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Abstract #0454

In Vivo Dynamic Contrast Enhanced MRI of Novel Contrast Agents Targeted to the Estrogen Receptor

Adi Pais1, Gunanathan Chidambaram2, Inbal Biton3, Raanan Margalit1, David Milstein2, Hadassa Degani1

1Biological Regulation, Weizmann Institute of Science, Rehovot, Israel; 2Organic Chemistry, Weizmann Institute of Science, Rehovot, Israel; 3Veterinary Resources, Weizmann Institute of Science, Rehovot, Israel

Molecular imaging of novel contrast agents, targeted to the estrogen receptor (ER), composed of Gd-chelate conjugated to estrogen (EPTA-Gd) or tamoxifen (TPTA-Gd), were investigated in vivo. DCE-MRI, applied in mice bearing human breast cancer tumors showed that EPTA-Gd induced a significantly higher enhancement in MDA-ER-positive tumors than in MDA-ER-negative tumors and muscle tissues, indicating specific binding to ER and heterogeneous ER spatial distribution. In contrast, TPTA-Gd showed high enhancement in muscle tissue and lower and similar enhancement in MDA-ER-positive and negative tumors revealing an unknown interaction with muscle components. In conclusion, EPTA-Gd is a potential molecular imaging probe of ER