Presentation Abstract

Abstract Number: 4341
Presentation Title: Tumor imaging via β-galactosidase fragment complementation with a multifunctional targeted-reporter complex
Presentation Time: Tuesday, Apr 20, 2010, 2:00 PM - 5:00 PM
Location: Exhibit Hall A-C, Poster Section 18
Poster Section: 18
Poster Board Number: 26
Author Block: Ann-Marie Broome, Kari Lavik, Gopalakrishnan Ramamurthy, Luther A. Liggett, Richard S. Agnes, James P. Basilion. Case Western Reserve University, Cleveland, OH
Abstract Body: Determining the status of cell surface receptors has become routine in the care of patients with cancer and has proven to be helpful in guiding treatment. Mutational events that drive a normal cell to become a cancer cell require the coordinated overexpression of not just one receptor at a time, but rather multiple biomarkers. A growing body of evidence from genomic and proteomic research asserts that several receptors contribute to tumor behavior and these expression patterns are referred to as the cancer signature. Many cancers are characterized by an abnormal increase in the activity of epidermal growth factor receptors (EGFR) and transferrin receptors (TfR). Our data of representative human cancer cell lines demonstrate unique, observable expression patterns for the two receptors. Targeted-reporter imaging agent platforms have real application for noninvasive imaging of the multi-step progression of cancer growth, creating the next frontier in in vivo imaging. To develop imaging tools that take advantage of the diagnostic molecular signature, new technologies must employ a contrast agent or signal-amplifying material conjugated to a targeting agent. By linking a reporter enzyme, such as β-gal, to a targeting moiety, either ligand or a short peptide, signal-amplification at the molecular level is achieved. We divided β-gal into unique, independent polypeptides that reassemble and complement enzymatic activity in bacteria and in mammalian cells. We created two sets of complementing pairs that individually have no enzymatic activity. However, when brought into close proximity, complementing pairs associate, resulting in detectable enzymatic activity. We then constructed a targeting complex composed of reporter fragment, linker, and targeting moiety. Our studies demonstrate a time course- and dose-dependent uptake in vitro. Further, we were able to simultaneously visualize the two cell surface receptors implicated in cancer development, EGFR and TfR, using complementing pairs of the targeted-reporter fragment complex. In addition, we are able to image tumor localization in vivo of the targeted-complexes when a fluorescence reporter is added to the complex, as well as immunohistochemical staining of the β-gal reporter complex ex vivo.