title: Radioiodine-labelled alpha-methyl-tyrosine in malignant melanoma: cell culture studies and results in patients.
abstract: Tyrosine is a precursor of melanin synthesis and might thus present a valuable marker for melanoma. The aim of this study was to evaluate the uptake of alpha-methyl-tyrosine (AMT) in melanoma cell cultures and to assess its usefulness as a radiopharmaceutical for staging melanoma patients with whole-body scintigraphy. Melanoma (M19-cell lines) and fibroblast (negative control) cell cultures were incubated with 125I-AMT and the radioactive uptake in the cell lines was measured in a gamma-counter over 24 h. For in vivo studies, planar whole-body scintigraphy and single photon emission computed tomography (SPECT) of the tumour region was performed following injection of 250-350 MBq 123I-AMT in six patients with known melanoma metastases. Findings were compared with results of whole-body positron emission tomography using 18F-fluorodeoxyglucose (FDG-PET) as a standard of reference. Fibroblasts showed an unchanged uptake of (mean +/- SD) 0.56 +/- 0.09% 15 min and 0.066 +/- 0.09% 24 h, respectively, after incubation of 125I-AMT, whereas there was an increased uptake in melanoma cell cultures over time from 0.9 +/- 0.05% to 7.5 +/- 1.6%. In staging melanoma patients, the sensitivity of whole-body AMT-scintigraphy compared with FDG-PET was 37% (10 of 27 metastases). AMT is transported and metabolized to a high extent in melanoma cells and 123I-AMT is accumulated in melanoma metastases. Owing to its low sensitivity, however, the clinical use of whole-body AMT scintigraphy cannot be recommended.
authors.affiliation: Department of Dermatology, University Hospital of Zurich, Switzerland.
authors.forename: R
authors.initials: R
authors.lastname: Böni
authors.forename: H
authors.initials: H
authors.lastname: Steinert
authors.forename: R
authors.initials: R
authors.lastname: Huch Böni
authors.forename: G K
authors.initials: GK
authors.lastname: Von Schulthess
authors.forename: J
authors.initials: J
authors.lastname: Meyer
authors.forename: R
authors.initials: R
authors.lastname: Dummer
authors.forename: G
authors.initials: G
authors.lastname: Burg
authors.forename: G
authors.initials: G
authors.lastname: Westera
mesh_terms: D000328:Adult; D000368:Aged; D002478:Cells, Cultured; D004791:Enzyme Inhibitors / Q000493:pharmacokinetics; D005260:Female; D005347:Fibroblasts / Q000378:metabolism; D006801:Humans; D007457:Iodine Radioisotopes; D008297:Male; D008545:Melanoma / Q000000981:diagnostic imaging* / Q000378:metabolism / Q000556:secondary*; D008781:Methyltyrosines / Q000493:pharmacokinetics; D008875:Middle Aged; D009367:Neoplasm Staging; D019275:Radiopharmaceuticals; D012680:Sensitivity and Specificity; D012878:Skin Neoplasms / Q000000981:diagnostic imaging* / Q000378:metabolism / Q000556:secondary*; D014055:Tomography, Emission-Computed; D015899:Tomography, Emission-Computed, Single-Photon; D019805:alpha-Methyltyrosine
chemical_list: D004791:Enzyme Inhibitors; D007457:Iodine Radioisotopes; D008781:Methyltyrosines; D019275:Radiopharmaceuticals; D019805:alpha-Methyltyrosine