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

Nucl Med Biol. 2013 Jul;40(5):670-5. doi: 10.1016/j.nucmedbio.2013.03.009. Epub 2013 May 3.


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.

MeSH terms

  • Amino Acid Transport System A / genetics*
  • Amino Acid Transport System A / metabolism*
  • Amino Acid Transport System ASC / genetics*
  • Amino Acid Transport System ASC / metabolism*
  • Animals
  • Biological Transport
  • Carboxylic Acids / metabolism*
  • Cell Line
  • Cyclobutanes / metabolism*
  • Gene Expression
  • Humans
  • Kinetics
  • Large Neutral Amino Acid-Transporter 1 / metabolism
  • Mice
  • Minor Histocompatibility Antigens
  • Oocytes / metabolism*
  • Xenopus laevis / genetics*


  • Amino Acid Transport System A
  • Amino Acid Transport System ASC
  • Carboxylic Acids
  • Cyclobutanes
  • Large Neutral Amino Acid-Transporter 1
  • Minor Histocompatibility Antigens
  • SLC1A5 protein, human
  • SLC38A2 protein, human
  • fluciclovine F-18