Abstract 1894: The lipogenic phenotype of HER2/neu-positive breast cancer cells.

Abstract

Abstract 15 - 30 % of all breast cancer cases are classified as HER2/neu-positive, a very aggressive form of breast cancer that correlates with a poor prognosis, reduced survival time and increased incidence of metastasis. Kourtidis et al. (2010) have recently shown that the HER2-positive breast cancer cell line BT474 relies on a unique Warburg-like metabolism for survival and aggressive behavior. These cells are dependent on fatty acid synthesis, presumably as a means to regenerate NAD+ for aerobic glycolysis. The nuclear receptors NR1D1 and PPARγ enable these cells to upregulate de novo fatty acid synthesis while avoiding palmitate-induced lipotoxicity by storing neutral fats (TAGs). The cells show markedly increased levels of stored fats compared to other breast cancer cell lines and disruption of the synthetic process results in apoptosis of BT474 cells. Metabolomic analysis of NR1D1 overexpressing cells compared to normal cells reveals profound differences in their metabolite profiles. This metabolic phenotype is operating at its limits in HER2-positive cells, as addition of exogenous palmitate results in cell death, whereas HER2-normal cells are not affected by this treatment. Microarray analysis suggests that palmitate induces an ER-stress response in the HER2-positive cells, ultimately resulting in cell death. Preliminary results suggest that this response is CHOP-dependent. Combination treatments with palmitate and HER2-targeted therapeutic compounds show synergistic effects and markedly increase the cytotoxic effects of either compound alone. The uptake of exogenous fatty acids as well as the de novo fatty acid synthesis are dependent on the essential co-factor coenzyme A (CoA), which is generated from the precursor pantothenate (vitamin B5). Based on our genomic analysis we predicted that HER2-positive breast cancer cells are more sensitive to changes in intracellular CoA levels. Our results show that HER2-positive breast cancer cells are sensitive to shRNA-mediated knockdown of coenzyme A pathway enzymes whereas MCF-7 cells are not. We observe the same pattern of sensitivity using the competitive CoA pathway inhibitor homopantothenate. Interestingly, limiting the supply of CoA in HER2-positive cells reduces the toxicity of exogenous palmitate. Our data suggest that HER2-positive breast cancer cells are metabolically different from other breast cancer cell lines and that these differences offer new possibilities for therapeutic applications. Citation Format: Jan M. Baumann, Antonis Kourtidis, Douglas S. Conklin. The lipogenic phenotype of HER2/neu-positive breast cancer cells. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 1894. doi:10.1158/1538-7445.AM2013-1894