Abstract
Patient premedication by carbidopa seems to improve the accuracy of 6-18F-fluoro-3,4-dihydroxy-L-phenylalanine (18F-FDOPA) positron emission tomography (PET) for insulinoma diagnosis. However, the risk of PET false negative result has been evoked using carbidopa. Consequently, we aim to evaluate the effect of carbidopa on 18F-FDOPA uptake in insulinoma beta cells and insulinoma xenograft model in mice. Methods: 18F-FDOPA in vitro accumulation was assessed in the murine beta cell line RIN-m5F. The in vivo microPET experiments were performed on tumor-bearing nude mice after subcutaneous injection of RIN-m5F cells. Experiments were conducted with and without carbidopa pretreatment. Results: Incubation of RIN-m5F cells with 80 µM of carbidopa did not significantly affect the cellular accumulation of 18F-FDOPA. Tumor xenograft was clearly detectable by microPET in all cases. Carbidopa-treated mice showed significantly higher 18F-FDOPA uptake on the insulinoma xenografts than non-treated mice. Irrespectively of carbidopa premedication, the xenograft was characterized by an early increase of 18F-FDOPA uptake followed by a progressive reduction over time. Conclusion: Carbidopa does not influence the in vitro 18F-FDOPA uptake accumulation in RIN-m5f cells but improves insulinoma imaging in vivo. Our findings increase the current knowledge about 18F-FDOPA uptake profile of RIN-m5F cells and related xenograft model. The present work represents the first preclinical research specifically focused on the insulinoma with potential translational implication.
- Copyright © 2016 by the Society of Nuclear Medicine and Molecular Imaging, Inc.