Nucl Med Biol 2013 Jul 01;405:670-5. doi: 10.1016/j.nucmedbio.2013.03.009.

Kinetic analyses of trans-1-amino-3-[18F]fluorocyclobutanecarboxylic acid transport in Xenopus laevis oocytes expressing human ASCT2 and SNAT2.

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INTRODUCTION: Trans-1-amino-3-[(18)F]fluorocyclobutanecarboxylic acid (anti-[(18)F]FACBC) is a promising amino acid positron emission tomography (PET) radiotracer for visualizing prostate cancer. We previously showed that anti-FACBC is transported by amino acid transporters, especially by alanine-serine-cysteine transporter 2 (ASCT2), which is associated with tumor growth. We studied this affinity to assess the mechanism of anti-FACBC transport in prostate cancer cells. METHODS: Kinetic assays for trans-1-amino-3-fluoro-[1-(14)C]cyclobutanecarboxylic acid ([(14)C]FACBC) were performed in Xenopus laevis oocytes over-expressing either ASCT2 or sodium-coupled neutral amino acid transporter 2 (SNAT2), both of which are highly expressed in prostate cancer cells. We also examined the kinetics of [(14)C]FACBC uptake using mammalian cell lines over-expressing system L amino acid transporter 1 or 2 (LAT1 or LAT2). Results: ASCT2 and SNAT2 transported [14C]FACBC with Michaelis–Menten kinetics Km values of 96.7 ± 45.2 μM and 196.5 ± 19.7 μM, respectively. [correted]. LAT1 and LAT2 transported [(14)C]FACBC with Michaelis-Menten Km values of 230.4 ± 184.5 μM and 738.5 ± 87.6 μM, respectively. CONCLUSIONS: Both ASCT2 and SNAT2 recognize anti-FACBC as a substrate. Anti-FACBC has higher affinity for ASCT2 than for SNAT2, LAT1, or LAT2. The ASCT2-preferential transport of anti-[(18)F]FACBC in cancer cells could be used for more effective prostate cancer imaging.

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Species referenced: Xenopus laevis
Genes referenced: slc1a5 slc38a2 slc7a5 slc7a8

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