Establishment of radioactive astatine and iodine uptake in cancer cell lines expressing the human sodium/iodide symporter.
The sodium/iodide symporter (NIS) has been recognized as an attractive target for radioiodine-mediated cancer gene therapy. In this study we investigated the role of human NIS for cellular uptake of the high LET alpha-emitter astatine-211 ((211)At) in comparison with radioiodine as a potential radionuclide for future applications. A mammalian NIS expression vector was constructed and used to generate six stable NIS-expressing cancer cell lines (three derived from thyroid carcinoma, two from colon carcinoma, one from glioblastoma). Compared with the respective control cell lines, steady state radionuclide uptake of NIS-expressing cell lines increased up to 350-fold for iodine-123 ((123)I), 340-fold for technetium-99m pertechnetate ((99m)TcO(4)(-)) and 60-fold for (211)At. Cellular (211)At accumulation was found to be dependent on extracellular Na(+) ions and displayed a similar sensitivity towards sodium perchlorate inhibition as radioiodide and (99m)TcO(4)(-) uptake. Heterologous competition with unlabelled NaI decreased NIS-mediated (211)At uptake to levels of NIS-negative control cells. Following uptake both radioiodide and (211)At were rapidly (apparent t(1/2) 3-15 min) released by the cells as determined by wash-out experiments. Data of scintigraphic tumour imaging in a xenograft nude mice model of transplanted NIS-modified thyroid cells indicated that radionuclide uptake in NIS-expressing tumours was up to 70 times ((123)I), 25 times ((99m)TcO(4)(-)) and 10 times ((211)At) higher than in control tumours or normal tissues except stomach (3-5 times) and thyroid gland (5-10 times). Thirty-four percent and 14% of the administered activity of (123)I and (211)At, respectively, was found in NIS tumours by region of interest analysis ( n=2). Compared with cell culture experiments, the effective half-life in vivo was greatly prolonged (6.5 h for (123)I, 5.2 h for (211)At) and preliminary dosimetric calculations indicate high tumour absorbed doses (3.5 Gy/MBq(tumour) for (131)I and 50.3 Gy/MBq(tumour) for (211)At). In conclusion, NIS-expressing tumour cell lines of different origin displayed specific radionuclide uptake in vitro and in vivo. We provide first direct evidence that the high-energy alpha-emitter (211)At is efficiently transported by NIS. Application of (211)At may direct higher radiation doses to experimental tumours than those calculated for (131)I. Thus, (211)At may represent a promising alternative radionuclide for future NIS-based tumour therapy.
Petrich
T
T
Department of Nuclear Medicine, Medizinische Hochschule Hannover, Carl-Neuberg-Strasse 1, Germany.
Helmeke
H-J
HJ
Meyer
G J
GJ
Knapp
W H
WH
Pötter
E
E
D000230:Adenocarcinoma / Q000000981:diagnostic imaging / Q000235:genetics / Q000378:metabolism; D000231:Adenocarcinoma, Papillary / Q000000981:diagnostic imaging / Q000235:genetics / Q000378:metabolism; D000818:Animals; D001246:Astatine / Q000493:pharmacokinetics*; D014408:Biomarkers, Tumor / Q000235:genetics / Q000378:metabolism*; D003110:Colonic Neoplasms / Q000000981:diagnostic imaging / Q000235:genetics / Q000378:metabolism*; D015870:Gene Expression; D005909:Glioblastoma / Q000000981:diagnostic imaging / Q000235:genetics / Q000378:metabolism; D006801:Humans; D007457:Iodine Radioisotopes / Q000493:pharmacokinetics*; D051379:Mice; D008819:Mice, Nude; D009368:Neoplasm Transplantation; D011877:Radionuclide Imaging; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics; D012016:Reference Values; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013670:Sodium Pertechnetate Tc 99m / Q000493:pharmacokinetics; D027981:Symporters / Q000235:genetics / Q000378:metabolism*; D013964:Thyroid Neoplasms / Q000000981:diagnostic imaging / Q000235:genetics / Q000378:metabolism*; D014018:Tissue Distribution; D014407:Tumor Cells, Cultured; D000099209:Sodium-Iodide Symporters
D001246:Astatine; D014408:Biomarkers, Tumor; D007457:Iodine Radioisotopes; D019275:Radiopharmaceuticals; D013670:Sodium Pertechnetate Tc 99m; D027981:Symporters; D000099209:Sodium-Iodide Symporters