Transcobalamin II receptor imaging via radiolabeled diethylene-triaminepentaacetate cobalamin analogs

Douglas A. Collins

Research output: Contribution to journalArticlepeer-review

51 Scopus citations


Rapidly dividing cells up-regulate the number of transcobalamin II receptors during DMA replication. We have developed diethylenetriaminepentaacetate (DTPA) cobalamin analogs for the purpose of imaging transcobalamin II receptors in malignant and nonmalignant tissue. Methods: Methyl-, adenosyl- and cyanocobalamin-b-(4aminobutyl)-amide-DTPA analogs were synthesized. In vitro binding of the analogs to the transcobalamin proteins was assessed by the unsaturated vitamin B12 binding capacity assay and compared to DTPA and cyanocobalamin. The biodistribution of the 111ln-DTPA cobalamin analogs was measured at 24 hr after injection into sarcoma-bearing mice and non-tumor-bearing mice and pigs. Results: Methyl-, adenosyl- and cyanocobalamin-b-(4-aminobutyl)-amide-DTPA analogs and DTPA were 94.0%, 90.4%, 66.4%, and 3.6%, respectively, as efficient in binding to the transcobalamin proteins when compared to cyanocobalamin. At 24 hr after administration, the cobalamin analogs had 5-17 times and 20-29 times, respectively, the amount of uptake within the resected tissue samples and transplanted sarcomas when compared to 111ln-DTPA. Conclusion: The radiolabeled DTPA cobalamin analogs are biologically active. Preliminary animal studies suggest that the analogs could be effective in vivo transcobalamin II receptor imaging agents.

Original languageEnglish (US)
Pages (from-to)717-723
Number of pages7
JournalJournal of Nuclear Medicine
Issue number5
StatePublished - Dec 1 1997


  • Receptor imaging
  • Tumor-seeking agent
  • Vitamin b12

ASJC Scopus subject areas

  • Radiology Nuclear Medicine and imaging


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