Targeted Hyperpolarized Molecular Beacons for Colorectal Cancer Detection

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ABSTRACT Colorectal cancer is the third leading cause of death in the United States. Early diagnosis is central to cancer care. Often, only tumors greater than 5 mm can be imaged using existing technologies, limiting the ability of early diagnosis. Our proposed constructs, "hyperpolarized molecular beacons,” will significantly increase the ability of detecting cancer by utilizing several amplification steps and combining the versatile binding affinity and specificity of antibodies with the sensitivity of hyperpolarized Magnetic Resonance (HP MR). Antibodies have high affinity to their protein targets, and several are approved for cancer treatment. Hyperpolarized molecular beacons will utilize antibody based molecular targeting and leverage >10,000-fold sensitivity enhancement by hyperpolarized MR technique to create a highly sensitive early detection method forcolorectal cancer. In a HP molecular beacon, an antibody is attached to a protein that catalyzes the conversion of hyperpolarized small molecules; therefore, metabolites of the hyperpolarized compounds are only observed in the presence of the reporter. We will attach a plant based protein to the N-terminus of an antibody that recognizes human mucin protein (MUC1). MUC1 protein positively correlates with tumor proliferation, invasiveness, and metastasis in colorectal cancer. Our proposed MUC1 antibody specifically recognizes a large section of MUC1. The HP molecular beacon will enhance signal amplitude through multiple MUC1 antibodies binding to one MUC1 protein, catalytic amplification of the signal and enhancement through the use of hyperpolarization. We will therefore, create a high affinity MUC1 targeted hyperpolarized molecular beacon, evaluate its ability to detect colorectal cancer in animal models and will expand the repertoire of HP molecular beacons to other cell surface markers to develop a multiplexed molecular beacon to recognize the full repertoire of colorectal cancer phenotypes in diverse patient populations. This methodology will significantly increase the capability of targeted molecular imaging in MRI and can be readily replicated with other antibodies in different cancer systems.