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.