Abstract 4241: Glioma stem cells perform oxidative phosphorylation, while the rest of glioma cells perform aerobic glycolysis
Authors: Vlashi Erina , Lagadec Chann , Donna Lorenza Della , Meng YongHong , Dekmezian Carmen , Pajonk Frank 
Published: February 2011

Abstract
We have previously demonstrated that glioma stem cells have low 26S proteasome activity. Therefore, in order to visualize the 26S proteasome activity in living cells we have engineered glioma primary lines to stably express a fluorescent fusion protein, ZsGreen-ODC, which is recognized by the 26S proteasome and immediately degraded in an ubiquitin-independent manner. This fusion protein, thus reports for low proteasome activity in a live cell - glioma cells that have high proteasome activity will degrade the fluorescent fusion protein (ZsGreen-negative), while the glioma stem cells with low proteasome activity will accumulate the fluorescent protein (ZsGreen-high). This system has allowed us to visualize, track and separate the glioma stem cell population from the bulk of glioma cells for further characterization. We have employed this unique feature of glioma stem cells to analyze their metabolic state. Using ATP production and glucose uptake assays, as well as analyzing the production of lactic acid and consumption of oxygen we have obtained insight into the metabolic state of glioma stem cells in established and primary glioma lines, stably expressing the ZsGreen-ODC fusion protein. These cells lines were propagated as neurospheres in serum-free conditions, supplemented with growth factors, and at the time of the experiments the ZsGreen-negative population was separated from the ZsGreen-high population by FACS sorting. We have found that glioma stem cells with low proteasome activity (ZsGreen-high) produce more ATP and consume less glucose than the rest of glioma cells with high proteasome activity (ZsGreen-negative). Furthermore, the stem cell population produces less lactic acid and consumes more oxygen, and expresses less Glut-1 protein on the surface. Interestingly, when lactic acid is added to the growth medium the number of ZsGreen-high cells declines, indicating that the amount of lactic acid produced by the bulk of glioma cells in the tumor microenvironment might affect the number of glioma stem cells in the tumor. Taken together these preliminary results suggest that glioma stem cells are performing oxidative phosphorylation, while the bulk of the tumor is performing aerobic glycolysis - thus, metabolic PET tracers designed to detect glycolytically active cells would miss the small population of glioma stem cells. Also, given that elimination of glioma stem cells is crucial for a successful glioma therapy understanding their basic metabolic needs will be very important in designing successful therapies, especially since these results indicate that the glioma stem cell population maybe metabolically quite different from the bulk of glioma cells.
Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 4241.