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Investigation of a vitamin B12 conjugate as a PET imaging probe.

Ikotun OF, Marquez BV, Fazen CH, Kahkoska AR, Doyle RP, Lapi SE.

ChemMedChem. 2014;9(6):1244-51.

Department of Radiological Sciences, Washington University School of Medicine, 510 S. Kingshighway Blvd., Campus Box 8225, St. Louis, MO 63110 (USA), Fax: (+1) 315-362-4696.

 

Abstract

 Nutrient demand is a fundamental characteristic of rapidly proliferating cells. Vitamin B12 is vital for cell proliferation; thus neoplastic cells have an increased demand for this essential nutrient. In this study we exploited the vitamin B12 uptake pathway to probe the nutritional demand of proliferating cells with a radiolabeled B12 derivative in various preclinical tumor models. We describe the synthesis and biological evaluations of copper-64-labeled B12 -ethylenediamine-benzyl-1,4,7-triazacyclononane-N,N’,N”-triacetic acid (B12 -en-Bn-NOTA-(64) Cu), the first example of a B12 derivative for positron emission tomography (PET) imaging. Small-animal imaging and pharmacological evaluation show high tumor uptake ranging from 2.20 to 4.84% ID g(-1) at 6 h post-administration. Competition studies with excess native B12 resulted in a 95% decrease in tumor accumulation, indicating the specificity of this radiopharmaceutical for B12 endocytotic transport proteins. These results show that a vitamin B12 PET  radiopharmaceutical  has potential utility for non-invasive imaging of enhanced nutrient demand in proliferating cells.

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