Abstract
.Significance: Glioblastoma multiforme (GBM) is the most frequently diagnosed adult primary brain malignancy with poor patient prognosis. GBM can recur despite aggressive treatment due to therapeutically resistant glioblastoma stem cells (GSCs) that may exhibit metabolic plasticity.Aim: Intrinsic nicotinamide adenine dinucleotide (NADH) fluorescence can be acquired with fluorescence lifetime imaging microscopy (FLIM) to examine its bound and free metabolic states in GSC and GBM tissues.Approach: We compared the mean NADH fluorescence lifetime in live human GSCs and normal neural stem cells and validated those results by measuring oxygen consumption rates (OCRs). We also examined the role that invasive versus less-invasive GSCs had on tumor metabolism by measuring the mean NADH lifetimes and the relative amount of the longer-lived component of NADH and correlated these results with survival in an orthotopic mouse xenograft model.Results: Mean NADH lifetime, amount of bound NADH, and OCR were increased in GSCs. Compared with normal mouse brain, mean NADH lifetimes were longer for all GBM tissues. Invasive xenografts had higher relative amounts of the longer-lived NADH component, and this correlated with decreased survival.Conclusions: FLIM offers cellular resolution quantification of metabolic flux in GBM phenotypes, potentially informing biomedical researchers on improved therapeutic approaches.
Highlights
Cancer is the second leading cause of death in the United States and one of the most pressing challenges faced by public health institutions.[1]
The oxygen consumption rates (OCRs) is correlated with oxidative metabolism, whereas extracellular acidification rate (ECAR) is associated with glycolysis
Results from the Seahorse assay and live cell fluorescence lifetime imaging microscopy (FLIM) are summarized in Fig. 1, which shows that mean OCR was greater in the 22 glioblastoma stem cells (GSCs) (43.04 Æ 29.84 pMole∕ min) than in the neural stem cells (NSCs) (26.10 Æ 7.92 pMole∕ min, Student’s t-test, p 1⁄4 0.0423) (Fig. 1)
Summary
Cancer is the second leading cause of death in the United States and one of the most pressing challenges faced by public health institutions.[1] Approximately 16,830 deaths in 2018 could be attributed to primary malignant brain and central nervous system (CNS) tumors.[2] It is further estimated that 86,970 new cases of primary malignant and nonmalignant brain and CNS tumors will be diagnosed in the United States by 2019, with 26,170 of those cases coming from primary malignant tumors.[2] Glioblastoma multiforme (GBM) is a grade IV astrocytoma and is the most aggressive adult primary brain malignancy with a median survival of ∼18 months with maximal safe surgical resection, radiotherapy, and adjuvant chemotherapy with temozolomide.[3] GBMs are a highly heterogeneous tumor, consisting of bulk tumor differentiated cells, proliferating cells, cancer stem cells, rare clones, resident microglia, and bone marrow-infiltrating immune cells.[4,5,6] While many efforts have been made to understand the metabolic demands of GBM through U251, U118, U87, and other differentiated glioma models,[7] an increasing number of groups have been investigating the role of stem-like or tumor-initiating cells on the glioma microenvironment to better understand how these cells perturb metabolic adaptations in such a way that make these cells resilient to current therapies.[3,8,9,10]
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