RT Journal Article
SR Electronic
T1 <em>S</em>-<sup>11</sup>C-Methyl-<span class="sc">L</span>-Cysteine: A New Amino Acid PET Tracer for Cancer Imaging
JF Journal of Nuclear Medicine
JO J Nucl Med
FD Society of Nuclear Medicine
SP 287
OP 293
DO 10.2967/jnumed.110.081349
VO 52
IS 2
A1 Huaifu Deng
A1 Xiaolan Tang
A1 Hongliang Wang
A1 Ganghua Tang
A1 Fuhua Wen
A1 Xinchong Shi
A1 Chang Yi
A1 Kening Wu
A1 Quanfei Meng
YR 2011
UL http://jnm.snmjournals.org/content/52/2/287.abstract
AB S-11C-methyl-L-cysteine (11C-MCYS), an analog of S-11C-methyl-L-methionine (11C-MET), can potentially serve as an amino acid PET tracer for tumor imaging. The aim of this study was to investigate the radiosynthesis and perform a biologic evaluation of 11C-MCYS as a tumor imaging tracer. The results of the first human PET study are reported. Methods: 11C-MCYS was prepared by 11C-methylation of the precursor L-cysteine with 11CH3I and purification on commercial C18 cartridges. In vitro competitive inhibition experiments were performed with Hepa1–6 hepatoma cell lines, and biodistribution of 11C-MCYS was determined in normal mice. The incorporation of 11C-MCYS into tissue proteins was investigated. In vivo 11C-MCYS uptake studies were performed on hepatocellular carcinoma–bearing nude mice and inflammation models and compared with 11C-MET PET and 18F-FDG PET. In a human PET study, a patient with a recurrence of glioma after surgery was examined with 11C-MCYS PET and 18F-FDG PET. Results: The uncorrected radiochemical yield of 11C-MCYS from 11CH3I was more than 50% with a synthesis time of 2 min, the radiochemical purity of 11C-MCYS was more than 99%, and the enantiomeric purity was more than 90%. In vitro studies showed that 11C-MCYS transport was mediated through transport system L. Biodistribution studies demonstrated high uptake of 11C-MCYS in the liver, stomach wall, and heart and low uptake of 11C-MCYS in the brain. There was higher accumulation of 11C-MCYS in the tumor than in the muscles. The tumor-to-muscle and inflammatory lesion–to–muscle ratios were 7.27 and 1.62, respectively, for 11C-MCYS, 5.08 and 3.88, respectively, for 18F-FDG, and 4.26 and 2.28, respectively, for 11C-MET at 60 min after injection. Almost no 11C-MCYS was incorporated into proteins. For the patient PET study, high uptake of 11C-MCYS with true-positive results, but low uptake of 18F-FDG with false-negative results, was found in the recurrent glioma. Conclusion: Automated synthesis of 11C-MCYS is easy to perform. 11C-MCYS is superior to 11C-MET and 18F-FDG in the differentiation of tumor from inflammation and seems to have potential as an oncologic PET tracer for the diagnosis of solid tumors.