title: Automated synthesis of 18F-fluoropropoxytryptophan for amino acid transporter system imaging.
abstract: OBJECTIVE
  This study was to develop a cGMP grade of [(18)F]fluoropropoxytryptophan ((18)F-FTP) to assess tryptophan transporters using an automated synthesizer.
  
  
  METHODS
  Tosylpropoxytryptophan (Ts-TP) was reacted with K(18)F/kryptofix complex. After column purification, solvent evaporation, and hydrolysis, the identity and purity of the product were validated by radio-TLC (1M-ammonium acetate : methanol = 4 : 1) and HPLC (C-18 column, methanol : water = 7 : 3) analyses. In vitro cellular uptake of (18)F-FTP and (18)F-FDG was performed in human prostate cancer cells. PET imaging studies were performed with (18)F-FTP and (18)F-FDG in prostate and small cell lung tumor-bearing mice (3.7 MBq/mouse, iv).
  
  
  RESULTS
  Radio-TLC and HPLC analyses of (18)F-FTP showed that the Rf and Rt values were 0.9 and 9 min, respectively. Radiochemical purity was >99%. The radiochemical yield was 37.7% (EOS 90 min, decay corrected). Cellular uptake of (18)F-FTP and (18)F-FDG showed enhanced uptake as a function of incubation time. PET imaging studies showed that (18)F-FTP had less tumor uptake than (18)F-FDG in prostate cancer model. However, (18)F-FTP had more uptake than (18)F-FDG in small cell lung cancer model.
  
  
  CONCLUSIONS
  (18)F-FTP could be synthesized with high radiochemical yield. Assessment of upregulated transporters activity by (18)F-FTP may provide potential applications in differential diagnosis and prediction of early treatment response.
authors.affiliation: Department of Cancer Systems Imaging, The University of Texas M. D. Anderson Cancer Center, Houston, TX 77030, USA.
authors.forename: I-Hong
authors.initials: IH
authors.lastname: Shih
authors.affiliation: Department of Cancer Systems Imaging, The University of Texas M. D. Anderson Cancer Center, Houston, TX 77030, USA.
authors.forename: Xu-Dong
authors.initials: XD
authors.lastname: Duan
authors.affiliation: Department of Cancer Systems Imaging, The University of Texas M. D. Anderson Cancer Center, Houston, TX 77030, USA.
authors.forename: Fan-Lin
authors.initials: FL
authors.lastname: Kong
authors.affiliation: Department of Cancer Systems Imaging, The University of Texas M. D. Anderson Cancer Center, Houston, TX 77030, USA.
authors.forename: Michael D
authors.initials: MD
authors.lastname: Williams
authors.affiliation: Department of Cancer Systems Imaging, The University of Texas M. D. Anderson Cancer Center, Houston, TX 77030, USA.
authors.forename: Kevin
authors.identifier: 0000-0003-3672-4222
authors.initials: K
authors.lastname: Yang
authors.affiliation: Department of Cancer Systems Imaging, The University of Texas M. D. Anderson Cancer Center, Houston, TX 77030, USA.
authors.forename: Yin-Han
authors.initials: YH
authors.lastname: Zhang
authors.affiliation: Department of Cancer Systems Imaging, The University of Texas M. D. Anderson Cancer Center, Houston, TX 77030, USA.
authors.forename: David J
authors.initials: DJ
authors.lastname: Yang
mesh_terms: D000818:Animals; D045744:Cell Line, Tumor; D005462:Fluorine Radioisotopes / Q000494:pharmacology*; D064593:Heterografts; D006801:Humans; D008297:Male; D051379:Mice; D009368:Neoplasm Transplantation; D049268:Positron-Emission Tomography; D011471:Prostatic Neoplasms / Q000000981:diagnostic imaging* / Q000378:metabolism; D011859:Radiography; D019275:Radiopharmaceuticals / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology; D014364:Tryptophan / Q000031:analogs & derivatives / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology
chemical_list: D005462:Fluorine Radioisotopes; D019275:Radiopharmaceuticals; D014364:Tryptophan