Optical Imaging of Glucose Uptake and Mitochondrial Membrane Potential to Characterize Her2 Breast Tumor Metabolic Phenotypes

Abstract

With the large number of women diagnosed and treated for breast cancer each year, the importance of studying recurrence has become evident due to most deaths from breast cancer resulting from tumor recurrence following therapy. To mitigate this, cellular and molecular pathways used by residual disease prior to recurrence must be studied. An altered metabolism has long been considered a hallmark of cancer, and several recent studies have gone further to report metabolic dysfunction and alterations as key to understanding the underlying behavior of dormant and recurrent cancer cells. Our group has used two probes, 2-[N-(7-nitrobenz-2-oxa-1, 3-diaxol-4-yl) amino]-2-deoxyglucose (2-NBDG) and tetramethyl rhodamine ethyl ester (TMRE), to image glucose uptake and mitochondrial membrane potential, respectively, to report changes in metabolism between primary tumors, regression, residual disease, and after regrowth in genetically engineered mouse (GEM)-derived mammospheres. Imaging revealed unique metabolic phenotypes across the stages of tumor development. Although primary mammospheres overexpressing Her2 maintained increased glucose uptake ("Warburg effect"), after Her2 downregulation, during regression and residual disease, mammospheres appeared to switch to oxidative phosphorylation. Interestingly, in mammospheres where Her2 overexpression was turned back on to model recurrence, glucose uptake was lowest, indicating a potential change in substrate preference following the reactivation of Her2, reeliciting growth. Our findings highlight the importance of imaging metabolic adaptions to gain insight into the fundamental behaviors of residual and recurrent disease. Implications: This study demonstrates these functional fluorescent probes' ability to report metabolic adaptations during primary tumor growth, regression, residual disease, and regrowth in Her2 breast tumors.

Tracking Photodynamic- and Chemotherapy-Induced Redox-State Perturbations in 3D Culture Models of Pancreatic Cancer: A Tool for Identifying Therapy-Induced Metabolic Changes

“…With a comprehensive image analysis workflow, they identified reduced redox state and increased volumes of lipid droplets in cells exposed to adipogenic media, indicative of cell differentiation [54]. More recently, Madonna et al presented an alternative metabolic imaging strategy on murine mammospheres [55]. A conventional confocal microscopy setup was used to image 2-[ N -(7-nitrobenz-2-oxa-1, 3-diaxol-4-yl) amino]-2-deoxyglucose (2-NBDG) and tetramethyl rhodamine ethyl ester (TMRE) as molecular probes for glucose uptake and mitochondrial membrane potential, respectively.…”

In Situ Metabolic Characterisation of Breast Cancer and Its Potential Impact on Therapy

“…Metabolic alterations such as glycolytic hyperactivation, glutamine uptake, lipid metabolism or mTOR activity have been the subject of intensive studies of breast cancer research [ 10 , 11 , 12 , 13 , 14 ]. Several attempts have been made to subclassify these tumours based on their metabolic characteristics [ 15 , 16 , 17 ]. Despite accumulating data highlighting the correlation between drug resistance and specific metabolic alterations, these studies were primarily focused on cell line-based experiments and/or the relevance of only one metabolic alteration.…”

Consideration of Ketogenic Metabolic Therapy as a Complementary or Alternative Approach for Managing Breast Cancer

“…We consider mSLP as the key mechanism that underlies energy production in tumor cells with defective respiration (46). Aerobic fermentation (Warburg effect) is a common metabolic phenotype in breast cancer regardless of histopathological type, grade, or gene expression profile (24,(66)(67)(68)(69)(70)(71)(72)(73)(74). In addition to glucose, glutamine is the other major fuel necessary for breast cancer cells (73,(75)(76)(77)(78).…”