss of extracellular matrix attachment using 13C Flux analysis

Abstract

Abstract Recent studies from our laboratory revealed the importance of extracellular matrix in regulating cellular metabolism. Briefly, detachment of mammary epithelial cells from extracellular matrix (ECM) causes a significant reduction in ATP levels due to reduced glucose uptake. ErbB2 overexpression restores ATP levels by maintaining glucose uptake in ECM detached cells. The loss of glucose uptake also increases ROS levels, and unexpectedly, antioxidants rescue the metabolic defect, by relieving an ROS-mediated inhibition of ATP generation by fatty acid oxidation. These findings suggest that ECM contact is an important regulator of cellular metabolism, and that tumor cells may be able to circumvent the requirement for ECM-attachment via overexpression of certain oncogenes. We used 13C metabolic flux analysis to more thoroughly investigate the metabolic changes induced by ECM detachment and ErbB2 overexpression in the immortalized, non-transformed human mammary epithelial cell-line, MCF10A. Our results show that matrix-detachment leads to a dramatic decrease in nutrient uptake, including glucose, glutamine and pyruvate. Interestingly, we found that there is a substantial decrease in glucose flux to the tricarboxylic acid (TCA) cycle; this is due both to the decreased glucose uptake, as well as an increased diversion of glucose towards lactate production (aerobic glycolysis). ErbB2 overexpression partially reverses these defects in the ECM-detached cells. Glucose entrance to the TCA cycle is regulated by pyruvate dehydrogenase (PDH), which are in turn negatively regulated by PDH kinases (PDK1-4). Interesting, we find a dramatic increase in PDK4 levels in ECM-detached cells, which is partially prevented by ErbB2 overexpression. While PI3K signaling has previously been shown to negatively regulate PDK4 expression, we find that Mek, but not PI3K, regulates PDK4 levels in our system. Ongoing studies will further examine the regulation of glucose and pyruvate metabolism by ErbB2 and ECM. These analyses will allow us to identify unpredictable nodes of metabolic regulation by ErbB2 and ECM and may provide rational treatment approaches for targeting tumor metabolism. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 2802. doi:10.1158/1538-7445.AM2011-2802