Characterization of high specific activity [16 alpha-123I]Iodo-17 beta-estradiol as an estrogen receptor-specific radioligand capable of imaging estrogen receptor-positive tumors.
16 alpha-[123I]Iodo-17 beta-estradiol (16 alpha-[123I]E2) has been characterized for use as a selective radioligand for estrogen receptor (ERc) that is capable of generating in situ images of ERc-positive tumors. High specific activity 16 alpha-[123I]E2 (7,500-10,000 Ci/mmol) was used in all determinations. Radiochemical purity was determined by thin layer chromatography, and the selectivity of radioligand for ERc was evaluated using size exclusion high performance liquid chromatography on ERc prepared from rodent uteri. Efficiencies of radioidination approaching 100% were achieved, and excellent receptor selectivity was obtained even when the efficiency of radioiodination was as low as 10%. Low radiochemical purity was always associated with poor selectivity for ERc. No new radioligand species was generated during the course of radiodecay; however, reduced binding over time, even when increased activity was used to compensate for radiodecay, indicated that the formation of a radioinert competitor does occur. 16 alpha-[123I]E2 demonstrated stable, high affinity binding to ERc and was concentrated by ERc-positive tissues. After injecting 16 alpha-[123I]E2 in vivo, images of ERc-containing tissues were obtained, including rabbit reproductive tract and dimethylbenzanthracene-induced tumors. The demonstrations of ERc selectivity and image formation both indicate that 16 alpha-[123I]E2 should have promise as a useful new radiopharmaceutical for imaging ERc-positive cancers.
Pavlik
E J
EJ
Department of Obstetrics and Gynecology, University of Kentucky College of Medicine, Lexington 40536.
Nelson
K
K
Gallion
H H
HH
van Nagell
J R
JR
Donaldson
E S
ES
Shih
W J
WJ
Spicer
J A
JA
Preston
D F
DF
Baranczuk
R J
RJ
Kenady
D E
DE
D000818:Animals; D001667:Binding, Competitive; D014408:Biomarkers, Tumor / Q000032:analysis*; D002855:Chromatography, Thin Layer; D003600:Cytosol / Q000378:metabolism; D004958:Estradiol / Q000378:metabolism*; D005260:Female; D006801:Humans; D007457:Iodine Radioisotopes; D000090204:Mesothelin; D051379:Mice; D008815:Mice, Inbred Strains; D010052:Ovariectomy; D011817:Rabbits; D011869:Radioligand Assay; D051381:Rats; D011919:Rats, Inbred Strains; D011960:Receptors, Estrogen / Q000032:analysis* / Q000378:metabolism; D014594:Uterine Neoplasms / Q000378:metabolism*; D014599:Uterus / Q000378:metabolism
D014408:Biomarkers, Tumor; D007457:Iodine Radioisotopes; C000715529:Msln protein, rat; D011960:Receptors, Estrogen; D004958:Estradiol; D000090204:Mesothelin