Abstract
1115
Objectives: To clarify the difference between system A and L amino acid transport imaging in clinical amino acid PET, we particularly focused on α-[N-methyl-11C]-methylaminoisobutyric acid ([11C]MeAIB), compared with [S-methyl-11C]-L-methionine ([11C]MET). The aim of this study was to assess the relativity of accumulation of these two radiopharmaceuticals with gene expression of amino acid transporters and cell proliferative activity in tumor cells in in-vitro.
Methods: Uptake studies of radioisotope analogs, [S-methyl-3H]-L-methionine ([3H]MET) and α-[1-14C]methylaminoisobutyric acid ([14C]MeAIB) were performed in human derived carcinoma cells (epidermal carcinoma A431, colorectal carcinoma LS180, and lung carcinomas PC14/GL and H441/GL). The carcinoma gene expression levels of a number of amino acid transporters were measured by microarray and quantitative polymerase chain reaction. Carcinoma proliferative activity was assessed using accumulation of [methyl-3H]-3'-deoxy-3'-fluorothymidine ([3H]FLT).
Results: The main transport mechanism of [3H]MET takes place via Na+-independent system L, that of [14C]MeAIB takes place via Na+-dependent system A. There was no correlation between [3H]MET uptake and total system L amino acid transporter (LAT) expression. In contrast, [14C]MeAIB uptake strongly correlated with total system A amino acid transporter (SNAT) expression and proliferative activity using four human carcinoma cell lines. The uptake of [3H]FLT was also correlated with total SNAT expression. Conclusion: According to our results, the analog [11C]MeAIB is supposed to be useful in oncologic PET imaging because [11C]MeAIB may provide an information of gene expression level of total SNAT and tumor cell proliferative activity.