Energy Metabolism Characterization of a Novel Cancer Stem Cell‐Like Line 3AB‐OS

Abstract

Cancer stem cells (CSC) have a central role in driving tumor growth. Since metabolism is becoming an important diagnostic and therapeutic target, characterization of CSC line energetic properties is an emerging need. Embryonic and adult stem cells, compared to differentiated cells, exhibit a reduced mitochondrial activity and a stronger dependence on aerobic glycolysis. Here, we aimed to comparatively analyze bioenergetics features of the human osteosarcoma 3AB-OS CSC-like line, and the parental osteosarcoma MG63 cells, from which 3AB-OS cells have been previously selected. Our results suggest that 3AB-OS cells depend on glycolytic metabolism more strongly than MG63 cells. Indeed, growth in glucose shortage or in presence of galactose or pyruvate (mitochondrial specific substrates) leads to a significant reduction of their proliferation compared to MG63 cells. Accordingly, 3AB-OS cells show an increased expression of lactate dehydrogenase A (LDHA) and a larger accumulation of lactate in the culture medium. In line with these findings 3AB-OS cells as compared to MG63 cells present a reduced mitochondrial respiration, a stronger sensitivity to glucose depletion or glycolysis inhibition and a lessened sensitivity to oxidative phosphorylation inhibitors. Additionally, in contrast to MG63 cells, 3AB-OS display fragmented mitochondria, which become networked as they grow in glucose-rich medium, while almost entirely loose these structures growing in low glucose. Overall, our findings suggest that 3AB-OS CSC energy metabolism is more similar to normal stem cells and to cancer cells characterized by a glycolytic anaerobic metabolism. J. Cell. Biochem. 115: 368-379, 2014. ß 2013 Wiley Periodicals, Inc. KEY WORDS: CANCER STEM CELLS; CANCER METABOLISM; WARBURG EFFECTU ndifferentiated embryonic stem cells as well as adult stem cells have recently been shown to have a different energetic metabolism as compared to fully differentiated cells. In fact, stem cells rely mostly on anaerobic metabolism rather than on oxidative phosphorylation (OXPHOS) [Varum et al., 2011]. In addition, it has been shown that undifferentiated stem cells have a reduced number of mitochondria, that appear also more immature, a low content of mitochondrial DNA (mtDNA), a reduced oxygen consumption rate and a low level of intracellular adenosine triphosphate (ATP) and reactive oxygen species (ROS) as compared to more differentiated cells [Chen et al., 2008[Chen et al., , 2010 [Chen et al., 2010]. Accordingly, inhibition of mitochondrial respiratory chain, which has recently been found associated with enhancement of hESC pluripotency [Varum et al., 2009] as well as over-expression of mitochondrial protein UCP2 favoring glycolysis, interfere with human PSCs differentiation . Therefore it is becoming clear that energetic metabolism could be used for stem cell recognition and characterization as well as a way of modulating their fate [Chen et al., 2012].Cancer stem cells (CSCs) or cancer-initiating cells are a population of cells with self-renewal ...

Ovarian tumor-initiating cells display a flexible metabolism

“…The metabolic phenotype of CSC/TICs is also controversially discussed; glioblastoma stem cells have been reported to be less[44] or more glycolytic than their daughter cells[45-47], or exhibit either phenotype in the same tumor[48]. Colon cancer or osteoblastoma CSC/TICs express higher levels of glycolytic genes[49] and are more glycolytic[50] than their differentiated counterparts. Our results indicate a more glycolytic and flexible metabolic function in the TICs.…”

“…However, a recent study demonstrated the glycolytic nature of an osteosarcoma stem-like cell line with minimal contribution of OxPhos to cellular ATP production but a reduced mitochondrial function with a low spare respiratory capacity and coupling efficiency, and the lack of adaptive response to glucose deprivation[50]. It is unclear at this point if species or tissue differences, the choice of cells serving as comparisons and the choice of stem-cell markers for stem cell isolation impact these contradictory results, or if the generation of our TICs via IP enrichment from a primary cell line may also select for a specific phenotype.…”

A short story of 3AB-OS Cancer Stem Cells, a possible model for studying cancer stemness

“…In addition, with respect to MG63 cells, 3AB-OS have fragmented mitochondria which rapidly networked in the presence of glucose-rich medium, whereas, growing in low glucose they entirely lose these structures. Overall, the findings suggested that the energy metabolism of 3AB-OS CSC strongly resemble that of normal stem cells and cancer cells which are characterized by a glycolytic anaerobic metabolism [20] .…”

Tumor Cell Complexity and Metabolic Flexibility in Tumorigenesis and Metastasis

“…Acquisition of certain mutations in key metabolic enzymes suggests that the metabolism of quiescent and self-renewing cells may also be biased towards glycolytic metabolism. Recent evidence from a variant human osteosarcoma cell line with cancer stem cell-like properties indicated greater dependence on glycolytic metabolism compared with parental cells (Palorini et al 2013). In addition, brain tumor-initiating cells have been shown to preferentially express the high-affinity neuronal glucose transporter, Glut-3, a Fig.…”