Magnetic resonance molecular imaging strategies have been explored by specifically targetingoncogenes such as HER-2 (c-erbB-2, Neu), bcl-2/bcl-xL, protein kinase A, and the transferrin receptorgene. The human transferrin receptor (hTfR) has been used as a molecular target to direct therapeuticagents to tumor cells and to shuttle drugs across the blood-brain barrier. Expression and regulation ofhTfR'receptors can be visualized by NMR imaging by studying the receptors with a sterically protectingiron-containing magnetic hTfR probe. A cationic immunoliposome system which covalently conjugatesthe single-chain antibody variable region fragment (scFv) against the hTfR has been used to improvep53 tumor suppressor gene therapy employed in the human breast cancer metastasis model. ThisscFv-immunolipdsome can systematically deliver the complexed gene to tumors in vivo. In comparisonto a whole antibody or transferrin molecule, scFv has a much smaller size, enabling it to penetrate moreeasily through solid tumors. In this study, we will utilize the TfR scFv-immunoliposome along with MRcontrast agents to improve contrast agent-tumor affinity and specificity. This will enhance MRdiagnostic imaging capabilities, particularly those needed for early detection.
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