A Novel Radiotracer to Image Glycogen Metabolism in Tumors by Positron Emission Tomography Available to Purchase

The high rate of glucose uptake to fuel the bioenergetic and anabolic demands of proliferating cancer cells is well recognized and is exploited with ¹⁸F-2-fluoro-2-deoxy-d-glucose positron emission tomography (¹⁸F-FDG–PET) to image tumors clinically. In contrast, enhanced glucose storage as glycogen (glycogenesis) in cancer is less well understood and the availability of a noninvasive method to image glycogen in vivo could provide important biologic insights. Here, we demonstrate that ¹⁸F-N-(methyl-(2-fluoroethyl)-1H-[1,2,3]triazole-4-yl)glucosamine (¹⁸F-NFTG) annotates glycogenesis in cancer cells and tumors in vivo, measured by PET. Specificity of glycogen labeling was demonstrated by isolating ¹⁸F-NFTG–associated glycogen and with stable knockdown of glycogen synthase 1, which inhibited ¹⁸F-NFTG uptake, whereas oncogene (Rab25) activation–associated glycogen synthesis led to increased uptake. We further show that the rate of glycogenesis is cell-cycle regulated, enhanced during the nonproliferative state of cancer cells. We demonstrate that glycogen levels, ¹⁸F-NFTG, but not ¹⁸F-FDG uptake, increase proportionally with cell density and G₁–G₀ arrest, with potential application in the assessment of activation of oncogenic pathways related to glycogenesis and the detection of posttreatment tumor quiescence. Cancer Res; 74(5); 1319–28. ©2014 AACR.