Abstract
Positron emission tomography (PET) imaging can assist in the early-phase diagnostic and therapeutic evaluation of tumors. Here, we report the radiosynthesis, small animal PET imaging, and biological evaluation of a L-type amino acid transporter 1 (LAT1)-specific PET probe, 18F-FIMP. This probe demonstrates increased tumor specificity, compared to existing tumor-specific PET probes (18F-FET, 11C-MET, and 18F-FDG). Evaluation of probes by in vivo PET imaging, 18F-FIMP showed intense accumulation in LAT1-positive tumor tissues, but not in inflamed lesions, whereas intense accumulation of 18F-FDG was observed in both tumor tissues and in inflamed lesions. Metabolite analysis showed that 18F-FIMP was stable in liver microsomes, and mice tissues (plasma, urine, liver, pancreas, and tumor). Investigation of the protein incorporation of 18F-FIMP showed that it was not incorporated into protein. Furthermore, the expected mean absorbed dose of 18F-FIMP in humans was comparable or slightly higher than that of 18F-FDG and indicated that 18F-FIMP may be a safe PET probe for use in humans. 18F-FIMP may provide improved specificity for tumor diagnosis, compared to 18F-FDG, 18F-FET, and 11C-MET. This probe may be suitable for PET imaging for glioblastoma and the early-phase monitoring of cancer therapy outcomes.
Highlights
Positron emission tomography (PET) imaging can assist in the early-phase diagnostic and therapeutic evaluation of tumors
Positron emission tomography (PET) imaging can assist in early-phase clinical evaluations of tumors. 2-Deoxy2-18F-fluoro-D-glucose (FDG) is the most commonly used PET probe for tumor imaging; this probe has several limitations. 18F-FDG is actively transported into cells via glucose transporters (GLUTs), which are expressed in tumor tissues, and in inflamed lesions in which they regulate glucose metabolism to facilitate the inflammatory response[1]
Radiolabeled amino acid PET probes, such as L-[methyl-11C]-methionine (MET), were developed to overcome the disadvantages of 18F-FDG4. 11C-MET was predicted to have a higher specificity for tumors; this probe was found to accumulate in tumor, normal, and inflamed tissues[5,6]
Summary
Positron emission tomography (PET) imaging can assist in the early-phase diagnostic and therapeutic evaluation of tumors. We report the radiosynthesis, small animal PET imaging, and biological evaluation of a L-type amino acid transporter 1 (LAT1)-specific PET probe, 18F-FIMP. This probe demonstrates increased tumor specificity, compared to existing tumor-specific PET probes (18FFET, 11C-MET, and 18F-FDG). 18F-FIMP may provide improved specificity for tumor diagnosis, compared to 18F-FDG, 18F-FET, and 11CMET This probe may be suitable for PET imaging for glioblastoma and the early-phase monitoring of cancer therapy outcomes. In order to improve the selectivity for tumor tissues, PET probes with tumor-specific molecular targets have developed[7,8,9]. Several PET probes targeting LAT1 have been reported, including 18F-fluoro-ethyl-tyrosine (FET)[7], and L-3-18F-fluoro-α-methyl-tyrosine (FAMT)[9]. We report the radiosynthesis, small animal PET imaging, and biological evaluation of 18F-FIMP
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