VPAC1 Receptor-Targeted PET Imaging of Prostate Cancer Abstract Prostate cancer (PC) affects one in every six men >60 years old and will kill over 32,000 US men in 2011. Serum prostate specific antigen (PSA) measurements, transrectal ultrasonography (TRUS) and magnetic resonance imaging (MRI) remain standard tools for diagnosis and management of PC. Each of these modalities requires invasive biopsy for histologic confirmation of PC. Biopsies are associated with morbidity and high cost. More than 65% of the 1.5 million biopsies performed each year in the US show benign pathology, indicating a high false positive rate for these standard diagnostic tools. These limitations demonstrate a dire need for noninvasive methods to a) accurately stage, localized high risk primary PC, b) detect recurrent disease and c) image metastatic lesions with improved reliability. To address these issues, we propose early, specific, noninvasive radioimaging of PC. We will target VPAC1 receptors, which are overexpressed on PC cells at the onset of oncogenesis. We have successfully applied VPAC1- specific Cu-64-peptides to image prostate cancer xenografts. Our results in TRAMP transgenic mice that mimic spontaneous human PC illustrate that our Cu-64-peptides specifically and effectively target VPAC1. We have also confirmed the specificity of Cu-64 peptides for VPAC1 in MMTV-neu transgenic mice that mimic spontaneous human breast cancer (BC), including overexpression of VPAC1. We have initiated PET imaging of BC in humans using Cu-64-VPAC1 peptides with highly promising early results. Therefore, we hypothesize that PET imaging with VPAC1 receptor-specific Cu-64 peptides will expedite the diagnosis of PC and contribute to its management, including reduction in unnecessary biopsy procedures and under treatment or over treatment that yield minimal benefits, incontinence, or impotence. We will test our hypothesis in four Specific Aims: i) Evaluate two Cu-64 peptides specific for VPAC1 by imaging human PC xenografts in athymic nude mice. ii) Determine the efficacy of the best Cu-64-peptide in TRAMP transgenic mice that mimic human PC pathogenesis and validate VPAC1 imaging of PC malignancy in TRAMP mice by comparison with F-18-FDG scans, PC histology, and VPAC1 RT-PCR and immunohistochemistry. iii) Perform toxicology, obtain eIND and iv) carryout a feasibility study in 25 pre-operative PC patients, using the best suited Cu-64-peptide. PET imaging results shall be statistically evaluated with those of the histologic findings, and the entire PC gland mapping. This translational research for molecular PET imaging of PC by targeting VPAC1 will yield a PET imaging peptide validated for PC detectability and imaging specificity. Our strategic partner, NuView, offers a multidisciplinary industrial team with expertise in radiopharmaceutical development, clinical trials, and marketing strategies that ensures successful translation of this technology from bench to bedside.
One in six men older than sixty years will have prostate cancer (PC), yet it remains a major challenge to diagnose it accurately and reliably, resulting in undertreatment or overtreatment of patients with minimal benefit, enormous morbidity, incontinence, and/or impotence, while costing hundreds of millions of health care dollars for invasive biopsies required for confirmation of PC. We will evaluate two promising small molecules that will be injected into patients with suspected PC, which will then attach to a specific cancerous alteration that shows up on PC cell surfaces, yielding signals from the attached molecules that are collected outside the body to provide highly accurate and specific images of malignant PC. Our preliminary imaging results using these small molecules are highly promising to eliminate the present drawbacks and to allow the combined expertise of our team from Thomas Jefferson University and NuView, Inc. to make this patented technology available for the benefit of PC patients.
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