Radiopharmacological evaluation of 6-deoxy-6-[18F]fluoro-D-fructose as a radiotracer for PET imaging of GLUT5 in breast cancer.
ABSTRACT Several clinical studies have shown low or no expression of GLUT1 in breast cancer patients, which may account for the low clinical specificity and sensitivity of 2-deoxy-2-[(18)F]fluoro-D-glucose ([(18)F]FDG) used in positron emission tomography (PET). Therefore, it has been proposed that other tumor characteristics such as the high expression of GLUT2 and GLUT5 in many breast tumors could be used to develop alternative strategies to detect breast cancer. Here we have studied the in vitro and in vivo radiopharmacological profile of 6-deoxy-6-[(18)F]fluoro-D-fructose (6-[(18)F]FDF) as a potential PET radiotracer to image GLUT5 expression in breast cancers.
Uptake of 6-[(18)F]FDF was studied in murine EMT-6 and human MCF-7 breast cancer cells over 60 min and compared to [(18)F]FDG. Biodistribution of 6-[(18)F]FDF was determined in BALB/c mice. Tumor uptake was studied with dynamic small animal PET in EMT-6 tumor-bearing BALB/c mice and human xenograft MCF-7 tumor-bearing NIH-III mice in comparison to [(18)F]FDG. 6-[(18)F]FDF metabolism was investigated in mouse blood and urine.
6-[(18)F]FDF is taken up by EMT-6 and MCF-7 breast tumor cells independent of extracellular glucose levels but dependent on the extracellular concentration of fructose. After 60 min, 30±4% (n=9) and 12±1% (n=7) ID/mg protein 6-[(18)F]FDF was found in EMT-6 and MCF-7 cells, respectively. 6-deoxy-6-fluoro-d-fructose had a 10-fold higher potency than fructose to inhibit 6-[(18)F]FDF uptake into EMT-6 cells. Biodistribution in normal mice revealed radioactivity uptake in bone and brain. Radioactivity was accumulated in EMT-6 tumors reaching 3.65±0.30% ID/g (n=3) at 5 min post injection and decreasing to 1.75±0.03% ID/g (n=3) at 120 min post injection. Dynamic small animal PET showed significantly lower radioactivity uptake after 15 min post injection in MCF-7 tumors [standard uptake value (SUV)=0.76±0.05; n=3] compared to EMT-6 tumors (SUV=1.23±0.09; n=3). Interestingly, [(18)F]FDG uptake was significantly different in MCF-7 tumors (SUV(15 min) 0.74±0.12 to SUV(120 min) 0.80±0.15; n=3) versus EMT-6 tumors (SUV(15 min) 1.01±0.33 to SUV(120 min) 1.80±0.25; n=3). 6-[(18)F]FDF was shown to be a substrate for recombinant human ketohexokinase, and it was metabolized rapidly in vivo.
Based on the GLUT5 specific transport and phosphorylation by ketohexokinase, 6-[(18)F]FDF may represent a novel radiotracer for PET imaging of GLUT5 and ketohexokinase-expressing tumors.
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ABSTRACT: We have expressed the human isoforms of the liver-type (GLUT2) and brain-type (GLUT3) facilitative glucose transporters in oocytes from Xenopus laevis via injection of in vitro transcribed mRNA. As reported previously [Gould, Thomas, Jess and Bell (1991) Biochemistry 30, 5139-5145], GLUT2 mediates the transport of fructose and galactose, and GLUT3 mediates the transport of galactose. We have examined the effects of D-glucose, D-fructose and maltose on deoxyglucose transport in oocytes expressing GLUT2, and D-glucose, D-galactose and maltose on deoxyglucose transport in oocytes expressing GLUT3, and show that each sugar is a competitive inhibitor of transport. Moreover, D-glucose and maltose competitively inhibit fructose transport by GLUT2 and galactose transport by GLUT3, indicating that the transport of the alternative substrates for these transporters is likely to be mediated by the same outward-facing sugar-binding site used by glucose. Cytochalasin B is a non-competitive inhibitor of glucose transport by the well-characterized GLUT1 isoform. We show here that cytochalasin B is also a non-competitive inhibitor of the transport of deoxyglucose and alternative substrates by GLUT2 and GLUT3 expressed in oocytes. Km and Ki values for each substrate and inhibitor are presented for each isoform, together with further analysis of the binding sites for alternative substrates for these transporter isoforms.Biochemical Journal 04/1993; 290 ( Pt 3):701-6. · 4.65 Impact Factor
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ABSTRACT: A substantial amount of macrophage infiltration occurs in both human and animal tumors. We previously showed that 2-deoxy-2-[18F]fluoro-D-glucose ([18F]FDG) uptake was higher in tumor-associated macrophages and young granulation tissues than in tumor cells. Differentiation of intratumoral non-neoplastic cells from neoplastic cells is important not only for the reduction of false-positives in FDG-PET tumor studies but also for patient management. A time-course study was performed using micro- and macro-autoradiography and tissue distribution in C3H/He mice bearing transplanted syngeneic FM3A mammary carcinoma and MH134 hepatoma was evaluated to analyze the intratumoral cellular dynamics of [18F]FDG and 2-deoxy-D-[3H]glucose in vivo. The volume-doubling time in vivo was 1.3 days for MH134 and 4.9 days for FM3A, and the survival time of the host was 32.1 and 40.3 days, respectively. The peak uptake of both tracers in the tumor was 60 min after intravenous injection. The uptake by MH134 was 1.7-2.1 times higher than that by FM3A. The intracellular concentration as determined by counting the silver grains on micro-autoradiographic sections showed that the uptake by macrophages and focal small necrotic areas in both tumors was faster than the blood clearance until 15 min after tracer injection. Thus, non-neoplastic cellular elements can be differentiated from viable neoplastic cells by means of the dynamic analysis of [18F]FDG uptake.Journal of Nuclear Medicine 02/1994; 35(1):104-12. · 5.77 Impact Factor
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ABSTRACT: The primary metabolic characteristic of malignant cells is an increased uptake of glucose and its anaerobic metabolism. We studied the expression and function of the glucose transporters in human breast cancer cell lines and analyzed their expression in normal and neoplastic primary human breast tissue. Hexose uptake assays and immunoblotting experiments revealed that the breast carcinoma cell lines MCF-7 and MDA-468 express the glucose transporters GLUT1 and GLUT2, isoforms expressed in both normal and neoplastic breast tissue. We also found that the breast cancer cell lines transport fructose and express the fructose transporter GLUT5. Immunolocalization studies revealed that GLUT5 is highly expressed in vivo in human breast cancer but is absent in normal human breast tissue. These findings indicate that human breast cancer cells have a specialized capacity to transport fructose, a metabolic substrate believed to be used by few human tissues. Identification of a high-affinity fructose transporter on human breast cancer cells opens opportunities to develop novel strategies for early diagnosis and treatment of breast cancer.Proceedings of the National Academy of Sciences 04/1996; 93(5):1847-52. · 9.74 Impact Factor