Imaging tumour ATB0,+ transport activity by PET with the cationic amino acid O-2((2-[18F]fluoroethyl)methyl-amino)ethyltyrosine

PURPOSE The concentrative amino acid transporter ATB(0,+) (SLC6A14) is under evaluation as a target for anticancer therapy. An ATB(0,+)-selective positron emission tomography (PET) probe could advance preclinical drug development. We characterised the cationic tyrosine analogue O-2((2-[(18)F]fluoroethyl)methyl-amino)ethyltyrosine ([(18)F]FEMAET) as a PET probe for ATB(0,+) activity. PROCEDURES Cell uptake was studied in vitro. ATB(0,+) expression was quantified by real-time PCR. [(18)F]FEMAET accumulation in xenografts was investigated by small animal PET with mice. RESULTS [(18)F]FEMAET accumulated in PC-3 and NCI-H69 cancer cells in vitro. As expected for ATB(0,+) transport, uptake was inhibited by LAT/ATB(0,+) inhibitors and dibasic amino acids, and [(18)F]FEMAET efflux was only moderately stimulated by extracellular amino acids. ATB(0,+) was expressed in PC-3 and NCI-H69 but not MDA-MB-231 xenografts. PET revealed accumulation in PC-3 and NCI-H69 xenografts and significant reduction by ATB(0,+) inhibition. Uptake was negligible in MDA-MB-231 xenografts. CONCLUSION ATB(0,+) activity can be imaged in vivo by PET with [(18)F]FEMAET