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