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99mTc-Diethylenetriaminepentaacetate-deoxyglucose .


Cheng KT.


Molecular Imaging and Contrast Agent Database (MICAD) [Internet]. Bethesda (MD): National Center for Biotechnology Information (US); 2004-2013.
2007 Mar 06 [updated 2008 Mar 12].


99mTc-diethylenetriaminepentaacetate-deoxyglucose (99mTc-DTPA-DG) is a radioligand developed for single-photon emission computed tomography (SPECT) of glucose utilization rates in normal and pathologic diseases that reflect tumor cell proliferation activities and viability (1). 99mTc is a gamma emitter with a physical half-life (t½) of 6.02 h. Movement of glucose into and out of cells is mediated by one or more members of the transport protein family of glucose transporters (2). There are different classes of glucose transporters for two forms of glucose transport. SGLT1 and SGLT2 are sodium glucose cotransporters involved in secondary active transport, and GLUT1 to GLUT13 are facilitated glucose transporters (3). They are similar in that they have a polypeptide chain of 500 amino acids. After glucose enters a living cell, phosphorylation catalyzed by hexokinase transforms the molecule to glucose-6-phosphate (G-6-P). There are four hexokinase isoforms (HKI to HKIV) that exist in mammalian tissues (4). The G-6-P isomerase then converts G-6-P into fructose-6-phosphate (F-6-P) by rearranging the carbonyl group from the C-1 to the C-2 position in the ring structure to enter further metabolic pathways. Cancer cells are known to have accelerated metabolism, high glucose consumption, and increased glucose uptake (5). In humans, high levels of GLUT expression in tumors have been associated with poor survival. Increased HK activities have also been associated with metastatic disease. Molecular imaging with glucose analogs is a useful tool in the detection, staging, and therapy response monitoring of various malignant neoplasms (6, 7). 2-[18F]Fluoro-2-deoxy-2-d-glucose ([18F]FDG) was the first successful radiolabeled glucose analog developed for clinical positron emission tomography (PET) applications (8). [18F]FDG, like glucose, is transported into cells by glucose transporters and is a substrate for hexokinase. However, it is converted to [18F]FDG-6-phosphate ([18F]FDG-6-P), which cannot be further metabolized. [18F]FDG-6-P is not a substrate for the G-6-P isomerase and therefore is metabolically trapped in the cell. The trapping of [18F]FDG-6-P within cells and tissues allows in vivo PET imaging of glucose utilization rates in normal and pathologic tissues. Because of the short t½ of 18F and the requirement of cyclotron production, it is desirable to develop a gamma-emitter for SPECT imaging (9). Early 123I-labeled glucose analogs were either chemically unstable or poor substrates for hexokinase (6, 10, 11). Bayly et al. (12) reported the successful synthesis of a glucosamine labeled with the tricarbonyls of 99mTc(I). Yang et al. (13, 14) also demonstrated the feasibility of synthesis and imaging of 99mTc-ethylenedicysteine-deoxyglucose in rodents bearing tumors. These studies did not attempt to determine whether these glucose analogs actually followed the key steps in glucose metabolism. Chen et al. (1) developed a one-step 99mTc-DTPA-DG kit and showed tumor accumulation of 99mTc-DTPA-DG in nude rats bearing MCF-7 human mammary tumors. However, the mechanism of tumor uptake was not investigated.

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