2-Deoxy--glucose is a glucosemolecule which has the 2-hydroxyl group replaced by hydrogen, so that it cannot undergo further glycolysis. As such; it acts to competitively inhibit the production of glucose-6-phosphate from glucose at the phosphoglucoisomerase level. In most cells, glucose hexokinase phosphorylates 2-deoxyglucose, trapping the product 2-deoxyglucose-6-phosphate intracellularly ; thus, labelled forms of 2-deoxyglucose serve as a good marker for tissue glucose uptake and hexokinase activity. Many cancers have elevated glucose uptake and hexokinase levels. 2-Deoxyglucose labeled with tritium or carbon-14 has been a popular ligand for laboratory research in animal models, where distribution is assessed by tissue-slicing followed by autoradiography, sometimes in tandem with either conventional or electron microscopy. 2-DG is uptaken by the glucose transporters of the cell. Therefore, cells with higher glucose uptake, for example tumor cells, have also a higher uptake of 2-DG. Since 2-DG hampers cell growth, its use as a tumor therapeutic has been suggested, and in fact, 2-DG is in clinical trials A recent clinical trial showed 2-DG can be tolerated at a dose of 63 mg/kg/day, however the observed cardiac side-effects at this dose and the fact that a majority of patients' cancer progressed casts doubt on the feasibility of this reagent for further clinical use. However, it is not completely clear how 2-DG inhibits cell growth. The fact that glycolysis is inhibited by 2-DG, seems not to be sufficient to explain why 2-DG treated cells stop growing. Because of its structural similarity to mannose, 2DG has the potential to inhibit N-glycosylation in mammalian cells and other systems, and as such induces ER stress and the Unfolded Protein Response pathway. Clinicians have noted that 2-DG is metabolised in the pentose phosphate pathway in red blood cells at least, although the significance of this for other cell types and for cancer treatment in general is unclear. Work on the ketogenic diet as a treatment for epilepsy have investigated the role of glycolysis in the disease. 2-Deoxyglucose has been proposed by Garriga-Canut et al. as a mimic for the ketogenic diet, and shows great promise as a new anti-epileptic drug. The authors suggest that 2-DG works, in part, by increasing the expression of Brain-derived neurotrophic factor, Nerve growth factor, Arc , and Basic fibroblast growth factor. Such uses are complicated by the fact that 2-deoxyglucose does have some toxicity. A study found that by combining the sugar 2-deoxy-D-glucose with fenofibrate, a compound that has been safely used in humans for more than 40 years to lower cholesterol and triglycerides, an entire tumor could effectively be targeted without the use of toxic chemotherapy. 2-DG has been used as a targeted optical imaging agent for fluorescent in vivo imaging. In clinical medical imaging, fluorodeoxyglucose is used, where one of the 2-hydrogens of 2-deoxy-D-glucose is replaced with the positron-emitting isotope fluorine-18, which emits paired gamma rays, allowing distribution of the tracer to be imaged by external gamma camera. This is increasingly done in tandem with a CT function which is part of the same PET/CT machine, to allow better localization of small-volume tissue glucose-uptake differences. Resistance to 2-DG has been reported in HeLa cells and in yeast ; in the latter, it involves the detoxification of a metabolite derived from 2-DG by a phosphatase. Despite the existence of such a phosphatase in human However it is unclear whether it contributes to the resistance of human cells to 2DG or affects FDG-based imaging.
